ELECRAFT KRX3 - Using the Sub Receiver; Dedicated Sub Receiver Controls; BSET: Additional Sub Receiver Controls; Sub Receiver Antenna Selection

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Using the Sub Receiver
The KRX3A option adds an independent, high-
performance sub receiver to the K3. It allows you
to monitor a second frequency, using different
bandwidths or modes. Diversity receive is possible
if the main and sub receivers use different antennas.
Dedicated Sub Receiver Controls
Tapping SUB turns on the sub receiver (and SUB
icon). VFO B then controls the sub receiver
frequency, and also serves as the TX frequency
during SPLIT.
You should leave the sub turned off when not in
use. This turns off the -3 dB passive splitter used
when the sub receiver shares the main RX path.
The VFOs may be linked (whether the sub receiver
is on or off) in the Configuration menu
(
CONFIG;VFO LNK ON or OFF). The kHz decimal
point of VFO B flashes as a reminder. VFO A is the
master, moving both VFOs in tandem.
Holding SUB turns on diversity receive (see next
page). The kHz decimal point of VFO A flashes as
a reminder. VFO A controls both the main and sub
frequencies in diversity receive, but VFO B remains
independent so it can be used as the SPLIT transmit
frequency.
SUB AF gain normally sets the sub receiver
volume level. Alternatively, SUB AF can be used
as a main/sub balance control (see
CONFIG:SUB
AF
). With stereo headphones or dual speakers,
you'll hear the sub on the right and main on the left.
Otherwise main and sub receiver audio are merged.
CONFIG:SPKRS must be set to 2 if you use
stereo speakers; otherwise, set it to 1.
SUB RF gain normally sets the sub receiver RF
GAIN level. If this knob is assigned to main/sub
squelch (
CONFIG:SQ MAIN), then both main and
sub RF gain are controlled by MAIN.
BSET: Additional Sub Receiver Controls
Normally, receive controls apply only to the main
receiver. This includes SHIFT, WIDTH,
PRE,
ATTN, etc., as well as MODE. To change these
settings for the sub receiver, first hold BSET. VFO
A will show
BSET, and the S-meter will show the
sub receiver signal level. After you’ve made the
desired sub receiver changes, tap
A/B or hold
BSET to exit BSET.
The sub receiver band cannot be set
independently unless
CONFIG:VFO IND is set to
YES. If it is set to NO, you’ll see =MAIN when
you tap BAND during BSET, and the sub
receiver band will always be set the same as main.
Sub Receiver Antenna Selection
The sub receiver gets its RF input either from the
main receiver (sharing ANT 1-2 or RX ANT IN), or
from its auxiliary antenna input (see your K3
Owner’s Manual, Main and Sub Receiver Antenna
Routing).
When using
BSET, you can tap ANT to switch the
sub between MAIN (shared) and AUX (the sub
receiver AUX input). When
MAIN is in effect, the
1-2 and RX icons show which antenna the sub is
sharing with the main receiver. When
AUX is in
effect, these icons will all be off (if
CONFIG:KRX3A is set for
ANT=BNC) or will
show the non-transmit ATU antenna,
1or 2 (if
KRX3A is set for
ANT=ATU).
Shortcut: If you’re not in
BSET mode, you can
quickly switch the sub between
MAIN and AUX by
holding RX ANT. (Tapping RX ANT turns RX
ANT on/off for the main path.)
The sub receiver AUX antenna must be well-
isolated from the main (transmit) antenna to
avoid activating the carrier-operated relay in the
sub receiver.
Using the AUX input for the sub receiver
slightly improves sensitivity of both the main and
sub receivers because the splitter is not used.
Sub Receiver Band Independence
If CONFIG:VFO IND is set to YES, you can set
the sub receiver to a different band from main.
Hold BSET, then tap BAND up/down to select the
band. If you only use band-independence for the
sub receiver occasionally, you may want to assign
VFO IND to a programmable function switch (See
your K3 Owner’s Manual, Basic Operation,
Programmable Functions).
If the two receivers are sharing the main
antenna path, putting the sub receiver on a
higher-frequency band than main may result in
signal loss in the sub receiver. This is because the
sub receiver shares the low-pass filters in the main