Hi Dave,
The main problem with transmitting loops is the enourmous current and
Voltage which is generated when exciting them with decent power. It's all
very well to put 1W
into a loop but try 1kW and see what happens..... High Q (which you MUST
have for good
efficiency) necessarily means high Voltage and current.
For the typical high Q LF loop with 50ft x 50ft dimensions, the max voltage
is about 7 times lower than the voltage at the top of a typical 50ft
monopole. With a loop conductor of #8 ga, or RG-8, the current at 1w is
approx 1.2A. At a 400w the current goes up by 20x to 24A, which is no
problem for these conductors.
What really looks interesting for a loop installation, according to the
math, is the effective power gain that can be achieved by stretching the
horizontal dimension. On my property I can make this 350ft (if it were
legal) because of this strange narrow "L" shape out back in the woods. The
effective power, then, increases 50x! Tried this for an hour at very low
power (don't tell the FCC), and it works!
My first TX loop article just appeared in the US Longwave Club's 'Lowdown'
publication. The second is to follow next month.
Bill Ashlock
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