[AMPS] amplifier "audio"

[Chris R. Burger]

Skip wrote:
> Yes, RF amplifiers can and do modify the audio responce of a signal, both 
> "good and bad".  A few of the AM broadcast transmitters I've dealth 
> with have sections in their manuals regarding amplifier operation for 
> certain "types of fidelity". 
Sure, if you're not using a linear (or approximately linear) amp.

Two points:

1.  Broadcast AM can use non-linear amps.

2.  Broadcast amps require matching over their entire audio bandwidth, 
which is a substantial percentage of the operating frequency.  For 
example, for a 1 MHz tx with 6 kHz audio, this ratio is less than 
170:1!  There may be a mismatch at sideband frequencies for high Q 
matching networks.

For amateur transmissions, the amp typically has to remain matched 
fairly well for several tens or hundreds of kHz (to allow you to 
QSY), at operating frequencies of several MHz.  Relatively low Q is 
indicated.  Also, it follows that the matching will not influence the 
audio, as the audio is within the matched band.

Chris R. Burger
ZS6EZ

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