at 200 meters don't even bother with RS232, I would recommend Rs485 or 422
if you don't like half duplex then use separate receiver and driver and
you'll have a 4 wire + ground interface that you can run at 100kbps
something like 4000ft

You want to use differential pairs for those kind of distances.  Rs485 is
actually a little easier if you do it right because you don't need +12V,
-12V power supplies of charge pump circuitry.

I recommend National Semiconductor DS1487 or related.
http://www.national.com/ds/DS/DS1487.pdf

On Sat, 15 May 1999, Robert Mellgren wrote:

> hi there i seem to recall that RS232 transmissions should be done over short
> cables. since there are only -3/+3v levels, is this true.
>
> Since this transfer shall travel from 0.3 M - 200M i may need a potent
> voltage level and a good shielding.
>
> Which do you think is the best way too boost such a signal, should i boost
> it straight from the output pin from the pic, with the help of a NPN
> transistor, that drains say.. 12v-24v then convert that level of voltage
> back to TTL with a 7805, is the 7805 fast enough? we are after all talking
> 1200 baud here, i do not seem to find a datasheet that describes this.
>
> Or make some sort of optic transmission, ( which is less cheap ), via optic
> cables, the positive side of this is that it wont be affected by
> distrubances.
>
> Hit me with some of your experiences in this matter, It would be be most
> appreciated.
>
>
> Greets
> Robert
>
> input...input... i need.. input...
>