Werner, Since you are using a very good rig and adding a great preamp, to hear what you are after and expense involved might be as simple as adjusting the gain (SP2000 indicates it is adjustable and already has a helical front end) so as to stop this interference. Doing this simple thing might correct everything--Let us know if it works. I adjusted the gain of my preamp to stop similar type intermod. 73, Dee, NB2F
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Werner Kullmann, HB9BNK Sent: Wednesday, April 27, 2011 9:42 AM To: amsat-bb@amsat.org Subject: [amsat-bb] searching advice on low hpass filter for 146 MHz
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 distorted.
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 !
Werner, HB9BNK _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb