On Wed, 12 Jan 2005 20:49:22 -0800 (PST), Douglas wrote:
>I don't want to use rotator cable and definitely want
>it shielded.
As I recall, the original cable that came with my 444 (purchased
used) was not shielded. Unfortunately, I can't confirm that by
looking at it right now -- it's 2,000 miles west of me at W6BX.
But I tested it with my old Omni A (before loaning the Omni to a
new ham) and it worked fine.
Most multi-conductor shielded cable you can find will have a
foil/drain shield. A foil/drain shield is as likely to CAUSE
problems below 20 MHz as to solve them. (see the tech papers on my
website re:Shield Current Induced Noise).
http://audiosystemsgroup.com/publish.htm
Twisted pairs will be the most immune to crosstalk from any RF.
Wire size is trivial -- we're talking less than 1 ma. It should be
obvious that you want a good (big) ground between the Omni and the
444.
If I were to make up such a cable today, I would be quite happy
with unshielded CAT5 cable, using one conductor of each twisted
pair as the hot and the other conductor of each pair as the
return. You'll need two CAT5's to have enough pairs.
BTW -- a problem I ran into with the 444 is that the p/s runs warm
and the voltage regulator regulates too high. When this happens,
the protection circuits in the 444 shut the amp down. I addressed
this by adding some fans to cool the supply. Ten-Tec service told
me this was chronic, and offered no ideas about fixes. This fix
has not yet been "battle tested."
Jim Brown K9YC
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