> -----Original Message-----
> From: N6ZO@aol.com [SMTP:N6ZO@aol.com]
> Sent: Tuesday, December 31, 2002 8:12 PM
> To: Steve Katz
> Subject: Re: [Towertalk] Coax
>
> Steve,
>
> I have always run my coax 90 feet vertically without a clamped loop. Not
> exactly sure what that is. My last run was rg8U was up since 1978, was I
> just lucky?
>
[Steve Katz] No, not lucky. RG8/U and RG213/U (.405" diameter,
fairly lightweight) doesn't really require a strain relief loop, however a
"drip loop" (to prevent water from running down the whole length of cable
internally should it penetrate at the top end) is always a good idea. My
comments regarding a strain loop specifically applied to heavy cables like
RG17/U, RG18/U, etc.
> the new 9913 went up in March of last year. what do I need
> to do to 160 foot run, 90 feet of which is vertical but taped to the leg
> of
> the tower. Please expand a bit about the clamped loop part. I didn't
> find
> out how easy it is to puncture the jacket on 9913 until after I had it.
>
[Steve Katz] Don't ever clamp 9913, or any "hollow" or "soft" coax
-- it's a sure recipe for failure. Such cables are very frail and should be
gently supported without any pinching or clamping action. I don't even use
electrical tape on this kind of cable, unless it's very gently wrapped
(without pulling on the tape as I'm wrapping) and spread over a large area
of cable. RG17/U, which is what the thread and the comments were about, has
a solid PE dielectric which is very thick, very strong and very heavy and
can take considerable clamping pressure, more than you can usually apply by
hand, using anything. The reason for the topside loop when using this cable
for vertical runs is that it is so heavy, the dielectric and center
conductor have a tendency to slide around inside the outer conductor, due to
gravity. It's not unusual to completely lose a connection using this kind
of cable in a vertical run unless a strain loop is provided at the top end
to prevent the internal slippage. But RG17/U is almost ten times heavier
than RG8/U. I've never seen the problem with RG8 types.
-WB2WIK/6
> Thanks,
>
> 73
>
> Chet N6ZO, KP4EAJ, VQ9XX, ZD8W, KG4ZO, VP2A
|