Many years ago, I built a tube amplifier with what I thought was a
fairly sophisticated ALC circuit. I could never get the ALC loop to be
stable. I know a lot more about control systems now, but I still don't
know how to get ALC around an amplifier to work, and apparently neither
does anyone else. What I don't understand is why it's so hard with an
external amplifier, as every transmitter has ALC for its internal 100 W
amplifier, and that works fine. Why the same design doesn't work with an
external amplifier is the mystery.
The problem with just limiting the drive power and using the
transmitter's ALC is that, especially for solid state amplifiers, the
required drive power can vary considerably with SWR and temperature.
That requires either riding the power control continuously or running
your amplifier well below rated output most of the time. (Unless, of
course, you're running a 2.5 kW amplifier, but that kind of margin is
expensive.) So, if anyone could figure out how to get ALC to really work
with an amplifier, I think that would be worth paying extra for.
73,
Scott K9MA
On 2/28/2019 13:12, Bob McGraw K4TAX wrote:
Yes, improperly or incorrectly using ALC with any amp or any
transceiver, for that matter, can and usually does produce distortion
and splatter. Just look at some of the signals on the bands and
observe the ALC overshoot which exists with many radios. And it is
made worse by the addition of an amplifier in line. It isn't
pretty!. Yet it has little impact on the on frequency signal as
heard and thus the "great signal" complements follow. But look at the
other factors where you will find "NOT so great signal". These
points should be addressed as well.
73
Bob, K4TAX
On 2/28/2019 1:04 PM, [email protected] wrote:
I have not used ALC with any amplifier since transceivers switched to
transistor finals. From what I have read on this list, using ALC
improperly can cause distortion. Just be very careful with your
drive level. I believe that the KPA500 can handle 100 watts in
bypass, 200 watts may be pushing it. The KPA500 is a very nice amp
and it is easy to use with any transceiver.
GL,
John KK9A
JIM LAGESON N0UR wrote
_Thu Feb 28 13:07:27 EST 2019_
-------------------------
I have never owned an amp before and recently put together a KPA500. All
seems to be working well, but I have a few questions. I am using with a
IC-7300.
How important is the ALC cable? I notice it is not included in the Basic
Cabling Diagram in the manual but is discussed later in the manual.
If I were accidently to run 100 watts into the KPA500 will the PWRIN HI
Hard Fault/STBY protect itself before any damage is done. Would ALC
protect
me from that?
Is it standard procedure to keep the KPA500 in line when turned off
and not
in use? I see you may run up to 200 through the KPA500 in STBY.
Is there any concerns or settings on radio when running full break in
on CW?
Thanks
Jim-N0UR ml
--
Scott K9MA
[email protected]
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