[amsat-bb] Re: searching advice on low hpass filter for 146 MHz

[Graham Shirville]

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 at fidmail.com>
To: "Werner Kullmann, HB9BNK" <hb9bnk at uska.ch>; <amsat-bb at 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 at uska.ch>
> To: <amsat-bb at 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
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