[Milsurplus] Placing of loading coil in MF transmitter

[Hubert Miller]

People interested in Part 15 MW broadcast band unlicensed operation, or ham radio in the 160 meter band
and the new 630 meter band, if you have not looked at the QST June 2019, might want to look up the article
'Mini Antenna for 630 Meters', pages 33 - 36. The antenna is 26 foot tall, with a long 50 ft. top hat. The top hat
at least is way above the Part 15 rules allowance, but another point may be worth looking at.
The antenna of course uses a loading coil; this is usually placed in the antenna lead itself. The article lists the
results of trying this with the loading coil inductance moving into the ground lead instead. With the final test
having ALL the loading inductance in the ground and zero in the actual antenna lead, the measured field strength
'power density' was 6x as strong. This seems almost miraculous to me.
The author says, "We don't know why, but we hypothesize that tuning the electrically short radial system did
more to mitigate ground resistance losses than tuning the antenna solely through the antenna coil."

This does of course not prove the same exact benefit applies to the higher bands.

For Part 15, 100 mW broadcasting, the antenna has to be attached right to the transmitter. So you would have
the < 10 ft antenna, transmitter, then loading coil attached to ground, all within the 10 foot limit. The power for
the transmitter could be run up through the load coil diameter. Just an idea.
But, intriguing, if this really is a way to get out better on low frequencies.
-Hue
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