On 07/ 7/12 05:45 PM, 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).
Dave
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