[ARC5] ARC-5 TX output circuit modeling

[J Forster]

 [snip]  I did not mean to claim that all these transmitters were
designed to operate
 into loads with a 4 ohm resistive part. I would think, however, that
most HF
 aircraft transmitters had to operate into antennas that were
electrically
 short (compared to ¼ wavelength), and had a radiation resistance
 significantly less than 50 ohms. The capacitive reactance is
irrelevant, of
 course, since it plays no part in radiating energy.

 73, ian K3IMW



First off, I don't have an ARC-5 Tx schematic handy, but many military
HF transmitters were designed to work into electrically short
(capacitive) antennas. The inductor, antenna capacitance, and radiation
resistance form a series LCR circuit. Such a circuit has a current peak
at resonance (hence the antenna current meter...  tune for max). THE LCR
also suppresses spurs.

To use them into a 50 ohm R load, you put in a series C (typically 50 to
100 pF) to simulate the antenna.

FWIW,
-John