[BC] Re:1 5/8 foam coax

[Dana Puopolo]

They have been running 50 kW through 1 5/8 foam since 1972, but they only
modulate at about 80% average.
They also run Power Side.

-D

------ Original Message ------
Received: Mon, 19 Feb 2007 09:42:42 PM EST
From: "Lamar Owen" <lowen at pari.edu>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Subject: Re: [BC] Re:1 5/8 foam coax

On Monday 19 February 2007, Xmitters at aol.com wrote:
> You have to remember that the 250 kW peak power that you mentioned is peak
> Envelope Power, which is defined as the equivalent unmodulated power that
> has the same voltage as the amplitude modulated carrier at peak crest of
> modulation.

But of course.  Basic stuff.

> Even at this [506kW]
> figure, we have not considered  the required headroom for possible VSWR
> excursions for this system yet. All of the 50 kW AMs that I have
> seen/worked on, either use three inch rigid coax or four inch andrew air
> dielectric.

Certainly one needs to think about the VSWR as well.  But have you tried 
1-5/8's at 50kW to see what it would do?

> Anyone here using 1 5/8 foam feedline for their 50 kW AM plant ? If so, you
> have more guts than I have.

I know of a 25KW using 1-5/8's.  And for that application it is sufficient.

Dana's original message somehow, to me at least, implied that it was desired 
to use 1-5/8 temporarily; not sure where or how I got that impression, 
though.
-- 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772
(828)862-5554
www.pari.edu
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