AL811H and 811 tuning supplement

Supplemental Tuning Instructions

Shooting AL811

AL-811 Myths

TOF Tuning Aid for Amplifiers

811A Tube
History and Construction


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Please take time to read!


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
carrier modes.

 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.


  • A wattmeter connected to the amplifier output (this can
    include the RF power meter in an antenna tuner) must be used to properly
    tune an amplifier. Be aware that many meters do not read correctly,
    especially for peak power. Accurate or not, almost all meters are usable for
    finding maximum power. You may not know the actual power but, with care, the
    amplifier can still be properly tuned for peak.


  • With 811A tubes, while using CW, FM, or RTTY modes for
    tuning, always limit transmitting time to no more than 5-seconds
    transmit with
    a 15-second cool down. The weak point in 811 tubes is not the grid, the grid
    current, or the drive power. The weak point is anode heat, and heat is a
    function of duty cycle and anode dissipation. The grid current is the best
    thing to watch to properly load the amplifier, but this is NOT
    the same as saying the grid is the point of failure!


  • It is probably best to use a tuning pulser. A tuning pulser
    of any type will greatly extend allowable transmitting time while tuning,
    and pulsers of all types will produce exactly the same results. It does not matter
    one bit, other than operator convenience, if the
    pulse is audio-injected or injected through the CW jack.


  • The goal is always to tune and load for maximum possible output power
    at maximum safe drive power. If you want to operate at reduced power, just
    load normally and then turn the exciter power down until desired power is
    obtained. Do NOT retune at lower power except in very
    special cases. These special cases would include RTTY or FM operation.


  • Read the manual. Even if you are bored or you are in a hurry
    to operate your new equipment, read the manual and dry-practice tuning. It
    takes longer to replace tubes than to read the manual tuning instructions
    and practice tuning a few times with power off.


Easiest Possible Tuning Steps with Tuning Pulser

 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.


  1. Preset the transceiver’s power to around 80 watts PEP, or
    nearly full power with a standard 100-watt transceiver.


  1. Preset the PLATE, LOAD and BAND knobs according to the
    manual’s band charts in step 5 of page 6.


  1. Transmit and alternately adjust the PLATE and then LOAD
    controls for maximum RF output meter peak power. Limit time to 15 seconds
    on, and 15 second no-transmit cool-off times.


  1. Set transceiver power to the proper level for the mode you
    intend to use, but NEVER more than used for tuning.


  1. In operation or tuning, never exceed or go above
    the following chart currents:


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:

750 mA plate current

200 mA grid current

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.


Easiest Possible Tuning Steps using a closed CW key, FM
(push to talk), or AM
(push to talk) Tuning


  1. Set the transceiver’s power to about 10-20 watts.


  1. Preset the PLATE, LOAD and BAND according to the presets
    listed in the manual.


  1. Transmit and quickly adjust the PLATE control for maximum RF
    output meter power. (
    DO NOT adjust the LOAD
    Limit to 5 seconds on, and 15 second
    no-transmit cool-off on standby.


  1. On standby (so amplifier is bypassed), increase
    radio power to 60 watts.


  1. Transmit through the amplifier and quickly adjust the LOAD
    control for maximum RF output power.  (Never exceed 5 seconds of
    transmission time). 


  1. After 15 seconds of cool-off, transmit and quickly turn the
    PLATE control back and forth a small amount to make sure the PLATE is at
    peak output power. Take no longer than five seconds to do this without 15
    seconds cool-off time.  


  1. After 15 seconds cool-off, transmit a steady carrier and
    quickly make sure the plate and grid current meters never go beyond the
    maximum rated values listed here. This paper supersedes all other maximum
    current ratings.


  1. If grid meter and plate meter currents are below
    maximum allowable values, increase the transceiver’s power until the grid
    meter reaches the maximum level for the tubes. If plate or grid current is
    too high, stop here and reduce transceiver power to bring the meter in safe


  1. In operation or tuning, never exceed or go above
    the following chart currents:


Allowable AL811H meter readings:

750 mA plate current

200 mA grid current


Allowable AL811 meter readings:

550 mA plate current

150 mA grid current


All 811Amplifiers with 572B tubes:

750 mA plate current

200 mA grid current


Note: Do not
attempt to force amplifier meters to this value on SSB voice or under
tuning-pulser conditions.


  1. After 15 seconds cool-off, if you have not reached maximum
    allowed plate or grid current, transmit and re-peak the LOAD control for
    maximum output.  Do not transmit for more the 5 seconds without a suitable
    15 second cool-down.

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.


SSB Operation

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.

RF Wattmeters

There are two types of RF power, average power and
peak envelope power. Both average and peak powers are
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. 

Antenna SWR

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.

ALC Adjustment and Operation

Never use ALC as a primary power
The ALC control is another way to reduce the
transceiver’s output power.  Unless connected to the radio, ALC has no

  1. Leave the ALC disconnected and tune the
    amplifier to the desired output level, not to exceed maximum plate or grid
    currents, or maximum output power. 


  1. Connect the ALC line with the ALC
    adjust fully clockwise (facing the back of the amplifier).


  1. Transmit with amplifier operating and
    adjust the ALC until the grid meter or output power starts to drop.  Stop at
    the point when the meter starts to drop.


  1. The ALC is now adjusted for the desired
    power limit.

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
safety measure.


2012-03-21 new rev 1 (clarified some wording)