The DCI filters are VERY good but are designed, as standard, to provide a bandpass between 144-148MHz!
I guess a special version that is either much narrower, or is setup for 142-146MHz, might give maybe 20dB of attenuation ...maybe this plus your cavity as a suck out notch/rejecter after preamp would be a winning combination?
good luck
Graham
G3VZV
----- Original Message ----- From: "John Geiger" aa5jg@fidmail.com To: "Werner Kullmann, HB9BNK" hb9bnk@uska.ch; amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 3:04 PM Subject: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz
I believe DCI makes a 144-146 bandpass filter.
73s John AA5JG
----- Original Message ----- From: "Werner Kullmann, HB9BNK" hb9bnk@uska.ch To: amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 1:41 PM 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
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