[Amps] Clean -vs- Unclean

[Tom Cathey]

> Yes the best radios on the market can put out a signal >with IMD Products 
> 50 db down, if you are willing to >spend $ 3000  to $ 12,000. That is the 
> equipment that >has distortion products 43 to 49 db down. Any radio >with 
> IMD Products  40 db down or better is a DG >radio.
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Some very good points in that last post and truth about the real world 
radios out there!

What stands out to me is the Class A mode of the FT-1000MP  and later rigs, 
etc.  Their 200W amplifier can be toggled to provide 75W of  classA 
at -80db? 3rd order. This is outstanding.

I'm convinced that there should be more of this available in modern rigs. In 
my case, I am forced to go down to the 5mW level in the early RF stages to 
find these kinds of numbers in my FT-1000D. It's 200W amp is no better 
than -32 3rd.  Drive a clean 3-500Z amp with that and you are lucky to 
maintain the -30db 3rd order area.

Until I upgrade to a newer "class A capable" ricebox, I will be using 
outboard class A stages to amplify my 5mW FT-1000D output. As Marv once said 
here, paraphrased... " don't give up hard won IMD figures in the early 
stages where they are easy to get"...  ie, make that low level driver as 
clean as possible considering how difficult it is to improve upon a high 
power class AB stage running full output.

73,
Tom, K1JJ