Input vs. Output

[Robert & Linda McGraw K4TAX]

You've seen all the answers on input vs. output power and calculation of 
efficiency and etc.

However, why did they specify input power.  That's the way the FCC rules 
were stated before SSB popularity.  Novice class license was limited to 75 
watts input power to the final stage feeding the antenna and the transmitter 
was to be crystal controlled.  And the others, general and above, were 
limited to 1000 watts DC input.  Originally there was no such thing as PEP 
values in the regulations.  That appeared after SSB became popular in which 
the maximum legal output power was stated as 1500 watts PEP.  For the AM 
operators that translated to 375 of carrier output, modulated 100%.

Most class C amplifiers run near 70% efficiency, some higher some lower. 
Today with linear amps, efficiency is not a consideration as the final 
determination is actual output power measured in a PEP domain.

73
Bob, K4TAX


----- Original Message ----- 
From: "Tom Buchanan" <tlbuch at SCRTC.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Saturday, December 10, 2005 12:01 AM
Subject: Input vs. Output


I just got my first tube type rig (Heathkit HW-16) on the air and have been 
enjoying making some contacts with it.  I notice the older rigs refer to RF 
power input and modern rigs RF power is output.  Is there a calculation to 
figure equivalency for input watts to output watts?

For example, the HW-16 manual specifies 50 to 90 watts input and on the 
antenna tuner/wattmeter it shows 30 to 60 watts output on 40m.

73,

Tom
KG4KGY

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