I have received the 40.5Mhz crystals I ordered for use in the SoftRock to
allow operation on 30M. It is not going to be strictly plug and play. I
built my first Softrock with a socket for the crystal, and have been able to
get it to run with several crystals that run at less than the "stock" 28.224
Mhz. Was listening to 80M last night with a 14.318 Mhz xtal in there (Rx
center freq abt 3.58 Mhz) signals were slightly down due to the front end
filter, but it worked pretty well- Except for some 40M SWBC images.
I cannot get the 40.5Mhz crystals to fire in an unmodified SR40. I
breadboarded the oscillator cicuit from the SR40, and WAS able to get the
crystals to work if I removed C6 and C7 (100pf). When I replaced them with
33pf caps, I could get both the original crystal, and the 40.5Mhz crystal to
fire up fine. However, I could not repeat this by replacing C6 and C7 on a
SR40 circuit board. I'm not sure yet what the difference is (between my
breadboard lash-up and the PC board, maybe other stray capacitances) I do
plan to do some additional experimenting. Possibly my stock of 2n3904s are
better(?) The ones supplied should work at this freq ok, so I'm not sure.
In any event, I am now sure these crystals work on the fundamental freq of
40.5Mhz. It looks like some mods will need to be done to a board to allow
operation at that high a freq.
I'll keep ya all posted.
73,
Bruce N1RX
