[TowerTalk] 8X center migration in a coax choke?

[Rob Atkinson, K5UJ]

thanks Steve, i looked at the radioworks 8X solid stuff--they say it has 
same center as foam except the copper is tinned.   I think the shield is 
tinned also.   I'm also looking at using 213.   On a 16" diameter coil form 
(a small garbage bucket from home depot) I calculate the L for 100' of 213 
would be 192 uH.  it seems to me that that would get the job done on 160, 
get the feed closer to 1/2 w.l. + no worries at QRO with high swr.
73,
rob/k5uj


From: Steve Katz <stevek at jmr.com>
To: 'Tom Rauch' <w8ji at contesting.com>, "Rob Atkinson, K5UJ" 
<k5uj at hotmail.com>, towertalk at contesting.com
Subject: RE: [TowerTalk] 8X center migration in a coax choke?
Date: Wed, 17 Nov 2004 08:08:18 -0800



 > Rob,
 >
 > I use thousands of feet of the stuff and none of it is
 > Belden.
 >
 > I consider it cheap coax, so I'm rough on it. I have 300 ft
 > long hunks hanging from high dipoles (I have a 318ft tower)
 > and I don't worry. To keep the wind from blowing
 >
 > ::Now, that's a good trick!  I wish I could stop the wind from 
blowing...!
 > -WB2WIK/6
 >
 >
 >  and
 > breaking the shield from the connector I just wrap #17 steel
 > wire right around the jacket tightly and tie it to a pipe
 > driven in the ground that supports my antenna switch.
 >
 > As for chokes.... I've been using chokes made with RG8X for
 > years and never had a problem regardless of power level or
 > stress. I use 4" maximum diameter. My 80 meter antennas have
 > baluns over 10 years old. The ONLY problem is the white
 > center insulation has powdered up where it is exposed to GA
 > sunlight. I cut one back a few weeks ago until I got to new
 > foam. This time I wrapped the foam in coax seal.
 >
 > ::As for solid-dielectric RG8X type cable, Radioworks is now selling
 > precisely that; advertised as "Super RG8X."  This design change obviously
 > violates the original RG8X "spec," it would have to with a solid
 > dielectric.  To maintain 50 Ohms Zo, they'd have to either make the 
center
 > conductor smaller gauge, or change the cable diameter; not sure which 
they
 > did, but I'd guess they decreased the center conductor gauge to maintain
 > the same cable O.D. and still hit 50 Ohms.  If so, the "new Super RG8X"
 > probably has a higher DWV (voltage) rating, but may actually have more
 > loss, and a lower power handling ability, since most of the loss in coax
 > is the skin resistance of the center conductor, and if you make that
 > smaller, you're going in the wrong direction.  Anyway, you might want to
 > look into this on the Radioworks website. -WB2WIK/6
 >
 >
 >

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