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Re: Replacing receiver filters for 38k4 reception



Hi Douglas
The CFW 455E is the NBFM type filter 15 Khz mostly black color, you can
replace it with a CF455B which is Orange in color mostly used in Broadcast
FM radios it has a bandwidth of maybe 75 khz or more should be available in
most electonic shops.
If you dont get it ask me I can put in a airmail cover to you.
Good luck
Best 73
Pop
VU2POP
Amsat India


----- Original Message ----- 
From: <Dquagliana@aol.com>
To: <amsat-bb@amsat.org>
Sent: Monday, March 28, 2005 2:29 AM
Subject: [amsat-bb] Replacing receiver filters for 38k4 reception


> I have an FM receiver kit that I'd like to
> modify for 38k4 reception from Echo. I need
> to make the bandwidth of the receiver wider
> in order to pass the 38k4 signal to the modem.
> According to the handy G3RUH reference at
>
> http://www.amsat.org/amsat/articles/g3ruh/109a.txt
>
> I need about 60 kHz bandwidth at the IF to
> pass a 38k4 signal.
>
> The first filter in the receiver is just a
> single crystal, which I think I can leave in
> the circuit as is.
>
> The second filter (FL2) in the receiver is,
> I think, a CFW455E, which has a bandwidth of
> about 15 kHz. This is too narrow for 38k4.
>
> Since this is a "no budget" ham radio project,
> can I get something that works if I replace the
> CFW455E filter with 0.001 uF capacitors? I'm
> not exactly sure how to do this since the
> filter has *three* pins.
>
> Suggestions? Has anyone already done this?
>
> Douglas KA2UPW
> ----
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----
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