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

[Tom Rauch]

> Remember that 3rd order products are generated from the mixing of the
> frequencies within the audio pass band of the rig. So the distortion
> (3rd  order products) will be close in frequency to the wanted signal.
> 2A + B + C. So 1kc x 2 + 1.5kc = 3.5kc etc. The 3.5 kc product falls
> just outside the wanted pass band of the signal. That equals adjacent
> channel splatter.

It is the higher order products that are normally the real problem. 3rd
order products are so close the slope of receiver and transmitter filters
make it difficult to tell what  is going on, unless you are using a CW
filter on an adjacent frequency.
Most of the tones on SSB are one high and one low pitch, not two
close-spaced high pitches. Hi-fi audio accents extra unneeded highs (the
ssss's) and aggrivates bandwidth by adding more highs to mix...as well as
increasing lows which pump power already poor power and bias supplies
decreasing IM performance.

> Do the multiplication with many different frequencies within the audio
> band width and you can see how far out some of them fall. 1.8kc x 2 +
> 2kc = 5.6kc. Also some 3rd order products of the lower audio frequencies
> fall within the wanted audio band. As Rich said, that is why distortion
> is sometimes heard on frequency.

There are multiple reasons you hear distortion on the signal, but it is
unlikely an operator would EVER hear troublesome 3rd order products from RF
sections on the actual operating frequency. The bandwidth problems fall
outside the passband of the receiver filters , and so we should NEVER assume
excess bandwidth just because we hear distortion (or clicks) on the actual
operating frequency.

This is actually where most people giving reports make errors. They either
listen on the operating frequency, or tune off using a wide filter or worse
yet use a "band scope".

The distortion you hear on frequency is a combination of harmonic distortion
(that do NOT indicate splatter), odd-order products in the transmitter audio
section (that do not indicate splatter). Both of tese defects appear from
distortion in the audio systems and modulators/demodulators of the equipment
as well as the audio systems from the microphone right up to the headphones.
Receiver AGC response is another source of distortion. Of all these points
of distortion, only stages after and before filters add noticeable
bandwidth.

73 Tom