Input vs. Output

[GPBATEY]

Greetings...

Back in 1955 when I first got my novice ticket, as has been pointed
out the novice station was limited to 75 watts of input power.

The measurement of input power is the product of the plate volts 
and the plate (or cathode) current.  This was relatively  easy to 
measure as all tube rigs had a plate meter so that you could tune (dip) the

final tuned circuit.  Since the voltage is a relatively stable value (some
rigs 
didn't even measure it) the output power could be controlled by 
dipping the plate current and adjusting the loading and grid drive for a 
specific value of current.  The Heath DX 100 that I had, used one
switchable meter to 
measure Plate Voltage, Grid Drive current and Plate current as I remember
it.

The common availability of OUTPUT meters came much later 
with the development of solid state diodes.  The ability to measure fwd and

reflected power and then calculate the VSWR was quite a blessing (I think).
Now we take for granted what the SWR meter tells us when we connect our
rigs 
to an antenna.

The percentage figures mentioned previously are about right for 
tube style amplifiers.  Solid state rigs final amplifiers have an
efficiency
but since we are allowed and readily able to measure output power, 
it is normally not considered a factor.

Have fun with the tube rig.

73 Gordon WA4FJC

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