Re: Microwave oven test


Neil Smith G4DBN
 

It will probably be uPVC then, which is not a great dielectric, but for this application, and if the sections are thin, you should get away with it.  Losses vary, but the figures I've seen are something like a tan delta of 0.02 at 1GHz for uPVC, about the same as polycarbonate, compared with 0.0003 or so for polystyrene, polypropylene, PTFE and polystyrene.  Just because the loss tangent is 70 times as bad isn't necessarily serious, seventy times a tiny amount is still a tiny amount. You wouldn't use it in a tuned cavity or as the dielectric in a capacitor or a microwave lens though.

I've seen lemonade bottles used to cover helicals, but there is always a problem with condensation if it is too enclosed, so think umbrella rather than wetsuit. PET loss tangent is something around 0.008 at 1GHz, and being thin, any loss would be very small unless you are also running 10GHz through the bottom of the bottle and it is one of those with a heavily moulded base, where you might get some weirdness.

Do the oven test and see if you detect any warming. If the material has unusual fillers or plasticisers, it could be radically different from raw uPVC

Neil G4DBN

On 23/09/2020 21:48, G8TZJ via groups.io wrote:
 Neil Smith G4DBN

It is going to be outside and probably subject to rain. (I'm unsure about a covering, as I want to limit the wind loading). The plastic type is unknown. Its the off cuts from soffits and bargeboards etc. from when the roof was done some time back.

73 Andrew G8TZJ
-- 
Neil
http://g4dbn.uk

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