Re: Topband: Palomar R-X Noise Bridge

["Carl" <km1h@jeremy.mv.com>]

The lowest loss cable I have here is 75 Ohm 1" General Cable Fused Disc; its 
under a differnt name these days. Mostly air with poly discs and used for 
the 200' runs for 10M, 2M, and 222 MHz.
For the 160/80 inverted vee it is 450' of regular foamed 3/4" 75 Ohm CATV 
hardline with a RG-11 jumper and plenty of ferrite to the feed point. Ive 
been using ferrite sleeve baluns since the mid 70's; I was introduced to 
them by the company I worked for who was building equipment for the joint 
CIA/DOD Tempest program.
Carl
KM1H


----- Original Message ----- 
From: "Charlie Cunningham" <charlie-cunningham@nc.rr.com>
To: <jim@audiosystemsgroup.com>; "'TopBand'" <topband@contesting.com>
Sent: Friday, February 14, 2014 10:00 PM
Subject: Re: Topband: Palomar R-X Noise Bridge


> 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.
>
> 73,
> Charlie, K4OTV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Jim 
> Brown
> Sent: Friday, February 14, 2014 9:42 PM
> To: 'TopBand'
> Subject: Re: Topband: Palomar R-X Noise Bridge
>
> On 2/14/2014 2:17 PM, Carl wrote:
> > Isnt that what "lowest loss" means? At least that was my intention.
> I must not have written clearly enough. I was not questioning the low
> loss, only that the high Vf was the way to get it.
>
> You DO get the low loss by going to larger coax, (like the 7/8-in hard
> line), but it's the fact that it's LARGER and has lower RF resistance,
> NOT the higher Vf.
>
> Think of it this way -- The higher Vf cable has less attenuation per ft
> because the higher Vf allows the center conductor to be larger.
> But a stub made with foam coax with Vf = 0.84 must be 27% longer than
> one with with a solid dielectric and Vf =.66. If those coaxes are the
> same diameter and of comparable quality, the stub attenuation and Q will
> be nearly the same.
>
> 73, Jim K9YC
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