There are number of factors Harold including the circuit design of how the SSB
Signal is generated. After that the number of amplifier stages and how clean
they are determine what type of signal is generated.
The commercial manufacturer you were talking with was gave you a steamy pile !
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. During the era of radios with 6146 Vacuum
Tubes 3rd Order IMD Products would range from 34 to 40 db down. 5th order IMD
Products would range from 38 to 45 db down. And that is not to say stinkers
didn't exist back then. There was a plethora of radios made using TV Sweep
Tubes for finals and they put out some really crappy signals. Fortunately at
the time the Ham Population was comparatively low, about 250,000, and there was
plenty of spectrum so the effect was minimal.
Returning to my point the Solid State radios that are marketed to the masses
today have signals that range from objectionable to positively dreadful.
Quantified that translates to 3rd Order numbers at or below 32 db and 5th Order
numbers below 38 db. The radios I'm talking about here are the FT-920, TS-570,
TS-2000 and most of the Icom Series. Ten Tec equipment has been all over the
map. The Omni V put up some very pedestrian numbers when the ARRL ran the IMD
test for its review. -30 db down for 3rd Order numbers comes to mind. The Omni
VI posted excellent numbers -39 db for 3rd order products. The 3rd order
numbers for the Omni VI+ are -26 db which puts that radio near the bottom.
As to your questions about components that is not something that can be
answered quickly but it now appears that top level vacuum tube equipment can be
manufacturerd cheaper than solid state equipment. At their best both types of
equipment put out very clean signals equal to each other but the solid state
stuff requires large sums of money to be spent.
Bob W6AH
-------------- Original message --------------
From: HAROLD B MANDEL <ka1xo@juno.com>
> This question concerns signal cleanliness.
>
> A recent thread talks about unclean signals
> from poor amplifier construction.
>
> As an aside, talking with one of the commercial
> manufacturers earlier, I was told that his products
> are -49dB down, as opposed to others that were
> -43dB down.
>
> What specific components lead to a betterment
> of this parameter?
>
> In a simple triode, running GG, does the choice
> of value of the plate blocker, padder caps and
> tune/load capacitors matter?
>
> Thanks,
>
> Hal
> W4HBM
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