[AMRadio] AM Amps


Geoff w5omr at w5omr.shacknet.nu
Tue Jan 11 00:11:49 EST 2005


Gary Schafer wrote:

> Here is a ruff rule of thumb for amps on AM:
> If the amp takes 100 watts to drive it on ssb then it will take 100 
> watts pep of AM to drive it. 100 watts pep of AM means 25 watts of 
> carrier with 100% modulation.

Kinda Sorta.  Depends on the quality of the transmitter.  If he 
reduces the carrier output power of the Ranger, then the audio 
output power will rise, because there won't be as much final 
current flowing through the secondary of the modulation 
transformer.  Depending on the impedance match of the final to 
the modulator through the mod transformer, determins how much 
more audio will be gained (or lost) when power is reduced from 
the exciter.  That, and the natural asymetricalness of the 
operators voice.  Lowering the output power, more audio, a 3:1 SR 
(Symmetry Ratio), the 25w of carrier could contain as much as 
200w PEP.  In order for the linear to 'cleanly' reproduce the 
audio, it's going to need more than what the plates of a pair of 
3-500Z's can deliver (*note: I said "Cleanly")

In the real world, there's likely to be some distortion, unless 
the carrier can be dropped down to around 10 to 12watts output of 
the Ranger.

73 = Best Regards,
-Geoff/W5OMR




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