As Project Yamhill nears actual physical implementation, it’s time to start building some more real-time, two-way communication. We’re starting to get some beta testing and discussions going! If you’d like to participate in Project Yamhill chat, please click on the link below. Thank you!
This is going to be a brief update, as I’m in the middle of looking for a new job yet again, trying to get some last minute projects done around the property, and squeezing in time to try to complete this transceiver soon so that I can get on to the stage of laying out a PCB and coming up with a mechanical design.
I managed to build up the transmit driver circuit, T/R switch, and write the firmware that will support keying and controlling the Si5351A on transmit. The transmit driver device that I’m using is a BS170 MOSFET, which when driven by the Si5351A at max drive power will provide well over 500 mW of output power, which is more than enough to drive the final power amplifier stage.
After rigging everything up and giving it some test keying on the bench into a dummy load, the muting and the T/R switching sounded great, and I figured it would be a lot of fun to try to get some QSOs in with the new transceiver even before finishing the 5 watt power amplifier. Conditions are good right now when we’re in between solar flares, so 500 mW CW should be able to snag some QSOs.
Without further ado, here is my very first QSO with the MAX2681 transceiver. At this point the keying is a bit funky because my firmware wasn’t 100% nailed down, but I was so eager to try to make a QSO that I did it anyway. Sorry to the op on the other end, but thank you for the QSO.
After this contact, I got back to the PC to tidy up the firmware so that the keying was rock solid, as to not inflict more bad keying and low power to the next op. They’ll just have to deal with low power.
A 579 on that one, not bad! POTA ops tend to be fairly honest with their signal reports, so I don’t think I was much of a burden to have a QSO with. This last one however, was a tad more difficult for the other op. Please excuse the slight overloading on the recording at the beginning.
329 report, but the op wasn’t too busy and it only took a couple of extra tries. Over all, the radio performed really well, and it was fun to use, even as QRPp.
What’s Next
The finish line is in sight for this rig! At this point, I have all of the receiver done and all of the supporting circuitry finished which will make this a complete transceiver. The last bit is to assemble the 5 watt power amplifier that I’ve sketched out in my notebook and give it a go. This is a bog-standard Class D MOSFET amplifier design, so I don’t expect any rude surprises here. The only difference between this PA and others is what I think is a unique choice of device. Once this is built up and ready to use, I’m hoping to drag this fragile monstrosity out for a POTA activation, to give it a real trial under fire. Stay tuned!
Congrats on your progress Jason -- well done. The BS170 part remains a stalwart in the QRP transmit chain arsenal. That's so cool (as it was 25 years ago). Glad to hear those QSO's -- sound great. Best! T