[SI-LIST] Re: Using Current Probes to Measure Cable Resonance

Hi Doug
A simple way is to use an echo-box:- an oscillator with a loop antenna 
tied into the tuning circuit with a
meter measuring the current in the oscillator with a fixed voltage 
source.  As the circuit is tuned, the
resonances peak.  The loop antenna is connected by a dual banana plug so 
different bands loops can
be inserted. 

Coupling is by proximity of the loop so anything that resonates will 
show up on the current meter and no
physical connection is necessary.

I havent seen them in many years but they should still be around.

Ron Miller

Doug Smith wrote:

> 
>Happy New Year everyone!
>
>I been running lots of experiments and taking data over the holidays. The
>first result of all this activity is my Technical Tidbit for January, 2008.
>The link to the article is the picture of a spectrum analyzer and two
>currentprobes at the bottom of the page at http://emcesd.com[1] .
>
>This month's Technical Tidbit discusses a method of using a spectrum
>analyzerwith a tracking generator and a pair of current probes to determine
>the resonant frequencies of wires and cables. This method can be used to
>findEMC and other noise problems in equipment. 
>Abstract: A technique for using current probes to measure cable resonances
>isdescribed. A swept frequency voltage is induced on a cable by one current
>probe and the resulting current measured using a second one. This technique
>can be especially useful in troubleshooting EMC emissions problems as well
>asother noise related problems in equipment designs.
>
>This quick and easy method can be applied to a new design for which circuit
>boards do not even exist yet to avoid EMC and noise problems. The method has
>many potential uses inside and outside of system enclosures.
>
>Doug
>
>-- ------------------------------------------------------- ___ _ Doug Smith
>\/ ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX:
>408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o |
>Email: doug@xxxxxxxxxx[2] \ _ / ] \ _ / Website: http://www.dsmith.org[3]
>------------------------------------------------------- 
>
>--- Links ---
>   1 http://emcesd.com
>   2 mailto:doug@xxxxxxxxxx
>   3 http://www.dsmith.org
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-- 
Ronald B. Miller, Microwave/SI Engineer  RAIL = NOISE + REFLECTIONS
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