[TenTec] re Ten Tec amps and ALC

[Bob Henderson]

Rob

It is important to remember there is no standard for alc circuitry and
operation.  It is eroneous for a third party amplifier manufactuers to have
an alc output and suggest you should use it regardless of your exciter.

Most amplifier manufacturers suggest you don't try to link exciter alc to
amplifier alc ccts because compatibility is unlikely.  Connection is for the
most part unecessary and frequently undesirable.

Strangely enough, many non linearity problems are caused by ineffective alc
operation which could be avoided if alc didn't need to be relied upon.

Bob, 5B4AGN


----- Original Message ----- 
From: "Rob Atkinson, K5UJ" <k5uj at hotmail.com>
To: <tentec at contesting.com>
Sent: Thursday, August 19, 2004 9:06 PM
Subject: [TenTec] re Ten Tec amps and ALC


> According to this then, Ten Tec ought to include an ALC output (I
> erroneously called it an input earlier, sorry for my haste) with their
amps
> so they may be operated properly with other mfr's exciters.  It almost
seems
> as if there is an assumption that you are only going to drive a ten tec
amp
> with a ten tec exciter.
>
> BTW, the amps made by specialty companies (Command for example) include
ALC
> circuits, no doubt so they may be operated with the widest variety of rigs
> possible.
>
> Rob/K5UJ
>
> <<<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
> >>>
>
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