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[AMPS] Re:

To: <amps@contesting.com>
Subject: [AMPS] Re:
From: nx7u@primenet.com (Scott Townley)
Date: Wed, 29 Apr 1998 17:14:21
At 18:45 29.04.1998 -0500, Jon Ogden wrote:
>>I don't want to poo-poo parasitics, but there are some fundamental
>>engineering points that you should be sure of before coming to that
>>conclusion:
>
>And they are good points indeed!
>>
>>Be careful about overloading the spectrum analyzer. Most of them will
>>immediately produce all sorts of spurs on the display if driven above 0dBM
>>or whatever the peak limit of the instrument is. It only takes one carrier
>>or harmonic to do this, and make a real mess on the screen.
>
>Yes, yes, yes...Absolutely!  Back in my days of designing 16 tone linear 
>amps, guys would make that mistake all the time (including me).  It's 
>amazing what adding some attenuation to the front end of a spectrum 
>analyzer will do.  Remember these things are capable of reading sinals 
>that are less than -100 dBm, so they are REALLY sensitive instruments.
>
>

FWIW, I recall reading in several different models of HP spectrum analyzer
literature (op manuals and a whole series of app notes) that the optimum
input level for maximum IMD dynamic range (i.e., internally generated IMD
will be below the noise floor and not appear as a phantom signal) is in the
range of -35 to -45 dBm.
Ring any bells out there?


------------
Scott Townley           
Gilbert, AZ
nx7u@primenet.com


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