Topband: Using RG-6 for 160m transmission purposes

Ford Peterson ford at
Wed Jul 2 09:52:52 EDT 2003

Steve wrote:


> As a result, I am considering using RG-6 of this kind for an transmitting
> antenna project, but would like to know about:
> 1. Its (typical) velocity factor (have you every tried asking a TV cable
> supplier what the velocity factor of a particular TV cable is?...)
> 2. What sort of power it can typically handle (the cable may have to
> something of a mismatch).
> Any information direct to me would be much appreciated.
> Vy 73,
> Steve, VK6VZ

I have two catalogs in front of me.  One is the Beldon Master Catalog and
the other is from Alpha wire.  There is no such thing as 'typical' 75 ohm
coax.  As in the 50 ohm variety, VF ranges from 66% to about 84% depending
on the flavor of wire.  You need to check the specs on a specific wire type
to be certain, or simply measure the VF.  You will find that VF varies a
little bit from spool-to-spool of the same wire.  Measure the VF and you
will know for certain.

The problem I see with 75 ohms stuff is that it is not rated to handle
power.  These particular catalogs do not indicate a voltage rating.
However, when researching it previously, I did find a source that placed the
voltage rating on some styles of low loss RG6 and RG11 styles at only 600V.
Compare this rating to some high performance 50 ohm stuff rated at 6KV.  A
slighly goofy load at 100W would be OK but any power into a serious mismatch
and it'll be toast.

My $0.02

ford at

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