[BC] RG-8

[RichardBJohnson at comcast.net]

Bob,
RG8/AU is pretty good. The insulation will handle 30 kV!
This doesn't mean RF connectors will. Many Hi-pot testers
use RG8 cable stripped back about 4 inches so there is
about 4 inches of polyethylene before the shield. From
a UL ampacity perspective, the inside wire is 11 gauge
and will therefore handle 25 amperes, MUCH more than
you would like!  That is 31,250 watts!

http://www.isotecwire.com/trans_data_rg8.htm

At 1 MHz, the attenuation is shown as 0.1 dB per
100 feet.

So the question is really how much power would you
like to lose? Losing modulated RF power is very
expensive because it took much more energy to
generate it so you are really losing about 1.5 times
the power being eaten up in the transmission line
overall.

For a short line, say from a transmitter to a phasor
within the transmitter shack, the losses are probably
quite acceptable. However, to run a few hundred feet
to some towers, no way. You will lose a hundred
watts of expensive power!

--
Cheers,
Richard B. Johnson
Read about my book
http://www.LymanSchool.org


 -------------- Original message ----------------------
From: Bob Groome <bobgroome at yahoo.com>
> This begs a question:
> 
> What is the power rating for RG8? Will it handlle
> 1.5 kW 1 kw 100% Modulated) and a little for
> safety in case there is a VSWR? My old books
> don't have plane RG8. A little math says you'd
> have about 225 volts of RF for 1,000 watts and
> 4.45 amps. I seem to recall that the coax is good
> to 500 volts. Maybe it's the PL259 that has the
> voltage limit. But I sure remember RG8 running
> very warm at 1000 watts.
> 
> Thoughts?
> Bob