[TowerTalk] Hardline for stubs?

[Steve Maki]

n4kg@juno.com wrote:

>AIR dielectric is even lower loss than foam.
>You've got the really GOOD  STUFF there!
>Many (most?) air systems are pressurized
>with nitrogen to keep the moisture out.

Many cable systems had to scrap the fused disc
hardline (which Bob has) when they expanded their
systems to 750 MHZ, after they discovered that
the spacing of the discs causes the cable to have
a cutoff frequency, above which performance is
very poor.  If you look at the bare aluminum
shield, you can see a small ridge at each disc.

I'm not sure whether it is the bump in the shield
or the discontinuous dielectric that causes the
problem.

At any rate, this type of cable is excellent up
to 500 or 600 MHZ.  I have a couple thousand feet
of the .625" in use with no problems.  BTW, the
center conductor of the .625" is a perfect fit
for a UHF barrel connector, which makes terminations
very easy.

--
Steve K8LX

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