USKI-5 Universal Sequencer & Keying Interface
© Copyright 2015 QSK, llc
www.qskllc.com
Page 4
FIGURE 1
Four pre-written programs are presented in the following sections which should satisfy the
requirements of most any amateur radio application. These programs are available for
download at
. Before using a program, delays must be set to values appropriate
for the specific application. Timing examples are presented in the addendum section at the end
of this document.
A transmit inhibit function is included with each program by the available interrupt function of the
PICAXE® 14M2 microcontroller. The input designated for transmit inhibit (interrupt) is
continuously monitored and when activated, will immediately execute the routine programmed
for such an event. If the program is in standby and the interrupt is activated, transmitting will be
inhibited, regardless of the state of other inputs. If the program has already begun the
transmitting sequence, an interrupt condition will cause the program to immediately “back out” of
the sequence with proper delays to protect sensitive equipment, just as in a normal transmit-
receive sequence.
USKI-5 Program (A)
is ideal for sequencing of all devices in the transmit/receive system
including TMA, transverter, power amplifier, etc. All keying functions (CW, PTT, etc.)
must be connected to inputs of the sequencer which then controls switching of each
device (see
USKI-5 Program (D)
for PTT operation only). This allows sensitive devices
such as a TMA and/or transverter to be switched into a safe condition before transmitter
RF power is applied. Transmitter external amplifier relay control output is monitored for
an open contact state to further ensure that the transmitter has returned to standby
before the system is returned to a receive condition. Direct activation of the transmitter