[TowerTalk] Polyamide (Stauff) Insulator Clamps

[Grant Saviers]

John,

Excellent data!  Which I have found very difficult to find.  Could you 
publish links or references to the sources you found useful?

Grant KZ1W

On 3/24/2022 19:59, John Keating wrote:
> I remember convincing myself that Stauff black polyamide (PA) clamps were ok
> when I constructed my 40M yagi. I dug up the data again to refresh my
> memory. This is probably more than anyone wants to know, but for the record
> or in case you have nothing else to read:
> 
>   
> 
> First, regarding W5FH's question, the green clamps are a polypropylene
> copolymer, not polyamide. They will be somewhat less mechanically robust
> than polyamide.
> 
>   
> 
> Next, to address the electrical characteristics, PAs have dielectric
> constants in the range of 2.5-3.6, (similar to mylar and PVC) with volume
> resistivity better than 10E12 ohms-cm (some as high as 10E16).
> 
>   
> 
> The complex permittivity for PA-6 in film form is fairly flat at about 3.7
> up past 1MHz then increases exponentially to about 4.5 at 10MHz and keeps
> ging. The imaginary part is nearly zero up past 1MHz then increases
> exponentially to about 0.7 at 10MHz. Still low in both cases over LF and MF
> ranges, and low is good for insulators like element clamps. The exponential
> trend could be trouble at higher frequencies. But, calculating AC
> conductivity from complex permittivity data requires more math than I care
> to do before I retire.
> 
>   
> 
> 
> NBS data from 1961 for 6,6 nylon (a typical polyamide) show dielectric
> contstants of 3.3 at 1MHz and 3.2 at 10MHz at 23 deg C., increasing a little
> bit with temperature. The loss tangent (aka dissipation factor) is well
> below 0.1 at LF and MF over temperatures to which antennas would be subject.
> 
>   
> 
> Those data are for neat PA. I could not find any published details of
> Stauff's PA material composition (I'm waiting to see if they respond to a
> recent request), so we don't know what material they use for colorant.
> Additives could impact the data and conductivity. For example some published
> data show resistivity decreasing rapidly once the volume fraction of carbon
> black in 66 nylon exceeds about 2%.
> 
>   
> 
> All that said, I chose the black PA for its dimensional stability and
> environmental robustness. I have not been disappointed, and have not noticed
> any impact on tuning my 40M yagi (it matches EZNEC prediction). No clamps
> melted when operated at legal limit. However, I would not be inclined to use
> them for VHF element clamps. I could be wrong.
> 
>   
> 
> 73, John AI6LY
> 
>   
> 
> John KK9A 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?
> 
>   
> 
>   
> 
> 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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