[TowerTalk] Polyamide (Stauff) Insulator Clamps

[Lux, Jim]

On 3/18/21 3:51 AM, john at kk9a.com wrote:
> My 40m OptiBeams use black clamps, I am not sure of the manufacture 
> but they look like Stauff clamps.  I wonder who is saying that the 
> black clamps have a carbon issue?  Can you buy one and test it?
>
> John KK9A
>
There are so many black colored plastics of so many different bulk 
resistivities and/or RF properties, you'd have to measure one to find out.

It is true that some black plastic uses carbon black as a filler to 
improve UV resistance. But hey, they also use Titanium dioxide (which is 
white) as a UV resistance improver. And there's other ways to get UV 
resistance (as by using a different kind of plastic).

There are plastics deliberately designed to be conductive or dissipative 
(for ESD protection purposes, usually). But whether they are DC 
resistive doesn't tell you a lot about the RF properties.

The other thing is that, like plastic pipe, the composition of the 
plastic in components is not the same from unit to unit. If it's a 
clamp, they're concerned about things like mechanical properties, maybe 
CTE or thermal properties.  The mix of plastic going into the molding or 
machining process could vary substantially - depend on what was in the 
bins of recycled plastic, etc.   When I used to build HV equipment, we 
used a lot of pvc pipe (normally a good insulator), but we always had to 
test it first, particularly if it was a leakage sensitive application.

For most plastic, there's a sort of gross conductivity check - people 
expect plastic to be an insulator - but that's about it.



>
>
> Byron W5FH wrote:
>
> Hello-    I am a little confused about the UV and electrical 
> properties of the polyamide insulator clamps (hydraulic and tubing 
> line support clamps) used on the VHF LFA yagis. I have viewed 
> commercially produced VHF LFA yagis that utilized green colored ones 
> to support 13mm tubing elements. I have read the black ones are better 
> in regards to UV resistance. However, some antenna manufacturers state 
> the black colored clamps have additional carbon in them and the 
> antenna element lengths will need adjusting.    My head is nearly 
> spinning after trying to research this. I have tried to look through 
> the thousands of polyamide clamps in the Stauff catalog. Can anyone 
> shed any light on whether the green colored polyamide clamps, such as 
> used on an E-Antenna 6 meter 7 element LFA yagi, are inferior in 
> regards to UV resistance? I see where a competitor (making mostly HF 
> yagis) states the black clamp assemblies they use are better in 
> regards to UV resistance of the green ones that E-Antenna uses, but I 
> wonder if the black clamps have identical electrical properties or 
> would corrections need to be made to elements? I see where G0KSC, an 
> authority on the LFA and their construction, offers the green colored 
> clamps.   Thanks,   Byron W5FH
>
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