----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: "'TopBand'" <topband@contesting.com>
Sent: Saturday, February 15, 2014 12:15 AM
Subject: Re: Topband: Palomar R-X Noise Bridge
On 2/14/2014 7:00 PM, Charlie Cunningham wrote:
All generally true, I expect, but I also believe that dielectric constant
and dielectric losses also figure in and the lowest loss lines would be
filled with air, dry nitrogen or evacuated. I expect those would likely
be
the lowest loss AND highest velocity factor cases.
If you run the equations, you find that below about 1 GHz, the losses are
all copper losses. Dielectric loss is a few percent of the total loss in
the 500 MHz range. The benefit of a foam dielectric at HF and VHF is that
it allows the center conductor to be larger for a given shield diameter.
But the improvement in loss of a foam dielectric coax below 1 GHz is
entirely due to the center conductor being larger.
BTW -- the relevant equation is on each Times data sheet.
73, Jim K9YC
Dielectric losses become evident at 2M with 1500W and at 432 400W of steady
carrier will heat up even the best N connectors and RG-213. For that reason
many are switching to the 7/16 DIN.
Carl
KM1H
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