Hello Andrew / KM4TRT,
I built the SPECAN approx. 2 years ago after almost 40 years of absence from ham radio.
I also had problems with the 100MHz oscillator: I also used a MPF102 and I could tune it to 100MHz with a wire instead of the crystal. After I put the crystal in, it was not more stable than with the wire!
Due to that I decided for a different design, depicted in the Analog Devices AN-419 "A Discrete, Low Phase Noise, 125 MHz Crystal Oscillator". I only built the oscillator with the MPSH10 replaced by a BFW92 as far as I remember. Instead of the MC10ELT21 as an amplofier I used (1) an MMIC together with the ADE-1 mixer, (2) fed with a 6dB attenuator an AD831 mixer instead of the ADE-1.
Generally I have not been able, to get the SPECAN free of spurs, so that I finally abandonded the project and moved to the TinySA. The TinySA design was started by Erik Kaeshook also in this HBTE group. I built several of those following the evolution of the project.
--
Joerg, DB2OO
