Topband: Insulator problems- Notr og caution

[Bill Wichers]

Yep, that's the "black pigment commonly used" that I refer to. It's used in the PE jacks of coax too!

I can't say I've tested black - vs - white materials in the microwave region, but I've never seen a problem with them down in the HF (or 2m/6m) range.

Regarding acetal itself, I have a white bearing block on a boat lift that (was) in the sun pretty much all day, all summer, every year, and it lasted about 15 years. It gets "chalky" after that time and starts to fracture. It would be a problem in tension, and it was a problem in constant used as a rotary bearing. The black material I replaced it with is about 5 years old now and still like new. 

  -Bill

> -----Original Message-----
> From: Charlie Cunningham [mailto:charlie-cunningham at nc.rr.com]
> Sent: Monday, December 16, 2013 2:33 PM
> To: Bill Wichers; 'Greg - ZL3IX'; 'Topband Reflector'
> Subject: RE: Topband: Insulator problems- Notr og caution
> 
> 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