Elecraft K3 Owner's Manual - Manual (Page 41)

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Main and Sub Receiver Antenna Routing
The simplified block diagrams in this section show how antennas are routed to the main and sub receivers.
Heavy lines show the default RF path. All antennas are protected from electrostatic discharge by surge arrestors.
Receive-only antenna inputs, indicated by asterisks (*), include carrier-operated relay circuitry (C.O.R.).
Basic K3 (no KAT3 or KXV3)
As shown in Figure 1, the basic K3 is supplied with one antenna jack (ANT1, SO239). The signal from ANT 1
is routed through the antenna input module (KANT3) to the main receiver (as well as to the transmitter). The
KRX3 sub receiver, if installed, can share the ANT 1 signal via a passive splitter and relay K1. When the sub
receiver is off or is switched to its AUX RF input (dotted line), K1 bypasses the splitter so it will have no effect
on either receiver.
An extra RF I/O connector location is provided (AUX RF, BNC). The sub receiver’s AUX RF input can be
routed to this connector internally. K1 then selects either the main RX path or AUX RF as the sub receiver’s RF
source. Any receiving antenna connected to AUX RF must be isolated from the transmit antennas so the sub
receiver’s C.O.R. will not be activated during transmit. Note: The sub receiver has its own full set of ham-band
and optional general-coverage band-pass filters (KBPF3), but its image rejection will be best when sharing the
main path, which includes the receive/transmit low-pass filters.
Main RX
Ant 1
KRX3
KANT3
Ant. Input Module
Sub RX K1
*
SA1
SA4
* Includes C.O.R.
Aux RF
Figure 1. Basic Main/Sub Receiver Routing (no KAT3 or KXV3)
K3 with KXV3 RF I/O Module
If the KXV3 option is installed (Figure 2), a separate receiving antenna can be connected to the RX ANT IN
jack. Relay K2 then selects either ANT1 or RX ANT for the main receiver. Note: The low-pass filters will not
be in the path when RX ANT is selected. This will rarely be an issue, since the main receiver has a full set of
ham-band band-pass filters. You can use external filters with RX ANT IN if required.
Relay K1 allows the sub receiver to share the main receiver’s RF source, or use its AUX RF input. This means
that two receiving antennas could be used – one for each receiver. The two inputs could also be joined externally
with a ‘Y’ adapter.
Not shown is the RX ANT OUT jack. The RX ANT IN/OUT jacks can be used together to “patch in” an
external band-pass or low-pass filter or low-noise preamp such as the Elecraft PR6 (6 meters). If such a device is
powered, it can be turned on or off on a per-band, per-antenna basis using the CONFIG:DIGOUT1 menu entry.