No my mistake as the spacing of the two parallel conductors would
determine the impedance but the mismatch from 600 ohms to 450 would
also not be good. It wold be easier to get working IMHO with a single
run of WD-1a and the proper feed and termination transformers. Perhaps
Gary KD9SV would give you the winding ratio for a home built ferrite box
of your own. In this case it is the same principle but only a turns
ratio that counts.
Herb
On 9/20/2014 11:04 AM, MU 4CX250B wrote:
Thanks for the info and suggestions, Herb. One additional question,
however. Are you certain the 100 ohm impedance of the WD – 1 pertains
to two parallel links of the wire, with 6 inch spacing? I know that
open wire feeders with 6 inch spacing typically have about 600 ohms of
impedance.
73,
Jim W8ZiR
Sent from my iPad
On Sep 20, 2014, at 8:34 AM, Herbert Schoenbohm <herbert.schoenbohm@gmail.com>
wrote:
Jim, The DXE boxes are designed for 450 ohm ladder line which has a much higher
impedance than WD1-A wire. Using the DXE boxes may work but Gary's boxes
(KD9SV) will work better as they are designed for the 100 ohm impedance of
WD-1A. I also understand that DXE may now sell the boxes designed for WD-1.
Herb Schoenbohm, KV4FZ
On 9/20/2014 10:06 AM, Jim Garland wrote:
I want to replace the 450 ohm ladder line for my two DXE 720 ft long
bi-directional beverages with two lengths of WD-1/TT field telephone wire.
The wires will be secured only at the ends, but will be suported along their
length by ceramic insulators mounted on 4x4 posts spaced every 60 ft. The
spacing between the parallel wires will be about six inches. Here are my
quesetions: First, does anybody know what the likely impedance is of this
configuration, or if not, how to measure it? Second, if I keep the DxE
matching trnsformers used with the 450 ohm ladder line, will beverage
performance be degraded noticeably with the new wures if, say, the impedance
of the new line turns out to be 600 ohms or so? In other words, as a
practical matter how important to performance (e.g., F/B ratio and
low-noise) is it to make sure impedances are matched.
Finally, a mechanical question. I want to have a pulley at one end of the
parallel wires to equalize the tension in the wires. I've not been able to
find a good pulley with a five or six inch diameter, except for nylon
pulleys used for clotheslines. Do you think one of these could be used.
There will be no motion of the pulley, since it is only used to equalize
tension. The field telephone wire is rated at 200 lbs maximum tension, and
I'm guessing the actual tension will be about half that.
Thanks!
Jim W8ZR
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