[1000mp] Improving the Close Spaced IM3 DR on the Mark V with Inrad Roofing Filter Mod

[Pete Smith]

Perhaps I missed it, but I did not see anything in the article about how to 
determine if your particular roofing filter has the excessive gain.  I 
tried mine (a fairly early one) with an Elecraft XG-1 signal source, and 
adjusted the IF gain for S-9 at 50 uV, which required a setting of 12.  I'm 
not sure now what the original default setting was, because before the 
roofing filter I had the Inrad IF mod in there.

I have not noticed the IMD deterioration that Mike talks about.

73, Pete N4ZR

   At 08:46 AM 1/27/2008, cherokeehillfarm at earthlink.net wrote:
>Improving the Close Spaced IM3 DR on the Mark V with Inrad Roofing Filter Mod
>
>Hello 1000MP Fans:
>
>I came across an interesting posting on the Contest Group of Quebec website.
>The posting is from November 26, 2007, from Gilles, VE2TZT.
>
>Although written in French, it appears that Gilles had quite a problem
>during contesting with the new Inrad Roofing Filter installed in his Mark V.
>You can see his posting here:
>
>http://contestgroupduquebec.com/index.php?option=com_simpleboard&Itemid=41&func=view&id=528&catid=2
>
>My rough translation of his problem is as follows:
>
>"For the last WPX CW, I had installed the roofing filter INRAD (other
>modifications Noise Blanker and key clicks already carried out with by
>before) and I had been rather disappointed by the results (not found an
>unspecified improvement, to see even a degradation of intermodulation on
>strong close signals in particular on 40m where I have a good antenna). This
>observation appeared to me in contradiction with the measurements taken by
>the ARRL in the QST of February 2005."
>
>So basically he says that he didn't see any improvement advantage after
>installing the Inrad filter, and he even experienced a degradation of the
>resistance to intermodulation products on 40 meters where he has a
>particularly good antenna.
>
>His article concludes that performing the simple modification to the Inrad
>Roofing Filter board as suggested on the VA3CR website, fixed the problem,
>and he has now no issues while contesting.
>
>For those of you that are interested in addressing the same issue, you may
>read about this modification here:
>
>http://www.va3cr.net/mods/roofingfiltermodmarkV.htm
>
>73 and Happy DXing,
>
>Mike
>W2AJI
>
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