Hi Ron,
> I agree with Rich, I have never found any material that could survive at
> 2.4 ghz and did not offer excellent insulating properties at a lower
> frequency. If there is such a material I would appreciate knowing what
> it is for future reference.
> Ron W4WA
I agree with that also, as a general rule for determining losses.
But remember the microwave does not put voltage stress on the part,
or UV light, or other real world things that are important.
Plus it might easily exclude a useful material because it does not
fare well with an electromagnetic radiation field at 2 GHz.
My point wasn't that Delrin is good, just that assumptions based on
experience with a PVC insulator near the end of a dipole while
running 13 kW or so, or a nylon insulator of unknown electric field
stress levels, really doesn't answer questions about all
applications.
It takes a very strong and concentrated electric field to heat those
materials at HF, although that limitation is something we should be
aware of. But that does not mean the material would fail as a
spreader in an open wire line at all, especially since I found the
conductor has to get very near the corona point of a number 14 wire
to heat (at 13 MHz)!
I'd worry about using it for feedthroughs where the electric field
gradient is very high (chassis close to the hot conductor), or the
end insulator of a 10 kW dipole, but not as a long spreader or
insulator subjected to only 5 kV or less.
I feel it's important knowing why something fails rather than just
dismissing it with a wave of the hand (or finger might be more
correct in the case of a microwave). In this case POWER has nothing
to do with it (I cooked the nylon with 50 watts), voltage per unit
area does (it took TV CRT second anode level RF voltages to do
the cooking).
73, Tom W8JI
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