[Premium-Rx] Racal A6A1 Board Setup Help Needed

[John Kolb]

One of the frequent problems I've seen in telecommunications
is gender confusion.

One thing to check is the data flow connection on the cable to insure
you are connecting a "DCE" top a "DTE". If the computer and radio
are both DTE or both DCE, they won't communicate.

A DTE outputs transmit data (TxD) on pin 2 of a DB-25 or pin 3
of a DB-9 connector, and receives on receive data(RxD), which
is pin 3 of a DB-25 or pin 2 of a DB-9, relative to signal
ground, pin 7 of the DB-25 or pin 5 of the DB-9.

A pin can be identified as connected to a RS-232 driver or
receiver with a scope or voltmeter. Looking at the connector
at the computer or radio or cable end, measure pins 2 and 3
relative to signal common. The pin connected to the receiver
will measure somewhere between 0 and +1.4 V. The pin connected
to the driver should be either more positive than +5V (5-15V
is the spec) or more negative than -5V. If pin 2 of theDB-25
or pin 3 of the DB-9 reads < +/- 5V, that's the TxD pin.
Otherwise that's the RxD pin, and the other pin should have the high
voltage.

If you have one DTE and one DCE, then you will need to connect
them with a straight through cable (pin 2 connected to pin 2,
3 to 3, etc) If you have two DTE's or two DCE's, you will need
a null modem adapter or crossover cable between them.

John
<http://members.cts.com/king/j/jlkolb>


On Fri, 20 Feb 2004, Guy Atkins wrote:

>
> I have a newly-installed A6A1 remote board in my Racal RA6790GM, and the
> setup has me stumped. I'm attempting to verify that it's communicating in
> RS232 protocol by following the instructions at
> http://vradio.home.att.net/Racal_6790.htm
>
> I've followed everything exactly and checked connections, but I cannot get
> any response when using Windows Hyperterminal. One thing that puzzles me--
> the instructions at the web site mention settings of "8 bits, no parity N
> and 1 stop bit", while the RA6790GM manual on page 3-21 says "The data
> format used for remote control of the receiver via the serial asynchronous
> interface is the standard ASCII asynchronous format which consists of a
> start bit, seven data bits (one ASCII character), a parity bit, and two stop
> bits." This sounds like conflicting information to me, but I'm not
> knowledgeable enough on serial communications to say for sure.
>
> I've tried settings both ways, but still get no response through the
> terminal program. Just to see if the PC and receiver are communicating, I'm
> sending a "S2" command to put the Racal in REMOTE mode, but no luck yet.
> Like the web page indicates, I've set up the rig for an address of 37, and
> send the full command of "$37S2".
>
> What is the receiver's default address if connector pins K through T are
> left open? Perhaps it results in no address at all. (I don't understand the
> receiver parameters in Table I on schematic page 7-31.) After I got no
> results with various serial port settings and the receiver wired for address
> 37, I returned pins K through T to their open state and tried using
> addresses of $00, $01, and $99, thinking that maybe one end or the other of
> the address range would be the default with K through T "open" (ungrounded).
>
> I also tried various combinations with pin U grounded for parity, based on
> the info from manual page 3-21, without success.
>
> Any tips to get this board up and running would be appreciated. BTW, all my
> efforts have been with the baud rate at 19200, and with connector pins W
> through Z left "open".
>
> Guy Atkins
> Puyallup, WA USA
>
>
>
>
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