DB cables for exterior use are over kill and normally wasted money.
They are typically heavier than normal coax which makes them unsuitable
for vertical runs, or feeding, center fed, half wave slopers. On
vertical runs I'd double the number of stress relieving coils as they
make a good support anchor point.
DB cables have the shield braid impregnated with a gel to prevent water
migration if a stone compromises the jacket.
As as been said by many on here, the UF versions of LMR coax are not for
exterior use. Times Wire lists the life at 10 years. I found this out
after taking delivery of a 1000 feet of LMR600UF. I've been using it in
buried conduit and hope for the best.
I had the same problems as others using LMR400UF. The standard LMR
cables work fine. You can even use them for rotator loops with at least
two turns in a watch coil spring fashion laid out on a flat plate. I
much prefer BuryFlex for rotator loops though.
73, Roger (K8RI)
On 8/23/2017 Wednesday 4:41 PM, Clay Autery wrote:
Curious as to why y'all don't use the LMR-400-DB or LMR-xxx-DB cable
INTENDED for exterior use?
______________________
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
On 8/23/2017 3:04 PM, Mike & Becca Krzystyniak wrote:
Bill etal,
I had some LMR-600-UF going to several UHF antennas on a rotating tower.
It showed signs of sun damage and the outer jacket crinkle cracked on me
too.
The salesman warned me upfront it might not make 10 years.
But even cracked with some exposure to the shield, the integrity of the coax
(loss & Z) was still in spec.
IIRC, I actually found a footnote on the LMR site that UF was not intended
for outdoors, but it will survive for a number of years.
Bill, YMMV but the Jafa-Tek specs are not the same as LMR-xxx.
But for jumpers it's probably in that bucket called diminishing returns.
I have also used SuperFlex in rotor loops but over time I had one crack
along the annular shield rings, opening the shield.
Not sure if that was a one off, or something attributable to the SuperFlex
construction.
At the time I decided to replaced them all but I am reconsidering SF vs. UF.
Mike K9MK
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
--
73
Roger (K8RI)
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|