Topband: VF drift in coax

[Tom Rauch]

>> 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.
and
> 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...

No matter what, this is a simple process. Heat comes only 
from loss. Doesn't matter what the cable is intended to be 
used for, it is always a matter of power lost in the cable, 
how hot the materials can be run, and how easily the cable 
gets rid of the heat.

CATV cables are no worse than cables of a similar size 
designed for transmitting. I regularly use 75 ohm F-6 (or 
RG6 size) foam core CATV cable in dipoles and that cable 
very easily handles 1500 watts. As a matter of fact my six 
meter Yagi by M2 uses small 75 ohm F6 or "RG-6" size cable 
in the matching system and I ran 1100 watts carrier into 
that antenna on CW on 50MHz without incident for hours on 
end.

If the cable arcs over or gets limp and melts, then I'd 
worry.

I'd bet there a lot of people using foam CATV cable on 
transmitting four squares too.

I don't think twice about using what people wrongly call 
"RG-6" in my HF system on lower bands. It's cheap, light 
weight, and works just fine. Keep it away from the  bigger 
tubes with handles though!!

73 Tom