[AMRadio] AM Power Level

N6DGY at kirtland.com N6DGY at kirtland.com
Sun May 18 13:14:47 EDT 2003

I'm a new subscriber to the list, and I have not discovered the way to do a search 
through the old archives.  Forgive me if this has already been covered.

I'm currently in the process of collecting the parts to build a Class-E Am transmitter 
and Class-H modulator for 75 meters.  (I was quite surprised at the relative 
simplicity of the circuit!)  While I have been a boatanchor collector for years, and 
also an on-and-off-again Electric radio subscriber (though I have every issue) I have 
never yet been on the air in AM mode.  Listening on 75 off and on over the years 
has me itching to finally change that.

I'm interested to know if I understand the newer FCC power guidelines correctly and 
how peak power on AM is measured.  The FCC now stipulates 1500 watts peak 
output.  Am I correct in understanding that in AM, the peak output at 100% 
modulation is four times the carrier level?  Does this mean that if one is to be strictly 
within the FCC rules, you can have a carrier of only 375 watts in the AM mode?

My proposed transmitter will be capable of a unmodulated 600 watt carrier.  
Fortunately, it appears to be a simple matter to reduce power in a Class-E amp just 
by lowering the supply / modulation voltage to the MOSFET drains.

Any help in furthering my understanding is appreciated.



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