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Re: Plagued with Mode J "noise" on TX



I have found the 70cm filter works fine here.  Most of the problem was
caused in my radios by the 2M signal getting into the 70cm receiver front
end where the third harmonic was then generated in non linear devices.  The
70cm banspass filter keeps out the 2M signal and then no third harmonic
signal is generated.  There could be some third harmonic stuff generated
externally and then pass through to the 70cm receiver, but in my case that
part was minor.

Jim Walls wrote:
> 
> Douglas Cole wrote:
> 
> > Scott Townley wrote:
> > >
> > <snip>
> 
> > What you really need to do is get a seperate antenna for each band and use the
> > DCI filters as they are a real "brick wall" when it comes to mode J desense (
> > well ok it is just my opinion) , or find yourself a nice bandpass cavity for the
> > vhf port etc.....
> 
> Keep in mind that a cavity filter will pass the 3rd harmonic just as well as the
> fundamental.  You need a low-pass filter of some sort.  That's why the multi-band
> diplexer has been suggested.
> 
> 73
> -----------------------
> Jim Walls - K6CCC
> k6ccc@amsat.org
> http://home.earthlink.net/~k6ccc/
> 626-302-8515    FAX  626-302-9999
> AMSAT member 32537 / WSWSS member 395
> 
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-- 
73, Roy

Internet: w0sl@amsat.org
Home Page: http://home.swbell.net/rdwelch
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