Tag Archives: Antennas

Guest Post: Switching a Remote Antenna, Low Noise Amplifier, and an Antenna and Audio Between Two Radios

Many thanks to SWLing Post contributor, Bill Hemphill, who shares the following guest post:

Remote Antenna Switching Remote Low Noise Amplifier Switching and Switching an Antenna and Audio Between Two Radios

by Bill Hemphill, WD9EQD

Remote Antenna Switching

I have two YouLoop Antennas. I had been placing them at right angles to each other. I would then put one of them on the AirSpy software defined radio. But manually switching from one antenna to the other was a real pain. If only there were a way to electrically switch between the two antennas.

It would be nice to place the antennas remotely from the radio (and computers) and then have some sort of remote switch that would select an antenna and then a single feed line to the radio. It was research time.

The YouLoop and the Airspy both use SMA connectors. An SMA switch would be required. A little research and I came across the following small board that can switch between two SMA antennas:

From Amazon Description: 50 Ohms RF Switch Module, 3-5V Remote Wireless RF Switch Single Pole Double Throw Board Input Output Impedance for DIY Electric Doors (HMC349)

This board is perfect for RECEIVE only projects. Apply 5V to the board and then 5V to the VCC (control pin) to switch from RF1 to RF2.

Now that I had the SMA switch module, a way to actually do the switch remotely was required. Maybe WI-Fi or Bluetooth module would do the trick. I found a nice Wi-Fi module on Amazon that looked like it would do the trick:

Amazon Description: DIYmalls SV Safe Low Voltage WiFi Wireless Switch Module DC 5V-24V Phone APP Remote Control Smart Home for Amazon Alexa Google Assistant

But do I really want to use a phone app to switch antennas. Further investigation discovered a really neat module that uses a Car Fob type control:

Amazon Description: RODOT Mini Relay Wireless Switch, 433Mhz Remote Control Relay Switch, DC 6V 12V 24V 1CH Channel Relay Wireless Secure RF Transmitter and Receiver kit, Momentary Toggle Latched Mode

BIngo!! I could just press a button and switch antennas. But a problem quickly arose. I hadn’t fully read the description of the RODOT switch:

The blue output wire is ALWAYS Vcc (input voltage)! The device only switches the ground.

So the RODOT switches the ground but the HMC349 uses positive voltage to switch. OOPS. Next step was to place a latching relay to take the on/off ground and convert it to on/off positive. Again, another nice board was found:

Amazon Description: HiLetgo 2pcs 5V One Channel Relay Module Relay Switch with OPTO Isolation High Low Level Trigger

The nice thing about the Relay Module is that it can be latched either High or Low, so the RODOT switching ground can be used to latch the relay and then provide a positive voltage to the HMC349 antenna switch.

All modules are powered by 5V. There are other modules available that use higher voltages. But I wanted to be able to use a 5V power source for everything.

I learned a quick lesson on the first layout I did. I had directly connected the antenna cables to the HMC349 module. A quick accidental side yank on one of the antenna cables and the SMA connector tore off the board. A replacement board and some quick wiring and I had a workable antenna switch that with the press of the car fob button, either antenna could be selected.

I found a nice small plastic box that allowed for the HMC349 module to be suspended between SMA bulkhead connectors. By using bulkhead connectors, there is no strain placed on the HMC349 connectors. The relay module was attached to the box lid. The modules are mounted using brass standoffs. The finished box is about 3”x4”x 2” high. Either battery or a 5V wall module can be used to power it.

Overall, I’m quite pleased with the results. I find that sometimes switching antennas (and their orientation) can make a big improvement in the signals. Other times, there’s very little difference.

Remote Low Noise Amplifier along with Antenna Switching

Now that the antennas can be switched, it would be nice if a Low Noise Amplifier could be switched in and out of the circuit. Something like the Lana HF Barebones LNA made by NooElec:

For testing purposes, I first did a quick layout of just using one antenna with the ability to switch the LNA in and out. Note: I took a gamble on hooking the antenna cables directly to the HMC349 modules. Luckily, the SMA connects didn’t tear off the boards.

Two HMC349 modules are used. The first module selects the bypass or the LNA. Likewise, the second module also selects either the bypass or LNA. Note that the second module is turned upside down so that the switches match up when activated. Two modules were used so that the LNA is totally switched out of the circuit. Continue reading →

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Radio Waves: DW Launches “Sudan Now” on Shortwave, Mayor Saves AM Station, Tape Measure Turnstile Antenna, and Where Does AM Go From Here?

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Radio Waves: Stories Making Waves in the World of Radio

Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Dennis Dura and David Iurescia for the following tips:

“Sudan Now” – DW Arabic launches new radio program for Sudan (DW)

DW is now broadcasting a 30-minute daily Arabic-language radio program entitled “Sudan Now” on shortwave, Hotbird and SES-5 satellites and via the DW Arabic website.

As an unbiased radio program, “Sudan Now” will provide listeners in the target region with unbiased coverage of current issues in the region and will promote political, social and cultural dialogue through interviews, talk shows and reports.

Given the lack of independent information sources in Sudan and the limited ability of established media to broadcast due to internet outages and ongoing fighting, “Sudan Now” was specifically designed to be broadcast on shortwave and via the Hotbird- and SES-5 satellites. The satellite broadcast enables listeners in the target region to receive the program via their TV sets.

DW Managing Director Programming Dr. Nadja Scholz: “The conflict in Sudan is ongoing and has far-reaching effects on the entire region. It is absolutely necessary to provide the people there with a dedicated program that enables them to access independent, current and in-depth information. With shortwave radio, we further increase our ability to reach as many people as possible.”

Manuela Kasper-Claridge, DW editor-in-chief, said: “The humanitarian situation in Sudan remains catastrophic. There is a lack of everything – including free, independent information. This Arabic-language radio program is therefore urgently needed.”

The program broadcast will begin on Monday, June 26, 2023. It will air daily from Monday to Friday at 2:30 pm (local time, GMT+2) for a duration of thirty minutes. A repeat of the radio program will air daily at 8:30 pm.

“Sudan Now” can be heard in the afternoon on shortwave 15275 kHz/17800 kHz and in the evening on shortwave 15275 kHz/17840 kHz.

In addition, all broadcasts will be available on the DW Arabic website.

AM Matters: This CO Mayor Saved His Town’s Station (Radio Ink)

[…]Radio Ink: When Justin Sasso briefly mentioned KLMR’s story at Hispanic Radio Conference, it piqued the room’s interest. That’s a powerful AM story. How did this come to pass with you both?

Dan: So about a year ago in late July, KLMR was blown off the air from a micro-downburst. The previous owners couldn’t fix it and they were in danger of losing the license. When I saw the building, half the roof was gone and the antenna was dangling in the wind.

I’ve been in the radio business in Colorado for 40 years, with the last 20 in Colorado Springs, but I’ve never owned a radio station. And so when this opportunity came about, I reached out to Kirk. We had talked about possibly buying a company in Lamar previously. He’s not just the mayor, he’s my brother-in-law, but it was great that the mayor wanted to get involved in it too. So we’re off and running.

Radio Ink: For a mayor to step up and say, “This AM station is so important to my community that if nobody else will save it, I will,” is a huge testament to AM radio’s power and value.

Kirk: It’s vital. That’s what I had mentioned to Justin in that meeting about AM. When we look at rural Colorado and the ag market there, there’s a necessity for that. [Continue reading…]

A Quick And Easy Tape Measure Turnstile Antenna For Milsat Snooping (Hackaday)

The number of satellites whizzing by over our heads at any moment is staggering, and growing at a rapid rate as new constellations are launched. But sometimes it’s the old birds that are the most interesting, as is the case with some obsolete but still functional military communications satellites, which thanks to a lack of forethought are largely unsecured and easily exploitable. And all that’s needed to snoop in on them is a cheap ham radio and something like this simple and portable satcom antenna.

As proof of the global nature of the radio hobby, the design in the video below by Brit [Tech Minds] borrows heavily from previous work by Italian ham [Ivo Brugnera (I6IBE)], which itself was adapted to use 3D-printed parts in a German blog post a few years ago. [Continue reading…]

Not just cars: Where does AM radio go from here? (YouTube)

Joe and Jeff Geerling discuss AM radio station ownership, emergency use, rural listeners, and more.

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Frans checks out the MRA-QRP 20W QRP Passive Loop Antenna

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Many thanks to SWLing Post contributor, Frans Goddijn, who writes:

Dear Thomas,

In the following video, I show a little loop antenna that I bought online from AliExpress:

On arrival one of the parts, the semi-transparant box with variable capacitor for antenna tuning turned out to be broken due to the bigger box having been thrown around in transit.

The seller promptly provided me with the necessary part (plus extra) for repairs.

Yesterday I repaired it and today I assembled the antenna and tested it a bit in the afternoon and early evening as soon as reception started to get well enough.

It’s a fun antenna, affordable too.

The video shows how effective the variable capacitor is.

Best regards,

Frans

Thank you, Frans. That is certainly a very affordable passive loop option. If you’re an urban QRPer, all the better. I should also mention, you have one of the nicest radio operating positions out there!

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A DXpedition to East Sandy

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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.

Our DXpedition home. Coordinates 41°19’23″N 79°46’08″W (Don Moore)

ANTENNAS

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 →

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PDF: Analysis and Design of FSL Antennas

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Many thanks to SWLing Post contributor, Zoltan Azary, who has written an extensive theoretical analysis of ferrite sleeve loop antennas. This article has a very academic flavor and for those who are interested in antenna design, he welcomes your comments!

Click here to download the 14 page PDF, “Analysis and Design of FSL Antennas: Open Source Hardware Engineering” by Zoltan Azary.

Thank you for sharing this work with us, Zoltan!

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Born in the ER: Andrew’s portable SULA antenna

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Many thanks to SWLing Post contributor, Andrew (VK2ZRK), who writes:

Just thought I would share some pics of my SULA build which I constructed in the Emergency department’s antenna building section in between catastrophies here in Australia.

I built it out of 8mm fibreglass tube from a kite supply, 8mm kite nocks, 13mm equal cross irrigation fitting and lots of double wall glue lined heat shrink. The 8mm tube with a short bit of heat shrink is a slip fit into the id of the 13mm equal cross which I secured with more heat shrink.

I then cut the frame to length allowing for the length of the kite nocks. I secured the kite nocks with more heat shrink. I then soldered the resister to 2 lengths of Davis RF 12g antenna wire and fed this through the kite nocks terminating it at the nooelec balun on the opposite side to the resistor.

I think it worked out well. It is very light. I built it to use with my SDRPlay RSPdx.

Thank you to everyone involved in the design process and for providing it to the swling.com community.

Cheers
Andrew VK2ZRK

In all the years I’ve been hosting the SWLing Post, I can safely say that we’ve never featured an antenna constructed in an Emergency Department of a hospital. Thank you, Andrew!

The feedback from the SULA antenna build has been phenomenal. The three-part series detailing the SULA antenna from concept to build was the most popular of 2022 on the SWLing Post.

Thank you for sharing the photos of your antenna. What a professional job, Andrew!

Readers, if you’d like to learn more about the SULA antenna, check out this three-part series–a collaboration between the amazing Grayhat and 13dka.

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A little daytime Medium Wave DXing . . .

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By Jock Elliott, KB2GOM

Let’s get one thing clear from the start: it’s all Ken Reitz’s fault. When the search for the guilty begins, the finger should point squarely at Mr. Reitz.

Who is Ken Reitz? He is the Managing Editor and Publisher of The Spectrum Monitor.

The Spectrum Monitor is a radio hobbyist magazine available only in PDF format and can be read on any device capable of opening a PDF file. It covers virtually aspect of the radio hobby, and you can find it here: https://www.thespectrummonitor.com/ I am a subscriber, and I can heartily recommend it without reservation.

So what is it that Mr. Reitz did that set me off? Short answer: he wrote a really good article entitled “AM DX Antennas: Long Wires and Loops Big and Small.” In it, he mentioned that he could hear, from his location in Virginia, WCBS on 880 in New York City, some 300 miles away. He also mentioned that he could hear, during daylight hours, WGY in Schenectady, NY, about 400 miles distant.

WGY is a local station for me in Troy, NY, but I wondered: Could I hear WCBS in New York City? That’s nearly 150 miles from me. Hmmm.

So I started firing up various radios and radio/antenna combinations on 880 kHz. I tried my Icom IC706 MkIIIG ham transceiver, hooked to the 45-foot indoor end-fed antenna. Nothing heard.

Next, my Grundig Satellit 800 connected to its 4-foot whip antenna. I could hear WCBS barely, but with a horrible buzzing noise. Switching the Satellit 800 to the horizontal room loop antenna I could hear WCBS better, but the noise was really, really nasty.

One way to preserve domestic tranquility is to hide the MFJ Loop behind a curtain!

Then I connected the MFJ 1886 Receive Loop Antenna. Tah-dah! I could hear WCBS just fine, with some noise in the background, but “armchair copy.” The MFJ loop made a huge difference in the quality and strength of the signal. I also tried the MFJ loop with another radio I have under test (its identity to be revealed in the future) and found, while I couldn’t hear WCBS at all with the radio’s internal antenna, the 1886 made an enormous difference, pulling out a fully copyable signal with noise in the background.

Finally, I tried a couple of my portables. My Tecsun 880 could hear WCBS, but the noise level was high enough to be annoying. Finally, I tried my CCrane Skywave SSB. The Skywave did a better job of pulling the signal out of the noise. I got the same result with the CCrane Skywave SSB2. Both Skywaves were using their internal ferrite antennas. Impressive.

Bottom line, for this very small foray into daytime medium wave DXing, the MFJ-1886 Receive Loop Antenna was a powerful and useful tool, one I can easily recommend. Second, when it comes to portables, the CCrane Skywave SSB (either model) continues to show that it is “The Little Radio That Could.”

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