Elecraft K3 Owner's Manual - Manual (Page 27)

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External ALC
External ALC should only be used to protect
your amplifier during operation into a failed
load, or during a prolonged overdrive condition.
ALC should not be used as a way to clip or
compress fast voice peaks, or as a primary
means of amplifier or K3 power output control.
DO NOT set the K3’s power level to
maximum and adjust amp output using the
amp’s ALC control. This will result in splatter
and key clicks. Instead, adjust the drive on each
band so it’s just below ALC activation level.
Preparing the K3 for use with External ALC
You may need to modify the K3 to use
external ALC, depending on its date of
manufacture. Please refer to our K3 Modifications
web page. If you turn on external ALC without
making necessary modifications, power will be
reduced to a very low level during transmit.
External ALC Setup
External ALC is set up using the CONFIG:EXT
ALC menu entry. EXT ALC defaults to
OFF . To
turn it ON , tap 1 . 6 meter external ALC can be
turned on/off separately from HF.
The EXT ALC menu entry provides a default ALC
threshold of
-4. 0 V, used by many amplifiers.
If you select CMP / ALC metering at the K3,
external ALC activity is indicated by 8 or more
bars. If you select
SWR / RF metering, the
CMP / ALC meter icons will flash during external
ALC activity to make you aware of the condition.
Some experimentation may be required to
determine the proper setting of the amplifier’s ALC
output control, if one is provided. Start with the
control set for minimum ALC output. Then adjust
the K3’s power output such that the amplifier is just
reaching its maximum level on voice peaks (in SSB
mode) or peak CW power in CW mode.
Next, adjust the amplifier’s ALC output control
upward until ALC action just begins (or adjust the
K3’s ALC threshold with the EXT ALC menu
entry). Finally, reduce the K3’s drive power just
slightly to provide some safety margin. The goal is
to have no amplifier ALC action during normal
operation. If you see an ALC indication at the K3 or
the amplifier, reduce the K3’s power output.
Per-Band Power Control
If the CONFIG:PWR SET menu parameter is set
to
NOR , power output on all HF bands follows the
present setting of P WR . (6 m and transverter
bands are always independent of HF.) If you change
PWR SET to
PER -BAND , the power level will
be saved independently on each HF band. This is
especially useful with external amplifiers, or for
those who use QRP levels on one band and QRO on
another.
When per-band power control is used with an
external amplifier, you can adjust the drive ideally
on each band to prevent external ALC activation
during normal operation.
TUNE Power Level
If CONFIG:TUN PWR is set to NOR , power
output during T U N E will follow the present setting
of P WR . If you change the TUN PWR
parameter to a fixed power level, that level will be
used during
T U N E , whether or not you’ve selected
per-band power control (see above).
Transmitter RF Delay
Some amplifiers have slow relays whose switching
time must be accommodated to prevent key clicks
during CW operation. If your amplifier requires
more than 8 ms of relay switching time, you can
increase the delay from key-down to RF output at
the K3 using CONFIG:TX DLY.
Use the smallest value of TX DLY that works
with your amplifier. Larger values will affect QSK
and keying timing at high code speeds.
Transmitter Inhibit
Some multi-transmitter stations require that
transmitters be able to mutually inhibit each other in
order to prevent simultaneous use of resources. The
K3’s transmit inhibit input (TX INH) can be set up
for low- or high-active control (pg. 19).
Fan Speed
The K3/100 includes two large, quiet fans. Fan
speeds are normally selected automatically, but you
can manually select a minimum fan speed if
desired. See the CONFIG:KPA3 menu entry.