64
CW Keying and PTT
There are three basic ways to key the K2 when using a computer:
Microphone, hand key, or paddle directly to the K2:
This is
preferred if you don't use the computer to generate CQs and contest
exchanges.
Serial or parallel-port
control line
keying:
Many programs support
this method. In SSB mode the computer turns a selected control line
on to activate PTT. In CW mode, the computer generates the dots and
dashes, turning the selected control line on and off in response. The
control line(s) used--which may be at RS-232 or TTL/CMOS levels--
must be level-shifted for connection to the K2 key and/or mic jacks.
"Virtual" keying, using computer commands sent to the
KPA100's serial port:
In this case, no connection to the key or mic
jacks is required for keying the K2. In SSB mode, the computer sends
the K2 "TX" and "RX" commands, which the K2 responds to by
turning PTT on and off internally. In CW mode, the computer sends
typed characters to the K2 using a "KY" command, and the K2
converts the characters to dots and dashes internally. This method of
keying is supported by only a few remote-control applications,
including Elecraft's K2REMOTE program. (For details on the TX,
RX, and KY commands, refer to the KIO2 Programmer's Reference.)
For control-line keying, you can use the spare wire (white) in the 4-
conductor cable. You'll need to connect this wire to the specified control
line at the PC end. At the K2 end, a level converter using an NPN
transistor will be required (usually diagrammed in your program's user
manual). The white wire must then be brought out from the connector at
the K2 end and routed to a 1/8
th
inch stereo plug for the key jack. You can
optionally use two diodes (or two transistors) to take advantage of the
K2's "auto-detect" feature, allowing both the computer and a keyer paddle
to be connected to the K2's key jack at the same time. Additional
information on this topic can be found on our web site.
Connecting Other Equipment to the KPA100
J8 provides a number of signals in addition to those needed for the RS-
232 serial interface (Table 2).
Note:
Use pin 1 as the electrical ground for
any external devices. Pin 5 should only be used as the RS-232 ground
return to the computer.
Table 2.
J8 Signal Descriptions.
Pin
Signal
Notes
1
Chassis GND RF/DC ground
2
TxD
RS-232 data from K2 to computer
3
RxD
RS-232 data from computer to K2
4
--
Not connected
5
RS-232 GND RS-232 ground return
6
AuxBus
K2 configuration network, intended for use
with AuxBus-compatible peripherals.
Connections made to this line must be
shielded, and total bypass capacitance should
be between .001 and .005 µF.
7
RF Detect
RF level feedback (DC), intended for use
with an external automatic antenna tuner.
Improper use of this line could result in
incorrect K2 power settings, high current, or
other difficulties.
8
12CTRL
This is intended as a power-on signal from
the K2, and/or for powering low-current
external peripherals. Total load current
should be kept under 50 mA continuous, 80
mA peak. A 150-Ω or larger series current
limiting resistor should be used.
9
8 V Receive
8 V on receive, 0 V on transmit (approx.)
This signal is intended for use sequencing
external amplifiers, although the use of the
PA KEY output is preferred because it can
drive amplifier relays directly.
