Topband: VF drift in coax

[EP Swynar]

On Monday 2nd April, Cris wrote...

> One time I intended to use a hard line CATV 75Ohm Coax cable (about 1/2"
in diameter) for a phasing line on an TX/RX system. Bad choice. Why? Because
the foam from such cables are not design to work on a high RF environment
(1KW or more!). The results, the coaxial gets hot and detuning the system.

*************************

Hi Cris,

I don't for a moment doubt what you've described here --- however, speaking
strictly from the perspective of my own personal experience at this end, I
must say that I have been VERY pleased (so far!) with just how well my
particular strain of "...el-cheapo" RG-6 satellite TV coax has held-up in my
station...

...And I employ very LONG runs of the stuff, too: each of my three inverted
"L's" has some 130' of foam coax connected to it --- and then I use the very
same stuff for all of my 135-degree phasing lines. The antenna has been
subjected to 600-watts RF output from a pair of paralleled 813's since last
September, on a near DAILY basis --- I can not say that I've borne witness
to any inordinate change(s) in SWR in the whole of that period of time, to
date, that might indicate a change of any kind, anywhere in the feed line.

My only apprehension, initially, about using the stuff was how best to
attach it to PL-259 plugs --- I ultimately pressed RG-59-type reducers in
service, as well as generous applications of quick-cure epoxy glue, to
physically secure the cable to each connector. The "bonding" of the outer
braid to the shell of the PL-259's is strictly a matter of
catch-as-catch-can "friction fit" --- the glue does the rest, and I am
careful to ensure that the connectors are not subjected to any undue stress
that might compromise the physical & electrical bonding thus made...

As the saying goes, Cris, "...So far, so good"...!

~73~ Eddy VE3CUI - VE3XZ