Category Archives: Field Radio

Introducing the amazing SULA: An affordable unidirectional DX-grade loop antenna that you can build!

Many thanks to SWLing Post contributor extraordinaire, 13dka, who brings us a three part series about the new SULA homebrew antenna project. This first article describes this affordable antenna and demonstrates its unique reception properties. The second article will focus on construction notes. The third and final article will essentially be a Q&A about the SULA antenna. All articles will eventually link to each other once published.

This wideband unidirectional antenna is an outstanding and innovative development for the portable DXer. I love the fact that it came to fruition via a collaboration between Grayhat and 13dka: two amazing gents and radio ambassadors on our SWLing.net discussion board and here on the SWLing Post. So many thanks to both of them!

Please enjoy and share SULA Part 1:


Introducing the Small Unidirectional Loop Antenna (SULA) 1-30MHz

A small and simple, unidirectional and DX-capable loop “beam” for SWLs!

by 13dka

In early June, Andrew (grayhat), SWLing Post‘s resident antenna wizard suggested a variation of the “cardioid loop” on the SWLing Post message board: The original “cardioid loop” is a small loop receiving antenna deriving its name from a cardioid shaped (unidirectional) radiation footprint. The design is strikingly simple but it has a few downsides: It relies on a custom preamp, it needs a ground rod to work and it is unidirectional only up to 8 MHz.

Andrew’s version had the components all shuffled around and it did not only lose the ground rod, it also promised a nice cardioid pattern over the entire shortwave, from a small, diamond shaped loop. Wait…what? It can be made using parts available on Amazon and your DIY store:

You need some 3m wire and PVC tubes to create a support structure to hold the wire, a 530 Ohm resistor and a 9:1 balun like the popular “NooElec One Nine”. Since it’s a “lossy” design, adding a generic LNA like the NooElec “LANA HF” would help getting most out of it. When you put that all together you have what sounds like an old shortwave listener’s dream: a small, portable, tangible, and completely practical allband shortwave reception beam antenna with some more convenient properties on top, for example, it is a bit afraid of heights.

That sounded both interesting and plain crazy, but the .nec files Andrew posted were clearly saying that this antenna is a thing now. Unfortunately Andrew suffered a little injury that kept him from making one of those right away, I on the other hand had almost all the needed parts in a drawer so I ended up making a prototype and putting it through some of its paces, with Andrew changing the design and me changing the actual antenna accordingly, then mounting it upside down. Let me show you around:

  •  Small, diamond shaped wire loop (with 76cm/29.92″ sides), needing as little space as most other small loops.
  • Unidirectional with a ~160° wide “beam” and one pronounced minimum with a front/back-ratio of typically 20dB over the entire reception range 1-30MHz.
  • Moderate height requirements: It works best up to 3m/10′ above ground, where it gives you…
  • …a main lobe with a convenient flat takeoff angle for DX
  • Antenna is comparatively insensitive to ground quality/conductivity.
  • Wideband design, works best on shortwave and is pretty good up to 70cm.

A functional small beam antenna for shortwave reception that’s just as small and possibly even more lightweight (prototype:~250g/9oz) than your regular SML, that can be easily made out of easy to obtain parts and easily carried around for mobile/portable DXing and due to its cardioid shaped directional pattern also for direction finding, a “tactical” antenna that’s also doing DX? Unlike conventional, Yagi-Uda or wire beams it can achieve a low takeoff angle at only 3m/10ft height or less, the front/back ratio is typically better than that of a 3-element Yagi, with a particularly useful horizontal pattern shape. That it’s rather indifferent to soil quality could mean that more people get to reproduce the good results and being a real wideband antenna is making the SULA an interesting companion for multiband radios and SDRs. Really? A miracle antenna? Is it that time of year again? If I had a dollar for every….

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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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How Giuseppe protects his Icom IC-705 during travels

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

Dear Thomas and Friends,

Giuseppe Morlè (IZ0GZW) here from Formia, central Italy.

This my latest video is about everything I have done to protect and transport my Icom IC-705.

I bought an aluminum case, light and very resistant with everything one needs inside to be able to use the IC-705.

    • 2 power banks, one of which is solar-charged to be able to recharge the battery while in operation
    • 2 wire antennas: a dipole type with BNC / banana socket with 10 meters of cable per arm and a 20 meter row, monopole, to be used in reception as you saw during the DXpedition to the Island of Ponza
    • I also bought the Mydel protective “cage” with antenna attachment on the front and PVC protection of the display

Given the high cost of this little jewel, it is advisable to take all precautions for its safety during transport and use.

Click here to view on YouTube.

I hope I made you happy …
Thank you all,
73. Giuseppe Morlè iz0gzw.

This is great, Giuseppe! Like you, I’ve taken extra measures to protect my Icom IC-705 as well. Your kit looks comprehensive–I love the fact that pretty much everything you need is inside. 

Thank you again. We always enjoy your posts from beautiful Italy. Ciao!

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Today (14 May 2022): Annual Armed Forces Day Crossband Test

Many thanks to SWLing Post contributor, Ulis (K3LU), who notes that today is the annual Armed Forces Day Crossband Test.

Click here to download a PDF document with all details including frequencies, schedule, and QSL info. Thanks for the tip, Ulis!

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Egil is pleased with his new Belka-DX and Tecsun ICR-100 cases

Many thanks to SWLing Post contributor, Egil (LA2PJ), who writes:

Hi Thomas,

In the middle of march, Steve Allen (KZ4TN) posted this article showing a case for the BELKA-DX.

I found his idea so good that I ordered two of the small boxes, using the Amazon link given in his article.

The boxes arrived here in Norway just twelve days after ordering, and was delivered to my door by a local transporter.

Never before have I experienced that kind of service on any purchase via Amazon!

 

Tecsun ICR-100

While packing the BELKA-DX in one of the boxes, I discovered that my Tecsun ICR-100 speaker/audio recorder fit snugly in the other box. The two boxes also contains a six meters long wire antenna, charging cables for both units, earphones, and even an USB charger, just in case I get the opportunity to recharge the batteries.

Belka-DX and accessories

The attached pictures show my new setup. Two items are not shown in that picture: a wire antenna plus a 20Ah powerbank from Anderson. We are going to an off grid cabin for the Easter holidays, and hope that when leaving home with everything fully charged, the powerbank will keep this setup plus my smartphone happy for a whole week.

73s Egil – LA2PJ

Thank you so much for sharing this, Egil!  It’s absolutely amazing that the shipping service to Norway was so efficient. 

I think you’ll have no problem at all enjoying hours upon hours of DXing with the Belka-DX in your off-grid cabin.  No doubt you’ll be escaping the RFI and enjoying much lower noise floors while on vacation–this will give you an opportunity to truly take advantage of the Belka-DX receiver. You’ll have to report back with your experience and photos (hint, hint!).

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Guest Post: Following the Ethiopian war over shortwave radio

Many thanks to SWLing Post contributor and political cartoonist, Carlos Latuff, who shares the following guest post:


Carlos Latuff at Catacumba Park in Rio de Janeiro, monitoring Ethiopian broadcasts.

ETHIOPIA: A WAR THROUGH RADIO

by Carlos Latuff, special for The SWLing Post

We just entered 2022 and the civil war in Ethiopia has already completed 1 year. On the one hand we have the  Tigray People’s Liberation Front (TPLF) guerrillas from northern Ethiopia and its allies, and on the other hand we have the armed forces of Ethiopian government and its allies. The dead are piling up, accusations of war crimes from both sides, local and international political interests at stake, and no perspective for a peaceful solution. Without going into the reasons for this new war in Ethiopian territory, I’d like to focus on the use of radio waves by both parties of this conflict.

I monitored shortwave broadcasts from Ethiopia and to Ethiopia between October 21, 2021 and January 4, 2022. The receivers were Tecsun PL-606 and XHDATA D-808, using both the telescopic antenna and a long wire. In all cases, listening was carried out in Brazilian cities.

Carlos at Catacumba Park monitoring and recording clandestine Ethiopian broadcasts.

The monitored stations were: Continue reading

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Guest Post: A synchronous detector crash course!

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


Revisiting the Belka’s “pseudo-sync detector”: A sync detector crash course!

by 13dka

“It’s usually hard to assess whether or not a sync detector helped with a particular dip in the signal or not, unless you have 2 samples of the same radio to record their output simultaneously and compare.”*

That’s what I wrote about the “pseudo sync detector” in my review of the Belka DSP last year.

Since I was recently upgrading to the Belka DX in order to pass on the Belka DSP to a friend, I had briefly two examples of almost the same radio on the table at the dike. I tuned them to the same stations and recorded some audio clips with one radio on sync detector, the other in regular AM mode, to answer the question whether or not sync has “helped with a particular dip in the signal”. Then I thought that demonstration would be an opportunity to try an explanation on what exactly (I think) sync detectors are all about anyway, hoping to find a middle ground between “technical” and “dumbed down beyond recognition”.

The trouble with sync detectors

Perhaps no component of a shortwave receiver is surrounded by so much misconception and confusion as sync detectors. Full disclosure: Until quite recently, I had an, at best, vague concept on what they do myself. It seems it’s not so much that people don’t know how they work, what they actually do when they work is where the ideas often diverge. Continue reading

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