[TowerTalk] Hardline for stubs?

[Tom Rauch]

> I have learned so much in the past seven hours thanks to everyone!  As I
> was preparing to start making stubs (to trap harmonics among other things)
> and I opened up the 3/4" CATV hardline, I noticed that under the PVC
> coating and the thin top layer of aluminum, not only was the dielectric
> not foam, but all there was was a little plastic "plug" inside about 1/4"
> long followed by about 1" of space (inside the hardline) followed by
> another 1/4" plug followed by another 1" of air and so on.  This is
> apparently what the local cable company is using.
> 
> With all this "air" inside and very little dielectric, is this what I want
> to be using for antenna transmission lines and stubs?  The center
> conductor is quite thick but I am pretty unsure about all this air where I
> would think foam or something else should be.

Geesh, that's good cable! That must be old trunk cable. Really low 
loss stuff.

I hope you aren't wasting it!

It will work fine as a stub, but the Vf is over .90 usually. It makes 
super feedline for long runs, if you can keep the water out! Normally 
it has small holes or slots in the dielectric plugs to let air pass 
through. CATV companies purge it with dry air or inert gasses.

 
 

 
73, Tom W8JI
w8ji@contesting.com

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