Tag Archives: Homebrew

Christoph’s homebrew custom hotkey pad for SDR applications

Last week, I saw a fascinating post by Christoph Jahn on the SDRplay Facebook page.

Christoph created a custom hotkey pad for use with SDRuno.  The project is actually quite simple and his finished product looks amazing:

The steps involve downloading “LuaMacros” a freeware macros utility that allows you to map macros to an external USB device like a cheap numeric keypad. Christoph then designed the key templates and printed them on a strong adhesive vinyl foil.

I asked Christoph if I could post his project on the SWLing Post and he kindly sent me the followed PDF with step-by-step instructions.

Click here to download the instructions as a PDF (6.71MB).

Christoph also shared the macros file he used for his project (download .XML file 8.77 KB).

Thank you so much for sharing this, Christoph!  Your finished product is so professional, I would have thought it was produced by SDRplay!

This could be a useful tool for a radio friend who is visually-impaired and, of course, could be compatible with a wide range of SDR apps and rig control software that allow keyboard shortcuts.

Readers: Have you done a similar project? Please comment with your experience and any details–especially noting applications and programs you find are compatible with keyboard shortcut mapping. This could be very beneficial for radio enthusiasts with disabilities!

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Patrizio’s simple homebrew NCPL antenna

Many thanks to SWLing Post contributor, Patrizio Cardelli, who writes:

I’m Patrizio (SWL I – 5184 /AN) from Riva del Garda, Italy.

A few days ago, I built a Noise-Cancelling Passive Loop (NCPL) antenna. I built the 1:1 balun with a couple of ferrite 175 – 285.

I got a good result on medium wave on my ICOM IC R 71 E with the antenna inside my house installed behind the desk just to avoid any problems with my wife.

On shortwave, the signal was low in comparison with the Bonito mini whip but in my QTH I have a lot of QRM and with this antenna I solved my problem.

Yesterday I tried the balun with my random wire (15,2 meter long) also with good results.

About my NCPL antenna: I made mine with RG-58 coaxial cable just to have easy portability in SOTA (please see photo) and also the feed line is made by the same coaxial cable. OK, you are right…it’s ugly:

Electrical connections are not soldered, still I don’t see any mechanical issues and this antenna since it is made for SWL / BCL purposes (meaning, RX only, no TX).

Concerning the binocular ferrite core, I didn’t have one, so I used two ferrite core type 175 – 285 (28,5 mm length, external diameter 17,5 mm and internal diameter 9,5 mm) normally used to reduce HF interference:

For the winding I used PVC insulated cable cat no: 7/0,2 type 2 (def61 – 12) conductor 7/0,2mm TSCu X 0,3mm R/T type single (4 turns primary and 4 turns secondary). It’s the same cable with which I built my random wire antenna (also portable for SOTA but now installed on my balcony until the COVID – 19 emergency is over).

The attached videos show the situation in comparison with my BONITO MINI WHIP active antenna (also installed inside my house). Recently I changed my QTH and unfortunately here I have a lot of interference both on MW and SW. The better results that you can hear are achieved with my NCPL antenna.

I have made this test with my ICOM IC R 71 E + BHI noise cancellation speaker…..you can assess yourself, the better results that you can hear are achieved with the NCPL antenna and in the case of Tecsun PL-660 without any noise cancelling filter (BHI speaker off).

Thanks for sharing this, Patrizio! As you say, the NCPL loop seems to do a fine job helping to eliminate local RFI/QRM. The Bonito Mini Whip is a fine antenna, but not optimal for environments with a lot of radio noise–that’s where the NCPL antenna really shines.

You also make a good point that if you’re simply experimenting and only using an antenna for receiving, you can be more relaxed about the build because you’re not sending RF through it. In the end, however, properly soldered and protected connections will last much longer and provide better, more reliable performance.

Thank you, again, for sharing your build, Patriio! Those reception results speak for themselves!

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John adds a pre-amp and rotatable stand to his homebrew NCPL antenna

A couple weeks ago, we featured John Mills’ homebrew Noise-Cancelling Passive Loop (NCPL) antenna (see photo above) in a post with two other Post community designs.

John recently shared an update to his project:

As promised, some more pictures of my antenna mounted on a rotatable stand. I have used standard (in the UK) 20mm electrical plastic conduit and fittings to make the frame.

Fitted a small plastic box to house the balun and have put a BNC socket on the underside of it for connection the coax cable to my Rx.

I have also been experimenting with cheap low cost amplifiers (LNA) found on eBay (see picture) which do seem to improve the general strength of signals by 10-15db, but the baseline noise also rises.

I did manage to hear a QSO on 160M using one of these which was inaudible without the LNA but I cannot say for sure yet if they are worth the extra noise introduced.

Thank you for sharing your update, John! The plastic conduit support is simple and effective! Indeed, it looks very professional. What I love about your NCPL build (loop, stand, and LNA) is it that it’s all incredibly affordable as well.

Read more about John’s NCPL build in this post.

Post Readers: Has anyone else experimented with implementing a pre-amp in their NCPL antenna design? Please comment!

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A compact homebrew Si5351-based SDR

(Image source: Circuit Salad)

Many thanks to SWLing Post contributor, Paul Evans, who writes:

I see this receiver as a remarkable break through. Using audio processor to emulate modes from IQ is very, very clever. This is perhaps the article of the year!:

(Source: Circuit Salad)

[…]This is a revised version of my FV-1 based SDR. I replaced the CS2100 clk generator with the Si5351 clk generator. The Si5351 has some advantages over the CS2100, namely you can generate quadrature clks directly. This simplifies the hardware design and improves the quadrature accuracy. The sideband rejection in LSB/USB modes is impressive..somewhere around 60 db as best I can measure. The DSP processing is accomplished by the use of a FV-1 audio processor. The device makes the base band signal processing a snap. It requires some code to be loaded on a EEprom but the circuitry is simple and allows for up to 8 selectable programs. I created three: AM/USB/LSB . The FV-1 provides for three analog POT inputs to control any parameters you choose. Gain, variable filter bandwidth and depth, AGC are some examples of adjustable parameters if you desire. I kept it simple and created fixed band pass filters to taste. I did use one of the controls for AF gain. The design has no tuned circuits or band pass filters but they could easily be added.  It works just fine without them. Occasionally, I come across a ghost signal from harmonic mixing, when tuning, but not enough to matter. The design uses an OLED display and a rotary encoder for tuning. The frequency coverage is from 2.7 Mhz to 25Mhz. The bottom limit is created by the inability of the Si5351 to support quadrature below this frequency. Although I have improved my DSP programs for the FV-1 and have developed new display drivers and the new code for the Si5351, useful detail about using the Fv-1 can be found in my original design from a few years ago: https://circuitsalad.com/2015/06/19/comming-soon-stand-alone-software-defined-radio-baseband-demodulator-no-computer-required/

The design uses a LTC6252 low noise op amp as an RF input with gain. It provides a constant and reliable resistive Rf termination for the sampling detector.  This allows for random antennas to be used without adversely affecting the input termination to the detector. All the code to operate the main processor(display/clk generator/tuning, band select and receive mode) was written in MikroC which is a C compiler for PIC and AVR processors. The generation of quadrature signals out of the Si5351 is not difficult to implement once you know how but..figuring that out took me a couple weeks of experimentation! You can connect switches, the encoder, volume pot and display directly to the main board for operation but I created a secondary board to mount the display and encoders. Instead of an analog pot and selection momentary switches, I used another microcontroller and two encoders(with one built in momentary push switch each) to create all of the switching signals, gain control, etc. This allowed me to have just two controls for all features.  The controls include: tuning, audio gain, mode, and tuning step. Tuning resolution is from 1Hz to 100KHz . For fun, I made the output of the FV-1 differential into the audio amp. This is not necessary.

Here is a link to all the files used to build this radio in a zip file(updated 1/18/20):


Demo video

Click here to read the full article, download all design notes/files and watch videos at Circuit Salad.

Wow–that is fascinating! Thanks for sharing, Paul. I’m curious if any SWLing Post readers have experimented with the Si5351.

Interestingly, SWLing Post friend Dave Richards (AA7EE), also recently shared this video of an amazing Si5351-based VFO built by JF3HZB:

This must be one of the best analog emulations I’ve seen on a display. Marry the SDR receiver above to this VFO and you could have a top-shelf homebrewed receiver!

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Video: Tube radio transmitter designs from the 1920s

Many thanks to SWLing Post contributor, Paul Evans (W4/VP9KF), who shares the following article from Hackaday:

The origin of the term “breadboard” comes from an amusing past when wooden bread boards were swiped from kitchens and used as a canvas for radio hobbyists to roll homemade capacitors, inductors, and switches. At a period when commercial electronic components were limited, anything within reach was fair game.

[Andy Flowers], call sign K0SM, recently recreated some early transmitters using the same resources and techniques from the 1920s for the Bruce Kelley 1929 QSO Party. The style of the transmitters are based on [Ralph Hartley]’s oscillator circuit built for Bell Telephone in 1915. Most of the components he uses are from the time period, and one of the tubes he uses is even one of four tubes from the first Transatlantic contact in 1923.[…]

Click here to continue reading at Hackaday.

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Guest Post: Summer Daytime DXing 2019

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

Summer Daytime DXing 2019

by TomL

I took note of the mediocre band conditions this summer amongst amateur radio operators as they were making off the cuff comments about still being in a solar minimum.  Some had gone out and bought upgraded transmitters to solve the problem (MOAR WATTS!). And more power thrown at a weak ionosphere does seem to help get a signal farther.  I had not been out since the spring and decided to find out for myself. But instead of more watts, I wanted more height.

Greene Valley Scenic Overlook is open to the public from May through October on weekends only (and only from 11am-6pm).  It was the largest land fill (aka, garbage dump) in Illinois, now covered over and producing captured methane gas. On August 3 & 4, I ventured over there to see if its 190 feet above the surroundings might help my radio reception.

After trying my luck with a 12 foot vertical antenna on a tripod (and numerous children running around it chasing butterflies or looking at the view of Chicago), I went out the next day and parked away from anyone and put up my 19 foot vertical on the roof of the car.  This setup is still amazing to me and works much better than the tripod mounted antenna, probably because it has a proper ground plane as well as being 7 foot taller.

So, yes, the conditions were so-so, not too bad and not too good.  Lots of weak signals and some empty frequencies that I had expected to hear some South American stations around the 5 – 10 kw range.  Weak stations from Asia were more scratchy sounding than usual even with the extra 190 feet of height. Here are 5 broadcast recordings as a sample (times in UTC):

9920 kHz at 21.14 – Radio Thailand in Thai, just catching the end of the broadcast:

9685 kHz at 21.20 – Radio Free Asia in Chinese from Kuwait:

9650 kHz at 21.23 – Radio Guinea in French:

9445 kHz at 21.30 – All India Radio in English (fighting off computer generated noise on my SDR and cheap Dell laptop) and just getting a station identification:

11780 kHz at 21.44 – Radio Nacional de Amazonia booming in with the usual annoying host yelling enthusiastically over every tune he played:

Running out of things to listen to, I wandered over to the 20 meter amateur radio band and found a different situation.  Propagation was decent between the Western hemisphere and Europe. Lots of “pile ups” going on with people trying to make contact with their trans-Atlantic counterparts.  Some said they were running 500 watts or more, so more power does seem to help! Here are 5 recordings to show how active it was:

14171 kHz at 21.55 – Inaki (F5RAG) from southwestern France conversing with Carlos (YV3CRT) in Venezuela (surprised anyone is left in Venezuela with operating radio equipment and not sold off for food with the ongoing difficulties there).  Then Inaki makes contact with Alejandro (CE2ATS) from Chile with a good signal. All in Spanish:

14199.38 kHz at 22.04 – Ervin (VE3GAL) tries his QRP portable setup from Ontario to contact Ron (F4VSM) in Southwestern France who has a 500 watt setup and large Yagi antenna. Sometimes things do not go so well but that is the challenge of using low power, maybe around 10 watts (meaning that just because you can hear them, you cannot always transmit to them with the same effectiveness and vice-versa, for various reasons):

14228 kHz at 22.12 – “BAN” (IZ1PNT) from Italy makes contact with Norman (N3PVQ) in FL after asking everyone to be quiet. Good control over the frequency:

14238 kHz at 22.17 – Slavko (S57DX) booming in, making a contact (Rob, KK4HEQ) in Florida:

14245 kHz at 22.24 – Gabrielle from the Czech Republic, participating at a Youth event using station OL88YL contacting Ira (VP2EIH) in the British Virgin Islands and then another dude from Florida, Roy (AD4AN).  She handled it very well:

This outing was quite educational and I find it curious that people running 1000 watts or less are able to be heard well between continents but the large broadcasters were difficult to hear.  Antennas pointed in the right direction, at the right time of day and frequency, can certainly do amazing things, plucking those weak signals out of the air so easily. And I do think the extra height had something to do with hearing this magic, too!

Happy Listening,



  1. An easy way to lookup amateur radio operator “call signs” is to go to web site QRZCQ.com which does not need a login.  Some records may be out of date, but most of it is accurate.
  2. Setup used was a cheap Dell laptop, Windows 10, SDR Console 3.03,  connected to the AirSpy HF+, a Palstar amplified preselector, and an old Kiwa BCB filter, then going up to the car roof magnetic balun (a Palomar MLB2) which is then connected to the 4 magnet base and the MFJ 19 foot stainless steel antenna.  You can read about it here:


Brilliant report, Tom! It’s true: the bands are fickle, but like you I always find interesting things to hear on HF. I think your setup using your vehicle as the ground plane for the antenna is a fantastic idea. Plus, set up is easy, self-supporting, and you’ll never have to worry about a park ranger, for example, complaining because you have a wire suspended from a tree. And when there are no trees? You’re still golden. 

Thanks for sharing your experience and DX! Amazing that even with mediocre conditions, you still snagged some distant signals.

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Taking the new Mission RGO One transceiver to the field!

SWLing Post readers might recall that last year at the 2018 Hamvention, I met with radio engineer, Boris Sapundzhiev (LZ2JR), who was debuting the prototype of his 50 watt transceiver kit: the Mission RGO One (click here to read that post).

Since last year, I’ve been in touch with Boris, and we arranged to meet again at the 2019 Hamvention so I could take a closer look at the RGO One, especially since he has started shipping the first limited production run.

The RGO One delivers everything Boris promised last year and Boris is on schedule, having finished all of the hardware design and having implemented frequent firmware updates to add functionality.

Excellent first impressions

I’ll be honest: I think the RGO One was one of the most exciting little radios to come out of Hamvention this year. Why?

First of all, in contrast to some radios I’ve tested and evaluated over the past two years, I can tell immediately that the Mission RGO One was developed by an active ham radio operator and DXer.

Here are some of the RGO One features and highlights as taken from the preliminary product manual (PDF):

    • QRP/QRO output 5 – 50W [can actually be lowered to 0 watts out in 1 watt increments]
    • All mode shortwave operation – coverage of all HAM HF bands (160m/60m optional)
    • High dynamic range receiver design including high IP3 monolithic linear amplifiers in the front end and diode ring RX mixer or H-mode first mixer (option).
    • Low phase noise first LO – SI570 XO/VCXO chip.
    • Full/semi (delay) QSK on CW; PTT/VOX operation on SSB. Strict RX/TX sequencing scheme. No click sounds at all!
    • Down conversion superhet topology with popular 9MHz IF
    • Custom made crystal filters for SSB and CW and variable crystal 4 pole filter – Johnson type 200…2000Hz
    • Fast acting AGC (fast and slow) with 134kHz dedicated IF
    • Compact and lightweight body [only 5 lbs!]
    • Custom made multicolor backlit FSTN LCD
    • Custom molded front panel with ergonomic controls.
    • Silent operation with no clicking relays inside – solid state GaAs PHEMT SPDT switches on RX (BPF and TX to RX switching) and ultrafast rectifying diodes (LPF)
    • Modular construction – Main board serves as a “chassis” also fits all the external connectors, daughter boards, inter-connections and acts as a cable harness.
    • Optional modules – Noise Blanker (NB), Audio Filter (AF), ATU, XVRTER, PC control via CAT protocol; USB UART – FTDI chipset
    • Double CPU circuitry control for front panel and main board – both field programmable via USB interface.
    • Memory morse code keyer (Curtis A, CMOS B); 4 Memory locations 128 bytes each

What really sets the Mission RGO apart from its competitors is the fact that it’s compact, lightweight (only 5 lbs!), and has a power output of up to 50 watts. Most other rigs in this class have a maximum output of 10 to 15 watts and require an external amplifier for anything higher.

The RGO One should also play for a long time on battery power as the receive current drain is a modest 0.65A with receiver preamp on.

The RGO is also designed to encourage a comfortable operating position. The bail lifts the front of the radio so that the faceplate and backlit screen are easily viewed at any angle.

The keypad is intuitive and–hold your applause!–all of the important functions are within one button or knob press!

The front panel design is simple and clean. There are no embedded menus to navigate to change filter width, power level, RF gain, keyer speed, mic gain, pre amp, or audio monitor level. Knob spacing is excellent and I believe I would even be able to operate the RGO while wearing gloves.

Even split-operation is designed so that, with one button press, you can easily monitor a pile-up and position your transmit frequency where the DX station last worked a station. (This is similar to the Icom XFC button). The user-interface is intuitive; it’s obvious to me that Boris built this radio around working DX at home and in the field.

Speaking of the field…

Parks On The Air (POTA) with the Mission RGO One

At my request, Boris has kindly loaned me one of the first production run units to test and review over the next few months. I intend to evaluate this radio at home, in the field, and (especially) on Field Day. By July, I should have a very good idea of how well this Bulgaria-born transceiver performs under demanding radio conditions!

I had planned to begin my RGO One evaluation after returning home from Hamvention, but I couldn’t resist taking it to the field, even though the propagation forecast was dismal.

The first leg of my journey home from Hamvention took me to Columbus, Ohio, on Monday, so I scheduled a Parks On The Air (POTA) activation of Delaware State Park, K-1946.

Delaware State Park (POTA K-1946) in Delaware, Ohio.

My buddy Miles (KD8KNC) and I met our mutual friend Mike (K8RAT) at the park entrance and quickly found a great site with tall trees, a little shade, and a large picnic table.

We set up the RGO One and, for comparison, my Elecraft KX2 for the POTA activation.

I won’t lie: band conditions were horrible. Propagation was incredibly weak, QRN was high, and QSB was deep. Yuck!

Still, this activation gave me a chance to test the RGO One in proper field conditions.

I was limited to SSB since the only CW key I had with me, the paddle specifically designed to attach to the front panel of the Elecraft KX2, wouldn’t work with the RGO One. In addition, I was limited to 25 watts output because the antenna I deployed, the LnR Precision EFT Trail-Friendly end-fed antenna, can only handle power up to 25 watts.

Although I had never operated the radio before, I was able to sort out most of its functions and features quickly.

The receiver audio was excellent and the noise floor seemed quite low to my ears. The internal speaker does a fine job producing audio levels that are more than ample for a field setting.  Still, I prefer operating with a set of earphones in the field–especially important on days like this when propagation equates to a lot of weak signals.

Although I failed to make a total of ten contacts to claim a proper POTA activation, I was pleased with offering up K-1946 to seven lucky POTA hunters/chasers. I simply didn’t have enough time available to work three stations more at such a slow QSO rate.

Of course, my signal reports were averaging “5 by 5” and were never more than “5 by 7” regardless of which rig–the RGO One or the KX2–I was using. The reports on the RGO One transmit audio reports were great.

Stay tuned!

I will publish my first review of the Mission RGO One in The Spectrum Monitor Magazine, most likely in August or September.  In the meantime, I will post updates here as I put the RGO One through its paces. I’m especially excited about using it during Field Day with my buddy Vlado (N3CZ) to see how it holds up in such an RF-dense environment.

And now that the POTA bug has bitten me?  Expect to catch me on the air with the RGO One over the next few weeks!

If you’re interested in following the Mission RGO One, bookmark the tag: RGO ONE.

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