[geeks] RJ-45

[gsm at mendelson.com]

Thanks everyone for the suggestions. I was being vague for a reason, but
I'll explain why I can't cut, splice or extend the cables.

Back in the PC/XT days, the company who made the radios I want to program
found that the UARTs used on XT's were not good enough for what they wanted
to do, so they wrote code to generate serial data via rapidly changing
the state of control lines on the serial port, bypassing the UART and 
and the normal RD/SD lines.

They also use something similar, if not TTL levels, on the programing port.

So they developed a box called a RIB (Radio Interface Box) which did the
conversion. The input of the box is a standard serial port, the output
is a DB-25. The DB-25 contains jumpers in it to set levels and other things,
the radio part is three wires. 

There is a fair amount of logic in them, they draw 40ma at 9 volts.

The cables have a specific length and impedance, and if they are not right, the
whole house of cards collapses and it does not work.

I think the tolerances are a lot wider than specified as you can buy all sorts
of cables and ones with the RIB built into a DB-9 connector from China. They
all seem to be made of the same cable and all the same length. 

You can also buy a US made one third party one designed from scratch with 
an RJ-45 socket on it, so you can use a standard ethernet cable. 
Or at least some ethernet cables. :-)

My problem is that I have the Chinese ones that do not have a hood and you
can't cut them and expect them to work. :-(

If anyone has a clue how to find the ones that go on after crimping, I'd love
to have that information. Meanwhile I've ordered some extra long ones, I a
couple of weeks I'll have them. It will be interesting to see if they really
are longer and if they work. 

Thanks,

Geoff.

-- 
Geoffrey S. Mendelson N3OWJ/4X1GM
Making your enemy reliant on software you support is the best revenge.