[Lowfer] Ultimate LOWFER Transmitter? (LONG)

[Stewart Nelson]

Hi Steve and all,

John has answered the loss questions quite well, but I'd like to
clarify the effect of external lossy structures.

> How about these other losses (like trees, bushes etc.).  Do they suddenly
> dissipate half the power in the same field strength ???    How does this
> work ?    They still have the same induced currents flowing in them and so
> dissipate the same power. If not, how do the trees know what they are
> supposed to do :-)

Suppose we have a reference system "A" with a total loss resistance of 20
ohms, including the effect of a tree "A1", 20 feet away, which dissipates
100 mW when system A is fed with 1 W (antenna current at base is about
224 mA).

Now let's add an identical system "B", 100 feet from "A".  There is
another identical tree "B1", 20 feet from antenna B.  I contend that
if you drive system A alone, negligible power (< 1 mW) is lost in
tree B1, and vice versa.

When we connect the two systems in parallel, the impedance seen by
the Tx is about 10 ohms, the Tx current (fow 1W total) is about 316 mA,
158 mA into each system.  Tree A1 is now dissipating only 50 mW,
because it is in a smaller reactive field.  Of course, tree B1 is
also dissipating 50 mW, so we are still losing 100 mW in the trees.
But the total antenna current is now 316 mA, so the far field will be
almost 3 dB greater.

73,

Stewart