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RE: webpage



Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <paul-at-abelian.demon.co.uk>

Duncan wrote:

> My 1954 copy of the ARRL Antenna Book states that RG-8U will
> take 4kV rms.  If we allow a factor of five for safety under
> damped wave conditions, then 800V into 50 ohms would still
> be 12,8kW :-) but this assumes a VSWR of 1:1 i.e. no
> standing waves on the line.  Even 400Vrms would be 3,2kW, so
> it's going to be OK for quite reasonable power levels. 

VSWR isn't an issue - the lengths of feeder required are tiny compared
to the free space wavelength of TC frequencies, so no need to make the
same allowances as you would at HF. The characteristic impedance of
the cable is irrelevant for the same reason.

I've seen RG8 and N type connectors used for a few tens of kV quite
successfully, although you have to watch out for that metallic dust
that falls off the plating and spreads across the PTFE bits - some
risk of explosive failure if there's a lot of stored energy behind it.

> Then there's the hardline used by the broadcast industry 

I use this stuff for a primary feed - liberated from a commercial
installation many years ago when I was young enough to climb those
masts. It served its time as a feedline for an EME antenna and now I
just use the outer conductor which makes a nice insulated copper pipe.

Cheers,
--
Paul Nicholson,
Manchester, UK.
--