[TowerTalk] Flexible jumper on top of the tower ? *reply DE K0FF

[K0FF]

Here we get RG-389 on the surplus market and it's inexpensive and quite
flexible. I use it for the flex section between the hardline and relay box
on the crankup towers. Don't know how well it would stand up around the
rotor, but a large loop would take most of the stress away. )I'll report on
that later as there are some UHF applications coming up that can't stand the
extra connectors involved in the usual setup, and will require a straight
piece all the way from the bulkhead to the feedpoint). It's rated at 2000V
RMS and 8KW is only 632V. The 1/4 inch of stranded center conductor will
take a lot of current and the Neoprene outer covering is pretty much
impervious. The sections available here come with LC connectors on each end.
At .875 diameter it is a lot larger than the RG 225 which is only .390, so
the loss factors will be lower.

Question: What connectors do you use, and what kind of relays to handle such
high power?

Comment: I always put the relay box above the rotor with the understanding
that the rotor loop is the weak link and will eventually need to be
replaced. No need to replace multiple cables that way, nor is there a need
to take the antennas down to reach the feedpoint, which may be many feet
from the center.

Geo>K0FF
-----Original Message-----
From: z.pitman@libertel.nl <z.pitman@libertel.nl>
To: towertalk@contesting.com <towertalk@contesting.com>
Date: Thursday, September 07, 2000 4:23 AM
Subject: [TowerTalk] Flexible jumper on top of the tower ?


>
>Hi guys,
>
>Can you advise me about the best jumper cable type for a rotated Yagi ?
>
>The setup is the following:
>
>25m high steel self-supporting tower, one antenna on the top and one at
12m.
>Spinner antenna relay will be mounted at 18.5m. The cable from the shack to
>the relay box is LDF-50 (7/8"). The distance between the relay box and the
>feedpoint is 14.5m (6.5m vertical, 5m horizontal and 3m bending arc). This
>jumper cable should be very flexible, tolerate -30 / +50 degs C, should be
>rated to 8 kW (the antenna system is used as backup by a government agency)
>and low loss. My best guess is RG-225/U or RG-393/U (made by Suhner) so
far.
>
>
>They have the same properties (power rating, loss) but the 225 has 1mm
>thicker silicon varnished glass fiber braid jacket and the 393 has FEP
>(fluor-ethylene-propylene) jacket. Which of these two material has better
>mechanical properties and UV-resistance ?
>
>Or maybe you know a better type ?
>
>73 de Zoli HA1AG
>
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