> With regard to IMD performance, again from knowledge and experience,
> to achieve optimum, one must have very carefully matched beta devices.
> Thus the reason why some companies sell components in match pairs.
> While ideal, and typically a bit costly, and I'd expect from a Tentec
> viewpoint the factor of production output (yield) vs. scale of
> economics and a few other factors, general devices will make the FCC
> guidelines all of the time. (Tentec may wish to comment on this to
> the reflector or direct to me.)
>
> Ideally, some standard production lot could be submitted for test, the
> results obtained and then some percentage of the high and low numbers
> discarded then publish the mean mathematical number as a
> specification. It works, time consuming and expensive. The question
> to be answered, is it worth it for a hobby?
Geesh, it sounds like we are tying to get -80dB IM3 performance. That
simply isn't the case!
A zero-bias class-C amplifier can do almost as well as some modern
radios for IM3 performance. Is it really too much to ask that radios
be 10 or 20 dB better than class C performance?
I think the important point is radios are going downhill, and are
almost certainly doing so because designers either are not taking a
few extra hours to "tweak" designs or don't have a clue how the radio
should work or what is important.
For example?
1.) Radio manufacturers have released radios that click like hell,
even though adjusting the value of a few components would virtually
stop the problem.
2.) CW quality is getting poorer on some brands, even though a few
changes in a few lines of software would correct most of the
problems.
3.) SSB IM products are varying from acceptable performance to
horrible performance barely better than a class C amplifier.
All of this has to be rooted in the fact they either don't care what
they are doing, or don't know what to do. None of it is a cost issue,
or a manufacturing QC issue.73, Tom W8JI
W8JI@contesting.com
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