Hi all, I have fixed the broken inductor ground connections in the 206 MHz band-pass filter and have trimmed the amplifier-filter combination. This solved my 14 dB gain loss issue in the RF part, see picture
. I have a gain adjustment margin of about +1.5 dB (cal. screw) and this is ok for the moment. I managed to do the auto calibration and for what I have seen so far is that it does not freeze anymore. I have trimmed the 206 MHz BPF based on the service manual instructions on page 11-65. According my paper manual version the maximum gain ripple has to be smaller than 0.3 dB, a symmetric response with a maximum level. The picture in the manual suggests that it has to be flat in a certain bandwidth but this not specified. I’m not sure what the right response has to be, I assume a narrow bandwidth, see my picture. Jeremy do you want to perform one more measurement for me, please? You only have to connect the tracking to input-1 and press some key’s. I’m curious how your 206 MHz BPF response looks like.
Best regards,
Lex