Dear Jeff: Many thanks! Comments below. . . as: **

"Jeff Liebermann" wrote in message
...

On Mon, 8 Oct 2012 23:34:11 -0400, "J. C. Mc Laughlin"
wrote:

One such coax appears to be the expensive RG-400. Only need a few feet.
Question: What might be a source for short lengths of RG-400? I have tried
Newark, Mouser, and the like. . . .

http://www.ebay.com/itm/230756316444
http://www.ebay.com/itm/160856544191
http://www.ebay.com/itm/380086386242
** I will look at these sources. Ebay, well, it is Ebay. . . Thanks.

Question: What other small diameter coax uses no steel and has a solid
dielectric?

Are you looking for low triboelectric noise or low piezoelectric coax?
** Fortunately, mechanical forces will be tightly suppressed and thus these
factors are not expected to be an issue. What are expected to be the two
most important factors are a need not to have non-linear effects (no Fe and
attention to avoiding braid issues - you are familiar with the extensive
testing of harmonic production in/with some coax) AND a desire to minimize
the probability of center-conductor migration (staying away from foam)
** A story from long ago: I saw center-conductor migration in RG8 type
(solid dielectric) in a piece of coax that was in a horizontal, outdoor
cable trough. This was a long time ago and it is possible that a
manufacturing defect was involved. Today, one would scan the long piece of
coax and discover such a latent defect if it existed.

RG58A/U also known as "Cheapernet". The problem is that I've seen it
with both solid copper center conductor, and cheaper copper clad steel
center conductor. It also only comes in polyethylene foam dielectric.
If it's solid dielectric that you want, you're stuck with Teflon.
** Thanks. I had just about reached the same conclusion.

For RG58A/U in Teflon, there's Belden 88240:
http://www.belden.com/techdatas/english/88240.pdf
which also has a solid copper center conductor.
** I had gone through Belden's info, but must have missed this entry.
Thanks.

There's a potential problem with using RG400 or any Teflon dielectric
coax in a torroidal balun. It might cold flow. The center conductor
might shove its way through the Teflon dielectric and short to the
shield braid. I've only seen this in smaller diameter RG188 Teflon
coax, but it might happen with RG400. I don't really know if it will
be a problem, but methinks you should be aware of the possibility.
** As always with your contributions, this observation is right-on.
Fortunately, volume is not excessively restricted and thus a somewhat larger
radius will be used than the minimum, which should improve the probability.
** Thanks for the help. You are a great source of useful information. 73,
Mac N8TT
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


J. C. Mc Laughlin
Michigan U.S.A.
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