This document is written in English for overseas OMs. -DS1ORJ-
R-2008 BFO oscillator is very simple structure.
The SSB modulation/demodulation BFO of R2008 has poor frequency stability.
BFO stability can be improved with a 455KHz ceramic resonator (2 terminals).
I use the ceramic resonator pictured above.
Please refer to the circuit diagram below for the installation location.
With this modification, the BFO variable bandwidth is reduced to 80Hz.
If you want a wider range, add a 300pF varicap (varicap for MF broadcasting -AM- ). This provides a variable width of about 300 Hz.
With this modification you can reach BFO accuracy below 1Hz.
Despite the stable BFO, you can still feel the frequency shift in SSB demodulation.
This is a stability issue of the RF synthesizer of this equipment.
And the stability of the RF synthesizer depends on the stability of the power supply.
We can see improved the powersupply stability in later model schematic. (with modifications to the RF synthesizer)
If you have any questions, please send an email to codeart74@daum.net.