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Subject: [AMPS] IMD
From: Mike" < (Mike)
Date: Tue, 18 Sep 2001 22:05:41 -0700
What is the limitation, the close-spaced IM of the typical receiver, or 
is it actually a limitation in Spectrum lab's FFT algorithm (I haven't 
tried resolving closely spaced signals with spectrum lab)?

I have done some very crude tests here with 1 KHz tone spacing
and using the CW filter in my R4C and a step attenuator to resolve 
level of IM sidebands coming from my rig. The levels seem about
right, but I have never done any tests to validate this (I don't have
a spectrum analyzer here). 

This brings up another question that I have been meaning to ask. 
When testing amplifiers how does ARRL generate the two-tones.
Are they high level combining  the output of two trasceivers each 
generating a CW signal, or do they combine tones at a low level
and run them thru an ultra clean "golden" PA?

Mike, W4EF.............

----- Original Message ----- 
From: "Tom Rauch" <>
To: "AMPS" <>; "Peter Chadwick" 
<>; "Mike" <>
Sent: Tuesday, September 18, 2001 6:59 PM
Subject: Re: [AMPS] IMD

> > Has anyone had any luck using receiver feeding a soundcard in
> > conjunction with a program like Spectrum Lab to resolve the closely
> > spaced IM sidebands from a PA?
> No, and it won't work in that application Mike. 
> I do use spectrum lab for receiver testing, but only to sort out the 
> desired signal from filter blowby and other noises.
> 73, Tom W8JI
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