Rudy Bakalov wrote:
> Hello all,
> As I am getting closer to having the new tower and antennas go up,
> questions that I have never considered in the past keep on coming up. One of
> them is the choice of coax.
> As the title suggests, I am trying to decide between LMR400 and BuryFlex.
> I estimate that I will need a total of 1000' to connect all 4 beams, the
> phasing lines, 2 cables to the shack, etc. The max distance between an
> antenna and the shack will be less than 300' (or 0.3db loss).
> I like the LMR400 option due to its lower cale loss and cost. However, I
> don't understand the practical impact of the fact that LMR400 is NOT
> non-contaminating- is there going to be any impact from bundling cables,
> attaching them to the tower legs, etc.?
Probably not. I've never noticed any adverse effects from taping the
coax (I have 5 runs up the tower) to a tower leg.
> The cables will go in a PVC conduit between the tower and the shack.
As do mine.
> I do recognize the difference in flexibility (and its applicability to
> rotating antennas) and my solution is to have a 10' BuryFlex attached to each
> yagi, followed by whatever length of LMR400. I have to install Polyphaser
> coax in-line protectors anyway and I will install them between the 10'
> BuryFlex and LMR400 sections.
I'm replacing my runs with LMR-600 and using LMR-600UF for rotator
loops. As to the Polyphasers, I'd never put one at the top of the
tower or at the antenna. Remember they are sacrificial devices and when
one does its job it may fail and need to be replaced. The bottom end of
my rotator loops go to bulkhead connectors mounted in 1 1/4 X 1/8"
Aluminum angle fastened to the tower legs using saddle clamps. The coax
shield is again grounded at the base of the tower before it goes into
the conduit. All polyphasers are mounted at a grounded bulkhead at the
entrance to the house.
http://www.rogerhalstead.com/ham_files/cablebox.htm has some earlier
photos of the installation.
However I think the Davis Buryflex is much more rugged than the LMR UF
versions and would not hesitate to use it instead of them for the
LMR-400 rotator loops. I think you will find Buryflex is easier to
handle (pull through conduit) than the LMR-400 but I think both are good
cables. So far I've had no problems with the LMR 400 except some
rotator loops made from LMR-400UF, but that really wasn't the fault of
the cables although Buryflex may have withstood the abuse a bit better.
The rotator limits failed and the big array wound the rotator loops
tight around the top of the tower and over the edge of the top plate.
Where they skidded over the edge of the top plate it peeled the jacket
right off. Using tape and "heat shrink" I repaired them instead of
replacing them which would have easily have been a full day's job. Now,
as everything is coming down they are getting replaced with the
LMR-600UF IF I stay with the present antenna set up. If I go with the
4L "shorty fourty" then most likely the UHF/VHF antennas up top will not
go back up and I'll have less need for the LMR-600UF.
> Any thoughts? The difference in cost is about $150 at 1000'
I think either will work fine, but even using Buryflex all the way I'd
still put in bulkhead connectors to ground the shield at the top and
bottom of the tower. My runs are about 230 feet from rigs to the
antennas up top. However I'm using a "six pack" at the base of the
tower for HF which eliminates 4 100' runs of LMR-400 and lets me use
those antennas from either the den or shop, or rater it will once I'm
finished with the overhaul. <:-))
http://www.rogerhalstead.com/ham_files/tower.htm (It's a big page with
lots of photos)
Roger (K8RI - ARRL Life member)
N833R (World's oldest Debonair)
> Rudy N2WQ
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