Tag Archives: Field Radio

Loop-On-Ground Antenna Part 3: Tom’s low-noise, low-profile, portable antenna evolves

Loop on Ground Antenna Part 3

(using multiconductor wire)

by TomL

It dawned on me recently, perhaps due to sloppy thinking or unintended distractions, that I never wrote about my modified Loop on Ground (LoG) receive antenna that I use at parks and such.  For over a year now, I have been using 3-conductor rotor wire bought cheap at the local hardware store and have wired the conductors in series.  Grayhat (Andrew) was the inspiration when he decided to create a folded dipole along the side of his house.

The usual construction of a LoG antenna for shortwave is a single wire of about 60 feet in circumference in order to not go above one wavelength for 20 meter band usage.  If you recall, going above one wavelength will start creating weird lobes in the reception pattern.  See – Loop-On-Ground Antenna Part 2.

However, I did not like this 19 foot diameter wire on the ground in public parks just waiting to be tripped over.  Like, the time when a horse got loose from its owners and almost tripped over my 60 foot wire.  I don’t think I would have liked the resulting lawsuit!

So out of fearful necessity I took some leftover RCA 3-conductor rotor wire, about 29 feet of it, and wired a loop with the conductors in series.  This gives about 81 feet of total conductive length.  But since it is folded onto itself, there is an undetermined loss of resonant length.  Callum (M0MCX) of DXCommander fame has experimented and found folded dipoles need three times more length in the folded section to reach resonance, so my loop is probably around 69 feet (electrically).  See – Fold the end of a Dipole Back – What’s Happening?.

In the picture below, the black wire with Ring Terminal at the bottom goes all the way around to the other side, soldered to the green wire, which goes around and is soldered to the red wire, which goes around to the Ring Terminal at the top, plus tie-wraps to hold the wires together.

The next picture is how the Wellbrook Medium Aperture preamplifier is connected to the loop with BNC cable that goes to the 12V power injector.  I have had this Wellbrook unit for maybe 6+years with no signs of problems.  WARNING – do NOT use the Wellbrook preamplifier in the presence of high powered RF energy like your Amateur Radio antenna pumped with 1000 watts from a  linear amplifier; the Wellbrook premap might just overload and get damaged!  I did use this loop and preamplifier at last year’s 2022 ARRL Field Day and was able to get away with it because we were only using 100 watts per station.  Listening to the 9pm 3916-net trivia group was fun but I still needed to keep it away from the transmitting antennas. Continue reading

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Treetop Antennas: Featured with my friend Wlodek (US7IGN) on BBC Radio 4 Short Cuts

I’m very honored to be featured with my good friend Wlodek (US7IGN) in a short radio documentary on BBC Radio 4 today.

Wlodek is long-time reader and subscriber here on the SWLing Post and QRPer.com. Wlodek lives in Kiev, Ukraine and we keep in touch these days over email. Like me, he is passionate about field radio work and before the Russian invasion, you’d often find him in nearby forests experimenting with some pretty impressive field antennas.

Sadly, when Russia invaded Ukraine earlier this year, it very quickly brought an end to all of that for Wlod. Not only were amateur radio operators not allowed to transmit under the state of emergency, but it’s no longer safe to venture into nearby forests.

Radio producer, Cicely Fell, learned about our love of all things field radio and put together an audio piece that airs today on BBC Radio 4:

BBC Radio 4 Short Cuts

From the forests of North Carolina, USA to the city of Kyiv, Ukraine – two ham radio enthusiasts seek each other out and a voice from the past prompts a dialogue on listening between a rabbi and a radio producer.

Click here to listen via the BBC Radio 4 website (note that the audio can be streamed shortly after the program airs today).

Many thanks to Cicely and her talented team at Falling Tree Productions for spending a little time with us in the forest and on the air! Truly an honor.

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A little off-line, off-grid camping

You might have noticed a lack of posts this weekend and that would be because I was completely off-grid and off-line, camping with two good friends in Pisgah National Forest.

It was brilliant, actually. I got to hang with friends I’ve known for over 30 years, test my new one person backpack tent (a.k.a. the “Bear Burrito”–the one on the right above), and of course I played a bit of radio.

Black bears are a fact of life here in the mountains of western North Carolina and we spotted three hanging out within 25 meters of our campsite.

By the way: the trick when camping with bears? Don’t put food in your tent, else that whole “bear burrito” thing becomes a reality.

I had a fabulous time putting my Elecraft KX1 “Ruby” on the air. I made perhaps 15 contacts in CW (Morse Code) with 3 watts of power.

One of the cool things about the KX1 is you can change the mode to SSB and actually tune through several shortwave broadcast bands (if you have the three or four band version of the KX1). Of course, I had to do a little SWLing.

As I mentioned in my previous post, I’m also a proper coffee snob and I firmly believe coffee tastes better when brewed outdoors. Yesterday morning, I brewed a pot of Rock Creek French Roast.

Off-grid, off-line camping recharges my internal batteries and it’s for this reason, I’ll be doing a lot more this year with my family.

It’s is also a brilliant way to experience an environment without any forms of radio interference (QRM or RFI). If you want to do some proper DXing, take your radio on some primitive camping experiences. It’ll remind you what life was like before switching power supplies ruled the world!

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“Anatomy of a Field Radio Kit” series on QRPer.com

If interested, I’ve now published both parts of my Anatomy of a Field Radio Kit series over on QRPer.com. This series was originally featured in the June and July 2021 issues of The Spectrum Monitor magazine. Here are links to both articles:

These articles primarily focuses on portable amateur radio field kits, but many of the concepts are ones I also use for my field portable receiving setups like this one.

I hope you enjoy!

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Giuseppe’s improved read-to-go case for the Tecsun S-8800

Many thanks to SWLing Post contributor, Giuseppe Morlè (IZ0GZW), who writes:

Dear Thomas,

I want to share my latest version of my case / antenna for Tecsun S-8800 to make it immediately operational: simply open and listen.

In addition to the loop inside the case with a 3-meter wire at one of the ends that join two telescoping style whips of one meter each short-circuited to take advantage of the entire length. At the other end of the loop, a cable that goes to the ground of the variable capacitor.

I can tune the whole range from 3 to 16 MHz with truly amazing results.

You can see the video from my Youtube channel at the link:

Thanks to you and all the friends of SWLing Post.
Regards.
73. Giuseppe Morlè iz0gzw.

This is incredibly clever, Giuseppe! AS I mentioned before, I love how self-contained this makes the entire listening station and I especially love the built-in antenna options! This is truly a shack-in-a-case!

Thank you for sharing this.

Click here to read Giuseppe’s other contributions here on the SWLing Post!

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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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