Many thanks to SWLing Post contributor, Don Moore–noted author, traveler, and DXer–for the following guest post:
A DXpedition to East Sandy
By Don Moore
When I was in college over forty years ago, seven of us had a small DX club in central Pennsylvania. A couple of times a year we would gather at the house of one of our parents for an all-night DX session. We shared tips and ideas, had fun, and always heard some new DX. Good DX can happen anywhere if conditions are right and most of mine over the past fifty years took place at wherever home happened to be at the time. But most of my best experiences and best memories of DXing were not made at home. They were made by getting together to DX with other hobbyists such as we did back in college.
Nowadays when I get together to DX with other hobbyists it’s to go on a DXpedition, which is nothing more than taking your receiver to a place where DXing will be better than at home because there’s less noise and you can erect better antennas. Simple DXpeditions can be done from cars. My old friend Dave Valko used to go on what he called micro-DXpeditions. He drove to a remote spot in the mountains not far from town, laid out a few hundred feet of wire, and then DXed from his car for a couple hours. He frequently did this around dawn and around sunset and got some great DX. I know several other DXers that do this today, either at countryside locations or in large parks.
I’ve done micro-DXpeditions a few times. It’s fun but it always lacks an important element: other DXers. For me, the best DXpeditions aren’t just about hearing interesting stuff (although that is very important). They are also about sharing the hobby with other interested friends. And the best way to do that is to go on a real DXpedition with them.
For three years in a row prior to the pandemic a group of eight of us had rented a lodge in rural central Ohio for an annual DXpedition. Covid shelved our plans for 2020 but by the summer of 2021 we were all looking forward to a fourth DXpedition in September. Then another wave of covid swept across the country and we canceled a few weeks before the event. Fortunately, the worst of those days are behind us and we finally had our fourth DXpedition the first week of October of this year. Unfortunately, only five of us could make it – Ralph Brandi, Mike Nikolich, Andy Robins, Mark Taylor and I.
For four nights our DXpedition home was the same place in western Pennsylvania that we had canceled at in 2021. The location was a rural house on the bluffs overlooking the Allegheny River near the old East Sandy railroad bridge (now a hiking trail). It’s always a gamble going to a new place chosen solely based on the AirBnB listing and other information found online. But this site had all the appearances of being a good place to DX from. The pictures and Google satellite view showed that there were trees around the house and large nearby open fields surrounded by woodland. The terrain was relatively flat when viewed on 3D satellite view. We would have plenty of space for a variety of antennas. Furthermore, it didn’t look to be a noisy location. The nearest neighbor was over a quarter mile to the south and because the house was the last one on the road that powerlines stopped at the driveway. I couldn’t have done much better if I had designed the location myself.
Good antennas are the most important part of any DXpedition and erecting them is usually the most time-consuming part of set-up. Still, you never really know what’s going to fit until you’re there. I arrived at 2 p.m. and Mark pulled in a few minutes later. We immediately walked the grounds and were pleased with what we saw. Ralph arrived while we were laying out the first antenna. Mike and Andy arrived later in the afternoon in time to help finish up.
Our DXpedition antenna farm consisted of two delta loops, a DKaz, and two BOGs. The delta loops used Wellbrook ALA-100LN units and are as I described a few years ago in my article on radio travel. These are easy to erect and are good all-around antennas for anything below 30 MegaHertz. The DKaz (instructions here) is a rather complex-to-build antenna designed for medium wave. Ralph uses one at home which he had taken down for the summer to make yard work easier. He brought the pieces and put it up by himself. The two BOGs (Beverage-on-the-ground) were a 300-meter wire to the northeast and a 220-meter wire to the north. Beverages are good for long wave, medium wave, and the lower shortwave frequencies. Continue reading →
In mid-October I received an invitation to attend the annual DXpedition in Cappahayden, Newfoundland with Jean Burnell, John Fisher, and Jim Renfrews. It didn’t take long for me to say yes. Newfoundland is one of the best places in the world to DX from and all kinds of amazing stuff has been heard there. I was excited at the prospect of great medium wave DX and being able to log low-powered European private and pirate shortwave broadcasters.
But something else was at the top of my try-for list. One of my many DX interests has always been logging coastal marine stations in the 1600 to 3000 kHz range. In preparation I started checking online sources to update my spreadsheet of schedules. In going through a recently added section on Marine Broadcasts in the DX Info Centre website I came across listings for twice-daily weather broadcasts from Hopen Island on 1750 kHz and Bjørnøya (Bear Island) on 1757 kHz.
I didn’t remember ever seeing anything about broadcasts from these remote islands in the Norwegian Arctic before. Were these stations actually on the air, I wondered. And if they were, could I hear them in Newfoundland? Continue reading →
Many thanks to SWLing Post Contributor, Christoph Ratzer, who recently shared the following video tour by Mika Mäkeläinen. Mika desxribes this video on YouTube:
Join me on a virtual tour of the Aihkiniemi DXing base in Lapland, in northern Finland. This is a nonscripted five-cent tour looking at what the Aihkiniemi cabin can offer for visiting AM DXers. The video was shot in November 2020 during DXpedition AIH124 – meaning that during the first decade of its existence, Aihkiniemi has already hosted 124 successful expeditions. The antennas (a total of 14 Beverage-type wire antennas) are permanent, but participants bring their own receivers and laptops. There’s one essential activity missing from this video though: checking the antennas, which is a major job. Every DXer is expected to check – and if necessary, clean and repair – all the antennas, which run in the forests around the cabin. So there might be a part 2 in the future.
Wow! This little DXing cabin is on my bucket list. I will, someday, make my way to north Finland and spend time DXing from this unique reception spot. The quality of the equipment and antennas is truly amazing.
Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:
Gone fishing…for DX: Reception enhancement at the seaside
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 coastline.
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? I mean, even if there is virtually no local QRM at my “happy place” – there is still natural noise (QRN) and 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 (but more inland) 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)!
A little update (2023):
Like I said, the +10dB signal boost works both ways and here’s a nice example that I thought should be here. This is W4SWV, literally standing with both feet in the Atlantic ocean at the South Carolina coastline, carrying a 25W backpack radio with a whip and talking to F6ARC in France on 17m – received at my side of the pond using my simple vertical 33’/10m monopole antenna at the dike:
This was recorded on July 4th, 2021 and does not provide a reference to demonstrate how good or bad this is of course, all you have is my word that getting such a solid and loud signal from a 25W station on the US East Coast was just outstanding (compared to a fair number of coastal QRP stations I copied at the dike over the years, or the average 100W inland stations).
Meanwhile I found out that I’m luckily not the only (or the first) person who tried to make some practical experiments to reassess the theories in recent times: Greg Lane (N4KGL) made measurements by transmitting a WSPR signal simultaneously off 2 locations, one near the shoreline and one more inland. Measuring the signals created in distant WSPR receivers, he got similar results. He made a presentation about it in 2020:
I have enjoyed three to four medium wave and shortwave DXpeditions per year since 1988, to sites on the Washington and Oregon coasts. I love the chance they give to experiment with antennas in a (hopefully!) noise-free location, and concentrate on catching stations that might not be heard from home.
All of my DX trips have been via car–until now! I’ve just returned from nine vacation days in Hawaii (Waikoloa Beach, on the Big Island), and I thought others might like to see the radio related items I chose to take along for air travel. I’m pleased to report that everything worked as planned, and I have five days of SDR IQ WAV files of the MW band for review, all recorded in the time frame surrounding local dawn.
My goal was not the smallest, most compact portable setup, but one with high performance and modest size. Fitting everything into a day pack was another requirement. A simple wire antenna and an even smaller Windows tablet or laptop than the one I’ve used (and a smaller SDR like the HF+ Discovery, for that matter) would make a much smaller package. However, the items I’ve assembled worked excellently for me during my enjoyable Hawaii vacation. The directional loop antenna provided nulls on medium wave of 30 dB during preliminary tests indoors, a less-than-ideal test situation.
Waikoloa Beach–just one of a zillion picturesque scenes in Hawaii.
Here is a list of what I’ve put together for my DXing “kit”:
Short USB cable for receiver<>PC connection, with two RFI chokes installed
Lenovo X1 tablet— a Windows 10 device with magnetically attached keyboard; this model is a competitor to Microsoft’s Surface Pro tablet
Wellbrook Communications’ ALA1530 head amp module, modified for female SO239 connectors enabling use of large diameter LMR-600 coaxial cable as a 2-turn loop element. My antenna setup is similar to Wellbrook’s commercial flexible loop
Wooden base for the antenna (ALA1530 is bolted to the base)
20 feet of lightweight RG-174 coax
Wellbrook DC interface module for the ALA1530
3.0 Ah LiFePO4 rechargeable battery for the Wellbrook antenna
15 foot long section of high grade “Times Mfg.” LMR-600 coax cable with PL259 connectors (bought from Ebay already assembled/soldered)
Fold-up beach mat
Small day pack to hold everything
All the contents of this DXing setup fit a standard size day pack.
You’ll note the absence of headphones in the list. This is because my intent from the start was to record all the DX (MW band) as SDR WAV files for DXing post-vacation. That said, I did have headphones in my travel luggage for later spot checks of a few frequencies. That’s how I found 576 kHz Yangon, Myanmar lurking at their 1700 sign-off with national anthem and English announcement. The remainder of the DX to be uncovered will have to wait until I’m back home near Seattle!
The LMR-600 is a very thick and stiff coax cable, whose diameter approaches that used in the standard aluminum tubing ALA1530 series from Wellbrook. It has the benefit of being self-supporting in a 2-turn configuration and will also coil up into an approx. 12-inch package for transport. It just barely fits within the day pack I’m using. As I understand it, magnetic loops with tubing or large coax as the active element, versus simple wire, are more efficient in operation. Whether or not this holds true in practice remains to be seen.
I fashioned a wooden disc 3/4″ thick to attach the ALA1530 head amplifier, as I didn’t want to bring along a tripod or other support stand. The Wellbrook antennas all work well near or at ground level, so I was able to get great reception with the antenna right on the beach. The diameter at two turns of the coax is only a few inches smaller diameter than Wellbrook’s aluminum tubing loops. Three strips of strategically placed Velcro straps help keep the turns together when deployed as well as during storage.
In theory a two-turn loop should give 5 dB less gain than a single turn version; however, my older ALA1530 module has 5 dB more gain than the newer “LN” type, according to Andrew Ikin of Wellbrook Communications. The net result is that my two-turn antenna should have equal gain to the larger one-turn variety. Future experimentation with this DIY coax loop antenna is in order!
The Wellbrook loop antenna, RSPdx receiver, and Windows 10 tablet on the beach in Waikoloa, Hawaii.
Another view of the DXing position. Being this close to the water with my radio gear was unnerving at first, but the wave action on a calm Hawaii beach is totally different from the Oregon/Washington beaches with waves that can move in and out by a hundred feet or more.
The Wellbrook “DIY FlexLoop” works fine at beach level, and is less conspicuous this way, too.
The ALA1530 module is bolted to the 11-inch wooden disc for support. I’ve modified the module’s sockets to securely hold SO239 female connectors.
The commercial Wellbrook FLX1530LN is a fine product, and worthy of your consideration as a compact and high performance travel antenna. Full details can be found at this link.
SDR WAV Files for Download
One of my goals from the start for my Hawaii trip was to bring back SDR “IQ” WAV files for sharing with others. These approx. 900 Mb files cover the entire medium wave band as heard from my beach location in Waikoloa.
The overall page is: https://archive.org/details/@4nradio Clicking on any of the entries will bring you to a details page. From there just right click on the “WAVE” link, and choose “Save as…” to download. For a few of the recordings I also posted the file that precedes the one that goes across the top-of-the-hour, because things seemed a bit more lively prior to 1700 (which was at local sunrise, give or take a couple of minutes).
The IQ WAV files are only playable with suitable SDR radio software: SDRuno is first choice (but you need a RSP receiver connected). The files are also is compatible with HDSDR and SDR-Console V3. It may also play on Studio 1 software.
I hope other DXers enjoy the chance to tune through the MW band, as heard from the Big Island of Hawaii.
Guy Atkins is a Sr. Graphic Designer for T-Mobile and lives near Seattle, Washington. He’s a regular contributor to the SWLing Post.
Many thanks to SWLing Post contributor, Joachim von Geisau (DH4JG), for the following guest post:
Signal distribution at SWL camps: The new JK-1000 HF distributor
by Joachim von Geisau (DH4JG)
The Friends of Radio NRW – an independent group of shortwave listeners and radio amateurs in Germany – have been organizing 2-3 SWL camps per year for a number of years, where they meet as far away as possible from electrical noise in order to listen to shortwave together.
To distribute antenna signals, we have previously used an RFT AVV01 antenna distributor.
At an SWL camp there are high demands on signal distribution. Both very weak and strong signals should be distributed well, un-distorted, without noise and other interference. The signal levels are approximately between 0.2 ?V (S1) to over 5 mV (S9 + 40 dB), with a frequency range of at least from 150 kHz to 30 MHz, thus broadcast bands from LW to SW are covered, also all amateur radio bands from 160 m to 10 m.
Popular among listeners are RFT AVV01 RF distributors from the former GDR, at least 30 years old. However, the use of an AVV01 has several disadvantages: high power consumption, difficulties in getting spare parts, high upkeep with corroded contacts and the like. In addition, the transmission of the LW/MW range drops, which is a disadvantage especially for MW listeners. The NV-14 system from Rohde & Schwarz from the late 1960s has the same weaknesses.
Two years ago, the desire arose to develop a concept for the replacement of the RFT system.
The following aspects were important:
Frequency range at least 100 kHz – 30 MHz, as linear as possible
frequencies below or above desirable
Running on 12 V DC or integrated noise-free power supply
Remote power supply for active antennas
Hobby friendly budget
The amateur radio market offers several products for RF signal distribution (e.g., ELAD, Bonito et al.), but no solution to distribute 6-8 antennas to 10-12 receivers. It was clear from the beginning that DIY development was inevitable.
The starting point of the considerations was to integrate remote power supply for active antennas, an amplifier stage and a distribution network.
Such a distributor is able to distribute an antenna signal to several receivers; several antennas require several such distributors, which led to the decision to implement the project in plug-in technology.
With OM Frank Wornast DD3ZE (www.dd3ze.de), known e.g. for his converters, filters and the like, a well-known RF developer could be won, who took over the implementation of the concept based on the detailed specifications. OM Wornast first produced a prototype without remote power supply, which already did an excellent job of RF signal distribution.
A “hardness test” at an SWL camp showed that this distribution module easily fulfilled our requirements: Frequency range 10 kHz – 50 MHz (also usable with a few dB loss above 50 MHz). Supplemented by a switchable remote power supply and a 90V gas discharger at the antenna socket, the final PCB layout was created, representing the core of the new HF distribution system of Radio Freunde NRW
The distribution block consists of the following components:
Input with 90V arrester & 100 kOhm MOX resistor to dissipate static interference
Remote power supply, switchable, 10-14 V, max. 350 mA
Amplifier stage with 14-14.5 dB
Resistor network for distribution
The device is characterized by a very smooth frequency response and has a very low inherent noise. It offers the possibility of using levels of -120dBm with very good SNR
to process up to strong levels of up to + 14dBm. In addition, the reception on VLF is now possible, which did not work with the previous system.
The PCB is designed in a very practical way: series resistors for LEDs are integrated as well as fixing points for coaxial cables. The remote power supply can be switched separately, but can also be used permanently by means of a jumper.
With this concept, the distribution block can be used universally: use on an active or passive antenna with distribution to several receivers, by means of a step switch in front of it also for several antennas; if you leave the remote feed path unconnected, the block can also be used as a simple distributor, so it is almost universal for hobby purposes.
For use on SWL camps, we decided to install them in 19 “rack-mount technology. A standard rack can thus accommodate 4 distributors and a power supply, allowing distribution of 4 antennas to 12 outputs each. An example of the installation is shown in the following picture: Parallel to the input is another BNC socket, which is connected via a C 100 nF where the input signal can be used DC-free for measurement purposes or the like. The distribution unit is installed in a transport case. The components themselves are mounted in slide-in housings which are provided with a corresponding front panel: Such front panels might be obtained from CNC manufacturers.
On the back + 12V DC must be supplied as operating voltage. For the power supply units, we opted for linear power supplies because we have made the best experience with these without interference. For a distribution unit with 4 slots, a power supply with 12V 1A is sufficient – each distribution block takes about 55 mA, an active antenna up to 150 mA, so even with “full load” a power supply with 1 A is sufficient. The distributor was tested with various well-known active and passive antennas, including a PA0RDT MiniWhip, active loops, long wires and T2FD.
Due to the wide input voltage range, the module can handle nearly any antenna. The cost for a distributor for 4 antennas amounts (depending on the version: housing, sockets, switches, power supply, etc.) to about 700-1000 €. That may seem a lot at first glance. However, taking into account that a simple 5-gang distributor from mass production costs already around 250 ¬, the cost of the distribution of 4 antennas to each up to 12 outputs are not that much. The Friends of Radio NRW use two of these distribution units for SWL camps.
If you are interested in building one, please contact the author ([email protected]) for further information. The development history of the distribution unit is also available at www.dx-unlimited.eu.
Wow! What a beautifully engineered antenna distribution solution, Joachim! I love how you worked together to sort out all of the requirements for your system then build it for ultimate performance and flexibility. No doubt, you and your colleagues at Radiofreunde NRW posses a lot of design and engineering skills! Simply amazing and thank you for sharing your design with the radio community!
Photo: Ivan Dias & Martin Butera, during the first Dx-Camp 15.61 Crew Radio Listeners’ Marajó Island – Amazon Rainforest, North of Brazil – November 2019
Many thanks to SWLing Post contributor Martin Butera, founding member of the 15.61 Crew, for the following guest post:
The 15.61 Crew Radio Listeners, Martin Butera and Ivan Dias, give us a small video preview made in the first Dx-Camp on Marajó Island in the Amazon Rainforest, North of Brazil on November 2019.
There are more than 11 hours of SDR recordings and videos of the Ultralight radios, which will take much additional time to process, of course.
Crew is working on the report with a complete story that includes videos and photos of everything experienced during the DX-Camp–this will be published in several languages and the first LOG, which we estimate will be the first months of the South American summer 2020.
Above, you’ll see a short stretch of the medium wave band with plenty of interesting content: 585 kHz, alternating between National Radio of Spain (Madrid), BSKSA (Saudi Arabia), 590 kHz, alternating with Poty Radio (Crateús / CE), Radio Diffuser (Boa Vista / RR) and Radio Continental (Buenos Aires), 594 kHz BSKSA (Saudi Arabia), 595.9 kHz SNRT (Morocco – operating off-frequency for years), 600 kHz Mirante Radio (São Luís / MA), Vale Radio (Barreiras) / BA) and Radio Gaucha (Porto Alegre / RS) and 603 kHz National Radio of Spain (Sevilla).
All of the following videos were captured during the November 2019 Dx-Camp:
Brazil is a country with vast continental distances. The following three videos showcase Brazilian radio from across the country.
Radio Diffuser Boa Vista (1408 km distance)
Radio Itatiaia 2191 (km distance)
Radio Band B (2747 km distance)
Photo: Ivan Dias & Martin Butera, during the first Dx-Camp 15.61 Crew Radio Listeners’ Marajó Island – Amazon Rainforest, North of Brazil – November 2019
More photos of the DX-Camp from the official site: