Could the problem have something to do with the field "leveling"
algorithm?

Perhaps there is a transient spike in the field as it sweeps from one
frequency to another?  

I only say this because I have been to a lab that manually controls the
field (well, they used to about 9 years ago anyway).  While testing
there, the technician would sometimes have a tough time leveling the
field at certain frequencies, possibly due to resonances in the chamber.


The technician would watch the output of a field probe and adjust the
amplifier for the proper field strength.  At some frequencies, the amp
would be set for 3V/m; then when the frequency was stepped to the next
level, the field strength would either jump or almost disappear.  The
amplifier would need quite a bit of adjustment to bring the field back
to 3V/m.

I'm just wondering if this same effect may be going on; and maybe you
don't see it when you dwell on those frequencies.

Good luck and please let the group know what you find.

Chris Maxwell
Nettest


From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John
Woodgate
Sent: Thursday, August 18, 2005 1:38 PM
To: emc-p...@ieee.org
Subject: Re: RF Susceptibility: Sweep v/s spot check

"Chileshe, Chris" <chrischile...@eaton.com> wrote (in 
<97976b56b6309e45bf7378c2c39329ed01a73...@havuksmb01.euro.ad.etn.com>) 
about 'RF Susceptibility: Sweep v/s spot check', on Thu, 18 Aug 2005:

>What is the explanation for this and there are techniques for getting 
>round this 'problem'?

Are you using a real continuous sweep, which inevitably includes 
sideband frequencies, or a stepping sweep, which doesn't (after the 
initial transient after the step shift in frequency has decayed)?
-- 
Regards, John Woodgate, OOO - Own Opinions Only.
Deadlines are 90% of deadliness.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk


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