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Re: webpage



Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Date: 10 January 2001 02:26
Subject: RE: webpage

Hi David!


>Original poster: "David Dean by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <deano-at-corridor-dot-net>
>
>Hi
>
>Excellent page. Should be considered a _Must_Read_ by all.
>
>I was especially intrigued by the article on magnifiers,
specifically the 50
>ohm tuned link design. I wonder just how much power could
be transmitted
>along a RG-8 cable. Something to think about.
>
>later
>deano

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.  More
than this and you may be looking at Andrews Heliax (TM)
which I have seen at UK ham rallies but which is undoubtedly
going to be more common in the USA since you have many more
high power ham stations.  I think that holds good for at
least 12kVrms which ought to be enough for more power than I
am ever likely to run!  Then there's the hardline used by
the broadcast industry . . . if the pros can run hundreds of
kW then there is plenty of mileage in 50 ohm coiling.

I confess to being a little sceptical regarding just how
well this will work out in practice.  The spark transmitter
is an inherently broad band device (Heisenberg & short
pulses etc) whilst the 50 ohm matching system is very narrow
band.  That, of course, only adds extra interest to doing
the experiment!  Where the 50 ohm tuned link method is
likely to work extremely well is of course with VTTCs in
which the source is itself narrow band.  But then that's
where I plagiarised it from ("Plagiarise, plagiarise,
plagiarise, only be sure always to call it please
_research_!" Tom Lehrer) - valve transmitter output
impedance matching, so if it works well with VTTCs it
shouldn't be much of a surprise, more of a surprise if it
doesn't.

>> http://home.freeuk-dot-net/dunckx


Feedback encouraged on the theoretical stuff, some of which
I know is iffy, but I would rather it was pulled apart
independently from my own ideas.

Dunckx