USKI-5 Universal Sequencer & Keying Interface
© Copyright 2015 QSK, llc
www.qskllc.com
Page 7
FIGURE 4
USKI-5 PROGRAM (D)
is similar to Program (A) and applies to stations configured as
shown in Figure 2 but has no provision for CW break-in operation. In some applications
the required sequencing delays are of sufficient length that CW break-in operation at any
reasonable speed is not possible. In these cases Program (D) can be used with only
PTT control of transmit-receive operation. CW keying is still connected to input J1T, as
shown in Figure 2, but CW keying output from the sequencer is only applied to the
transmitter if PTT is activated via input J1R. With no CW activation of the timing
sequence, Program (D) only requires setting of PTT sequencing delays.
TIMING CONSIDERATIONS
If the sequencer is controlling RF sensitive devices such as TMAs or transverters, make
sure to allow a sufficient amount of time for switching to avoid component damage from
transmitter power output. If in doubt, add extra time to be on the safe side!! The user is
responsible for correct programming and use of the USKI-5 sequencer.
During normal receive-transmit-receive sequencing, the transmitter will be the last device to be
turned on (started) and first to be turned off (ended). In CW operation it is important to have the
transmitted signal’s time duration the same as that of the control signal. Therefore it is
necessary to compensate for the time lost in the START delays. This is easily done by simply
setting END_DEL_5 equal to the sum of all the START DELAYS.
For modes of operation other than CW, timing delays for various components during transmit-
receive switching is not usually as important. Tens or hundreds of milliseconds delays can often
be tolerated without adversely affecting operations. For CW full break in (QSK) operation
however, proper timing is critical. Sequencing delays are necessary but in the interest of
maximizing receive time, it is important that the delays be as short as possible consistent with
proper operation.
For a given sum of START and END delays, there is a maximum CW speed possible without
introducing errors. If the sum of is too long, the control signal could go low or “key down” before
