 |
RC640 radio unit
...with... RC690 control head |
RC640 meets RC690
See the RC640 and RC690 pages first for some background.
RC690 is the AM version used by many police forces. Over 3000 were made and large numbers have appeared on the surplus market.
RC640 is the FM version used by the Met police. Far fewer were made so they're more difficult to find.
From an operational point of view, the FM version is more useful to amateurs as that's what packet nodes and repeaters and simplex chit-chat uses. Not to say AM is entirely dead, It would suffice for many kinds of packet link, beacon, tele-control etc.
Both types of radio have a matching control head. In practice if you get hold of an RC640, getting the matching head is another problem.
This begs the Question... does an RC690 control head work with an RC640?
Simple Answer: Yes!
Longer answer:
The PA key doesn't work as RC690 has a PA in the base but RC640 doesn't.
The repeat keys don't work. This is because the radio unit fails to ID itself as a repeater variant RC690 to the control head. Firmware may get tweaked later to fix this
Make sure you get an RC690 handset to match the control unit.
This page is written from the point-of-view of the RC640 and RC690 models I have. There are several other variants about. define
How?
There are 2 steps:
One
Make a lead to connect the RC640 radio to RC690 head
unit.
Two
Replace the EPROM firmware in the RC640 radio unit with
the latest firmware on the RC640 page. Set the CTCSS dip-switch as
desired. Leave the firmware in the control head alone.
That's it.
You also need a power lead to match the RC640 radio and a handset to match the RC690 head unit. Facilities link plugs are also required.
| Inter-unit cable pinouts | ||
| RC690 37-way |
RC640 15-way |
signal function |
| pin 4 | - | - +12V |
| pin 7 | pin 1 | - on/off switch A |
| pin 8 | pin 2 | - on/off switch B |
| pin 9 | pin 3 | - Rx AF from radio |
| pin 10 | pin 4 | - +12V |
| pin 11 | pin 5 | - bal AF ancilliaries Tx in |
| pin 12 | pin 6 | - bal AF ancilliaries Tx in |
| pin 13 | pin 7 | - TxD+ |
| pin 14 | pin 8 | - RxD- |
| pin 22 | - | - 0V |
| pin 26 | pin 9 | - 0V |
| pin 27 | pin 10 | - 0V |
| pin 28 | pin 11 | - Tx AF to radio |
| pin 29 | pin 12 | - bal AF ancilliaries Rx out |
| pin 30 | pin 13 | - bal AF ancilliaries Rx out |
| pin 31 | pin 14 | - TxD- |
| pin 32 | pin 15 | - RxD+ |
| pin 35 | - | - +12V |
 |
Development system setup
The RC690 radio connected to the RC690 control head. |
Connecting RC640 to PC
A cable can been made to connect the radio unit to the serial port of a PC without needing a head unit. This was originally done for firmware testing. Fudge warning! This is a bodge as proper RS422 converters are not used.
| Inter-unit cable to PC connections | |||
| RC690 37-way |
RC640 15-way |
signal function | PC 9-way |
| pin 7 | pin 1 | - on/off switch A | link |
| pin 8 | pin 2 | - on/off switch B | |
| pin 14 | pin 8 | - RxD- | pin 2 |
| pin 26 | pin 9 | - 0V | pin 5 |
| pin 31 | pin 14 | - TxD- | pin 3 |
The protocol is ascii so you can talk to the radio with a terminal program. I recommend Teraterm). Set serial port for 2400 baud, 7 data bits, odd parity, one stop. Select local echo and send CR and receive CR.
Power on the radio. You should get "R"s coming in. Hit a capital-H and it should stop. The radio sends some status characters and the selcall.
Type a number and hit "*" and the radio should change channels. Hit "P" to make the radio transmit. Hit "Q" and it should stop.
Be a little careful as power RF can easily get into the serial ports on the back of PCs and cause lockups. It'll test fine on a dummy load but on an antenna the problems start. If it won't go out of Tx this is why - switch the power off and add some filters.