[TowerTalk] Inner conductor migration in Heliax(TM)

[Steve Maki]

Agreed that the main concern has been transportation and rough handling. 
Fork lift operators are evil people.

AVA with it's thinner shield is more prone to fork damage for sure, but 
it's lighter weight probably will be a wash in the scenario where a reel 
gets flipped on it's side.

BTW flat spots can be easily removed with a short piece of properly 
sized pipe split length-wise and a c-clamp. Or some other other rube 
goldberg method. The impedance lump goes away like magic.

-Steve K8LX

On 4/12/2016 7:33 PM, Jeff DePolo wrote:

>> I've handled many hundreds of reels of Heliax over decades, and never
>> worried much about that warning, which has more to do with
>> creating egg
>> shaped cable (from the weight of the upper layers) than to center
>> conductor migration. Heliax is very robust. Measure the impedance if
>> you'd like, but I'd bet that it's still perfect if it's been kept dry.
>>
>> -Steve K8LX

> Right-O.  It has nothing to do with migration of the center conductor, but
> rather deformation of the shield.  If the reels if LDF were laid down gently
> (as opposed to being flopped on its side as what typically happens at a
> freight depot to make it easier to move around with a forklift), it should
> be OK.  Even if there are a few flat spots, the eccentricity is usually not
> enough to make that huge of a difference in Z0.
>
> In broadcast, digital cellular, and other applications where very low VSWR
> is important, a flat spot would result in the reel being rejected, but for
> ham use, it's a matter of what you're willing to tolerate.  Sweep it with a
> TDR/FDR and see what it looks like.
>
> FYI, newer cables with much-thinner shield material such as Andrew AVA
> series are MUCH easier to dent/flatten.  If a reel of AVA comes in laying
> flat, it gets rejected without even bothering to unwrap it.
>
> 				--- Jeff WN3A