[Collins] mech. filter

[Gerald]

On Wed, 2005-06-15 at 08:05 +0000, Jochen Wittmann wrote:
> Jochen Wittmann   Ahornallee 86   D33330 Guetersloh  
> Germany                                    
> Fone : 00495241/38737   Fax: 00495241/39893 
> Call : DE1JWE                                                                      
> Email: jwguetersloh at t-online.de                                                                
> WEB: www.jgtfunk.de  
> x
> -----------------------------------------June,15.,05 
> Re. : Collins-mailing-forum 
> Here: mech. filter      
> Email: collins at mailman.qth.net   
> x
> Good morning ! 
> Again I need the help of the Collins-community. 
> Here I have a heavy problem with the signal process in an KWM-2. 
> Definitely the mech. filter (pno:526-9427-000 or 526-9337-000) is defective. No signal from the BFO passes this filter using TUNE or LOCK KEY. Is there anybody having such a filter on >stock< before I ask INRAD ? 
> Another question : 
> Is there anybody who can show me the files about mech. filters which were published on the CRA-site ? I have lost this files after a computer-crash. 
> Thank you for your troubles.  
> Regards from Germany (73) 
> Jochen (Jo) 

Then the radio should not receive as all received signals have to pass
through the same filter. In most KWM-2, the BFO signal never passes
through the filter, instead an audio tone from the sidetone oscillator
modulates the BFO in the balanced modulator to produce a carrier. That
audio tone frequency was chosen to be higher than nice for receive so
that its harmonics would not pass through the filter. Like the 32S-1,
not like the 32S-3. Its possible later KWM-2 might have been changed to
work like the 32S-3, but I don't know of it.

The 526-9427-00 and 526-9337-00 filters are in different cases. The 9337
is a F455Y21 in a round metal case with solder terminals out the ends.
The 9427 is the later plastic cased filter generally used in the later
75S receivers as a plug in though it was soldered in in the 32S-3. Its
type F455FA21, electrically interchangeable but not mechanically
interchangeable.

The Collin Collector's Association web page has a copy of the Collins
Mechanical filter bulletin 1031B available for download. Start at:
http://www.collinsradio.org/ There may still be filter information on
the CRA site as well.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer