Michael Ryan wrote:
> Interesting comments on the cables. I was under the impression that LMR-600
> UF ( ultra flex ) was plenty flexible to use up the tower including the
> rotator loop area. It looks and feels heavy but does indeed appear to be
>
My only complaint about LMR-400 UF is the jacket which appears to be a
rubber like material with poor resistance to abrasion and has not held
up well. I had to replace it once when the pins in the mast sheared and
let the antennas windmill. This pulled the cable tight over the edge of
the tower top plate and stripped the jacket right off. It came of like
a rubber tube. Of course that may have ruined any cable from either
kinking (the 400 didn't kink), or abrading a strip off the jacket for
other cables. The cable is plenty flexible, and I was able to use the
regular connectors on it. Unfortunately after 6 years it's time to be
replaced.
> much more flexible than 1/2 heliax which one would never use for a rotator
> loop. Has anyone has negative results with the 600Uf in such an application
> as I have suggested I wonder? - Mike
>
The only reason I've chosen to go with the Davis "Bury Flex" is its
reputation for resistance to abrasion. IOW the stuff is rugged.
Otherwise I'd prefer the LMR 600 UF, but that is over twice the price of
the Davis cable and I'm a bit cautious after the LMR-400UF. There are
pigtails for 144, 440, and 50 MHz. Probably a second 144 as I want to
add a horizontally polarized yagi. The Tribander has a short pigtail
and doesn't gain anything worth while using the larger coax so that
would certainly remain the Davis Bury Flex. There is also the
possibility of a Wi max antenna going "up top."
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Roger (K8RI)
> Sent: Tuesday, March 25, 2008 4:27 PM
> To: Rob Atkinson
> Cc: towertalk@contesting.com
> Subject: Re: [TowerTalk] LMR and CNT
>
> Rob Atkinson wrote:
>
>> My advice--if you are considering going with LMR or CNT and the cost of a
>> run of one of them, you may as well spend a bit more and go with 1/2 inch
>> heliax LDF4-50 and get it over with. There's always this debate about
>>
> how
>
>> on HF the reduced loss isn't enough to make it worth it but that's not the
>> point--the stuff is almost indestructible with its jacket and solid shield
>> it would probably jam a wood chipper and you'd be done with feedline
>>
>>
> We all have different viewpoints. I replaced LDF4-50 with LR-600. For
> my use (laying on the ground from the shop to the tower 6-pack and then
> up the tower) I found the Andrew to be more fragile, (easily dented,
> easily kinked, and has a much larger minimum bend radius than even
> LMR-600). So once I finish all runs up the tower will be LMR-600 and the
> LMR-400 currently on the ground will be replaced with 600 in underground
> conduit. The LMR-600 on the ground will also go into the conduit.
>
> I use CNT240 and LMR-400 runs from the antenna switches to the slopers.
> As I use all crimp connectors I never noticed any problem, but both
> cables are listed as tined copper braid over Al foil shields from the
> suppliers. Neither CNT240 or the LMR cables are what you would call
> flexible when compared to the RG8X family.
LMR or CNT 240 can be a royal pain in the backside to strip without scoreing
the braid, so you use a properly adjusted stripper for that one or a lot of
care. Scoring the jacket and then breaking it works very well. The pigtails at
the top of the tower are currently LMR-400 ultraflex which has not proven to be
all that durable. The pigtails (with integral rotator loops) will be
replaced with Davis bury flex.
>
>> forever. If you don't care about that go with 213. I have never really
>> understood why anyone bothers with the times microwave coax. All that
>>
>>
> It's good, it has a short bend radius and it's relatively inexpensive
> and I find it to be very robust. The only cables that have given me
> problems have been the Belden and the ultraflex versions of LMR-400.
> I've had 3 runs of LMR 400 laying on the ground between the shop and
> tower since last fall. They've been walked on, run over by the yard
> tractor, tripped over and show no damage. Normally they'd not be on the
> ground but some of this work started after the ground got kinda hard. IE
> frozen last fall.
>
> 73
>
> Roger (K8RI)
>
>> expense for a feedline that is not all that robust.
>>
>> 73
>>
>> rob / k5uj
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