On 4/8/2025 2:46 PM, Mike via groups.io wrote:
Never mind, I looked it up and its a custom 10.7MHz crystal filter using four discreet crystals. If you have the equipment you could sweep it for response then shop for a packaged filter with better specs. I don't see any adjustment or matching on the filter output to the receiver IC so its hard to say how well a drop in filter will perform but it may not be too bad.
The OP has inquired how to improve input selectivity - not I-F selectivity.? Go back and re-read the inquiry.
Kevin W3KKC
Kevin Custer