[ARC5] RF Ammeter Puzzle

[sbjohnston at aol.com]

The ARC-5 was made for short wire antennas on aircraft, wasn't it?  
Those antennas would have quite low radiation resistance (which is the 
load that pulls the current detected by an RF ammeter).  The ART-13 
might have been designed for longer antennas with higher radiation 
resistances.  The lower the resistance, the greater the current, for 
the same power.

For example, suppose the ARC-5 was used with an antenna with R=10 ohms. 
  50 watts of power would be about 2.24 amps.  The same 50 watts on a 50 
ohm antenna would be 1 amp.

The formulas are P = I x I x R   or   I = SqRt(P/R)   etc

Steve WD8DAS