Tag Archives: 13dka

From Cuba with noise? Massive jamming on the 40 meter band.

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


Massive jamming on 40m (possibly from Cuba) is bugging the radio community

by 13dka

Apparently this is going on for a week now on 40m:

Spent last night at my beach listening post on the German North Sea coast and found this fairly strong signal and a 40m band mostly cleared of any other signals. As soon as I found out that it wasn’t something local, I was wondering who’s responsible for this mess again. It looks like Josh (“Ham Radio Crash Course” YouTube channel) may have found a possible origin of that signal:

Here’s what it sounds like on each of the apparently manually controlled jamming channels:

Cuba would’ve probably been my last guess here on the other side of the big pond. 🙂 In other words, they – whoever they are – jam the band for at least half of the world. Luckily 40m isn’t exactly a pleasure in most of the summer anyway but after having to suffer OTH radars, FHSS blips and politically motivated broadcasting with associated jamming on 40m for a long time, this is a new low. I don’t want to get all political here but trying to erect some electromagnetic fence around a country has never really worked out, it’s just a futile, at most temporarily effective and symbolic act, perceived as pointless and aggressive vandalism out of blank despair by the rest of the world.

Ollie

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Guest Post: Dikeside Icom IC-705 RX action

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


The IC-705 in action at the dike

by 13dka

When I got the IC-705 in late October 2020, I didn’t get that much chance to enjoy it at the dike: After a couple of initial tests and 2 nightly “FYBO” MW DX sessions in November, a way too long and wet winter struck the German North Sea coast, with nighttime temperatures recovering to 2-digit Celsius figures only in the past few weeks. I took the opportunity to do more experiments with loops, preamps and a phasing unit to improve the RFI-stricken reception at home, so I could at least listen to European hams on 80 and 40m raving about their new 705s and start to write my own musings about that lovely little radio, recently posted here.

SSB DX

June 1st, 202

Finally, acceptable temperatures at night! But they come with a downside: When I connected the vertical around 8:00pm (local time), it was still almost 2 hours before sunset and a lot of thunderstorms in Europe made even 14 MHz very noisy, my hopes for some nice catches were immediately taking a dive. A short scan of the bands brought up nothing special, the only notable thing being the CB and 10m bands being moderately open. I should’ve known better: As soon as the sun splashed into the ocean, grayline propagation worked its magic!

Grayline while receiving Japan, June 1st

As the image probably hints, a couple of Japanese “big guns” produced some nice, comfy signals on the monopole, in addition to the South American and Carribbean stations usually booming in here!

Video: A short collection of ham stations heard around midnight

After midnight I noticed a residue signal of WWV on 20 MHz and still a few EU beacons on 10m. Both incredibly weak with QSB making them disappear but that’s where the 705 really shines – it’s not only picking up these grassroots signals just fine, it shows me that they’re there, or that they were there – a waterfall display keeps on proving that a perceived lack of activity on a band is often pure bad luck – you can tune across an entire band without hearing anything because on each frequency with some activity there’s the other (inaudible to you) station speaking right now, QSB is dipping the signal just when you tune past it…

June 5/6, 2021

That evening the Japanese stations were missing on 20m, I thought I picked one up on 17m, and like so often, the one odd Australian station came in on 20m. After midnight I noticed the 10m beacons again, there were even a few more of them. This time I brought my Belka DSP to the dike so I could compare it with the IC-705, after all the Belka proved to be my most sensitive portable before! The devastating result is likely owed to the fact that the Belka is pretty picky about passive antennas not being matched very well to its input (which is much optimized for the whip) but it picked up diddly squat. If it isn’t a testimony for the sensitivity of the IC-705, it might be one for its aptitude to cope with all sorts of antennas.

Then I tuned into the 10m SSB range and I was veeeery surprised to hear VO1FOG from St. Johns, Canada! This is the first time I heard a transatlantic signal on 10m in a solar minimum ever, but it was with condx only elevated enough for some daytime DX within the EU…and literally in the middle of the night! The signal was very unstable though, he later switched to the 12m band which worked better. Back to what I said about the waterfall display above: Without it, I could’ve missed this station with a pretty high probability simply because I didn’t expect any activity up there, so I wouldn’t have tuned across that band for very long, and without seeing the signal while the VFO is already somewhere else…

I also heard another new country (Ecuador) in SSB, the usual collection of Carribbean islands and some participants of the “Museum Ships Weekend Event” including NI6IW, which is the vanity call of the history-charged USS Midway in San Diego. The “Japanese” station JW4GUA turned out to be on Svalbard island, with the main town Longyearbyen being the northernmost town in the world, only 650 miles from the north pole, and I don’t hear stations from there very often!

Video: June 5th

June 10/11

The past days saw the SFI passing 80 and 11/10m becoming quite busy. By the time I parked the car at the dike, SFI had dropped to 73. That evening the grayline confined itself to colorizing the horizon. 10m and 11m were still full of signals, I could still hear 2 British chaps chatting on 27 MHz at 3:00 in the morning, but nothing really “extraordinary” was coming in – the one odd VK, more Carribbean islands, one Argentinian but not much from other parts of South America, it never gets boring how this all defies predictability. But as always I heard most of the North American continent, not booming in much that night but I followed 2 POTA activations for a while, which are usually at most 100W stations working a lot of other “barefoot” stations and I heard almost all of them. In the morning grayline window for the west coast I finally got one solid signal from Oregon. All my radio life, the US west coast has been a tough target for some reason.

The signal had that typical “over the pole” sound, a relatively quick phasing imprinted into the signal by the charged particles converging over the pole, causing northern lights in the region and that exiting feeling when observing really big, planetary scale physics in realtime, over here at my listening post. The magic of shortwave. 🙂

Broadcast bands

After the post touting the IC-705 as a SWL/BCL receiver, demonstrating it on the broadcast bands seems mandatory to me. However, capturing cool BC DX is a very different business than waiting on the ham bands for interesting stations coming and going and collecting spectacular (-ish) results in a single night this way. Broadcast schedules have to be studied, current “hardcore” DX targets identified… and I have to admit that I’m out of that loop currently. Just turning the knob and recording whatever is populating the bands, and doing that between 21-22:00 UTC, when all programs are directed towards anywhere except Europe turned out to yield pretty boring results. Here it goes anyway:

Video: Browsing the most important BC bands

CONDX and antenna:

The antenna I was using in these videos was a simple wire running up a 10m/33′ fiberglass pole, forming a very archetypical “monopole” or “Marconi” antenna, just a vertical wire, no counterpoise, no matching network, no un-un, transformer or flux capacitor. I planned on using this to make some experiments about the practical benefits (for reception) of all the components it’s now lacking, but it already demonstrates that the beauty of receive-only antennas is that they often don’t require crazy efforts: On the conductive soil at the dike it works pretty well (good signals all over the bands and sufficiently low takeoff angle) as it is.

The evening and the 2 full nights at the dike once again had condx that nobody would phone home about:

SFI, A and 3-hourly K-indices while I was at the dike.

It’s not that these numbers always fully explain actual and current condx but decreasing SFI and rising A/K-indices mean low expectations. Despite the condx still characterized by the solar minimum that way, the location is always delivering proper DX for my radios. Unless stormy or severely unsettled geomagnetic conditions give DX a day off, there’s almost always something to take home, be it a new country, a rare island, unexpectedly loud signals from the other end of the planet at unusual times and/or on unusual bands or other ionospheric mysteries.

Speaking of location: These videos demonstrate the properties of that listening post as much as the capability of the IC-705 to harvest them, and they don’t put that into relation to other radios, so you have to rely on my word on this: Compared to what I brought to that place so far it’s jaw-droppingly good, but a big contributor to that is that only few of my other radios can really cope with the antennas I like to use out there in first place. A radio like the IC-705 is sure making the most out of location and antenna, but it’s not the key component because a low-noise location is everything, it always was and it is today more than ever. Without it, radios and antennas can’t really play their jokers.

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The Icom IC-705: Is this really a new holy grail SWL/BCL receiver?

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


The Icom IC-705: Is this really a new holy grail SWL/BCL receiver?

by 13dka

When Thomas got wind of its development in 2019 he immediately asked “could the Icom IC-705 be a shortwave listeners holy grail receiver?”. I usually wince a little when I hear “holy grail” because it means very different things to different people, it’s also a moving target with many people aiming at the spot where it was decades ago. But Thomas certainly had a very level-headed assembly of technical performance, quality and practicality requirements in mind when he used that term, and I thought he might be onto something!

There are some excellent, trustworthy reviews of the IC-705 out there. The following is not one of them, I just want to share an opinionated breakdown on why I think this is an interesting radio for SWLs/BCLs indeed, also deliberately ignoring that it’s actually a transceiver.

Jumping shop

While the era of superhet/DSP-supported tabletop holy grails ended with the discontinuation and sell-off of the last survivors more than a decade ago, powerful PC-based SDR black boxes were taking over the mid-range segment and it became very slim pickings for standalone SWL receivers: Thomas just recently summed up the remaining options here.

Between the steady supply of inexpensive yet serviceable Chinese portables, upgraded with a least-cost version of DSP technology, and the remnants of the high end sector there’s very little left to put on the wish list for Santa – that doesn’t need to be paired with a computer that is.

No surprise that SWLs/BCLs in search of new quality toys with tangible controls are taking a squint over the fence to the ham transceiver market: Hams are still being served the best and the latest in radio technology in all shapes and sizes, and even entry-level rigs usually come with feature-rich general coverage receivers. But transceivers never had SWLs much in their focus in the past decades, and particularly not BCLs: Frontend adaptation, additional AM filters, switches and functions would’ve meant increasing costs and so transceivers were never perfected for that purpose. DSP and SDR technology allowed for improvements on that without actually adding (much) hardware and so some interesting alternatives surfaced in the past years, but most of them still come with little downers, at least for BCLs.

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Armed with loops, fences, and an Icom IC-705, 13dka battles transatlantic MW DX

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


Dipping my toes into transatlantic MW DX

by 13dka

Most of my SWLing life I wanted to dig into MW DX but never managed to make that really happen for some reason. Then last November, I fetched my first transatlantic station while I wasn’t even trying, in a rather surprising setting:

I have to explain that my home and neighborhood got so infested with a multitude of QRM sources that I did not put my outdoor antennas back up after a storm blew them out of the trees in winter 2018/19. I just used an ML-200 loop indoors, which also has to put up with my own additional QRM sources in my den, consisting of 3 computers running 24/7 and a couple of switching power supplies, a TV, LED lighting… allowing for very basic reception as long as my neighbors don’t watch TV or use the internet. On top of that, medium wave is badly beaten by a mowing robot’s boundary wire here, making reception on several portions of the band completely impossible.

I never expected receiving any US stations on MW in that noise, but I couldn’t sleep that night and scanned the bands a bit with the IC-705 hooked up to my new YouLoop hanging over my bed for testing. I had seen the characteristic transatlantic carriers on MW many times before on my SDRs, but for some reason I never picked up anything intelligible on them in any winter season, now a lot of these carriers were there again but on 1130 there was actually modulation and it wasn’t the only station!

Small bedside loop: SWL’s dreamcatcher!

Bloomberg Radio 1130 came in with almost enjoyable quality at times, but Bloomberg is also kind of a surefire station for MW DX over here. I also picked up a station on 1120 and another one on 880 which was briefly so strong that it surmounted the strong interference from BBC Radio Wales on 882 kHz. 1120 was confirmed the next night to be KMOX in St. Louis, 880 kHz was *not* KCBS in NY – I checked that immediately, I have a KiwiSDR set to that frequency booknarked on my cellphone in case I have a craving for the 1-877-Kars-4-Kids commercial. Powerwise likely candidates for that would be CHQT (50kW) in Edmonton, CKLQ (10kW) in Manitoba or KRVN in Nebraska (50kW class B station) but this may be hard to verify due to the dominance of the BBC on that frequency. Anyway, KMOX wasn’t a bad catch for a small, passive indoor loop, that’s 7,150km or 4,440 miles from here!

Bloomberg Radio on the YouLoop:

Here’s KMOX:

This was A) quite encouraging for nighttime DXpeditions to the dike (brrr…cold!), B) a testimony for the YouLoop’s good performance on MW and C) a testimony for the IC-705 having pretty much all one could wish for in a capable MW DX radio – notch filter, passband tuning on AM, stable ECSS, waterfall display to detect stations and last but not least loads of sensitivity to make the most out of low-output antennas down on MW.

Going to the dike

Of course I just had to put on some long johns and drive to the dike around 3:00am local a few nights later, to try my luck with my ML-200 (lacking a better idea) with an 80cm diameter rigid loop. I was mildly surprised that reception wasn’t that much better than with the YouLoop at home. The overall yield wasn’t exactly outstanding compared to other people’s logs but a lot of stations were hidden in the frequency ranges that are submerged in QRM at home. My log has US/Canadian stations on 20+ different frequencies, unfortunately most of them UNID. Here are some recordings I made that night, hunting for unambiguous station IDs from North American broadcasters:

ML-200, Nov. 16th, 2020

1130 Bloomberg Radio on the ML-200:

Presumedly WABC 770 in NYC: In MW DX, never think you ID’d something properly just because you heard a city name and the frequency has a clear-channel station located there!

This is more unambiguously 1010 WINS in NYC (with a twist described later)

1030 WBZ Boston, MA – the first part of the clip is showing how it sounds when the signal is good, the second part demonstrates how reliably propagation is taking a rest while a station identifies itself.

The grandpa of AM broadcasting, 1020 KDKA:

Moving away from the east coast, this is WHAS 840 in Louisville, KY:

760 WJR Detroit, MI

Here’s a tough one, the religious content I heard with a great signal before doesn’t warrant a proper ID alone, and as per usual the station ID’d while fading out. I could ID this only with a set of big, closed headphones, which is a mandatory accessory for all extreme DX (CHRB 1140 in High River, Alberta):

Of course I was occasionally checking other bands too and got some serviceable signals from Brazil:

Clube do Para on 4885 kHz:

VOA Pinheiro from Belem, Brazil on 4960:

Going to another dike, this time it’s personal!

Time to try something completely different: A ~1,000m/3,000′ straight (and preliminary considered continuos) stretch of mesh fence along the dike heading ~345° (NNW), pointing roughly to mid-/western mainland North America. I had briefly tried its aptitude for being a “natural” Beverage antenna before – with mixed but encouraging results: Due to the fence not being terminated at the far end it may be kind of bidirectional, and according to my latest insights a Beverage style antenna doesn’t work well over very good (conductive) ground, probably even less so close (maybe 200′) to the ocean. Also, I forgot to pack the 9:1 balun I prepared for that purpose, so I just had some wire with alligator clip to connect the fence to the radio. Boo.

Accordingly, what I saw on the waterfall display didn’t look so much different than what I got from the ML-200 before – there were clearly more stations visible (as a carrier line on the waterfall) but nothing was really booming in. However, I managed to log a few more stations, such as WRKO in Boston and (the highlight of the night) 1650 KCNZ “The Fan” in Cedar Falls, IA which has only 1kW to boot at night to make the 6,940 km/4,312 mi to my dike. This may or may not be an indication that the “Beverage sheep fence” isn’t so bad after all!

“Fence”- reception, Nov. 18th, 2020:

VOCM 590, St. Johns, New Foundland, Canada’s easternmost blowtorch is like Bloomberg an indicator station for European MW DXers:

680 WRKO, Boston, MA:

1040 kHz, presumed to be WHO, Des Moines, IA: No ID, only a matching frequency and a commercial for “Jethro BBQ”, which has locations only in and around Des Moines:

Here’s 1650 KCNZ, Cedar Falls, IA with 1KW:

To put that into some relation, this is what 1KW sounds like on a very quiet 40m band in SSB (K1KW from Massachusetts on 7156 kHz producing a 9+20 signal that morning on the “Fence antenna”):

BTW, interesting bycatch – not the first time I caught WWV and WWVH on the same frequency but that morning was the first time I could hear both on 5 MHz:

 

So where have you been all my life, American AM stations?

A question remains – how could I miss the existence of these stations forever, then in modern SDR times see the carriers on the spectrum scope and still miss the modulation on these carriers? Or the other way around – why did I hear them now?

To begin with, when I started out with the radio hobby many decades ago, the reason for the occasional whine and whistle on some stations (particularly past midnight) wasn’t obvious to me: The last thing I suspected was that this could be interference from across the pond, with the pitch of the whine (or “het”) having a direct relation to the 9kHz vs 10kHz difference in channel spacing. Of course these stations were there all my life! Then, with just some regular radio you’d have to pick one of very few frequencies where a strong station from across the pond coincides with a nice silent gap in the local channel allocation. But until this millennium, European medium waves had no such gaps and a lot more local blowtorches.

Since that time many MW stations were turned off and demolished and whole countries abandoned MW here in Europe, so we’re in a much better spot now for transatlantic DX. Unfortunately the opposite is true for listeners on the left side of the pond, you guys still have a very crowded AM band but less potential DX targets in Europe. On the bright side, the remaining European stations are often not restricted to 50kW and you have another ocean with very distant and rewarding DX stations that are very, very hard to catch in Europe!

Wrong time, wrong place

Another bunch of factors are – of course – propagation, season and location/latitude. The MW DX season is roughly fall to spring nights (when TX and RX are in the dark) with a period of increased absorption in the middle (the “mid-winter anomaly”), signals are potentially stronger at lower latitudes and weaker at higher ones but the distance to the noisy equator and a lack of stations interfering from the N can be a huge advantage for using over-the-pole paths on higher latitudes. The big showstopper is solar activity: Good condx on shortwave can be rather bad for skywave propagation on medium wave, so a solar minimum is the long-term hotspot for (transatlantic) medium wave DX.

I’m glad that I learned how intense that relationship is right away: When I discovered that Bloomberg is pretty good on my indoor YouLoop at home, condx were pretty down with SFI in the low 70s and very little excitement of the auroral zones. 2 weeks later the SFI was only slightly higher in the 80s-100, many of the carriers were missing on the waterfall and Bloomberg could be heard only in much bigger intervals.

Speaking of which – even with favorable condx, a proper radio and a half-proper antenna, patience is key! In my very fresh experience the fading cycles on those over-the-pond signals are long! So far I have seen everything fading in and out over the course of a few minutes to half hours or more, with less favorable conditions or a worse antenna it may take much longer until it sticks out of the noise for a while. So you may have to park on a frequency for a long time to not miss the station coming up so much that it becomes readable at the right time to ID it. Multiple DX stations on the same channel can make identification difficult unless one station really dominates the other and that all may take hours or days until it happens. Here’s a lucky example on 1010 kHz:

Lucky because in this case one station is already known – it’s WINS but it often has another station underneath and I was curious what that station might be. On this occasion, the station ID’d itself as “Newstalk 1010” (which is CFRB in Toronto, 0:05 in the clip) just in a short talking break on WINS. Again, this can’t be heard on my laptop speakers but on headphones:

Waiting for a moment like this to happen isn’t exactly fun, that’s why spectrum recordings are incredibly valuable particularly on MW – you won’t miss a possible station ID on frequency A because you were listening to frequency B, but a part of me thinks this is taking a bit of the challenge away, like blast fishing. 🙂

Fancy equipment


The IC-705 fits snuggly-wuggly into my steering wheel for extra-comfy tuning!

Fun fact: While Bloomberg NY on 1130 was (kind of) booming in at home so I knew for sure it was there, I could hear it even on the XHDAtA D-808 with its tiny loopstick and only average sensitivity on the AM band! So for “easy”, loud and undisturbed stations some persistence and a simple portable radio may suffice to catch some transatlantic DX. But most of the stations will be hit by interference from closer stations, then the radio needs at least to be capable of stable sideband reception, with a corresponding narrow filter and proper suppression of the unwanted sideband – luckily this isn’t an unusual feature on inexpensive portables anymore. So if you already have an SSB capable radio that’s all you need to address the most common issue with transatlantic DX, US and EU stations being too close in frequency. Of course passband tuning and notch filters are most helpful assets in a radio for this, rescuing reception in even more severe interference situations and the spectrum/waterfall display on an SDR helps a lot with finding the carriers and SDRs also have all the nice tools but with some more patience you may find stations with many conventional receivers.

Of course antennas are the crucial component again: If conditions are excellent, even a loopstick may bring the first stations into the log, some small magnetic (wideband) loop could dig up some more stations, from there it’s quickly going a bit esoteric – AFAIK there are no commercial offers for multi-turn (tuned) loop antennas nor are FSL antennas easy to come by, you can’t buy EWE et al antennas either and Beverage antennas for MW are quite a project – not that hard to get a kilometer of wire and there are even kits to buy but it could be much harder to find a place to roll it out in the direction you’re interested in, in an area that doesn’t have electric fences or high voltage power lines within a radius of at least several miles. I guess once you become addicted, you’ll stop asking yourself whether or not it’s worth the effort.

So it’s pretty clear what happened: For catching TA DX stations, the ionospheric conditions must be good, to receive that with a loopstick they must be ideal and that’s what they are currently – it’s winter in what’s still a deep solar minimum and on top of that, some of my radios are very apt for MX DX and I was lucky to listen on the right time on the right frequency. When I started writing this article, my enthusiastic bottom line was supposed to be something like “MW DX isn’t rocket science”, which is certainly true but I think my history with it shows that it’s not exactly trivial either. Maybe that’s why it’s so rewarding, it sure is some hardcore DX challenge that complements the shortwave activity quite nicely and may give you something to look forward to when solar activity is down.

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Taking the Icom IC-705 on a shortwave and mediumwave field trip

Many thanks to SWLing Post contributor, 13dka, who shares the following:

Yesterday evening, I took the Icom IC-705 to the dike for the first time (got it on Thursday and spent a lof of time with familiarization).

Since it was already too dark, wet and cold for all the fuss with antennas, I decided to just put a telescopic whip on a tiny magmount on the car roof, curious what the 705 would make out of that. That magmount is the worst thing ever, too much cheap RG-174 seems to attenuate the signal from the whip (possibly some impedance catastrophe), my portables don’t like that thing at all.

So the antenna was as bad as it gets but…it demonstrated what the 705 can do with extremely faint signals! I had really good and quiet reception even when signals were not at all showing up on the S-Meter or much on the waterfall. I had to turn on preamp 2 and crank up the scope “Ref” gain up to see anything, but SNR was great, I didn’t have the feeling that I’m missing many stations and it even worked pretty well on medium wave to longwave, with the signal really tapering off only below 500 kHz and I learned why omnidirectional whips never caught on on MW! ?

AM band scan:

31m band scan:

So yes, as an SWL/BCL receiver it will likely perform as good as it possibly gets with literally any antenna or anything that could stand in for an antenna, the only thing it doesn’t have is sync but since it can tune in 1 Hz steps it can truly zero beat in ECSS, it has notch/autonotch (indispensable also on congested broadcast bands), passband tuning, if I didn’t get that wrong it has 10,000 memories and the 32 GB SD card I was putting in is good for more than 3 weeks of recording 24/7. With some regular BNC whip it’s still a cool bedside radio in a hotel room (no alarm function tho), also good for some VHF/UHF in-house good night 88s between licensed dads and daughters if you plug in the mic, which you don’t have to.

What a cool toy, I’m sure I will still love it when the honeymoon is over!

Thanks for sharing this, and for those band scans. Wow! And I love the “also good for some VHF/UHF in-house good night 88s between licensed dads and daughters”–! Ha ha! That is a real possibility.

Your IC-705 experience on MW and SW is similar to mine. I’ve used the IC-705 a number of times in the field and find that it has a superb and capable general coverage receiver. I’ve also coupled it with my homemade NCPL antenna and have been very pleased with the results. I couldn’t be more pleased.

You’ll find the twin passband filters are incredibly effective at knocking out adjacent signal spill-over. And, yes, the auto notch feature is excellent for killing hets in your audio. I’ve even used the notch manually and like many of my PC-connected SDRs, the filter can be adjusted in width.

I think you’ll continue to enjoy the IC-705 well beyond the honeymoon phase and I’m hoping you might even post some more comparisons at the dike!

AS I mentioned in previous posts, I had fully intended to sell the IC-705 after my review period, but I’ve grown to love this radio so much, that is no longer going to happen.

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Guest Post: Why does radio reception improve on saltwater coasts?

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


Gone fishing…for DX: Reception enhancement at the seaside

by 13dka

In each of my few reviews I referred to “the dike” or “my happy place”, which is a tiny stretch of the 380 miles of dike protecting Germany’s North Sea coast. This is the place where I like to go for maximum listening pleasure and of course for testing radios. Everyone knows that close proximity to an ocean is good for radio reception…but why is that? Is there a way to quantify “good”?

Of course there is, this has been documented before, there is probably lots of literature about it and old papers like this one (click here to download PDF). A complete answer to the question has at least two parts:

1. Less QRM

It may be obvious, but civilization and therefore QRM sources at such a place extend to one hemisphere only, because the other one is covered with ocean for 100s, if not 1000s of miles. There are few places on the planet that offer such a lack of civilization in such a big area, while still being accessible, habitable and in range for pizza delivery. Unless you’re in the midst of a noisy tourist trap town, QRM will be low. Still, you may have to find a good spot away from all tourist attractions and industry for absolutely minimal QRM.

My dike listening post is far enough from the next small tourist trap town (in which I live) and also sufficiently far away from the few houses of the next tiny village and it’s located in an area that doesn’t have HV power lines (important for MW and LW reception!) or industrial areas, other small villages are miles away and miles apart, the next town is 20 km/12 miles away from there. In other words, man-made noise is just not an issue there.

That alone would be making shortwave reception as good as it gets and it gives me an opportunity to check out radios on my own terms: The only way to assess a radio’s properties and qualities without or beyond test equipment is under ideal conditions, particularly for everything that has to do with sensitivity. It’s already difficult without QRM (because natural noise (QRN) can easily be higher than the receiver’s sensitivity threshold too, depending on a number of factors), and even small amounts of QRM on top make that assessment increasingly impossible. This is particularly true for portables, which often can’t be fully isolated from local noise sources for a couple of reasons.

Yes, most modern radios are all very sensitive and equal to the degree that it doesn’t make a difference in 98% of all regular reception scenarios but my experience at the dike is that there are still differences, and the difference between my least sensitive and my most sensitive portable is not at all negligible, even more because they are not only receivers but the entire receiving system including the antenna. You won’t notice that difference in the middle of a city, but you may notice it in the woods.

When the radio gets boring, I can still have fun with the swing and the slide!

2. More signal

I always had a feeling that signals actually increase at the dike and that made me curious enough to actually test this by having a receiver tuned to some station in the car, then driving away from the dike and back. Until recently it didn’t come to me to document or even quantify this difference though. When I was once again googling for simple answers to the question what the reason might be, I stumbled upon this video: Callum (M0MCX) demonstrating the true reason for this in MMANA (an antenna modeling software) on his “DX Commander” channel:

To summarize this, Callum explains how a pretty dramatic difference in ground conductivity near the sea (click here to download PDF) leads to an increase in antenna gain, or more precisely a decrease in ground return losses equaling more antenna gain. Of course I assumed that the salt water has something to do with but I had no idea how much: For example, average ground has a conductivity of 0.005 Siemens per meter, salt water is averaging at 5.0 S/m, that’s a factor of 1,000 (!) and that leads to roughly 10dB of gain. That’s right, whatever antenna you use at home in the backcountry would get a free 10dB gain increase by the sea, antennas with actual dBd or dBi gain have even more gain there.

That this has a nice impact on your transmitting signal should be obvious if you’re a ham, if not just imagine that you’d need a 10x more powerful amplifier or an array of wires or verticals or a full-size Yagi to get that kind of gain by directionality. But this is also great for reception: You may argue that 10dB is “only” little more than 1.5 S-units but 1.5 S-units at the bottom of the meter scale spans the entire range between “can’t hear a thing” and “fully copy”!

A practical test

It’s not that I don’t believe DX Commander’s assessment there but I just had to see it myself and find a way to share that with you. A difficulty was finding a station that has A) a stable signal but is B) not really local, C) on shortwave, D) always on air and E) propagation must be across water or at least along the shoreline.

The army (or navy) to the rescue! After several days of observing STANAG stations for their variation in signal on different times of the day, I picked one on 4083 kHz (thanks to whoever pays taxes to keep that thing blasting the band day and night!). I don’t know where exactly (my KiwiSDR-assisted guess is the English channel region) that station is, but it’s always in the same narrow range of levels around S9 here at home, there’s usually the same little QSB on the signal, and the signals are the same day or night.

On top of that, I had a look at geological maps of my part of the country to find out how far I should drive into the backcountry to find conditions that are really different from the coast. Where I live, former sea ground and marsh land is forming a pretty wide strip of moist, fertile soil with above average conductivity, but approximately 20km/12mi to the east the ground changes to a composition typical for the terminal moraine inland formed in the ice age. So I picked a quiet place 25km east of my QTH to measure the level of that STANAG station and also to record the BBC on 198 kHz. Some source stated that the coastal enhancement effect can be observed within 10 lambda distance to the shoreline, that would be 730m for the 4 MHz STANAG station and 15km for the BBC, so 25km should suffice to rule out any residue enhancement from the seaside.

My car stereo has no S-meter (or a proper antenna, so reception is needlessly bad but this is good in this case) so all you get is the difference in audio. The car had the same orientation (nose pointing to the east) at both places. For the 4 MHz signal though (coincidence or not), the meter shows ~10dBm (or dBµV/EMF) more signal at the dike.

3. Effect on SNR

Remember, more signal alone does not equal better reception, what we’re looking for is a better signal-to-noise ratio (SNR). Now that we’ve established that the man-made noise should be as low as possible at “my” dike, the remaining question is: Does this signal enhancement have an effect on SNR as well? Even if there is virtually no local QRM at my “happy place” – there is still natural noise (QRN) and that wouldn’t that likely gain 10dB too?

Here are some hypotheses that may be subject of debate and some calculations way over my head (physics/math fans, please comment and help someone out who always got an F in math!). Sorry for all the gross oversimplifications:

Extremely lossy antennas

We know that pure reception antennas are often a bit different in that the general reciprocity rule has comparatively little meaning, many antennas designed for optimizing reception in specific situations would be terrible transmitting antennas. One quite extreme example, not meant to optimize anything but portability is the telescopic whip on shortwaves >10m. At the dike, those gain more signal too. When the QRN drops after sunset on higher frequencies, the extremely lossy whip might be an exception because the signal coming out of it is so small that it’s much closer to the receiver noise, so this friendly signal boost could lift very faint signals above the receiver noise more than the QRN, which in turn could mean a little increase in SNR, and as we know even a little increase in SNR can go a long way.

The BBC Radio 4 longwave recording is likely another example for this – the unusually weak signal is coming from a small and badly matched rubber antenna with abysmal performance on all frequency ranges including LW. The SNR is obviously increasing at the dike because the signal gets lifted more above the base noise of the receiving system, while the atmospheric noise component is likely still far below that threshold. Many deliberately lossy antenna design, such as flag/tennant, passive small aperture loops (like e.g. the YouLoop) or loop-on-ground antennas may benefit most from losses decreasing by 10dB.

Not so lossy antennas, polarization and elevation patterns

However, there is still more than a signal strength difference between “big” antennas and the whips at the dike: Not only at the sea, directionality will have an impact on QRN levels, a bidirectional antenna may already decrease QRN and hence increase SNR further, an unidirectional antenna even more, that’s one reason why proper Beverage antennas for example work wonders particularly on noisy low frequencies at night (but this is actually a bad example because Beverage antennas are said to work best on lossy ground).

Also, directional or not, the “ideal” ground will likely change the radiation pattern, namely the elevation angles, putting the “focus” of the antenna from near to far – or vice versa: As far as my research went, antennas with horizontal polarization are not ideal in this regard as they benefit much less from the “mirror effect” and a relatively low antenna height may be more disadvantageous for DX (but maybe good for NVIS/local ragchewing) than usual. Well, that explains why I never got particularly good results with horizontal dipoles at the dike!

Using a loop-on-ground antenna at a place without QRM may sound ridiculously out of place at first, but they are bidirectional and vertically polarized antennas, so the high ground conductivity theoretically flattens the take-off angle of the lobes, on top of that they are ~10dB less lossy at the dike, making even a LoG act more like something you’d string up as high as possible elsewhere. They are incredibly convenient, particularly on beaches where natural antenna supports may be non-existent and I found them working extremely well at the dike, now I think I know why. In particular the preamplified version I tried proved to be good enough to receive 4 continents on 20m and a 5th one on 40m – over the course of 4 hours on an evening when conditions were at best slightly above average. Though the really important point is that it increased the SNR further, despite the QRN still showing up on the little Belka’s meter when I connected the whip for comparison (alas not shown in the video).

The 5th continent is missing in this video because the signals from South Africa were not great anymore that late in the evening, but a recording exists.

Here’s a video I shot last year, comparing the same LoG with the whip on my Tecsun S-8800 on 25m (Radio Marti 11930 kHz):

At the same time, I recorded the station with the next decent KiwiSDR in my area:

Of course, these directionality vs noise mechanisms are basically the same on any soil. But compensating ground losses and getting flat elevation patterns may require great efforts, like extensive radial systems, buried meshes etc. and it’s pretty hard to cover enough area around the antenna (minimum 1/2 wavelength, ideally more!) to get optimum results on disadvantaged soils, while still never reaching the beach conditions. You may have to invest a lot of labor and/or money to overcome such geological hardships, while the beach gives you all that for free.

But there may be yet another contributing factor: The gain pattern is likely not symmetrical – signals (and QRN) coming from the land side will likely not benefit the same way from the enhancement, which tapers off quickly (10 wavelengths) on the land side of the dike and regular “cross-country” conditions take place in that direction, while salt water stretching far beyond the horizon is enhancing reception to the other side.

So my preliminary answer to that question would be: “Yes, under circumstances the shoreline signal increase and ground properties can improve SNR further, that improvement can be harvested easily with vertically polarized antennas”.

Would it be worthwhile driving 1000 miles to the next ocean beach… for SWLing?

Maybe not every week–? Seriously, it depends.

Sure, an ocean shoreline will generally help turning up the very best your radios and antennas can deliver, I think the only way to top this would be adding a sensible amount of elevation, a.k.a. cliff coasts.

If you’re interested in extreme DX or just in the technical performance aspect, if you want to experience what your stuff is capable of or if you don’t want to put a lot of effort into setting up antennas, you should definitely find a quiet place at the ocean, particularly if your options to get maximum performance are rather limited (space constraints, QRM, HOA restrictions, you name it) at home.

If you’re a BCL/program listener and more interested in the “content” than the way it came to you, if you’re generally happy with reception of your favorite programs or if you simply have some very well working setup at home, there’s likely not much the beach could offer you in terms of radio. But the seaside has much more to offer than fatter shortwaves of course.

From left to right: Starry sky capture with cellphone cam, nocticlucent clouds behind the dike, car with hot coffee inside and a shortwave portable suction-cupped to the side window – nights at the dike are usually cold but sometimes just beautiful. (Click to enlarge.)

However, getting away from the QRM means everything for a better SNR and best reception. In other words, if the next ocean is really a hassle to reach, it may be a better idea to just find a very quiet place nearby and maybe putting up some more substantial antenna than driving 1000 miles. But if you happen to plan on some seaside vacation, make absolutely sure you bring two radios (because it may break your heart if your only radio fails)!

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State-Of-The-Art Spy Radio: A comprehensive review of the Belka DSP portable shortwave receiver

Many thanks to SWLing Post contributor, 13DKA, who shares the following guest post:


From Belarus with love: The Belka DSP

by 13DKA (international man of mystery)

I do have a thing with tiny radios. However, the Belka DSP is so very, very tiny and disguised in understatement that it squirreled itself out of my sight for a while. There wasn’t a lot of information when I took notice of its existence last year, having to order it from a Cyrillic script website prevented an impulse purchase and to be honest, I didn’t think that a shortwave receiver so small could do anything as good or even better than the radios I already own. Then, when this fine blog spread the news about the Mobimax.bg shop in Bulgaria offering this radio, I started another research and I learned that I’m not the only one who had some serious misconceptions about the little squirrel. (“Belka” = “squirrel” in Russian).

The outside: Spy radio reloaded

Admittedly, the tiny metal box with 4 buttons and a (metal) knob, antenna, headphone and a micro USB jack on the side, bringing less than 100 grams onto the scale, in a size that could make this radio as hard to find as your car keys may look like something that must have traded functionality for size. This is no doubt a solid little piece of gear though, one that doesn’t try to be anything but functional.

The form factor could be described as “bigger than a box of matches but smaller than a pack of cigarettes” to the ex- and still-smokers, and the elderly people among us who watched all the classic spy flicks out there may inevitably associate it with “spy radio”. It’s not quite 007’s clothes brush communicator or the U.N.C.L.E. pen radio but it would sure beat classic spy radio equipment which could be anything from a suitcase full of electronics to small boxes with comparatively few transistors in it, and they all wouldn’t have lasted much longer than it takes to be killed by 007 before the batteries would run out of juice.

The Belka DSP is very different from those, while it could possibly be smuggled into the country in a shoe heel, it boasts an endurance of 18h and it consists of 100,000s of transistors due to its highly integrated and low-power consuming electronics. These innards deserve some examination, because there seems to be some confusion about the nature of this radio out there on the interwebz:

Much bigger inside – technicalities:

It seems that some people read “DSP”, see the price and automatically dismiss it as yet another SiLabs 473x radio like many of the bargain Chinese shortwave portables, and the Belka’s miniscule size may suggest that it might not be the best of them either. Some presumed it’s based on an RTL chip… but that’s all as far from the truth as it gets. For starters, said Chinese radios, albeit digitally controlled, are actually still “conventional” analog radios which employ digital signal processing only at some varying later stage in the circuit and use only parts of the many features provided by the SiLabs chip (of which DSP is only a part), some even still rely on analog ceramic IF filters and use the chip only to provide AM/FM (e.g. PL-6xx). If they do use the DSP features, that’s how some end up as “triple conversion” receivers – 2 conventional IF stages with a 3rd, DSP IF stage – and some common quirks.

The Belka DSP, on the other, hand is not exactly a conventional radio to begin with but a basic (“direct conversion”) SDR. If I interpret the information on this site correctly, the only Silicon Labs chip used is a Si5351A multi-clock generator to provide high-precision oscillators to be fed into some TI chips serving as the quadrature detector/mixer, their output is then processed in a pretty decent ADAU1761 audio DSP (24-bit AD/DA), a PIC is controlling all that, and a 1W audio amplifier IC (TS4890) is providing the needed power to drive headphones or a passive external speaker directly. One comment somewhere was putting it in the same category as the Commradio CR-1 and while there’s some truth to it in some way, that’s not quite right either because the Belka DSP doesn’t use some pre-fabricated and re-dedicated TV tuner chip. While the functional principle may be similar, the Belka is made out of “discrete” components.

The different architecture also explains why it has so little in common with the Chinese DSP radios, there’s no muting, chuffing or hissing, no “softmute” or similar slightly malfunctioning attempts at making the radio appear quieter than it actually is, no distortion due to a seemingly uncurable lazy AGC… Instead, everything is predictable, precise (frequency!) and quiet and it behaves and sounds like a classic communications receiver or any reasonable piece of modern ham radio gear.

The Belka DSP ships with a detachable (BNC) 74cm/29″ short telescopic whip, and the receiver is said to be designed to develop full sensitivity with that whip. This may be raising some apprehension about how it would perform on full-sized antennas, but most of the YouTube videos about this radio demonstrate it with all kinds of passive and active antennas and (almost) surprisingly the Belka DSP appears to cope just fine with them, which in turn made me concerned about how good it could be on its whip – I mean it can’t be super-sensitive on a whip and have a decent dynamic range and be cheap all at the same time, right? How does it compare to the typical Chinese portables it’s being confused with? Do I need this radio anyway?

Q would be jealous – performance

Meaningful technical data beyond what’s provided on the purchase pages is hard to find. For example, Fenu Radio has listed the MDS (= minimum detectable signal) threshold as “-135 dBm” (without stating a source), whereas MDS was possibly taken synonymous for noise floor. A Russian YouTube radio channel seems to have actually measured an excellent sensitivity of 0.16µV on 40m in SSB. These would be rather typical figures for such a design and that would make it a quiet and sensitive radio indeed.

My other portables, on the other hand, don’t come with any specs beyond frequency range and features and the proof is in the pudding anyway. Let’s go north by northwest (the correct compass point name would be “northwest by north” BTW) to the secret 13DKA proving ground at the dike to find out if it shows!

Practical results

Actually I took it to the dike on several days/evenings/nights during the past 4 weeks to test it under varying conditions, to compare it with different radios and to serve as a nutrition source for the local lady mosquitos. The first one I took to the dike was my XHDATA D-808, it seemed like a natural candidate to compare with the Belka because I would use both in the same role – as a very sensitive “wearable” shortwave receiver to carry around on walks. To summarize that quickly – while the D-808 is already a sensitive radio, the difference between the two is represented pretty well by this short audio clip I picked out of many – this is Radio New Zealand International on 13840 kHz, 2 hours before midnight local time (UTC +2):

[No time indications needed here. The portions with mostly noise: D-808, When you hear someone talking: Belka]

So the Belka won the competition for the intended purpose already and it wasn’t exactly a “photo finish” either…mission accomplished, case closed, end of the review, thank you for reading. But… how would it compare to the S-8800, the most sensitive and quiet of my Chinese DSP radios? I felt like this would be an unfair comparison, I mean c’mon, the Tecsun’s whip is almost twice as long as the Belka’s…

So to level the field, I compared them with my favorite lazy makeshift antenna: A few meters of litz wire coupled (inductively) to an old 24ft steel flagpole on my “proving ground”, connected to the radios with a short stretch of coax to shield the “hot” wire inside the car. Not exactly a proper antenna but it would do to compare the radios better and I used this contraption to boost signals (a lot!) in the past years with great success. Indeed, the radios performed very similar on this contraption in terms of sensitivity, so there was no clear winner in this regard. Then on a hot, sunny day I decided to spend the afternoon at the beach with the Belka and the other radios, this time letting the Belka and the S-8800 run against each other on their whips only. To my surprise, the beneficiary of the external antenna the other day was the Tecsun, not the Belka! But let’s break this up into the different modes:

SSB

On the Belka DSP, “15,000 kHz” means 15,000.000 kHz, not 15,000.030 or 14,999.790 or worse, no matter how you shake it or where you touch it, it’s dead-on on WWV or many well-maintained broadcast transmitters and calibration or regular retuning is not necessary. Of course it doesn’t have trouble suppressing the other sideband, LSB and USB sound and behave absolutely identical/symmetrical and demodulation, even of strong stations is free of artifacts. This is SSB (or ECSS) reception how it’s supposed to be.

Of all my Chinese portables, only the S-8800 could come close to that “analog” feeling when turning the VFO knob, or particularly its fine-tuning knob with 10-50Hz steps …if that fine-tuning knob wouldn’t cause a terrible frequency jitter while tuning and if the AGC wouldn’t cause clipping and if the BFO had even remotely the stability of the Belka. In the following audio clips you may notice that the Tecsun is slightly off frequency most of the time – after retuning the radio for the 10th time because the sun sets and the air temperature is dropping slowly, I usually stop caring about that.

These clips were all recorded with the S-8800 @2.3 kHz and the Belka @2.4kHz bandwidth. Please, if you really want to hear the differences do yourself a favor and use some headphones or external speakers with some decent bass response, otherwise the important bits may get lost (like on my laptop speakers):

– This is the Gander/NY VOLMET on 10051 kHz the night I used the external antenna:

[0:00: Tecsun, 0:15: Belka]

– Here’s Argentina (LU6FOV) in QSO with Scotland (GM1DSK) on 20m around midnight:

[0:00: Tecsun, 0:18: Belka]

– Same band, a ham in Louisiana later that night:

[0:00: Tecsun, 0:15: Belka]

– 75m after midnight, ragchewing guy from NC on 3927 kHz (alas a noisy band at this time of the year):

[0:00: Belka, 0:15: Tecsun, 0:30: Belka]

Here are a few clips with the radios only using the whip, both recorded on 20m around sunset, when the atmospheric noise was finally going down and the band was slowly closing, at least for north-south propagation paths. Like I mentioned above, the Tecsun with its long whip and great independency from a counterpoise etc., clearly won the comparison with my other portables a few years ago and I was really expecting it to beat the Belka.

– ZS1OPB near Cape Town, South Africa in QSO with an unknown OM, possibly in Scandinavia or Germany. The latter has a pretty borderline intelligible signal, and it shows when switching to the Tecsun:

[0:00: Belka, 0:13: Tecsun, 0:21: Belka, 0:33: Tecsun, 0:41: Belka, 0:48: Tecsun, 0:56: Belka, 1:15: Tecsun]

– Here’s KB3RHR calling CQ even later on 20m, which had just dropped into the quiet period between daytime and the South America route greyline enhancement:

[Again, no time indication needed!]

CW

CW is another mode where the Belka shows how it’s different in that it has a dedicated CW mode to begin with. Most of the portables based on a SiLabs 4735 come with typical CW filter bandwidths like 500Hz, but to receive CW you may have to switch to USB, then to the proper bandwidth first. The Belka DSP has a dedicated CW mode doing these settings for you and a way, way superior 300Hz filter. The passband of that filter can be shifted in 100 Hz-steps between 500 Hz and 1 kHz to match your favorite tone pitch. CW reception is like you’d expect it from a regular ham RX/TRX, proper AGC action, proper filter, no artifacts, clean tone. Tuning through the band with 10, 50 or 100 Hz steps is smooth, quick, easy and fun. While there are of course tiny QRP transceivers particularly for CW, I’m almost sure that this level of CW goodness in such a small general coverage all-mode receiver hasn’t been seen before.

Here’s all 3 radios in one go. I deliberately picked a frequency with someone producing terrible clicks to the left and another pretty loud station to the right:

[0:00: D-808, 0:08: Belka 0:16: D-808, 0:21: S-8800, 0:40: Belka]

I think it’s awesome that the multi-banders kind of cover CW now but as you can likely hear, CW is also where the inherent (chip-related) and newly acquired (wanderlusty BFO on the S-8800) shortcomings of the Chinese radios are most obvious. Both distort on the onset of AGC action of course and turn a pure-ish sine CW signal waveform into some more square-ish shape thereafter and their “500 Hz” filters are letting a lot of signals through from beyond the filter slopes, which makes me think that setting is maybe not really meant to be used for CW. In the Tecsun example at 0:21 I had to use the fine-tuning knob and you’ll also hear the S-8800’s strange quirk with trying to mute the audio, despite soft-/automute is being turned off in the “hidden” settings. The D-808 is less quirky and very stable but using the fine-tuning knob to scan the CW segments on the bands is rather tedious with it, because it doesn’t tune the radio continuously and just jumps back to -99 on the same frequency once you reached +99.

NFM

When I saw this on the specs list, I thought this must be some error. On second thought it was pretty obvious: A proper shortwave receiver designed by a ham (Alex, EU1ME) for hams (among others of course) must be capable of receiving the local 10m-band FM repeater and of course you could also enjoy European 40-channel CB radio with that. Many ambitious tabletop receivers of the past had that option too. While this is nice, a squelch is more or less mandatory for FM or the listening pleasure will have its limits, and the Belka DSP does not have one. Unfortunately the next FM repeater is too far away, so is the next proper 10m-band opening and to receive any CB (apart from freebanders worldwide around 27,555 kHz USB) in my neck of the woods I have to be very, very lucky and I never managed to hear anything local with any of the portables. By coincidence, on the 2nd test evening on the dike I did pick up some CB stations in FM with the Belka and it did a great job, given the faint (but domestic) signals I got out there. So, the FM function was unsurprisingly tested OK and much more surprisingly, the FM noise is rather untypically unobtrusive.

Noteworthy: NFM has the same filter options as the other modes, so unlike aforementioned receivers with FM option or a dedicated CB radio, you can try a narrower filter setting which can improve SNR on FM (at the cost of some more distortion) in order to dig a weak station a bit more out of the mud.

AM reception

Receiving international SW broadcasters is what almost all, even some particularly cheap SW portables do quite well. Of course, like any decent receiver aiming for demanding hobbyists, spies and other commercial users alike, the little squirrel is even apt for more elusive DX, due to its versatile filters, stability and sensitivity. On top of that it sports what the manual calls “pseudo-synchronous detection”. I can foresee people misunderstanding this, so I think this could use a bit of an explanation:

“Pseudo”-Sync

Alex likely didn’t use this somewhat unwieldy term for no reason, instead of just putting a slightly misleading “sync detection” on the feature list: To put my limited understanding in simple words, regular sync detection is extracting the modulation content from the carrier, then replacing the original carrier that was battered by the ionosphere with a phase-locked, fresh and stable one from an oscillator, and finally bringing that back together with the modulation content.

“Pseudo sync” does the same except it doesn’t use an oscillator and a phase-lock-loop to recreate the carrier, instead it regenerates the original carrier by squashing it in some limiting amplifier to stabilize it and remove the modulation content. This is a quite smart and parts-saving arrangement and it’s inherently in phase with the signal. But that also means the original carrier must be somewhat intact, the less damage it has taken the better, while the “true” sync detector doesn’t rely on the original carrier and the signal can be reconstructed as long as modulation could be extracted.

That explains why recovering ultra-weak and downright broken signals from clandestine stations at the other end of the globe may not be the strength of a “pseudo-sync” detector, on the Belka it may even desensitize the radio and you will hear less than without…unless the opposite happens. Like with any sync detector I’ve tried so far, sometimes it works, sometimes it won’t. What always works is improving reception of stations that still have some headroom, mitigating phasing effects and making it generally a little more comfy to listen to and I think the Belka’s sync detector does that very well but unobtrusively. It’s usually hard to asses whether or not a sync detector helped with a particular dip in the signal or not, unless you have 2 specimen of the same radio to record their output simultaneously and compare.

ECSS (Exalted Carrier Single Sideband)

Besides the “pseudo-sync” detector, the Belka’s excellent frequency precision and stability also makes the technically similar sideband-reception of AM broadcasts a no-brainer: Just switch to USB or LSB and if the transmitter itself isn’t badly off frequency, that’s all you need to do because the radio is dead-on on the frequency, LSB or USB.* Since the available filter settings are the same for all modes (other than CW), you can also use the widest filter setting for maximum fidelity in ECSS. In comparison, all of the Chinese portables I have (and most if not all of the Chinese, Korean or Japanese portables I owned in the past) need some fine tuning to zero in on the station, each meter-band and each sideband their own setting and some just lacked the stability to stay zeroed in.

*With a tuning resolution of 10Hz, it’s technically impossible to entirely “zero-beat” a station with an offset other than exactly 10 Hz or multiples thereof. However, a small residue beat of a few Hz isn’t that bad and the ability to select the sideband suffering the least interference, the recovered modulation content and the decreased noise through narrower bandwidth still make ECSS a great way to improve reception.

AM reception examples

…beginning with some clips captured using the external antenna:

– This is RHC 5040 kHz, shortly after fading in after midnight local time, followed by some music from Radio Rebelde on 5025 kHz. The Belka’s 2.4 kHz filter setting has not only 100 Hz more bandwidth but also a much more presence-friendly shape than the Tecsun’s rather muffled sounding 2.3 kHz filter. The other notable difference is some high frequency hiss the Tecsun likes to emit, it becomes more evident when the channel noise doesn’t play such a significant role anymore, like on AM:

[0:00: Belka (RHC), 0:15: Tecsun (RHC), 0:29 Tecsun (R.Rebelde), 0:43: Belka (R.Rebelde)]

– Next is CHU 7850 kHz. While CHU is technically transmitting AM with one sideband suppressed (H3E) I threw those in this category, even though at the end I switched the radios to USB to demonstrate the SNR gain this means for both radios:

[0:00: Tecsun (AM), 0:17: Belka (AM), 0:34 Tecsun (AM), 0:51: Belka (AM), 1:06: Tecsun (USB), 1:21: Belka (USB)]

– CHU again, but now on a late afternoon on 14 MHz with really bad condx and with the radios [b]using their whips[/b]. Unfortunately I lost the clip with the Tecsun in USB but if you consider how little CHU you hear from it in AM, you can probably imagine that it wasn’t that much better in USB:

[0:00: Belka (AM), 0:12: Tecsun (AM), 0:21 Belka (AM), 0:34: Tecsun (AM), 0:48: Belka (USB)]

– Finally 2 clips (again using the whips only) taken from a German station with the imaginative moniker “Shortwave Radio” (www.shortwaveradio.de) transmitting from a site little more than 100 miles from here on 3975 kHz, in the afternoon. Despite the station being so close to my QTH, there’s some pronounced fading on it that makes the Tecsun suffer a bit more than the Belka:

[Left channel: Belka, right channel: Tecsun]

– Same station, but now with both radios switched to wide filters (4.7 on the Belka and 4.0 on the Tecsun):

[Left channel: Belka, right channel: Tecsun]

It’s very subtle but I find the Belka presents AM signals with less harshness and distortion and a more “solid” feel to it. Please note that these clips were recorded with a cellphone (with some decent built-in stereo mic though) and I used my CC Radio 2E as a powered speaker for the speakerless Belka, which is admittedly a great combination.

Selectivity

The Belka has one variable IF filter, whereas both low and high cutoff frequencies can be adjusted for each mode individually and will be memorized for SSB, CW, AM and NFM individually. If you ever played with a more recent SDR, you’ll know what to expect from the filter.

While this perceived superiority over conventional filters may be subject to heated discussions among radio connoisseurs, it will beat whatever cheap ceramic filters usually ended up in consumer-level portables and low-end to mid-range tabletop shortwave receivers and it also beats what the aforementioned Chinese DSP radios have to offer in filter quality and flexibility. For example, those come with pre-defined settings, with arbitrary, varying and not always great sounding filter shapes and lower filter skirts tending to roll off the signal a bit too high for my taste, which can be both an advantage and a disadvantage depending on the signal: Some ham operators put considerable amounts of energy into a fat sounding bass. With a filter roll-off around 200 Hz and a weak signal, only a small remainder of modulation will make it to the speaker and you may not even notice that there’s a station while you tune the band*. With the filter reaching down to 100 Hz or even lower, that station’s existence will be immediately obvious and the now more complete modulation content could even be somewhat more intelligible. On the other hand, when splatter from a neighbor channel is creating a lot of rumble you’re happy if the lower edge of the passband can be shifted upwards.

What the Belka’s filter doesn’t quite match is the variety – some the latest China-portables have many presets including 1.7, 1.2 and 1 kHz while the lowest upper filter frequency you can get on the Belka DSP is 2.4 kHz. While this is consistent with common ham radio rigs, I find a filter <2 kHz quite useful on crowded SSB bands. Given the great presence and intelligibility the 2.4 kHz setting provides and the filter not entirely (95%) passing my “4XZ” test, where the filter has to suppress 4XZ’s CW signal on 6407 kHz while the radio is tuned to 6604 USB (Gander/NY VOLMET), maybe 2.3 kHz would have been better for optimum (but in the ham bands very theoretical) channel separation. This is some high level nitpicking for a radio that costs less than one plug-in filter for a Japanese transceiver though.

In AM, the shown filter bandwidths are per-sideband like on some other DSP radios, which equals “audio bandwidth”. That means you have to multiply the number by 2 to get an AM IF filter bandwidth figure comparable to conventional radios with “tangible” filters, the 2.4 kHz setting would be a 4.8 kHz filter and 4.7 means 9.4 kHz.

AGC

The Belka has a properly working AGC, but it seems to reflect the radio’s emphasis on SSB: It has a fixed, slow release constant for SSB reception and that appears to be in effect also on AM. Actually, the AGC release time is quite slow (2+ seconds?), just as slow as I would have preferred it if I’ve had a choice, however, this can turn out less than optimal in rare cases of fast fading intervals on an AM station. But that’s still way better than having to live with a fast AM AGC setting on SSB, and it doesn’t really diminish the general AM listening experience with the Belka for me, which I find quite a joy. Being able to listen to SSB stations without compromises for a change and not having to cut the radios some extra slack when they do not quite behave like normal radios is actually a relief.

This may reach into the “signal handling” category, but the Belka does also not exhibit any AGC pumping effects when a loud station is on a neighbor channel. For comparison, this is one of the issues that make the D-808 a little more uncomfortable, particularly on SSB – the constant change and modulation of noise and signals, often triggered by strong signals quite far away at the other end of a band or even worse in another band not exactly nice. Even the S-8800 tends to emit soft modulations or sudden faint hisses in response to stations booming in outside of the IF passband. It’s the sum of all those little behavioral bits that make the Belka play in a different league.

Signal handling capabilities:

Despite being so small, the Belka appears to have 3 bandpass filters for preselection of its coverage range, which is one more than for example the SDRPlay RSP SDRs have in the shortwave part of their coverage. However, all you need is 2 hefty signals within a frontend passband to put a radio’s dynamic range to a practical test. I don’t have any test equipment to quantify this robustness precisely, but I happen to have some big guns transmitting (often simultaneously) on several frequencies in the 41 and 31m bands at night over here, producing signals that none of my portables can swallow without hopelessly overloading when those signals (from sizeable dipoles/loops etc.) peak. In most nights at least one of these stations makes the virtual meter needle hit the stop pin (see screenshot above) and then my RSP SDRs start acting up as well.

Being too lazy Lacking the time to put up a proper “big” antenna at the dike, I simply tried a loop-on-ground with pretty substantial 60ft/20m circumference and a MegaLoop preamp deliberately left at its high gain setting, which was coincidentally just the right amount of trouble for the Belka. Here’s a video showing what was piling up on 41 and 31m in the hours before midnight local time (UTC+2) during the test:

I could’ve missed that if I hadn’t explicitly checked the broadcast bands neighborhood for it, but the Belka did show some mild signs of overloading: there were faint intermodulation products on some out-of-band frequencies and there was some very subtle onset of cross-modulation on e.g. Gander Radio 10,051 kHz, manifesting itself in some “rough” modulation:

[0:00: Tecsun cross-modulation, 0:22: Belka (slightly roughened up modulation)]

In the video, you can see that it was worse in the broadcast bands containing the offending signals (9635 kHz is an example and alas I didn’t check if the OTH radar signal on interfering on 9700 kHz was really there or not). This was however nothing compared to the S-8800, which really started acting up despite its improved frontend. This could be mitigated by using the “Local” switch (which I presume only turns off the input RF amp) on the Tecsun and given that the Belka doesn’t have any means of keeping overloads in check it’s a particularly good thing that it wasn’t anywhere near this level of misbehavior. I should also mention that I was scanning particularly the 40 and 20m ham bands the entire evening, and I didn’t notice any signs of overloading there while RRI, CRI, Vo Turkey and company were blasting the broadcast bands at the same time.

While the Belka doesn’t have a switchable preamp or even an attenuator like some multi-banders, it has a fully adjustable “sensitivity” control, a.k.a. “RF gain”. It’s useful even when using the whip only, because turning it down is effectively putting the radio in “manual” gain control mode and listening to a couple of strong stations with the noise turned way down and without the AGC pulling the schmutz back up is so much more relaxing. Unfortunately, RF gain controls never really help with an overloading frontend.

However, the Belka apparently takes a lot of a beating for a portable but maybe it should be duly noted that none of these radios are really meant to (fully) replace tabletop radios and that the little Belka is so good that it can be used in that role shouldn’t be leading to unrealistic expectations. If need be, there are affordable (<$20) attenuators built into male-female BNC adapters available and I think a -10dB type should suffice in most cases, -20dB if you can’t resist alligator-clipping the Eiffel tower to the Belka.

For your eyes only: Signal indicator and a display that speaks to me

The display is very readable from most angles and the bright backlight can be switched permanently on, off or to the usual automatic mode. The signal meter deserves some extra praise:

Similar to the numerical displays on the PL-880/990 or my D-808, it comes with a signal indicator in the unit of “dBµv/EMF”, indicating 0-90 (or 100? 95?) dBµv/EMF with marks every 10 units from 10 to 90. But this is a bar stretching over the entire width of the display and it has a really fine resolution (13 pixels per division, together at least 120 positions!) and that makes it not only quite a joy to watch but also quite useful for a change!

I find it refreshing to see some “analog-ish” meter on a small portable radio, giving me a very fine and immediate indication of the signal and – particularly valuable for me – the noise floor in a satisfyingly high resolution, albeit with the limitation of not showing anything below 0 dBµv/EMF, which is -113dBm or roughly S2. However, also owed to the radio’s high sensitivity with just the whip, I can not only see the atmospheric noise on 20m during daytime on the beach, I can also tell intuitively if it’s bad or not so bad and notice the drop when the band is about to close, because I have already 13 different positions between “no indication” and “10” where other portables have 5 positions for the entire level range or aforementioned numerical displays, which are abstract and slow due to the needed long averaging/integration time to provide readable numbers.

Converting dBµv/EMF into more customary units is way beyond my math skills but thanks to multiple converter pages I can hopefully help:

The thin line above the meter indicates the “sensitivity” (RF gain) setting and it works in reverse from right to left. This looks like a meaningful arrangement in that the signal meter indication doesn’t change with the gain setting (it still indicates the input signal even when sensitivity is turned all the way down!), so the meter may roughly indicate the ballpark for a sensitivity setting that keeps the AGC from riding the signal for most quiet and pleasant listening to some strong stations in SSB.

Operation, ergonomics

Despite only having 6 controls and several sub-menus for settings, I think even for less experienced users the operational concept should sink in pretty quickly because it’s quite intuitive or at least not hard to figure out even without the manual. The English manual is short but well-written and a separate download, the radio comes only with a small slip explaining the different power-on modes because it is set to “safe mode” for shipping and doesn’t initially turn on by just hitting the PWR-button.

Basically, the push function of the rotary knob confirms a selection you made with it in one of the menus and gets you back to the frequency display, each of the 4 buttons can be pressed once to reach the first menu level, twice or more to get to the next levels etc. and a new setting becomes effective when you reach the end of the menu chain, if you don’t just push the big knob.

That being said, while the radio is pretty simple to use, having the only rotary knob controlling any variable parameter on the radio comes with a few ergonomical drawbacks and since that knob also dubs as pushbutton, there’s some opportunity to end up on a slightly different frequency than before after adjustments in the menus – the encoder is quite sensitive with many (100?) pulses per revolution and no indents.

There are 32 memories that store frequency, mode and sensitivity (!), but not bandwidth (which is saved per mode) or step width (which is memorized globally for all modes). Selecting, saving and loading memories is as straightforward as it gets but I quite often save a memory by accident instead of loading it, because the “Mem” button that calls up the memory page is also the “Save” button, while the “Vol” button recalls a memory, which is consistent with the operational concept of the radio’s menus but for some reason my internal logic for the memories is wired the other way around. If you pressed the ‘Mem’-button by accident, hitting the ‘Mod’-button gets you out of that menu to return to your currently set frequency.

BTW, the “spy radio” theme of this review wasn’t only inspired by the size and origin of this radio but also the memory slots, which came pre-loaded with band centers etc, and a few pretty odd frequencies (USB), of which some were showing up in logs of number station monitoring sites only. Using memory slots to jump to bands is not the only way to quickly reach another band though: keeping the knob pushed while turning is putting this into a “fast” mode. If you have selected a step width of 1 kHz or more it’s quite easy to jump to a band several MHz away with very few turns of the knob. With 100Hz step width, each encoder pulse is 10 kHz and it’s often only one quick push-and-twist to go from one segment of a band to another.

Doing the first evening walk with it, I immediately appreciated its particular aptitude for that job: It’s not only more sensitive and has better audio (which belongs into the “ergonomics” category because it’s less dreadful to listen to), it also fits in way more pockets than the D-808. Just hold the ‘Vol’-knob for 2 seconds to lock the frequency, then put it knob ahead e.g. into your breast pocket and there may still be room for some other items in it. The radio is so quiet and sensitive that you can even leave the whip partially or even fully collapsed when you’re just listening to strong stations.

Codename Tinnitus: Downsides and quirks

As per usual, this is the place for the reminder that the perfect radio does not exist, no matter how much money you are willing to throw at it, and the cute little squirrel is no exception.

– The radio is showing a considerable number of birdies across the entire coverage range, something between 1 and 4 noticeable ones per MHz, sometimes very faint ones in between. This is usually a huge showstopper for some people, including me. But then again, birdies are a fairly common thing among all the hyper-sensitive portables and entry-level SDRs and of course they are only an issue if they happen to be on a frequency you want to listen to, in a mode that makes the birdie obvious and it all depends on how likely that is in your personal usage pattern. Even more, some disappear if I connect an external antenna, some only exist if I disconnect any antenna (so that turned out to be a wrong way of assessing how many birdies it really has) and only few of the birdies are having a considerable signal, most of them can only be heard quite faintly in SSB and some are spurs apparently coming out of the mixer so their “relative bandwidth” is only a few Hz, they wander off when you tune the radio a few Hz up or down. Being more of a ham band than a broadcast program SWL, the only (for me) really disrupting birdie I found so far is on 14,175 kHz. Weighing in the considerable strengths and qualities of this radio I concluded that I’m willing to live with that where I have to. Believe me, nobody is more surprised about that last sentence than me!

– In a somewhat related matter, the manual states that the display can cause some noise (unfortunately none of the birdies are created by the display), so the display can be turned off by holding the ‘Mod’-key for a while. However I never noticed any noise that would disappear by turning off the display (and I did that a lot) until I tried to operate the radio in the car with the doors closed and the whip not stuck out of the window. Apparently, within that closed Faraday cage the display noise was reflected back onto the antenna and some hash was audible until the display was turned off. Then on my first walk with the Belka I heard it again – it turned out that putting the radio in one of my jacket’s breast pockets with the display pointing towards my body caused that reflection again – I just turned the radio by 180° so the display faced away from me and that solved the problem. Not really an issue, but something to keep in mind.

– Another observation is some slight loss of sensitivity on 17m. I’m not entirely sure that this is common to all Belka DSP but a Russian Youtube video comparing it with an FT-817 (on some wire antenna in the woods) seems to indicate the same – 18 MHz was the only band where the Belka couldn’t fully keep up with the 817 in that video, and in my tests the 17m ham and 16m broadcast bands were the ranges where it was only as sensitive as the other radios, which admittedly is a pretty subtle difference.

– I know that the soldered-in battery will likely be perceived as a downside by anyone who’s not fond of opening the radio and soldering in a replacement in an unknown and very variable number of years. But such a small radio with that kind of battery capacity just wouldn’t be possible with AA or AAA batteries. If you want to maximize the (easily obtainable cellphone type) LiPo battery lifetime, try to avoid charging it to more than 80%, particularly if you want to stow it away. Only charge it fully when you really need the full capacity and also avoid discharging it below 20% without need. The remaining 60% capacity should amount to ~10-14 hours endurance, which is still a lot of SWLing. The Belka can be recharged on any USB port and even the cheapest powerbank from the $1-store will recharge it at least once.

– Another thing I don’t mind personally but that has triggered criticism about other radios was their bright display backlight and the Belka is such a little reading lamp too, which also serves me well as a safety light when I do my walks in the dark so I won’t be run over by a cyclist.

– The volume control doesn’t turn the audio down to zero, only the sensitivity control can reduce the volume further but that’s just an observation, you don’t turn this radio on to hear nothing. 🙂 There is also a little hiss on the output (not half as bad as on the D-808 though) but that can be easily mitigated by simply using some phones with at least 32 ohms upwards. Most cheap earphones fit that bill, but my old-as-dirt Sony earphones have only 16 ohms and made that hiss obvious enough for me to notice. Without FM band on this radio, you’ll not be running into a listening scenario (classical music, jazz ballads or drama on a really strong FM station) where low impedance headphones or hiss could become a problem though.

– Lastly neither a quirk nor a complaint, but a reminder that this radio is specified to work from 3.5 through 30 MHz: Even with the short whip, most things you will receive below 3 MHz are images of stations above 3 MHz. Of course receiving Shannon VOLMET on 3413 kHz USB is not a problem yet but the lower you go, the more odd things start to show up, for example the Shannon and RAF VOLMETs around ~1.8 MHz in LSB (images from 5.5 MHz). Maybe with sufficient external preselection it will “have” 160m but otherwise take it as if it just doesn’t and it was never advertised as such. I did manage to hear my favorite funny British oldtimer ragchewing net on 1933 kHz though.

Now after all the boring stuff, here’s the radio in action – a compilation of some highlights received the evening I tried the Belka with the pre-amplified 60ft loop-on-ground. I could log some pretty interesting (particularly from a European perspective) stations again, despite the poor condx (SFI=69-70, A+Kpi=normal) we had on all the days/nights during the test, even though the ionosphere was slightly more excited that night, just like me when I picked up some rather unexpected callsigns:

BTW, a LOG is a great outdoor DX companion for the Belka: The antenna can be packed small and put down quickly with the least imaginable amount of hassle (dropping stuff on the ground in an educated way), the receiver is just another tiny box and all can still be brought to a place in your coat pockets. Due to its bidirectional pattern and reduced susceptibility to QRN it likely beats any wire you’d have to hurl up a tree, particularly when there’s no tree around.

The spy who…uh…spy radio I love…umm… summary and verdict:

I’m aware that this review may make the radios I compared the Belka with look bad, which they aren’t. So please don’t get that all wrong, I love my Chinese DSP portables, they’re doing a great job, some of them are very versatile and beat the Belka hands down on any other band than shortwave. But they also come with some common quirks and idiosyncrasies particularly on SSB, sometimes showing their low price…or a conflict with their not so low price here and there.

The Belka DSP on the other hand is a completely different animal (in this case, a squirrel) in terms of ingenuity, architecture, dimensions and likely also target audience – yes, it’s a portable and it’s not perfect either but that’s already the end of the similarities: It’s not a multi-band radio, it won’t wake you up in the morning so it’s not a travel radio by common (OK, by Thomas’ definition), it doesn’t even have a speaker and all it does is shortwave… but that’s what it’s really doing like a big one! It behaves and sounds refined like a regular modern ham radio receiver and generally matches that kind of performance. Its big strength is SSB and CW, but the great stability and precision making these modes so good is beneficial for broadcast listeners as well.

It had no trouble to best my D-808 in the “SWL walkman” role by several orders of magnitude in terms of both size and sensitivity and to my surprise it had no trouble beating my S-8800’s great sensitivity on the whip either, while not showing any of the weaknesses of said radios, except for the birdies. Also, its frontend can take bigger antennas. Underestimating what such a little radio could do, the Belka DSP exceeded my expectations in all aspects by far.

That’s why I never cared less about the quirks of a radio, including the birdies, which are the only really noteworthy issue to me. The overall sensation of a well-conceived radio with outstanding performance paired with irresistible cuteness is clearly dominating my feelings about this, and that it comes from what seems to be a little mom-and-pop business in Belarus at a very competitive price compared to the Chinese offers is explicitly not part of my technical assessment, but it sure is another plus for the Belka. It can be bought directly from Alex’ shop here for currently ~$120 plus shipping, I bought it for ~160€ including shipping via the Mobimax.bg shop in Bulgaria, which certainly included a markup for the middleman and the convenience of PayPal payment.

If you have a craving for communication receiver performance particularly on SSB/CW but lack the funds or just the space in your pockets for a communication receiver, if you want to have a stunning shortwave performer with you all the time even when your carrying capacity is limited to whatever kind of pants you’re wearing, if you’re doing mini-DXpeditions to escape the QRM and want to keep it light-weight but performant – this might be a radio you shouldn’t let pass. Its size-vs-performance ratio is mind-boggling and even though spy radios may be a bit out of fashion nowadays, it would still excel in covert radio operations, like when your XYL frowns at you packing more radios than pants for a vacation.

Please don’t forget to eat or burn this document after reading.

13DKA out.

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