TS440 Serial interface

The TS440 has a serial ASCII interface option. You have to insert two chips into sockets on the back of the control unit circuit board to
take advantage of this. IC54 is an 8251A Uart, and IC55 is a CD4040 divider. These chips are available from Kenwood together with a
interface manual, or you can buy them at your local chip shop for about $6.00 or so. When inserted, the transceiver speaks 4800 baud
ascii in/out the 6-pin DIN connector ACC-1 on the rear. The signals are from the 8251, but are inverted in a 74LS04 and RFI filtered
before being brought out to the world. An interface box with inverter, RFI filter, power supply, opto-isolator, RS232 level shifters, and
power supply is available from Kenwood for about $49.00, or you can build your own.
(Depending on how much your computer radiates and how sensitive to RF it is, you may only need 5v, +/-12v, a 74LS14, MC1488,
and MC1489. If your computer has a TTL level serial port, perhaps all you'll need is the 74LS14. If you're not confident of being able
to solve the possible digital/RF interface problems yourself, the $49 interface is proably a good buy.)
ACC-1 Serial Interface
pin signal
— —————————————————-
1 signal ground
2 data from transceiver
3 data to tranceiver
4 cts to transceiver - computer can throttle output
5 cts to computer - transceiver can throttle input
6 no connection
SSB frequency response dipswitch: located on the back of the control unit, this adjusts the frequency response of the upper and lower
sideband modulators to compensate for component variations. Changing it isn't a good idea, since you have to have a two-tone
oscillator and have to reset the carrier suppression adjustment if you do. The service manual explains this process; I'm including this
here so that people who have been wondering what the dipswitch does won't screw themselves by flipping switches to see what

GW1NGL NA7KR Kevin Roberts Ham Radio

Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information