Topband: Palomar R-X Noise Bridge

[ZR]

----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: "'TopBand'" <topband at 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