ELECRAFT K3, Owner'S Manual

Page: 27 / 78

27
External ALC
Exte rnal ALC should only be use d to prote ct
your amplifie r during ope ration into a faile d
load, or during a prolonge d ove rdrive condition.
ALC should not be use d as a way to clip or
compress fast voice pe aks, or as a primary
me ans of amplifie r or K3 powe r output control.
DO NOT s et t he K3’ s power l ev el t o
maximum and adjust amp output using the
amp’ s ALC cont rol . Thi s wi l l r es ul t i n spl at t er
and key clicks. Instead, adjust the drive on each
band s o i t ’ s j us t bel ow A
LC activation le vel.
Pre paring the K3 for use with Exte rnal ALC
You may nee d to modify the K3 to use
exte rnal ALC , de pending 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.
Exte rnal ALC Setup
External ALC is set up using the CONFIG:EXT
ALC menu entry. EXT ALC defaults to
O FF
. To
turn it O N , 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
S WR / RF metering, the
CM P
/
ALC
meter icons will flash during external
ALC activity to make you aware of the condition.
Some experimentation may be required to
det er mi ne t he pr oper s et t i ng of t he ampl i f i er ’ s ALC
output control, if one is provided. Start with the
control set for minimum ALC output. T hen adjust
t he K3’ s power out put s uch t ha t t he a mpl i f i er i s j us t
reaching its maximum level on voice peaks (in SSB
mode) or peak CW power in CW mode.
Next , adj us t t he ampl i f i e r ’ s ALC out put c ont r ol
upward until ALC action just begins (or adjust the
K3’ s ALC t hr es hol d wi t h t he
EXT ALC
menu
ent r y) . Fi nal l y, r educe t he K3’ s dr i ve power j us t
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
t he ampl i f i er , r educe t he K3’ s power out put .
Per-Band Power Control
If the CONFIG:PWR SET menu parameter is set
to NO R , power output on all bands follows the
present setting of
P W R
. If you change PWR
SET to
P E R-BAND
, the power level will be saved
independently on each band. This is especially
useful with transverters and 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
NO R
, power
output during
TU N E
will follow the present setting
of
P W R
. If you change the
TUN PWR
parameter to a fixed power level, that level will be
used during
TU N E
, whet her or not you’ ve s el ec t ed
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:T X DLY.
Use the smallest value of T X 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 provides a transmit inhibit input (TX INH) that
can be programmed for low- or high-active control.
See pg. 19.