On Sat, 21 Mar 2020 17:26:53 +0000 (UTC), you wrote:
D511 is a Toshiba RF PIN diode. The circuit switches capacitor C510 (10 pF) in parallel with C517 (12 pF)capacitor. This changes the characteristics of the low pass filter formed by C514, L505 and C517.Ah, I did not get that shift and hold register.
I was seeing it as a counter, sending pulses.
But your description is fine.
So it tunes the passband filter to various frequency ranges.
Will have to check that.
After the lightning I had to replace this D511 diode together with the
preamp FET and now sensitivity is down. Possibly another diode fault
or does it just need the receiver adjustment procedure, will see.
D511 was physically cracked in two parts, easy to spot.
ATTEN and PREAMP switching works obviously.
Must get that 7000 sensitivity back again.
Thank you for your help.