>-----Original Message-----
>From: Jim Eichner [mailto:jim.eich...@xantrex.com]
>Sent: Wednesday, May 22, 2002 12:55 PM
>To: emc-p...@majordomo.ieee.org
>Subject: RE: Coaxial Switches - use with spectrum analyzer and gear?
>
>
>
>In our pre-compliance lab, we've got a pair of LISN's, a LISN-mate type
>thing that I'll call a DMRN (DM rejection network), a
>transient limiter,
>some clamp-on RF current probes, an amplifier, the front end of the
>analyzer, and a 50 ohm terminator. All this gear is connected and
>unconnected a hundred times a day when we're deep into
>trouble-shooting, and
>I'm sick of doing up and undoing coax connectors. I don't
>trust push-on
>coax connectors.
>
>What I envision is a system with a few of these coax switches
>in it. The
>analyzer input would go to a switch that selected either the
>amp (used only
>with the clamp-on probes) or the transient limiter (used with
>the LISN's).
>The limiter input would go to a switch that selected between
>the output of
>the DMRN or the Line LISN or the Neutral LISN. Etc. You get the idea.
>
>Is there anything to stop me from using coax switches with suitable CW
>power, insertion loss, and frequency spec's? Am I headed for
>trouble if I
>have 2 or 3 of these switches in the signal path, due to cumulative
>insertion loss?
>
>Thanks for your feedback,
>
>Regards,
>Jim Eichner, P.Eng.
>Manager, Engineering Services
>Xantrex Technology Inc.
>Mobile Power
>web: www.xantrex.com <http://www.xantrex.com>
>Any opinions expressed are those of my invisible friend, who really
>exists. Honest.
>
Jim:
There's no reason why you can't implement the switching system you
described. The only concern is that you use really good parts. (Your
spectrum analyzer likely has a couple of internal relays in its signal
path.) Since you likely need to measure up to about 5 GHz, I would use
components rated for up to 18 GHz. This is not the place to skimp on cost.
Don't use Dow-Key relays with SO239 UHF connectors; go with something like
Agilent relays with SMA connectors. Connect the internal paths with
semi-rigid solid-wall coax, and use a good grade of flexible external coax
cabling too. If your system is computer-controlled, you can use something
like an IEEE488 Relay Driver interface to automate the switching functions.
Your lab procedures should be amended to include some type of periodic
verification of the loss along all signal paths.
Regards,
Ed
Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Services Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis
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