Jim Brown wrote:
>>> ,,, but the steel causes losses to increase at lower frequencies as
>>> compared to copper or silver coated copper.
It just so happens that I've been working with a fellow who has been
measuring loss in Wireman 551 (aka JSC 1318) window line. The
conductors are solid #18 CCS. Using a DG8SAQ VNWA in 1-port mode, he
made sweeps from 0.25 to 30 MHz with the DUT terminated first with an
Open and then with a Short. There was a CMC choke (with
characteristics unknown to me) on the test fixture cable and OSL
calibration was done at the end of that cable using 400 ohms as the
load, not the usual 50 ohm OSL load.
The OC/SC data was then manipulated using a variation on Chipman
equations 7.28 and 7.29 with the following results:
https://postimg.org/image/5mn0wh6bp/
The way I am interpreting the rise in loss at lower frequencies is due
to current flowing in the steel rather than the copper. I would very
much appreciate hearing comments on the shape of that curve from folks
more knowledgeable than me. (Of which there are many!)
BTW, here's a good N6LF article on the subject:
http://rudys.typepad.com/ant/files/antenna_wire_conductor.pdf
Dan, AC6LA
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