[Collins] MM1 mic and filters

[Dr.Gerald Johnson]

I don't find any information in my files on these particular filter part numbers. 
By the nomenclature they are case type C and bandwidths are as you 
have surmised.

As for used on, I have no idea. Collins sold and sells mechanical filters as 
components to the radio industry world wide, often through distributors so 
there may not be information at Collins to show what the parts were used 
on.

For all filter cases and nomenclatures except those with Z after the 
frequency, the last digits are the bandwidth in 100 HZ. So your F455C 31 is 
455 KHz center frequency, C case, and 3.1 KHz bandwidth.

An F455Z 05 probably has 455 KHz 20 dB down a slope, and is a single side 
band filter. Some are upper, some are lower, you need their specifications 
or to measure the filter. Z filters can have any case and can have any 
bandwidth and that bandwidth can be above or below the specified 
frequency.

In general measuring a mechanical filter with signal generator and indicator 
like RF VTVM or wide band oscilloscope will show the pass band 
accurately, but without proper tuning and impedance patching of the 
transducers the insertion loss may not be measure accurately. Termination 
may have some detectable effects on passband ripple.

I've been away from home since before Thanksgiving, but I'm home for a 
while. My dad, K0CPN, is now a silent key, his health was my main concern 
during most of that time period.

73, Jerry, K0CQ, Technical Advisor to the CRA

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.