[Antennas] Electrical length
George, W5YR
[email protected]
2002年7月11日 08:04:32 -0500
Randy, the classical approach to this is to put an analyzer at one end of
the cable and find the frequency of lowest impedance. This for the cable
open-circuited at the far end. If the cable is shorted, then look for the
frequency of highest impedance. This will be the frequency for which the
cable is a quarter-wavelngth long.
With an open cable, the frequency of highest impedance indicates the
electrical length of a half-wave line. Of course, appropriate even and odd
multiples of these lengths will give similar results.
With an SWR meter, one looks for the frequency of highest SWR for an open
cable or a shorted cable since either provides a reflection factor of
unity.
I am not aware of a procedure that shorts both ends of the coax unless they
have in mind dipping a small loop formed in the short at one end.
73/72/oo, George W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
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[email protected] wrote:
>> How do I find (measure) the electrical length of a piece of coax I have
> the Antenna Book it has me short the center conductor to the shield at
> both ends. The velocity factor is printed on the coax. NOW WHAT?
>> I have a MFJ 259 & Dip meter coils for it still in the box
>