Topband: Modification of the INRAD Roofing Filter Kit
pbaldock at verizon.net
Sun Oct 21 19:48:39 EDT 2007
You are right it does creep over time. What I finally noticed was not
a change in gain, but a difference in frequency response between LSB
and USB, most easily detected by listen to background noise - an easy test.
Once I determined that the roofing filter was fault INRAD replaced it
immediately for free.
At 07:32 AM 10/21/2007, Dennis W0JX wrote:
>Paul: Regarding filter failures, I believe there have been a number
>of them out there. What happens over time is that the resonant
>center frequency changes over time and inserion loss increases. It
>is very subtle and one does not notice it until the main RX starts
>acting like it is deaf. I finally found the problem by using an
>Elecraft XG-2. Thought I blew out the front end but it turned out to
>be in the IF.
> I had to crank the 9-1 menu setting up to 17 to restore the
> signal level to S-9. Obtaining a new filter fixed the problem. When
> installing a mod like this, it is valuable to record your original
> gain settings and check them from time to time.
> Bjorn: The INRAD roofing filter is still a valuable modification.
> There is a two stage amp following the filter which makes up the
> regular filter loss and adds a bit of gain. According to W2AGI, it
> adds too much gain which is why it might be deteriorating the IMD
> performance. Mike's mod cuts the gain in the two-stage amp back a bit.
> 73, Dennis W0JX/8 Milan, OH
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