> Using the band data output of the FT-1000, this data would be decoded and
> in turn would be used to address a string of potentiometers that would be
> used to individually set negative feedback levels back into the FT-1000.
> This in turn would allow the setting of the power output on any band to
> any power level simply by adjusting the pot for that band. Fairly easy
> explanation.....And I DID NOT even need to use 4 letter words to do it....
Actually that system would depend on leading edge response time
of the ALC.
A better system would decode band data and set fixed negative
bias for each band. That bias would get within ten dB or so of
proper gain. Then the loop could simply sum-in the correct amount
of additional ALC to hold level constant.
Most ALC systems aren't as bad for splatter as people seem to
think. The leading edge overshoot that exists on *some* radios is
so short it doesn't create much average energy. It mostly is an
aggravation for solid state PA's or firing an arc in tank circuits.
There are actually several problems that cause problems. One is
many new radios have very poor transmitter IMD performance. Look
at the TS-2000 as an example. It is almost class C quality, yet
reviews all ignore that fact.
Another problem is many exciters have poorer IMD performance if
power is substantially reduced. They have peak performance
around half or more of full PEP output, and if operated so they
spend most of their time at low power levels they have increased
IMD.
For people on adjacent frequencies it is a time duration and level
problem of the IMD, not just the fact it might have a leading edge
spike.
I haven't found a rig yet that has a keyclick from ALC problems, so
it appears to be a SSB problem. Keyclicks are designed in by
manufacturers using excessively fast rise and fall times as well as
the wrong filtering (producing the wrong shape of rise and fall, since
shape controls harmonics of the keying waveform). A second
problem on CW is some radios transmit while VCO's are still
settling to new frequencies, causing a leading edge thump as the
VCO system(s) sweeps to a new frequency.
I'm not sure if VCO settling time is a SSB problem or not, I've never
looked for it.... but I'd bet it happens because it sure happens on
CW. Meanwhile the ALC circuit gets 100% of the blame.
73, Tom W8JI
W8JI@contesting.com
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