This has been a very interesting discussion on TT and ALC. A lot
of good information has been included but the real question
hasn't been answered clearly.
TT amps and rigs lack an ALC jack because they don't need
them.
To answer why requires a discussion of why ALC and how developed.
ALC is used to keep from overdriving the amplifier past it's
linear point. If it is an AB1 amp then when it starts drawing
grid current it becomes nonlinear and at that point the amplifier
starts generating a ALC voltage that is fed back to the
transmitter and tells it to reduce power. If AB2 then some grid
current is allowed but when that current is reached the amplifier
then starts to generate the ALC voltage. There are several
methods to generate the ALC voltage but it doesn't matter how as
long as it's generated at the correct value in the amplifier. Now
remember that the amplifier will NEVER be over-driven until this
point is reached and it's excess power that causes the amplifier
to go past this point.
The ALC control on a TT transceiver is really a MAXIMUM power
control. If set to a setting that allows an output of say 80
watts at the transceiver then no matter how loud you speak into
the microphone you will not get more that the 80 watts. This is
not true with most of the other brands. Take the Kenwood TS-830s,
they don't have a power control just mic gain. If you talk louder
you get more output. With a TT and ANY brand of amplifier you can
advance the ALC control until you get maximum power out of the
amplifier or you drive it to it's maximum linear grid current
and back off very slightly (5 watts) and you can never drive the
linear into non-linear operation. Once you have set the power
out of the transceiver to the level the amplifier needs then you
should adjust the mic gain until the ALC LED on the transceiver
"winks" on modulation peaks and stays lit about 25-40 % of the
time. However if you watch it on a scope and you advanced the mic
gain all the way you still will not overdrive the linear
amplifier though the transceiver may have some distortion.
From this discussion you can see that a TT transceiver and ANY
amplifier doesn't need an ALC to prevent overdrive. With other
brands and models of transceivers and ANY amplifier you MAY well
need the ALC unless you have a way to set the power out of the
transceiver. I believe the any of the transceiver manufactures
that have a linear, design the linear to work properly with their
equipment. It would be very hard for them to design something
that will work with 100% of other brands though it may work fine
with most of them.
I run an Ameritron AL-80 and a Jupiter. I set the Jupiter to
about 80 watts for maximum output and never over drive the amp,
100 watts drives it into distortion easily. With my TS-830s I
MUST use the ALC or I will frequently drive it into distortion.
73 Jim K4CGY
--- "Rob Atkinson, K5UJ" <k5uj@hotmail.com> wrote:
> Why do Ten Tec rigs lack an ALC jack and why do Ten Tec amps
> lack an ALC
> input?
> It has occurred to me when I have been driving my Centurion
> with nonTen Tec
> exciters.
> No problems as far as I can tell, however, it seems to be
> something Ten Tec
> would want to
> include in their amps if they were interested in selling them
> to hams
> running other than Ten Tec
> exciters.
>
> Rob/K5UJ
>
>
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