Today’s success: one direction of a Hayward/Kopski bi-directional termination insensitive amplifier. I used KSP10 VHF transistors and it’s delivering more gain than expected (30dB!) rather than 20dB from 2n3904. Careful construction, so no oscillation. I’ll just put it into a pad rather than re-biasing. But it worked first try, again. Lucky weekend ☘️ I’m calling this mixed Manhattan/Ugly style “ugly man” haha
I soldered up the BFO from the BITX20 that I modified down to 9MHz and to use parts I have on hand. One of those rare moments when you draw it up, solder it together, turn it on… and it just works! 🎉
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Robert Bell
boosted
We’re excited to announce ARISS STEM activities for two new groups!
Congratulations to University Heights School of Medical Arts in Jonesboro, AR for their successful proposal.
They were selected for ARISS-USA #HamRadio contacts with the International Space Station during July-December, 2026.
We’re excited to announce ARISS STEM activities for two new groups!
Congratulations to University Heights School of Medical Arts in Jonesboro, AR for their successful proposal.
They were selected for ARISS-USA #HamRadio contacts with the International Space Station during July-December, 2026.
I cobbled together a 20m direction conversion receiver from the parts I had on my bench. All of these components are my own design except the mixer (ADE-1) and diplexer (W7EL) board. The audio amp is the one I designed and that @synx508 did the awesome testing work on, the VFO is the one I published yesterday, and the band pass is a 3 pole filter that I built as a starting point for a transceiver project. It sounds pretty good! Here's some video
I designed and built an analog varactor-based Colpitts VFO for the 20m ham radio band. It’s built around two BB910 diodes, a 10-turn pot, and two J310 JFETs. Has some warm up drift but is very stable after a few minutes. It was designed to use caps I already had. Very happy with this!
I used c0g caps and elevated the toroid and trimmer to keep heat away from them. Advice is to use air core here but the toroid takes less space. Note I removed the unnecessary heat sink.
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I just finished a 3 pole 20m band pass filter. Looks good on the NanoVNA. I used an odd mix of surface mount capacitors, hand wound Amidon toroids, and 1970s Soviet surplus trimmers. Very happy with the result though! #HamRadio #AmateurRadio
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Shipping notices from Mouser are always a little joy in the Inbox. 😊 #HamRadio #AmateurRadio
I got 90 of these quite good looking 6W-capable UHF MOSFETs for really really cheap and am looking forward to learning to build something with them. They are EOL, but with that many of them I should be able to do all the projects I'll want to do for quite some time.
https://www.renesas.com/en/document/dst/2sk3390-datasheet
They are being held for me in the US and so I need to arrange to get them sent over here. I have plenty of work to do first, though.
Here’s my BFR193 based discrete component audio amplifier. It does about 85dB of gain from two BFR193 transistors and one 2n3904. It’s pretty quiet for delivering all that gain. It’s derived from the Soldersmoke direct conversion receiver amplifier but with a lot of improvements, feedback, and different transistors and bias scheme. It will go into my next radio. I built it partly surface mount and partly with through hole in Manhattan style. Very happy with this! #HamRadio #AmateurRadio
Using BFR193 RF transistors in an audio amp introduces some interesting behavior! They will happily pick up stray high frequency (they are good to 2GHz) RF from even very short wires and amplify it quite a lot. I am running the first stage at nearly 35dB of gain at audio frequencies. When this UHF RF is damped, however, they are very quiet and sound very good. Quite a lot quieter than the general purpose transistors I previously used! #HamRadio #AmateurRadio
I'm designing a discrete component audio amplifier to stand in for the one from the Soldersmoke DCR for my next radio build. The original is intentionally simple, to make understanding it easy. That makes sense.
Mine is less simple but still only 3 transistors. I'm using two BFR193s and a 2n3904. It is derived from the Soldersmoke design, so it's still single-ended, with an audio transformer. It does 85-90dB of gain (much more!) with flatter audio frequency response. #HamRadio #AmateurRadio
The Ethernet transformer mixer with 1N4148 diodes works great! There’s a contest on 40 today and I have heard Italy, Spain, Russia, Germany, Britain, Belgium, the Netherlands, Switzerland, and Sweden on this radio with that mixer in the last hour. My transformer package contains two sets of transformers. Here I’m using only one set. But for a superhet radio you’d have two mixers worth in a small package. #HamRadio #AmateurRadio
I designed and 3D printed some subdividers for my Lidl storage drawer set so that I can put a lot of small components in there. Very happy with this! #HamRadio #AmateurRadio
If you are building your own radio stuff, this looks like a pretty darn great deal on a (5 pack of) 6W-capable UHF MOSFET:
https://theelectronicgoldmine.com/products/g28282
Ship to limited countries, be warned.
I got a much better video of my direct conversion receiver listening to SSB, after band conditions improved.
Very pleased with this radio! #HamRadio #AmateurRadio
I got a good idea from PA0PHH that you can use cheap Ethernet transformers for RF mixer transformers. Man, they are cheap. I ordered 10 for €8.25 from Aliexpress. Each one has two sets, so one will do a whole mixer. Cheaper than toroids and no faffing with trifilar windings! I will give it a try when they get here. #HamRadio #AmateurRadio
I got my direct conversion receiver working! Band conditions are not amazing at the moment, but you can clearly hear the SSB I was listening to.
I designed and assembled a case for my Pi Pico/Si5351 VFO that makes it a lot easier and safer to move around on the bench. Good learning for my 3D printer skills. I am working on a knob design but for now using one that’s a little short. That OLED is blue/yellow and looks good. #HamRadio #AmateurRadio
I finally assembled my Soldersmoke DC Receiver last weekend but it was not working well. I spent the week debugging. I could receive CW well but not SSB. It is very garbled. I swapped around some parts and tracked the problem to mixer build!
Today, I built a drop-in ADE-1 based mixer to test... and 💥 beautiful SSB. So I have to debug my mixer. I have a little oscillation in the audio amp, but here's a video showing how good it sounds when right #HamRadio #AmateurRadio https://youtu.be/Rvzcj72Q8lc