I'm 85 years old and I have too many projects. I learned radio in the USAF in the 1950's when they had tubes.
I have been studying the Burdick designs from the NC40 through the K3.
They are all based on the 4.915MHz crystal IF.
The NC-40 is a single band unit. All the others use the same conversion scheme. All the necessary crystals for the HF conversion are available.
The NC40, NC Sierra, and K1 do not have RF amps. The K2 and K3 do have RF amps.
I have been reading about the problems of using a QSD above 20M. Most old receivers had poor performance above 20M. The solution was a preselector or converter. NO MAGIC!
I'm looking to build a transceiver using a QRP Labs receiver module to replace the 4.915MHz IF stage. But I would run it as a 4.915 QSD. Then use a NE-602 mixer and RF amplifier in front of it.
My first effort would be to get a receiver working. Then do the transmitter. I would like both CW and SSB if possible. But I don't know how the SDRs generate SSB.
I have 3 NC-40 PCBs here ready to build. I found a lot of the capacitors on the parts list are no longer available. But I think I have found substitutes. I just need to accumulate the parts ONE PIECE AT A TIME when I have the money.
And I did order most of the parts for a NorCal Sierra from Germany. I hope they show up. I plan to use a DDS with it.
My intention is to produce a variation on the Burdick design that does not require the matched crystals.
If the good parts of what I read about the QSD are true it should work.
FWTW:
There are some things about the QRP Labs products I just don't like. I do have a QRP Labs VFO kit that I have not assembled. I also have their Arduino Shield with the SI5351 DDS.
Bob Macklin
K5MYJ
Seattle, Wa
