Category Archives: How To

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….

Continue reading →

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Soldering is Easy: An amazing soldering primer in comic book form

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Many thanks to SWLing Post contributor, David Goren, who shares a link to this PDF which is a primer on soldering…in comic book form!

Thing is, this primer is brilliantly illustrated and all of the soldering techniques are truly textbook. No wonder, though: the amazing Mitch Altman provided the “Soldering Wisdom.” (You might recall my love of Mitch’s TV-B-Gone kit.)

David didn’t know this, but I use this comic guide very heavily when teaching classes or individuals how to solder. It connects with all generations of makers and tinkerers.

It is the benchmark, in my opinion!

Mitch specifically designed this tutorial to be spread widely, so he licensed it under Creative Commons. Share this widely!

Click here to download the full PDF.

I’ve also stored a backup copy here on the SWLing Post.

Thanks for reminding me about this tutorial, David!

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Kostas pairs his Collins 51S-1 with a Heathkit SB-620 bandscope

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Many thanks to SWLing Post contributor, Kostas (SV3ORA), for sharing the following guest post which originally appeared on his radio website:

Collins 51S-1 band scope using a Heathkit SB-620

by Kostas (SV3ORA)

The purpose of this project, is to connect a Collins 51S-1 receiver with a Heathkit SB-620 “scanalyzer”, so as to give the 51S-1 band scope capability. Right into the schematic presented below, a slight modification is needed to the 51S-1. I usually do not do modifications to old equipment unless absolutely needed and even when I do so, I take care for them to be easily undone and to modify them as little as possible.

The modification to the 51S-1 is simply a small coupling capacitor connected to the plate of the mixer tube V4A and a short run of thin coaxial cable, connected as shown, to one of the several SPARE RCA connectors at the back of the 51S-1. Collins engineers were smart enough to include SPARE RCA connectors at the back of the radio, which are not connected to anything inside the radio circuit, to be used for different future purposes. So we do not have to drill any holes to the chassis of the precious receiver, which would be catastrophic.

Click to enlarge.

The coupling capacitor is just 5pF, so compared to C125, this presents only a tiny fraction of the loading to V4A plate, i.e. not affecting the normal operation of the receiver. Note, you cannot take directly the 500KHz IF output that is originally provided by the 51S-1 RCA in the back of the radio. This is because this IF is AFTER the filters, so it is a narrow IF. We need WIDE IF for the scanalizer to work properly, so you have to perform this tiny modification to the 51S-1.

No need to say that the SB-620 needs to be re-tuned for 500KHz instead of 455KHz. I was unlucky and my SB-620 did not have the appropriate L3 to be tuned to the IF of 455/500KHz. Mine had the L3 used for an IF of 5.2-6MHz. I converted the SB-620 to work down to 500KHz by using this original higher-frequency L3 and adding two additional inductors to it, one at its bottom and one at its top, so as to make L3 larger. The additional bottom inductor I added (connected from the bottom of L3 to the ground) was a 15uH choke. The additional top inductor I added (connected from the top of L3 to C3 and C5), was a 455KHz IF CAN transformer (the one with the adjustable yellow-painted cap) taken out of a transistor radio. Of course I have removed the internal capacitor of the transformer before using it. My transformer had something like 200-300uH in the mid-set point. It is not too critical as this is a tunable transformer.

By making this modification to the SB-620 you can bring the 5.2-6MHz L3, down to 500KHz. Of course the slug of L3 now has limited tuning range. But we can coarse tune the hybrid L3 now, by tuning the IF transformer that has been added. This solution worked like a charm and the original L3 is still fit in place, looking original and helps in fine tuning if needed. For the optional mixer input (points A, B, C on the SB-620), I used circuit #1, but I did not notice any real difference from circuit #3. RFC1 is 304uH and I connected three 100uH chokes in series to make this RFC.
The solution described in this page, will add a huge value to your vintage receiving station. SWLing feels just different by having an all-tubes computer-free band scope. Here is a picture of the setup, nicely glowing in the night. That P7 CRT blue phosphor with its green afterglow “memory” effect looks amazing! Narrow resolution is actually only achievable, because of this afterglow of the CRT, which allows for much slower sweep rates.

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Jock gets a good grounding!

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Many thanks to SWLing Post contributor, Jock Elliott, who shares the following guest post:

Getting grounded – at last!

By Jock Elliott, KB2GOM

Readers’ comments are among the best things about writing for the SWLing.com blog. When a reader responds to a post and leaves a comment, it does three things. First, it lets the author know that someone actually read the post. Second, it provides valuable feedback – “I liked it.” “Did you know about this . . .?” “I had a similar experience.” – and so forth. Finally, it provides the author an opportunity to learn something, and that perhaps is the most fun.

A case in point: when I posted this, Andrew (grayhat) said:

“If you want to make an experiment, connect the end-fed to the Satellit high-Z wire input (clamp), then pick a (relatively short) run of insulated wire connect one end of the wire to the high-Z “ground” (clamp) and the other end of that wire to the “gnd” hole in the wall plug

The above being said, I prefer keeping antennas outside and taking care of the feedline, this helps reducing or eliminating noise from indoor appliances like switching PSUs and other things, anyway, if you want, try the above idea and let me know how it works for you”

To which, I responded:

“Thanks for the comments.

Thanks to a tree falling on the powerlines, I now know that the inherent electrical noise in my radio room is basically down to the level of atmospheric noise.

Neverthless, experimenting with a ground is definitely worth trying. A thin wire, sneaked out the window to a ground rod, might do the trick. I’ll report back after I try.”

Andrew (grayhat) came back to me and said:

“I was serious, try the “wall plug ground” I described, it won’t start any “magic smoke” or the like, otherwise, if you can lay out a wire with a length of 5m max, cut to be NON resonant, and connected to a good ground stake, go for it

Then, if you want to discuss this further, just ask Thomas for my e-mail, I agree to share it with you.”

Now, I really appreciated Andrew’s comments, but what I had not told him was that there is just one wall plug in my radio shack; it is really inaccessible, and I am not sure I can get a ground off it. Further, the rest of the power “system” in my shack is a rat’s nest of power bars and extensions, and I have zero confidence that any of them will provide a useful ground.

But – and this is a big but – I did take Andrew’s point: that connecting an actual ground to the ground clip on the back of the Satellit 800 might improve things. Continue reading →

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Giuseppe’s Crossed Loop and the “VariabilOne”

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Many thanks to SWLing Post contributor, Giuseppe Morlè (IZ0GZW), who shares the following:

Dear Thomas and all friends of SWLing Post,

I’m Giuseppe Morlè iz0gzw from central Italy on the Tyrrhenian Sea, Formia.

A few days ago at a fair for radio amateurs in Latina, I bought an excellent very large variable capacitor–those of ancient military radios–and I found a splendid antique knob with a fantastic gear ratio.

I called this VariabilOne and it consists of two sections of 250pf each. It’s very portable and can be applied to any loop with crocodile clips.

I built another cross loop made up of 2 turns the internal loop, 35 cm. and only one turn for the external loop, 40 cm.

I can tune frequencies from 3.500 to 20.0 MHz. The crossed loop is strongly directive given the two loops that work together being joined on their ends.

I have made some demonstration videos and it is a pleasure for me to share them for our entire community (see below).

Thanks to you and I wish you all the best for you and your family.
Greetings to all.
73. Giuseppe iz0gzw.

Click here to view on YouTube.

Giuseppe, thank you once again for sharing your brilliant homemade antenna projects with us. I absolutely love that monster variable cap and tuning whee! What a thing of beauty–and obviously your loop is very effective.

Thank you as always, Giuseppe!

Readers: click here to check out Giuseppe’s other antenna projects.

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HanRongDa HRD-747: Expanding reception to include longwave

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Many thanks to SWLing Post contributor, Dan Robinson, who shares the following video which shows how connecting an external antenna to the HDR-747 extends reception range down to longwave:

Click here to view on YouTube.

Thanks for the tip, Dan!

Note: Dennis adds that the antenna used in this video can be found here.

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Radio Waves: Colorado Inmate Radio, Experimental Radio News 4, BBC World Service to Ukraine, DIY Radio, and When the World Tuned to Shortwave

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Radio Waves: Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers. To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Inmate-produced radio station streams beyond prison walls (NBC News)

Inside Wire, available 24/7 to incarcerated people in Colorado and to online listeners around the world, is said to offer a chance for prisoners and those they harmed to heal.

LIMON, Colo. — Herbert Alexander stares at the sound waves jumping on the computer screen in front of him, his shaved head partially covered by headphones. He’s editing a short audio feature on incarcerated fathers, a subject with which he is intimately familiar.

His two sons will soon hear his voice and his story because Alexander, 46, an inmate at Limon Correctional Facility, is preparing a segment for Inside Wire: Colorado Prison Radio, billed as the first radio station to be produced inside a prison and available to the world outside.

Other radio stations created in prisons generally air only within the walls of their lockups, but Inside Wire, which premiered March 1, reaches all 21 prisons in the state and beyond, online and by app, making the first of its kind in the country, organizers said.

“In spaces where isolation continues, this medium can cut through that,” said Ryan Conarro, general manager and program director of Inside Wire and creative producer for the University of Denver Prison Arts Initiative, which oversees the program in partnership with the Colorado Department of Corrections. [Continue reading at NBC…]

Experimental Radio News 4 (Experimental Radio News)

This issue of ERN includes novel aeronautical experiments, life-detecting radars and non-wearable health monitoring, the latest on those mysterious shortwave trading stations and more.

Click here to read a wide variety of topics in Experimental Radio News 4.

BBC World Service resurrects shortwave broadcasts in war-torn Ukraine (TPR)

The BBC has resurrected an old school way of broadcasting in order to reach people in the crisis area of Ukraine: Shortwave radio. What is shortwave, and why has the BBC decided to begin using it again? Continue reading →

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