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Stephen, thank you so much for the note. I plan to do more soon. I'm going to go through the latest build board by board and talk through the challenges. Some will be here and some will be on my blog.

Dino - the enclosure design is mostly in my head - but I bought a wooden craft box made famous by N2CQR and have lined it with copper tape. The plan is to have one ribbon cable from the Pi to the box - or maybe two - one for digital and one for audio. I'm going to 3D print an enclosure for the Pi, hat and touch screen display and set it on top of the wooden enclosure.

Yes - in the final version a voltage divider at the base. One 10K in series, and one to ground,

Thanks Andy! I did hit on the voltage divider idea as you'll see in one of the follow on videos. It hadn't occured to me to try a 2N7000 but that is a great suggestion. I wonder is the MOSFET will be less prone to partial conduction in the presence of RF. Given the low voltage output on the GPIO lines it makes wonder why virtually every online tutorial uses a 2N3904 and does not use a voltage divider at the base of the transistor. Does no-one test their circuits before they publish?

@@kk4das122 in their defense the GPIO pins are connected to the IO of the broadcom chip and the actual spec is not well published. I found a few bits on the web that gave the info. I suspect that many people fall into the trap of thinking that GPIO low = 0V. It's very unfortunate that the low output is right on the usual transistor threshold voltage and I suspect that is many cases it seems to work OK. Regardless you should have some sort of buffer / circuit that takes cane of such things. There are quite a few chips that will do level and logic conversion, but the cost is more components (The chips are cheap) The Pi 5 has a different GPIO interface, I think I read that they have taken the I/O control of the Pi Pico and used that to buffer the broadcom I/O. However I've not got a Pi 5 as yet so just going by what I've read. The 7000, they seem pretty solid, a resistor from gate to ground to ensure that it turns off and decouple that with a 0.01 ceramic and it should do the job nicely. The big plus is that it does not draw any current as such from the GPIO so that helps protect things. You have more danger from pick-up on the wires than anything else, so it pays to take a bit of care with that. Just about to have a look at the other videos... Andy G0POY

I picked up a pair of those speakers for $2 at the Vienna Wireless Winterfest last year. They are terrific little speakers and great for our applications.

Thank you Paul - it was a lot of fun to build and this was one of my very first successes with a homebrew transceiver. Much progress and learning since then - check out the rest of the channel and my blog at https:\\kk4das.blogspot.com

Yes, I bought a wood project box on Amazon. I'm going to line it with copper tape for shielding and ground plane. I'm just starting to Noodle over the design right now.

Hi - I doubt it will work with a Pi 1 Model B. Head over to groups.io/g/BITX20/ for all your sBitx questions.

Thanks Hank - I plan to do some re-engineering of some of the boards before I package it up. The IF module is about 4 times as large as it needs to be and I can consolidate the Tx stages. The IF was a repurposed spare from a prior project that was not nearly as space constrained. By the way, as of this AM I have worked 9 of the 13 Colony special event stations, plus one of the bonus stations - all SSB- on 80,40 and 20.

Thank you so much. I'm just starting to work on the box now. I had a couple of more Gremlins to get out but I think I licked at this point.

Me too! Now that I'm running out of problems to debug with the rig I can turn to my antenna. I have a hex beam, tripod and rotator brand-new in the box waiting for my attention.

Hi Todd - The RD15 is designed as 12.5V device. It is not meant to be a high voltage device like the IRF switching transistors. At 13.8V it is almost impossible to burn up. I have not tried running at higher voltage since the max Vdss is 30V and ideally you want to run no more than 50% of that for safety margin. If you run it at 24V I would think you would risk blowing it up. The advantage of the RD transistors over the IRF line is they are designed for RF and have much better operating curves for RF amplification purposes.

Dino - thanks so much. I'm looking forward to buttoning it up also - this has been a long-haul build - I began in ernest last fall. I'm putting up a hex and when Bill puts one up am I certain we can get a QSO. 73-Dean

Hi Frank, sorry for the delayed response. The SBITX software has a feature called IF gain. You reduce noise by lowering the IF gain control until you just barely see the peaks of the noise floor on the waterfall. The microphone is 100% homebrew using a hi-gain electret mic element. The commercial rig has a built-in mic and speaker but also has provisions for an external mic and speaker.

@@kk4das122 Thanks for the reply and info! 73

Thanks. Power out is 5 watts across HF for now. I plan to build a 20 watt PA using Mitsubishi RD16HHF1 transistors.

Todd - yes - pretty low noise floor on 75M. And the receiver just sounds good. I can adjust the IF gain (the SBITX SDR equivalent of RF gain) such that the signal really pops out.

Todd - you should definitely join me on this journey. I've asked but am not aware of anyone else actively homebrewing an sBITX. Anyone out there taking the sBITX challenge?

Indeed you do....and many more 3, 4 and 5 ways since. My latest project is a 10m double sideband rig. More to come on that soon.

The correct library is LiquidCrystal I2C. You should be able to download it from the Arduino Library Manager. Or you can get it from github. github.com/johnrickman/LiquidCrystal_I2C

Yes - thanks for the comment. I'll do an on-air demonstration when I get a chance. The rig is working great - with consistently good audio reports. I'm working up to a live demo for our club next week.

Thanks Paul. I only tested to 30MHz but it was pretty flat gain across the band. I haven't put it on the air except for a brief test - waiting for my o'scope to come back from Rigol. Wouldn't you know it, right in the middle of testing the amp one channel on the scope decided to die? .Left me puzzled for a bit until I realized the problem was the test equipment.

Hi Paul - in the rig I am getting 20 watts clean out on 20 and 40 meters (those are the only two bands my homebrew is setup for).

You are welcome. I think this is going to be a good little amp for my QRP rig. Love to hear about your progress. 73 - Dean, KK4DAS

Dean Souleles. Thanks for the reply Dean. My bps filter seems to test ok, although I had to remove one turn on the toroids to get it centered on the 40m ham band. I finally got to use the nanovna I bought months ago to check it ( I knew I bought it for a reason!). Next is the rf board with the 310’s. Also, I have to start mounting everything to piece of plywood. I’m learning a lot for a 63 year old. Bob

Bob - will do. Over the last few weeks I built the TX driver, final amp and low pass filter and made my first contacts with the rig just this morning! Check out the blog. I'm planning to do a series of posts and videos, board by board over the next few weeks. I can confirm that Pete truly is the Wizard of Newbury Park.

Dean, What Blog is that? Pete’s? I’m am into procuring parts online as I don’t have much of a junk box, but I will after this is done. This week, I’m hoping to get the vfo up and running.

@@icefloe78 Hi Bob - I'll be posting on my blog - kk4das.blogspot.com