[R-390] Filters

[Drew P.]

Bob Camp wrote: 

Another thing the filters share a background with are the Vibrasponder / Vibrasender PL tone reeds used in FM two way gear.

[snipped]

Another IF filter solution similar to that used in some old FM two way gear could be used - a big bunch of cascaded LC tuned circuits like the old "Permakay" filters.  These would occupy much space and hence would limit you to perhaps 2 bandwidth choices within the space inside the filter cover. Bandwidth curve shape would not be as good as the mechanical filters, but would be much better than a flat zero non-functional filter. 

I am following this thread with interest as I have a Stewart-Warner with a defunct 4 kc "mechanism a philharmonic".

Drew