[TowerTalk] hardline bending radius

[Steve Maki]

On 11/21/2012 10:43 AM, Jim Thomson wrote:

> That's a bit of over-generalization. Both RFS and Andrew make standard
> and flexible versions of their cables. The construction is virtually
> identical on comparable versions.

> ##  since when did andrew start making  7/8”  and  1.25”  heliax with  corrugated center conductors ??
> That andrew “flex” version  of 1/2”  heliax is nothing more than a corrugated shield, making a sloppy fit
> over the  dielectric.  All the andrew 7/8”  +  1.25”  heliax  I have ever seen always had a copper tube
> in the center... = zero flex.
>
> ##  I see andrew blathering on about the 1st to use corrugated aluminum for the shield, but have  yet to
> see any andrew hekiax with an AL corrugated shield.   Copper is 2-5% heavier than steel and almost triple
> the weight of aluminum.   That RFS heliax with the corrugated  AL shield + CU corrugated center conductor
> is the real deal.... super light,and super flexible, with no where near the turning radius of standard andrew
> offerings.
>
> ##  that  ‘superflex’  andrew 1/2”  heliax is spec’d to be rolled and unrolled X many times off a cable reel, that’s it.
> It uses Cu clad solid AL for the center conductor. Nick the CU..and you are in a real mess, esp if you ring it 360 degs.
> That CU copper tube used on the andrew 7/8” and 1.25”  heliax is no fun to work with...pita. You can have it.
>
> Later...... Jim   VE7RF

Jim,

You seem to have a thing about Andrew. At this point it would help to 
have actual model numbers and specs.

The traditional RFS "Heliax" is the LCF series, which is a virtual 
carbon copy of Andrew LDF (or LDF is a carbon copy of LCF if you 
prefer). These cables were, until recently,  the workhorse of the 
commercial segment. They are rugged and very easy to work with, at least 
for anyone who has worked with Commscope Cell Reach smooth wall cable, 
which is truly stiff as a board (yet has a minimum bending radius as 
small as corrugated). It just takes a lot more force to bend it.

Andrew "Superflex" 1/2" is the FSJ4 cable, which has always had a spiral 
shield and copper clad aluminum center conductor. There IS a spec for 
number of bends, given as (20) minimum and (50) typical. I'm not sure 
that any hardline is the right choice for a constant bending application 
though.... FSJ4 has a minimum bend radius of 1.25".

The RFS Superflex "CellFlex SCF-12" also has a spiral shield and copper 
clad aluminum center conductor, and is rated for 1.25" bending radius. I 
can't find a spec for number of bends, but I can't see a world of 
difference between the two cables, can you? Is there another RFS 1/2" 
cable I'm not aware of?

Andrew VXL5 is Andrew's Flexible 7/8", and DOES have a corrugated center 
conductor, weight .29lbs per ft, and bend radius of 5".

The RFS superfles 7/8" is UCF78, made similarly, weight of .302lbs/ft, 
and bend radius of 5". See much difference there? Is there another RFS 
7/8" superflex that I'm unaware of?

I don't think Andrew has made "flexible" cables in larger than 7/8", 
although their air-line cables have corrugated center conductors.

I'm not a fan of aluminum shield cables, for precisely the reason you 
gave for not liking CU center conductors (not sure I understand that). 
Aluminum is much more fragile if nicked than copper. However, I can 
assure you that there IS Andrew AL5 cable out there with corrugated 
aluminum shield, but I'm not interested in it.

Anyway, that's about all I'll say on this, except that both Andrew and 
RFS (and Eupen and Rosenberger for that matter) make high quality 
corrugated cables that are well accepted. I used to have trouble with 
RFS connectors meeting sweep specs at high frequencies (which RFS 
engineers admitted to me were an issue) but that has been sorted out 
with their later series.

73,
Steve K8LX