[R-390] Dave Curry R-390A Filters

[ToddRoberts2001 at aol.com]

In a message dated 8/28/2006 8:30:47 AM Eastern Standard Time, 
Craig.Anderson at saintpaul.edu writes:
I have a 6 KHz Dave Curry made R-390A filter and I am about to install
it in a '68 production EAC.  My question is...if someone out there has
installed one of these filters before do you leave intact the fixed and
variable cap that is across the current mechanical filters.  There were
no instructions about installation and yet I read an article in ER that
recommends bypassing the fixed and variable cap and hooking it up
direct.  If anyone has any other information I would appreciate hearing
from you before I install this in place of my 8 KHz filter.
Craig W9CLA

Hi Craig, it seems the filter should have come with clear instructions as to 
whether to use the existing resonating caps in the R-390A when installing the 
filter. My guess is he used one of the Collins Low Cost Series Torsional 
mechanical filters inside a metal tube the same size as the original filter. 
Collins recommends using fixed 30pf caps (mica preferred) across the input and 
output pins of the filter. I would guess that he installed the correct resonating 
caps already inside the metal filter tube, so there would be no need and would 
actually be harmful to try to re-use the original resonating caps as they 
would detune the filter. Only the original mechanical filters would correctly 
resonate with the original capacitors. 73 Todd WD4NGG