[Antennas] Re: Antennas digest, Vol 4 #245 - 12 msgs

[Dick Carroll]

 Tom, your problem will be keeping out the water, especially so in Oregon.
I once worked where we used a radio system remoted through underground 
metal
pipe (rigid,not oncjuiut) which was sealed-screwed together same as 
water pipe) ane
commercially sealed with an appropriate  plastic resinsealant at each 
end exit. And still, it
filled with water. How it did it I never could determine. But with time, 
we had to replace the entire
cable system,  with newly installed conduit (we used 4inch schedule 40 
PVC this time so that new cables could be easily pulled)..


 As to your situation- I'd consider using a very low loss coaxial cable, 
twin runs as you
noted, only I'd get something like hard line or fairly large diameter 
rubber coated  TV
cable trunk line. Of course you'd have to install the cable in the 
conduit as you buried it
since you  couldn't pull the hardline through installed conduit. But a 
reasonably short run
woiuldn't seem to degrade your signal enough to worry about.

If you're sure to have water enter the conduit, and I'm convinced it 
will, then installing
twin lead as you describe will prove to be an exercise in futility.

Dick W0EX

>Message: 2
>Reply-To: <tomrscott@sterlink.net>
>From: "Tom Scott" <tomrscott@sterlink.net>
>To: "Antennas Reflector List" <antennas@mailman.qth.net>
>Date: Mon, 13 Oct 2003 15:08:57 -0700
>Subject: [Antennas] Buried ladder line?
>
>Okay, this is really a serious question, despite the seeming
>contradiction in the title. 
> 
>Has anyone ever considered running ladder line underground through large
>diameter ABS tubing? It seems like you could add spacers (maybe
>margarine tub lids) to keep it centered? I need to go a short distance
>from my shack to a tower but it crosses a driveway and I hate to put it
>up in the air. I will be digging a trench anyway for the rotor cable and
>some control wires and probably some coax as well. I can easily get 5 or
>6 inch abs pipe and figure that ought to provide enough air spacing from
>the ground to minimize loss. Bends are a little bit of hassle, but it
>seems like there are a couple ways to deal with this. My case is almost
>a straight shot anyway, except for down into the trench and back up
>again.
> 
>This would be sort of like giant air-core twin-ax.
> 
>I'm not interested in proposals that involve burying pairs of coax; yes
>that can maintain balance, but is lossier with a mis-match than ladder
>line.
> 
>Thanks!
> 
>- Tom Scott
>27005 SW Neill Rd
>Newberg, Oregon 97132
>503-330-6867 - Cell
>503-538-5839 - Home
>503-554-9468 - Fax
>KD7DMH
>  
>