[Collins] Testing Collins mechanical filters

[Dr. Gerald N. Johnson]

On Mon, 2009-10-05 at 18:59 -0400, Greg Mijal wrote:
> Hi:
> 
> Picked up a batch of Collins mechanical filters and have a couple of questions
> 
> To check activity, would a 50k ohm resistor and 130 pf across each set of end terminals allow the filter to properly respond to a signal generator and oscilloscope or spectrum analyzer?
> 
More typically a 100K resistor. Series for the low impedance generator,
and shunt for the high impedance scope, series for the low impedance
spectrum analyzer. Alternatively the capacitor can be in series to
series tune either or both transducer coils for low impedance. Probably
not a perfect match to 50 ohms, but that will keep from loading down the
filter. The capacitors can be variable to allow peaking at the pass band
center which often improves the passband ripple.

> Also, I cannot seem to find data for all the various part numbers on the body of the filters.
> Such as:
> F 455 Z5 2V2
> F 455 Z5 8T2
> F 455 Z5 10T2

I think the 2V2, 8T2, and 10T2 are date codes of some sort. The filter
model for these is F 455 Z5, I think a single sideband filter for 455
KHz carrier frequency. 

In other filters like a F 455 FA 21 used in later S-line, the FA is case
and 21 is the bandwidth in 100s of Hz. Z filters don't fit that mold,
but any other letters in the middle designate the case. There is a
mechanical filter catalog available on line dating from about 1964.

> and about 15 more
> Thanks
> Greg
> WA7LYO
> Kinston NC

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer