Nice work Charlie ! I used a similar approach in my home brew ft8 rig , using a discrete transistor schmitt trigger to square off the input tones coming in from WSJT-X , then using the input capture modules to work out the timing and the frequency (I used a dsPic3012). Works quite well , I have logged a couple of ZL's on 20m using this arrangement. The front end receiver is not the greatest , just a crap ne612 neophyte arrangement with an Opamp/lm386 audio stage- but it works. Hopefully we can have a QSO once you are done with yours!! 73 Ash M0LKA
That's interesting Ash. I might have to clean up the Si5351 output before amplifying with the BS170s. Having said that, I didn't for the CW rig and that worked well. We'll have to see. As for the QSO, most definitely. 73 Charlie
As I recall, The si5351a didn't have enough umph to drive 3 paralleled bs170's hard enough to get usable output at 20m , so I used a the AC version of the 7414 with a couple of gates in parallel as a driver. This , at least in my case helped with getting faster edges and the ability to push more power in to the bs170's (which run class D), and finally I got around 2~3 watts . The squaring up helps keep the bs170's cool as the linear excursion time is kept to minimum (I didn't need heat sinks). I have to say a lot of the design decisions were influenced by your experiments on the class E amplifier videos you did a while back!
Neat idea to drive a simple Tx by counting the audio tones at an ADC port, I wonder how fast the trusty old Nano can go using the PJMS Frequency lib. The detected tone frequency becomes an offset to the si5351, so easy. Add 3xBS170 and youve got a beacon. Another idea, you could connect an electret up to Paul's 74HC14 squarer and hold a smartphone next to it running a ham digital app, like Peter Parker does to transmit WSPR using just a phone, the app and his FT817. 🤓👍
Hi Paul. Yes, it worked out very well. Just need to add the RF amplification and filtering, and the TX will be done. The smartphone app sounds interesting.
So if I understand correctly, Computer A sends an abbreviated FT8 signal (for test purposes) out to the usb sound card. The sound card output is input to the NANO then the S15351 then out on clock 0 to an rf antenna . The rf is picked up by a regular hf radio also on the bench that talks to computer B running ft8 software and shows the receive/send cycle. Sweet ! 8-) So the receive side on the ft8 signal on Computer A is just some sort of test signal ? The vox switching is a great idea ! Keeping the prototype on a breadboard is cool. But that leads me to my next worry. What will you use for the Tayloe detector on the receiver side ? Will you be using a surface mount chip ? I am a sub-par solderer. So my surface mount soldering might fail. Any hints ?
Gidday Phillip. Yes, it was full end-to-end check from one PC top another via RF. I'll be using through hole components, as I have not made the transition to SMD. I can prototype so much faster with through hole. One day though, I'll have to make the transition.
Does the USB sound card support both stereo output and stereo input? I have been searching unsuccessfully for such a device, preferably with line-level stereo inputs. I can find zillions of devices with stereo headphone output and mono mic input, but not with stereo inputs. If yours is stereo out and in, can you provide a link or a part number for ordering? Or can you provide the part number of the IC on the board? Thanks, I really enjoy your videos!
Hi. Yes it is stereo. Unfortunately, is a black blob with no markings. It cost 66c off our local TradeMe website. I've checked the listing and it does not have any part numbers or any other identifying features. Sorry about that.
Hi, Im Hans (OE2EJN) - I'think it's a Cmedia Chip CM108B or newer. It's a cheap chip, when available. It is a 16bit usb stereo audio codex. Its is also the chip inside DigiRig ! Charlie you inspire me to come back to ham radio and DIY. Thank you for all your very nice and very good videos !!! vy 73, Hans
