[amsat-bb] searching advice on low hpass filter for 146 MHz
Werner Kullmann, HB9BNK
hb9bnk at uska.ch
Wed Apr 27 06:41:31 PDT 2011
To improve the reception of the sats on 145.9xx MHz with my
little yagi, I recently acquired a SSB-preamplifier SP-2000. To my
dismay, the reception on my IC910H was intermittend heavily
After a while I found, that a nearby located commercial
transmitter (POCSAG) emitting bursts on 147.300 is so strong, that
the frontend of the IC910H (or its AGC) practically quites the
receiver on 145.900. When the bursts stop, reception resumes.
Difficult to qso.
I have experimented with a large cavity filter and found, that the
impact of the bursts can be reduced, so that normal satellite work
is possible again.
Now I am looking for advice on how to build a steep low pass
filter, eliminating everything above 146 MHz, to be mounted before
the preamp on the mast. The filter must however be capable to
accept the rf power, if I work in V/U mode.
Thank you for any ideas !
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