I think there are TWO incompatible applications being discussed:
1) The original request was for narrowband BPF for portable operating on a mountain top in the presence of commercial transmitters. Usually needs a relatively large cavity or heloical resonator. This is for the annual APpalachian Trail GOlden Packet event 17 July http://aprs.org/at-golden-packet.html
2) The more common AMSAT need for a LPF to prevent front end overload of the third harmonic of a VHF upllink into the UHF receiver.
The solutions are very different. - Bob, WB4APR
On Thu, Jun 10, 2021 at 2:08 PM Joseph B. Fitzgerald < [email protected]> wrote:
Mini-circuits has sub $100 filters available suitable for receiving applications:
https://www.minicircuits.com/WebStore/RF-Filters.html
Meeting the 0.5 dB insertion loss specification might be difficult though.
-Joe KM1P
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