We have been asked several times to introduce a carbon-fibre mast to our product range. Carbon-fibre gives a much better strength to weight ratio than fibreglass. However I have always resisted as we all know that carbon fibre is lossy don't we? That being said, it appears that quite a number of ultra-lightweight portable operators do use carbon-fibre masts without encountering any problems.
My curiosity was piqued so I bought one myself to investigate. After quite a number of portable trips I found (like others) that there was no noticeable loss. On thinking about it further it's not surprising really. I was using an inverted vee antenna that was crossing the mast at an angle of about 60 or 70 degrees so the RF would not be expected to couple strongly to the mast.
But what about using it for vertical antennas? We did some measurements on a Carbon-6 mast in our lab. This showed that the resistance of the base section was about 75 Ohms per centimetre. That gives a minimum resistance of about 3,000 Ohms per mast section. That suggests that the pole overall will be an effective insulator in most circumstances. Thus I think that it would be fine for any normal application, including for vertical antennas. The only use that I would not recommend is where a loading coil or trap is wound around the mast itself.
So will lightweight carbon masts replace all our fibreglass masts? No, they will not. To equal the strength of our current fibreglass range, the carbon masts would need to be a lot more substantial than the Carbon-6 - and thus will have a much lower resistance - and that might lead to problems.
My conclusion is that portable operators can use a Carbon-6 in almost any situation without incuring any excess losses. It's nowhere near as strong as our fibreglass masts but it's incredibly small and light which makes it a very useable option!