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Re: [TowerTalk] burying hardline

Subject: Re: [TowerTalk] burying hardline
From: K8RI on TT <>
Date: Sun, 03 Apr 2011 12:57:19 -0400
List-post: <">>
On 4/3/2011 9:22 AM, Steve Maki wrote:
> On 4/3/2011 3:08 AM, K8RI on TT wrote:
>> I've found LDF4-50 (1/2" Heliax) to be a bit on the fragile side and
>> easily crushed. Were it me, and it's not, I'd put all feedlines in PVC
>> conduit.  The reason is that yards can at times get soft and if your
>> tires sink in as you cross the feedlines it can be a mess. To me the PVC
>> is cheap insurance.  I'd run the control lines either under the conduit,
>> or in their own conduit.  OTOH although it's not good practice I do have
>> some control lines in the same conduit with the feed lines.  I use lower
>> loss LMR-600 which has a smaller minimum bend radius and is much more
>> crush/kink resistant than LDF4-50
> My experience runs counter to yours Roger.
> LDF Heliax is VERY crush resistant. Yes you can kink it, but on two
> occasions I've seen LDF cable that was laid out on a parking lot get run
> over by crazed teens in pickups with nary a scratch.

Yes, you are correct.  The flat plate crush resistance is 110# Vs 60# 
for LMR600 and 0.815db loss per foot at 150 MHz Vs 1.0 db loss for 
LMR-600.  I'm surprised that it survived being driven over unless they 
had the large tires to distribute the weight.

> So if the stuff is in a trench a couple feet down protected from sharp
> objects it should be fine.

 From his description I was thinking it would probably be just below the 
surface. I put the conduit just deep enough to cover it with grass and 
leave a good root system (bout 4")

> BTW, LDF4 has lower loss (by a bit) than LMR600 at all frequencies from
> the charts I've seen.

I took out two runs of LDF4-50 and replaced them with LMR-600 as I find 
it much easier to handle and make shorter bends without kinking.


Roger (K8RI)
> -Steve K8LX
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