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Re: Mode J Recieve Desense Problems



Steve,
You may want to give an inexpensive duplexer a try.  I use an MFJ duplexer to 
solve this problem:  they cost $29 and are rated at 200 Watts.  I'm sure the 
other brands are similar designs:  a low pass filter on the 2m side and a 
band pass filter on the 70 cm side.  I use only one side at a time for this 
application.

I had more luck with putting the duplexer just ahead of my 70 cm preamp (in 
the attic) than I did on the 2m output side.  The 2m "fix" cut the noise down 
by about 6 or 9 dB, but putting it ahead of the 70 cm preamp took the 
offending signals down into the noise.  The signal loss thru the duplexer is 
undetectable to me in everyday operation.

73 es GL,
Jerry, K5OE

>  Does anyone know a
>  less expensive 2m low-pass filter for sale? The Handbook seems to
>  suggest that one can build a Butterworth filter...and they supply the
>  engineering info in chart form to do it. Has anyone built one?
>  
>  I am opening this topic up for general comment. Anyone have alternate
>  suggestions for fixing 70cm desense? Also, does the same problem happen
>  in reverse in Mode B?
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