All good points. We have used gray UV-stabilized poly carbonate to mold covers for electricity watt-hour meters that had some rather stringent requirements fr with standing ambient sunlight.
The problems that I encountered with black plastic that was blackened with carbon-black, the cheapest and most readily available material for blackening plastic, was in portable and water-meter pit devices whose transceivers operated io the 902-928 MHz ISM band, The black plastic, containing carbon-black would totally destroy the tuning and radiation efficiency of embedded antennas. There are other dyes and materials that can be used to blacken plastic, but one has to take care to specify the materials and or the electromagnetic properties of the plastic that is used! It's not so much an insulating problem, rather it has to do with the absorptive properties o ftne material at VHF and UHF. Not so sure about HF. But I've made lots of end and center insulators for antennas from polycarbonate sheet stock! 73, Charlie, K4OTV -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Monday, December 16, 2013 4:09 PM To: 'Topband Reflector' Subject: Re: Topband: Insulator problems- Notr og caution I don't want to belabor this, because I think Greg was going to try Delrin, but Delrin homopolymer is slightly different than other acetal resin copolymers. They are similar, but not exactly the same. 1.) Black does not always mean poor insulating ability. It will be fine at HF 2.) Black also does not necessarily mean better UV resistance. It generally helps, but many white materials are good. I have white tower ropes that outlast black rope. It really depends a great deal on the UV inhibitors and the material. Most white nylon ropes contain UV inhibitors, for example. If he wants to get a special grade of Delrin, 527 UV would be most UV resistant. The little bit of carbon pigment won't hurt a thing at HF. Greg is in New Zealand, so he will probably have to buy what is available. Since nylon lasted a few years, the material doesn't have a high bar to jump. 73 Tom _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband