Universal Keying Adapter 3
05/05/2013
Page 7 of 10
Using the UKA-3
The Active-Low input
is on the tip of the 3.5mm stereo jack. It is used for most straight
keys, bugs, electronic keyers, amplifier keying relays or transistors, foot switches, etc. It
is in series between the input side of the solid-state relay and ground. Shorting the
ACTIVE-LOW input activates the output of the solid state relay K1, keying the attached
transmitter or transceiver. The current through the ACTIVE-LOW connector will be
limited to no more than 20 to 25 milliamps. The ACTIVE-LOW input is protected from
high positive voltages up to 60 V by a diode, but most not be driven below ground
potential (0 Volts). If you only plan to use the ACTIVE-LOW input, you can use a
3.5mm mono plug.
The IN HI input
is normally used for computer keying, but can be used for any signal that goes
to a high level when keying and near or below ground when not keyed. This input is pulled low
to ground by 100K Ohm resistor R2. Applying a positive voltage (approximately 3V or higher)
to the IN HI input turns on Q1, which turns on K1’s output and keys the rig. The MOSFET gate-
source voltage is rated for plus or minus 20 Volts maximum, meaning it will easily tolerate
computer parallel or serial port voltages.
Many programs use the standard computer port setup established by NA and CT. When using a
program such as this, the
IN HI
signal should be a positive logic signal to key the rig. Here’s a
table showing connections for various types of serial and parallel port connectors:
If you are not using the IN HI input, it can safely be either left floating (open) or
grounded.
Alternate Power
Your UKA-3 is designed for a nominal 12V power supply. The acceptable power input
voltage is from 10 to 14 Volts, AC or DC. If your power source varies significantly from
this, you may need to make a couple of minor changes to the power supply circuitry, as
shown in the table below.
LPT
25-Pin Serial
9-Pin Serial
IN HI input
17
20
4
3.5mm plug sleeve (ground) 18
7
5
Supply voltage
Recommended R1 value
Recommended R2 value
3V
None (jumper R1 with wire)
100 Ohms
5V
470 (Omit Zener diode D1)
220 Ohms (unchanged)
6V
100 Ohms
220 Ohms (unchanged)
9V
220 Ohms
220 Ohms (unchanged)
16V
560 Ohms 1/2W
220 Ohms (unchanged)
