Topband: Palomar R-X Noise Bridge

[Charlie Cunningham]

Thanks, Jim

Well, I confess that most of my professional work has been near or above 1
GHz

Thanks for tip about the Times datasheets!

73,
Charlie,K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Jim Brown
Sent: Saturday, February 15, 2014 12:16 AM
To: 'TopBand'
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
_________________
Topband Reflector Archives - http://www.contesting.com/_topband