Topband: Modification of the INRAD Roofing Filter Kit

Paul Baldock pbaldock at
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.

- Paul

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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