[TowerTalk] Ultraflex coax questions (Howard W6HDG)

Mon Dec 15 12:59:23 EST 2014

Howard and all:

About Buryflex: I've been told that it holds up better than LMR400UF from UV
exposure.
Although in my case I used the UF (four runs up the crankup USTower).
I put them in split-loom (spelling?) like used in auto engine compartments
for wirihg 1" or 1.25 "
The sheath also has cat5e and Siamese (24vac and 75 ohm coax) for cameras :)
When cranking up the cat5e and Siamese got caught on standoffs.  This change
took care of it.
No catching and tearing any more :).
73
Ivan
WK1W

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Today's Topics:

   1. Re: Strange coax failure (Tom LeClerc W1TJL)
   2. Ultraflex coax questions (Howard W6HDG)

----------------------------------------------------------------------

Message: 1
Date: Mon, 15 Dec 2014 11:20:12 -0500
From: Tom LeClerc W1TJL <wb1cby at gmail.com>
To: Patrick Greenlee <patrick_g at windstream.net>,
	towertalk at contesting.com
Subject: Re: [TowerTalk] Strange coax failure
Message-ID: <548F0A3C.90206 at gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I saw some coax a few years ago where the center conductor was not entirely
in the middle of the insulator.  Bad molding?  It was RIGHT up near the
shield in some spots and centered in others...  If I remember correctly it
was a foam dielectric...

Just a guess but I would assume that would cause some pretty weird reading
depending on movement, frequency and power levels...

73, Tom W1TJL

On 12/15/2014 11:09 AM, Patrick Greenlee wrote:
> Most all tower users have fairly extensive coax runs on which we 
> depend for near trouble free service.  Here is one strange tale...
>
> I had been having fits chasing an antenna/feedline/connector problem 
> that was common to all antennas/towers.  I whipped up a quickie 
> temporary 10 meter dipole and hung it with woodworking spring clamps 
> from bungee cords clamped to gutters.  I did use a nice balun at the 
> center.  Put Comet antenna meter on it and cut the length to resonate 
> at 29 megs where it was dead flat and 50 ohms.  Not having a piece of 
> coax long enough to make it to the transceiver I used some jumpers 
> joined with T's (didn't have enough barrel connectors handy)  and 
> reached the transceiver.  The antenna meter attached for a quick test 
> before hooking coax to rig and the needle went crazy and 
> uninterpretable.  I tried at the various junctions of jumpers until I 
> got good readings thereby identifying the bad jumper.  ( I had 6 each
> 6 ft jumpers and needed 3-4 for this lashup.)
>
> Brief digression:  I bought a 6 pak of 6 ft RG-58U jumpers with 
> PL-259's for a "bargain" price on evilBay.
>
> So, I visually inspected the suspect jumper and it looked brand new 
> with its nice part number tag and "made in China" prominently 
> displayed.  I grabbed a VOM and checked the bad jumper finding 
> continuity where and only where it was supposed to be and nowhere it 
> wasn't.  Connected the bad boy to a 50 ohm dummy load and other end to 
> antenna meter.  Really weird readings.  Substitute another jumper and 
> indications are perfect 50 ohms irrespective of frequency, as should 
> be expected.
>
> It isn't like the antenna meter is causing arcing given its low 
> output.  I haven't a clue as to what sort of anomalous defect could 
> cause these indications.  I have been using coax for over 50 years 
> (first ham lisc in 1962 and CB before that plus a year and a half as 
> field service engineer in marine electronics/communications) and maybe 
> I have just been lucky but I have never seen anything like this before.
>
> Anyone have an idea regarding what the defect might be?  I'm going to 
> cut the bad jumper in half and test the halves and then cut the bad 
> piece in half and test those pieces.  Whichever is bad will then be 
> dissected carefully to see, if possible, what was physically wrong 
> with the coax.  This is a real head scratcher for me.  The good news 
> is I'm back on the air with a pan adapter full of signals again and 
> loving it.
>
> Patrick     NJ5G
>
>
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------------------------------

Message: 2
Date: Mon, 15 Dec 2014 08:41:26 -0800
From: Howard W6HDG <W6HDG at arrl.net>
To: towertalk at contesting.com
Subject: [TowerTalk] Ultraflex coax questions
Message-ID:
	<20141215164127.MRSZ11247.fed1rmfepo203.cox.net at fed1rmimpo110>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Hi all.  I am about to order about 110 feet of coax for a new 
MA770MDP tower/ Steppir DB18 install.    I'm thinking of using either 
genuine LMR400 Ultraflex or Davis Bury Flex coax.

Davis BuryFlex is cheaper and I understand it has a tougher and more 
slippery jacket for crank up/down use?   Opinions?

I am going to try crimp-on RFU-507SI RF Industries PL-259's for the first
time.  For the center conductor crimp, I have alternatively 
heard of .118 and .128 crimpers being used.   I have the dies for 
both .118 and .128 as well as the .429 braid crimp.  Any opinions? Do you
use any dielectric compound such as STUF inside the PL259 to inhibit
corrosion?

Tnx, Howard W6HDG

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