Choice of cables for serious antenna systems

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Re: Choice of cables for serious antenna systems

Postby VK2AAH » Tue Jan 12, 2010 11:47 am

VK2CU wrote:Hi All,


As for tails, this is the way the professionals do it anyway, if water gets inside your antenna/balun, it may wick its way into the coax run. A short tail of RG214 prevents this. Replacing an antenna & tail on a tower is a lot easier than having to unclip and re-install 50m of coax - and the cable hangers are NEVER near the ladder! Also the 1m tail acts as a "sacrifical coax" for your neighbourhood cockatoo terrorist team! At the other end, the coax should go through a lightening arrestor block anyway, so a tail is needed at that end as a matter of course.

Don't forget to attach the LDF to earth(Structure) at the top, at the bottom(Where it changes plane) and before it enters the building. If you don't want the expense of buying an earthing kit, just strip off section of the outer jacket, and use a SS hose clamp and shove your earth wire under it.

73's

Justin


Hi Justin,

Is the big fella cleaning out the "shed" before Wyong? Sounds like he is lucky to have a ham on board...

Not sure about your comment on the RG214 sacrificial tail at the antenna- I haven't seen any rigging firm do that on jobs I've been involved in. What you say has merit in terms of water ingress, but it introduces an extra point of failure- connectors. You win one way, and lose in the other. As for the cockies while they like the antennas as a great source of a perch & cure for boredom they will chew all the way down to the cable tray- had an attack up near Moree where the feeders were ringbarked all the way down the tower.

The grounding you suggest is standard practice, or should be. It was published in the Andrews cabling catalogue which should be the bible for any rigger/antenna installer. I've always insisted on that, except for the grounding kit near the cable entry plate (normally only used where the horizontal run in tray is particularly long).

I'm trying to get to Wyong this year... might throw some LDF4-50 on to your pile for disposal! That might make my other half happy...

Cheers,


Richard
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Re: Choice of cables for serious antenna systems

Postby VK3OP » Wed Jan 13, 2010 7:52 am

It would be great to see a scanned copy of the Andrews cable installation advice. I too will be running LDF 4-50 and 5-50 up the tower
with flexible tails past the rotator. Initially as Scott suggested I was going to use 9913 for the tails, as I have had some experience with
it. All the talk of LMR 400 has me interested, how flexable is it ? What has been peoples experience with it running past a rotator for some
time. ie, how well does it stand up to the constant flexing.

Cheers

Frank VK3OP
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Re: Choice of cables for serious antenna systems

Postby VK2AAH » Wed Jan 13, 2010 10:29 am

Hi Frank,

Our office was painted 12 months ago & I've misplaced my old Andrews catalogue. Andrews don't seem to have the information on-line. However while Googling for it I found this, and it seems like an excellent reference on the subject:

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=10596

Go through the whole course (about 5-6 pages) and it covers almost everything in great detail.

Cheers


Richard
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Re: Choice of cables for serious antenna systems

Postby VK3HZ » Wed Jan 13, 2010 11:18 am

VK3OP wrote:All the talk of LMR 400 has me interested, how flexable is it ? What has been peoples experience with it running past a rotator for some
time. ie, how well does it stand up to the constant flexing.

It depends how big the loop of cable is around the rotator. I've heard of people using LDF4-50, but with a 720 degree "hula-hoop" loop. Even though the flexing would be small, I'm not sure how long it would last with a solid inner and outer.

Like 9913, LMR400 has a solid centre (copper-plated aluminium). And like 9913F, there is a flexible version LMR-400UF (Ultraflex) with a stranded inner. It is slightly higher in loss than standard LMR-400, but for use as a tail, the difference is negligible.

Personally, I use 9913F mainly because it was readily available when I put the antennas up, and have had no problems. I'd expect the same with LMR400UF.

Regards,
Dave.
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Re: Choice of cables for serious antenna systems

Postby VK3OP » Sat Jan 16, 2010 5:22 pm

Thanks for the responses guys, I grabbed a copy of the link you posted Richard and have skimmed through it, great reference material.
David it sounds as though the LMR 400 flexible might be the cable of choice for the tails past the rotator, I gather it is available through
Rojone here in VK3.

Many Thanks

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