Has anyone checked the validity of the equations given in Pappenfus, Bruene
and Schoenike (Single Sideband principles and Circuits, McGraw Hill, 1964)
for deriving linearity from from the input/output curve of an amplifier?
For 3rd order, it runs as follows:
If the output voltage at full input voltage is V2, and the output voltage at
half that input voltage is V1, then the signal to distortion ratio is
20Log [(8V1 - V2)/(2V1 - V2)]dB
If you substitute in the values for 1dB compression (i.e. V2 is 5dB greater
than V1) then I get the s/d to be 29dB. However, it is generally considered
that the 1 db gain compression is between 7 and 15dB (usually about 10dB)
below the third order intercept point, although the above would suggest it
is actually nearer 15 than 10.
So has anyone done any measurements to confirm or otherwise? Yes, I know I
could do it myself, but only on 'hollow state'.......I'd be interested to
know if solid state amps give different answers, and I don't have a solid
state HF power amp.
There is a very practical reason for this question......it's only likely to
concern G's who buy (as opposed to build) amps in the future, though.
73
Peter G3RZP
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|