Dr. David Kirkby wrote:
>> I know Nylon does not have great RF dielectric properties (PTFE is much lower
>> loss), but how bad is Nylon? I'm thinking of using a piece at the feed
>> points of
>> a folded dipole in a Yagi. I can't say the exact frequency, but it is close
>> to
>> 50 MHz.
>> The power is only 200 W, and the impedance at this point is 200 Ohms, so the
>> RMS
>> voltage is 200 V. This is across a 15 mm gap, so the electric field is not
>> very
>> high. (Assuming the field across the gap was constant, then the E field is
>> only
>> 200/15 = 13 V/m (RMS) or 19 V/m (peak). But I suspect it will be higher at
>> the
>> ends of the metal dipole.
> I should have perhaps clarified that. The material will only be at the feed
> point - nowhere near the high voltage points on the ends of a dipole. But
> since
> its folded, the ends of the metal tube are actually close together, but its
> still a low impedance point.
> Also, the voltages I gave were in V/mm, not V/m. But still, 19 V/mm is pretty
> low. I feel this wont be a problem, but since it will be potted and can't be
> removed later, I'd like to get this right. (I know the potting compound is
> not a
> problem).
All nylon has rather poor weather resistance, even the UV resistant flavors.
Use "delrin" if at all possible instead.
--
73 Ron KA4INM - All E-mail sent to this address shall linger in the Google
cloud forever!
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