Topband: Insulator problems- Notr og caution

[Charlie Cunningham]

Many black plastics are "blackened" by the addition of "carbon black" that
can make them rather lossy at RF!  "Been there, done that" in my work - at
900 MHz.

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Bill
Wichers
Sent: Monday, December 16, 2013 2:06 PM
To: Greg - ZL3IX; Topband Reflector
Subject: Re: Topband: Insulator problems

Delrin is a trademark for acetal. Acetal is the generic name so you'll have
a lot better time finding acetal most likely.

My recommendation is to get the *black* acetal as it will hold up much
better in UV outdoors. It machines easily, but it's a lot harder (and
stronger) than nylon. Acetal can be comparable to some mild metals in terms
of strength so it's great for bearings and clamps where you need a
non-conductive material.

Also, someone mentioned using polycarbonate (lexan). There's been a lot of
interest in that material since QST ran an article about it a while ago but
it's not always the best material to use for everything, and it's not the
only machinable plastic. If you do use it outdoors you should try to find a
UV-stabilized variant. For most other plastics just try to get them in black
since the black pigment commonly used will also generally provide improved
UV resistance to the material. 

My personal recommendation for most outdoor insulators that will be
subjected to any amount of mechanical stress/strain is to use black acetal.
It's readily available in sheet and rod stock, and the rod is a good
starting point for most insulators. You can find small pieces on ebay or you
can get it from most commercial plastic supply houses.

Teflon, BTW, is probably not a good choice since it is not very durable
mechanically.

  -Bill


> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of
> Greg - ZL3IX
> Sent: Saturday, December 14, 2013 12:10 PM
> To: Topband Reflector
> Subject: Re: Topband: Insulator problems
> 
> Many thanks to everyone who commented on the above.  The consensus is
> that nylon is a particularly bad choice of insulator for high field
environments,
> even on Topband.  Tomorrow I will be looking for an alternative that is
> available here in ZL.  I think Delrin will be the choice, if available.
> 
> 73, Greg ZL3IX
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