Allow me to make an unsolicited endorsement of Steve's submission below. I
have used 9913, Times LM-400UF and BuryFlex for low-loss coax applications.
I had massive problems with critters chewing through the jacket of the 9913
and LM-400UF. I think I replaced one 100' run to my 4-square a half-dozen
times. Others have had problems with condensation and water ingress with
standard 9913, though I never had that problem. I also had a serious problem
with LM-400UF turning out to be not-so-UF (i.e., not so flexible.) I used it
on my 72' tubular crankup and very nearly had a disaster when a stiff loop
of the cable migrated around the tower and snagged on the motor housing.
There were other problems contributing to this near-accident, but the stiff
LM-400UF was definitely part of it.
I have since switched to Bury-Flex for all my non-hardline needs, including
the run to the 4-square. I did some tests and found that Bury-Flex is
actually more flexible for my crankup application than RG-213. I also use it
for rotor loops on all my antennas. It's only been in use at my station for
6-10 years, but so far I've had zero problems with it -- it's very flexible,
low loss and the critters don't seem to like it.
73, Dick WC1M
From: Stephen Davis [mailto:firstname.lastname@example.org]
Sent: Wednesday, March 30, 2011 1:45 PM
To: Tower Talk
Subject: [TowerTalk] Use of Ultra Flex. Also: Cabling Crank Ups-DAVIS RF Co.
Hi, the following is a copy of a submission a few minutes ago which I made
regarding rotor loops. This also includes info on the above subject:
Any of the Times UltraFlex outer jackets use TPE (thermoplastic elastomer).
TPE is not good in UV for much
more than 6-9 years, depending on the ambient. That's too short for
effective/cost efficiency. Even the Times literature states "life expectancy
in excess of 10 years" (discount the "in excess of" ! ) The std. LMR
jackets are PE and so is Bury-Flex Tm (Tm and design of our company). The
PE formula I use is best and it is not subject to UV degradation. Also, it
is highly abrasive resistant due to its sufficiently high durometer, unlike
PVC. Bury-Flex Tm (Low loss) has a life of 30 + years. A good PVC jacket
should be UV resistant and a life of 18 + years.
There often is way over -concern and overkill as far as use of Ultra Flex
for rotator loops. Substitute in a loop of Bury Flex Tm or even 9913F7 (
Bellflex Tm blend of PVC which is highly UV resistant). Why use LMR 400UF
or 600 UF at the loop and certainly not all the way up the tower from the
shack? An excellent grade PVC, such as Mil Type IIA used in our RG-213 is
fine for a long life and more than adequate flexibility for a loop.
PE outer jackets like Bury-Flex Tm can be laid in water, also highly rodent
resistant, and makes the best cable that I could provide anybody for coiling
around crank up towers...and I sell any cable or wire made, or will design
to your special need.
Hope this is of some help,
73, Steve, K1PEK
DAVIS RF Co., Div. of Orion Wire Co., Inc.
Wire, Cable, RF Connectors and wire aerial parts.
LMR, Heliax, Eupen
Commercial / Military
Custom Cable Design
tel: 978-369-1738 Fax: 978-369-3484
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