USKI-5 Universal Sequencer & Keying Interface
© Copyright 2015 QSK, llc
www.qskllc.com
Page 2
OVERVIEW
The USKI-5 is a programmable microcontroller based Universal Sequencer and Keying
Interface suitable for use in many applications requiring accurate electronic timing between
switching events. It is particularly suitable for amateur radio applications allowing sequenced
keying of equipment such as transmitters (or transceivers), power amplifiers, receiver muting,
VFOs, antenna relays, T/R switches, transverters, TMAs (tower mounted amplifiers), etc., as is
typically necessary for equipment protection and QSK CW or EME operation. It is easily
programmed and provides four input control channels and five output channels. Each output
channel features a plug-in opto-isolated high speed MOS FET solid state relay, configured to
switch AC or DC loads of either polarity. A variety of pin compatible relays are available with
different output voltage and current ratings (up to 600 V and up to 4 A) that can be mixed
among the output channels as necessary making it ideal for keying modern solid state as well
as older tube equipment. This also allows for interfacing between for example, keyers, radios,
amplifiers, etc., which do not have compatible keying voltage or current requirements. Since the
USKI-5 is microcontroller based, it can be programmed for virtually any conceivable order of
events. Each output can be programmed for normally open or inverted (normally closed)
operation.
Once programmed, the USKI-5 can be operated with or without connection to the
programming computer. The stored program is nonvolatile and no backup batteries are
required.
The heart of the USKI-5 is a PICAXE®
1
14M2 microcontroller. It can be programmed or
reprogrammed in BASIC language via a computer USB connection using software available free
at the PICAXE® website
2
. There are also several manuals available on the website with
comprehensive information about the PICAXE® series of microcontrollers for anyone interested
in writing their own programs.
A number of amateur radio application programs, already written for the USKI-5, are available
for download at
. These programs are easily modified for the required
sequencing and timing, and in most cases eliminate the need for the user to learn the BASIC
language or write their own programs from scratch. Instructions for the use and modification of
these programs are included in the following sections of this manual.
REASONS FOR SEQUENCING
There are numerous reasons for sequencing events during the transition between receive and
transmit (T/R switching) states in radio equipment.
Mechanical relays are often used in communications equipment. Because they require a
relatively long time for actuation, typically between 5 and 25 ms, other events may need to wait
until relays have fully transitioned. Without proper sequencing, relays may
be subject to “hot
switching” (which can cause relay contact damage) and parts of transmitted messages may be
1
PICAXE® is a trademark of Revolution Education Ltd.
2
http://www.picaxe.com/Software