[Amps] Why hasn't solid state replaced tubes?

[Zyg Skrobanski]

>It is probably due to filters in the transceiver. Not all the third order 
>distortion is after the IF filter.
>Now show me the math that backs up your claim.

What claim?  I was looking at the IMD graphs that the ARRL publishes
whenever it tests a transmitter, and noticed that the IMD products, shown
on those graphs, were not symmetrically a mirror image around the center
frequency.  It was an observation not a claim.  

I don't know what is causing this asymmetrical behavior, and it's
impossible for me to do the math on something I don't understand.;)
--
Zyg AF4MP
Roswell GA USA