[Collins] Mechanical filters

[Dr. Gerald N. Johnson]

On Tue, 2009-10-06 at 08:02 -0400, Albert Santangelo wrote:
> Does anyone on the list that have information/experience, or has taken the case off or taken apart s F455F or F455D style mechanical filter. Can the coil/transducers from such filters can physically be retrofitted into a F455FA style mechanical filter housing.
> 
That might prove very difficult. The filter I had open was much earlier
and used all the available space in the case for filter elements.
Wouldn't shrink any, and needs a complex mounting. Besides its a
delicate assembly in the open.

> I would like to use a 3.1 kc filter in my 75S3B receiver. I have a F455F-31 and a F455D-31, with a F455FA-21 surplus to my needs to retrofit if this could done.
> 
Make a base to fit the two transistor sockets and wire the 3.1 KHz
filters to fit. You might not be able to fit the magnetic shield, but
each filter can be covered with a iron or steel magnetic shield if not
in a metal case. The magnetic shield is needed more for the plastic
cased (FA) filter. TO5 transistors fit the filter sockets directly. I
just checked a filter, it fits a perfboard with 0.1" spacing and one pad
per hole. Like a RS 276-152A. Use TO5 transistor leads for the pins.

The FA 21 has considerable value on its own. Unless its faulty its worth
way more than being taken apart for the base.

> Thanks,
> 
> Al Santangelo VE3AJM

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