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polarization



Brian Whatcott suggests:

If waveguides were too rarified, perhaps a twin line with dipole
termination would be more to the student taste... Its polarization
is less easily gainsaid, possibly?

Yes, that would be good, though I don't know what you mean by "dipole
termination". I wouldn't like to have to manipulate the "cake grids" of
size sufficient to do the demonstration with the long waves I envision
coming from a simple half-wave dipole. The grid must be large enough to
transmit a significant beam power and also block signal from
diffracting around it. X-band microwaves are an ideal collimated source
for domestic cake grids in this respect.

Can someone suggest an appropriate dipole radiation source and
receiver? John Cochran, a colleague of mine here at SFU, once made a
Hertzian dipole oscillator transmitter and a receiver based on a folded
dipole about 1.5 meters long. The receiver had a diode and a (battery
biased) neon lamp at the feed point. The receiver was mounted so it
could be rotated from vertical to horizontal, demonstrating the
polarized nature of the radiation from the Hertzian oscillator. The
demo worked well, but no cake grids were (nor could have been)
employed. I don't know why he used a folded dipole instead of the
conceptually simpler simple dipole. I asked him and he doesn't
remember, either. The voltage developed at the feed point should be
twice as high with a folded dipole, I think.

Leigh