> Apparently there is a rule of thumb that says the third order
> intercept is 10 to 12 dB above the 1dB compression point:
>
> http://www.rfcafe.com/references/electrical/p1db.htm
> http://www.arrl.org/qex/2006/09/qx9letters.pdf
>
>
> Mike
> KL7R
>
> PS
> Here are some docs I found on measuring third order intercept
>
>
http://www.downeastmicrowave.com/PDF/IP3.PDF#search=%22calculate%20third%20order\
%20intercept%22
> http://www.sm5bsz.com/dynrange/intermod.htm
>
http://www.odyseus.nildram.co.uk/Systems_And_Devices_Files/Linearity.pdf#search=\
%22calculate%20third%20order%20intercept%22
>
i Mike - thanks a lot for posting this material - it is extremely
informative, and answers my query about the sig level at which IP3
should be measured (it should be measured in a region wher e the 3rd
order output has a cubic relationship to input power). It also
encourages me to feel that the problems I have identified are real
(necessity of output attenuator, hybrid, etc).

The 1dB compression point should be very easy to measure - I shall go
for that !

Andy G4OEP