[Amps] Checking for IMD

[Tom W8JI]

> As I began thinking about that, it occurs to me that any 
> meaningful test would not be that easy.  As soon as I 
> remove the tuned input, the load for the exciter changes 
> substantially, which means impedances and drive changes. 
> Those things alone could change the imd sufficiently in 
> the exciter to show a few db difference in the imd of the 
> amplifier.
>
> That would imply that a lot more testing would be required 
> to understand what is being tested.  Perhaps one of those 
> class A transceivers would be useful as a driver.

You either need to run two radios through attenuators into a 
combiner and through a 50 ohm input class A amplifier into 
the amp (I use a class A 8877/3CX1500A7), or find a radio 
that by itself has -50 to -60dB IM products at full 
amplifier drive.

73 Tom