At 04:52 AM 8/12/2006, kd4e wrote:
>I read the text (see below) and wondered if anyone had
>experimented with a DK9SQ graphite-embedded telescoping
>mast as a vertical reflector?
>
>Or does the embedded graphite not possess sufficient
>reflective density?
>
>Just wondered ...
I would think that it's too lossy. The other thing to think about is that
while the material itself might be conductive (of some indeterminate, and
uncontrolled, value), the connections between the segments may not be
electrically consistent.
If DK9SQ is buying the tubing for its structural properties, it might have
fairly large variability in the electrical properties.
That said, there's no reason why one couldn't, for instance, get a thin
layer of metal deposited on the surface of the tubing. Most places that do
mirroring/metallization can do this. It's just a vacuum evaporation
process, and you can get almost anything metallized. Skin depth in copper
is about 20 microns (a bit less than 1 mil) at 10 MHz, so you don't need a
real thick coating. Copper wouldn't necessarily be a good choice.. silver
(better conductor, so you need less) or gold (doesn't corrode) might be
better choices.
>----------------------------------------------------------------------
>http://www.io.com/~n5fc/dk9sq.html
>I selected the DK9SQ mast over a similar (and $20 cheaper) mast sold by
>MFJ Enterprises, the MFJ-1910, because it was said to be better
>reinforced and sturdier. What I did not anticipate as a side-effect of
>the composition, was the effect that the graphite might exert on the
>antenna. This became apparent when I first used the DK9SQ mast to
>support a vertical wire. I originally wrapped the 33 foot wire loosely
>around the mast, so that my "vertical" would not be flopping around in
>the wind. Big mistake. Turns out the black graphite (or whatever) in the
>fiberglas rod is quite RF absorbent. On 20 and 15 meters, I could see a
>2-3 S-unit decrease in received signal strength with the wire wrapped
>around the pole. And I wasn't getting out well at all, getting S2 signal
>reports from my Elecraft K1. But angled away from the pole (with the
>wire unwrapped and about 3 feet offset at the bottom), everything was
>hunky-dorey. Now I'm suddenly getting S7 reports... much better. It took
>me about 2-1/2 hours to realize what was going on. So keep that in mind,
>when using the mast. This certainly wouldn't be an issue with a dipole
>or loop that stands away from the mast, nor should it normally be an
>issue with feedline.
>-----------------------------------------------------------------------
>
>--
>
>Thanks! & 73,
>doc, KD4E
>... somewhere in FL
>URL: bibleseven (dot) com
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