USKI-5 Universal Sequencer & Keying Interface
© Copyright 2015 QSK, llc
www.qskllc.com
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lost. In particular, beginning portions if not all of the leading CW symbol
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(dit or dah) may not be
transmitted when operating in full or semi-break in mode. Modern transceivers are generally
capable of good semi or full break in performance
when operated alone (“barefoot”). Some
external power amplifiers also have provisions for QSK operation. Amplifiers that do not should
have their keying sequenced with that of the transmitter.
When operating QSK with a separate receiver and transmitter (even without mechanical relays),
proper sequencing of receiver muting and transmitter keying is necessary for best QSK
performance. By muting the receiver from before, until after, any transmitted signal is present,
effect on the receiver AGC voltage will be avoided thus minimizing receiver recovery time after
each CW element.
T
o avoid “key clicks” a transmitted CW symbol must have properly shaped attack and decay
characteristics. Not only must the transmitter itself have proper shaping characteristics, there
must not be external factors which can cause truncation of the keying envelope. If an external
VFO is used as a transmitter frequency source, its RF output must be turned on before the
transmitter begins the attack portion of a symbol and must remain on until after decay is
complete. This same principal also applies to any power amplifier or antenna switching that may
occur along with transmitter keying.
Many VHF/UHF and EME operators may use transverters and remote low noise tower mounted
amplifiers (TMA). Being prone to damage from transmit signal levels, it is important for these
devices to be switched out of line from before, until after, the period of transmitter power output.
An electronic sequencer can provide the proper order and timing of events in these and many
other applications.
TIMING PROGRAMS AND EXAMPLES
The USKI-5 can be programmed for virtually any conceivable sequencing routine. The programs
presented here sequence the USKI-5 output channels in a sequential 1-2-3-4-5 fashion when
switching from receive to transmit and with the reverse order when returning to receive as
shown in figure 1. The control signals may be from a CW keyer or PTT switch in a microphone
or footswitch. Start and end delays are simply shown as START_DEL_# or END-DEL_# in this
figure as a general reference. Depending on the program and operating mode, they may have
different references such as
“CW_START_DEL_3”, “PTT_END_DEL_2”, or “TX_START_1”, for
example.
Users interested in modifying these programs or writing their own can review the PICAXE©
manuals for programming techniques and functions if necessary.
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The basic element “dit” has a duration in seconds equal to 1200/WPM