Quote:
Originally Posted by Skywave
Quote:
Originally Posted by Herald1360
+/ 2dB gain flatness in a 50W amp used as an RFPA for transmitting could be a pain  power out could vary between 50W and 20W whilst still being "in spec" for a particular input level.

By my arithmetic, +2 dB on 50watts is 80watts; 2 dB on 50watts is 32watts (all to nearest watt). So the output could vary between 32 to 80 watts. OTOH, 20watts to 50watts is a change of +4dB. But that corresponds to a gain variation of +4 dB / 0 dB. That is not the same as ±2 dB.
Al.

I was assuming that the amp was unlikely to produce MORE than 50W at any frequency, so given a dose of typical specmanship, gain "flatness" is just that you can draw a straight line at 2dB down from 50W and the output would vary no more than 2dB above and below when a constant drive level is applied. It could be driven harder to get 50W at a low gain frequency, but doing the same at a high gain one would overdrive it with consequent seriously distorted output.
Another way to look at it would be At some (carefully selected) frequency in the operating range it will need a particular drive power, P. To get 50W output anywhere else in the operating range, P will vary by no more than +/ 2dB from its original value.
Maybe I'm a bit cynical, but..........
Re Jeremy and power measurement doing it calorimetrically is one way to know just how much altogether is coming out.