[TowerTalk] LMR 400 UF issue and Low Loss cables in general

Wed Nov 13 10:37:57 EST 2019

Hi John

    I have used LMR-600uf outdoors for ~20 years.  I have not seen any
issues with degradations due to uV here is north Texas.  At least when
compared to LMR400 runs in parallel with it.

    I spoke with Times on this "uF" question several times. The input I
received from one of their engineers was that the "uF" life spec is similar
to plenum cables, or about 10 years.   I never found this published but it
may be out there somewhere.  He also said Plenum cables can be used outdoors
too but that is another question...

    I do know that many of the coax manufacturers have tweaked their
processes and the result maybe a product that degrades faster (or lasts
longer) than others.  We all want this stuff to last for as long as possible
but then there is the question of useful life in the rotor loop application.
Mine seems to get dings and scars in the loop from wind driven movements
more so than rotation.  YMMV.

73 Mike K9MK   

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
john at kk9a.com
Sent: Wednesday, November 13, 2019 8:46 AM
To: towertalk at contesting.com
Cc: sdavis at davisrf.com
Subject: Re: [TowerTalk] LMR 400 UF issue and Low Loss cables in general

I was going to ask a question on towertalk what is the best coax to go  
around a rotator but had not gotten around to doing so. Your post is  
very interesting. For decades I have used Belden 8267 and it has held  
up very well, even at my station in Aruba. I know that there are less  
lossy cables but I felt that 8267 was tough as nails. My concern is  
that the newer Belden 8267 that I put up five years ago has turned  
white on my NC tower and the older version on the tower is still  
basically black. Did the jacket change? I use Heliax up the tower  
which holds up well. I am making many monoband antenna changes next  
years and I am revisiting what I use for antenna coax leaders.  LMR400  
appears to be too stiff, LMR400UF seems flexible enough and I  
considered using it until I read the UV posts. I tired Belden 9913 in  
the 80's and it was the worst coax that I have ever used,  Does 9913F7  
hold up well and not have the same water ingress issues? If cost is  
not a concern what is the best coax for a rotating HF antenna?

John KK9A

Steve Davis wrote:

Mike, W4EF, hits it on the head ref. potential degradation of LMR 400  
UF, in outdoor environments vs. UV impact.

My firm, DAVIS RF Co., sells various RF cables, as well as control  
cables, and provides government, military and numerous industries,  
with cable design and solutions, not only in the RF spectrum.  We are  
not just wholesalers, we are cable design engineers fulfilling many  
custom needs.     One cable I designed, which many hams recognize, is  
Bury-Flex Tm, used also by Lockhead Northrup and NASA ground stations.

In the past on T Talk, I have pointed out the issue with LMR-400 UF,  
and suggested alternatives.

We sell a lot of Times LMR sizes, and in fairness to them, their  
cables in general are superb.  However, in order to max out  
flexibility of UF's, they chose to use a TPE jacket (Thermoplastic  
elastomer).
This outer jacket material does not hold up well to UV, over the  
longer term (depending on where  in the world it is used). Times  
latest specs have deleted ref. to the potential life of the cable.   
And W4EF'S experience, as noted, confirms the problem.

So, what is the alternative??:  Belden 9913F7, which has excellent  
flexibility, and same attenuation specs (only slightly different at  
and over 2 GHz).   And, 9913F7  is LESS expensive than 400 UF.
Why is it better vs. UV??  Because they use their own formulated  
"Belflex" Tm outer jacket material.  It is a highly flexible hybrid  
PVC.   NOTE: do not mix this cable up with Belden 9913, which at least  
in the ham market has had a bad reputation.   9913F7 is a totally  
different build. And I highly recommend it.

I will just add also that many customers come to me thinking they need  
to run their entire length of a cable using a UF type, where there are  
alternatives to that which results in our sale being less, but that  
also means saving the customer his $$, which is what we want to do for  
our fellow hams , without sacrificing performance and application sense.

Lastly,  we have very low prices on Low Loss cables, hardline, Andrew  
Heliax and RFS Cablewave Heliax Tm equivalent.  And we do the  
assemblies using mfr. Certified installers.  We provide our fellow  
hams with the same low wholesale pricing as we do  all other  
commercial customers.  And we provide free application consulting,  
unlike any other commercial or ham dealer that I am aware of.

Contact me anytime with any questions.  73,  Steve Davis,   DAVIS RF Co.

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