The first step is to understand the power ratings. The
AL-811H is rated at 800-watts PEP voice on a good peak reading meter. The
AL-811H is rated at 600-watts CW carrier in normal CW or tune. The AL-811 is
rated at 600-watts PEP voice, or just over 400-watts carrier in normal CW modes.
These ratings are ICAS with a reasonable conversational duty cycle.
The difference in power supply voltages on voice and carrier
modes is the major contributor to differences in peak power between voice and
Occasionally, first-time amplifier owners have difficulty
understanding manual tuning instructions. Reading all manual tuning steps and
“dry practicing” (without actually transmitting) all manual tuning steps will
make initial operation much easier and safer.
I wish amplifier-tuning instructions could be shorter.
Unfortunately, every step is necessary for proper amplifier operation, and we
have carefully removed all unnecessary steps. This procedure omits as much as
can possibly be omitted and still properly tune the amplifier.
Some previous supplemental procedures issued do NOT properly tune
the amplifier. Previous supplemental instructions can result in re-tuning when
it is not necessary. Previous supplemental instructions also result in improper
tuning, that while increasing tube life, also increase splatter.
Short of using a tuning pulser, there is no easy correct
two-step or three-step tuning process. Tuning takes some practice but is
something we must learn if we want good amplifier life and a clean signal.
Eventually tuning becomes easy.
Make sure the pulser has the shortest possible pulse duration or
“weight” for your radio. If you use dots on a keyer, make sure weight is 35% or
less if possible. The shortest possible pulse is one that is just longer than
the value that reduces peak output power. It is not
necessary to use any special ratio of on-time to off-time in the pulser, perhaps
as an attempt to simulate relative duty-cycle of voice modulation. It is also
not necessary, nor is it generally advantageous, to use an audio injected
pulsed tone. The only duty-cycle requirement is the exciter reach full peak
power. Use the shortest
possible pulse that allows full power. CW pulsers and audio-injected pulsers are
equal in results.
Allowable AL811H key down meter readings:
750 mA plate current
200 mA grid current
Allowable AL811 key down meter readings:
550 mA plate current
150 mA grid current
All 811Amplifiers with 572B tubes:
Do not attempt to force amplifier meters to these values on SSB voice or in pulsed
tuning conditions. These are maximum currents shown accurately by meters only in
steady carrier modes. Any carrier should be brief, the ratings above are NOT
steady long term ratings.
Allowable AL811H meter readings:
Allowable AL811 meter readings:
Note: Do not
attempt to force amplifier meters to this value on SSB voice or under
As a final adjustment, moving the LOAD control very
slightly clockwise of maximum produces a cleaner SSB signal. Move the LOAD no
more than ½ of a number position clockwise. It also helps to reduce the
transceiver’s power a few watts from tune power.
The amplifier’s meters are not fast enough to follow SSB voice
(or normal Morse code) signals. Never increase the transceiver’s power after
tuning the amplifier to make amplifier meters go higher. The transceiver power
control setting used in the last tuning procedure adjustment must be the same or
less for normal operation.
A good, accurate peak meter will show a voice RF outputs about
10-20% higher than obtained with FM, RTTY, or CW carrier tuning methods. This is
because amplifier high voltage on voice is closer to no-load voltage.
Depending on your voice and the amount of speech compression or
ALC you use, amplifier front-panel meters will indicate about 1/5 to 1/2 of
actual peak current. This is also true with average reading RF wattmeters.
There are two types of RF power, average power and
peak envelope power. Both average and peak powers are
envelope power. We rarely hear the term "average envelope power" but
that is what "key down" or CW power is.
Average power is the longer time average of envelope power, while PEP or peak
envelope power is the highest short-term peak of envelope power.
There is no such thing as “RMS power”. Audio marketing people
created RMS power along with other useless fictitious power types to help sell
RF wattmeters reading true peak envelope power (PEP) generally
require a power source of some kind to make the peak system work. Cheap PEP wattmeters often show only 50% of actual PEP when operating voice SSB. If a PEP
meter is working properly, the meter will show more power on SSB voice than a
steady, clean whistle or CW carrier indicates. The AWM-30 Ameritron is a very
good peak reading meter, as are meters in Ameritron tuners. Many other meters
(like older MFJ antenna tuner meters) do
not accurately read peak envelope power.
Cheap or poorly designed RF power meters may read half or less of
actual PEP on SSB voice. If a whistle and speech have greatly different power
levels the meter is most likely poor.
Normally the amplifier will match up to a 2:1 VSWR or higher. You
must use an external tuner between the antenna and the amplifier if your
antenna’s VSWR is too high for proper amplifier loading. When tuning or
operating the amplifier, be sure VSWR does not change. Do not use your
transceiver’s internal tuner when using an amplifier.
Never use ALC as a primary power
control. The ALC control is another way to reduce the
transceiver's output power. Unless connected to the radio, ALC has no
Increasing the transceiver’s power control
beyond this set point should not increase meter readings on the amplifier. This
will verify the ALC is controlling the transceiver. We do not recommend
depending on simple basic ALC systems for operating power control. It is only a
2012-03-21 new rev 1 (clarified some wording)