Tips for long null modem cables?

[Leif Bloomquist]

Hi all,

I've got a friend who wants to wire up his C64 to his PC so he can try out some of our BBSes. The problem is, the C64 is in the next room from the PC, about 40 feet away.

From a quick search of the RS-232 standard, it looks like the distance itself is not a problem, especially at 2400 baud (for now).

However, a 40' full null modem cable would be pretty expensive to make. For 'dialing' out he only needs RX, TX and ground though. So is it OK to just get 3x 40' long wires and solder them to the connectors? How about using speaker wire or phone cable? Any other suggestions?

[Riktronics]

How about a null modem adapter and a long serial extension cable? I just looked on ebay and you can get a 9-pin 50' straight through for $12.49. I don't know how well the radioshack null modem adapters work, I wired my RS232 with transmit and recieve reversed so I don't need a null modem cable...

[Jeff Ledger]

I've done several three wire null modem cables
at distances well over 40' feet.

The "book" says you can't do this, but it works

Use this pin out
2 - 3
3 - 2
7 - 7

translation
RX - TX
TX - RX
GN - GN

I've used cat5/3 with a couple 9pin connectors
from Rat shack.. Worked well for playing old
serial games with my neighbor.

Jeff

[Riktronics]

Good point Jeff, i had totally forgotten about it, but our cabling guru at work did make a null modem cable using DB-9 connectors and CAT-5 cable and it worked just fine... that would be the way to go.. if it was in a different room you could run the cat-5 through the walls or whatever and then put the ends on it and you wouldn't even need a big hole...

[Leif Bloomquist]

Thanks all, I'll try some cat5.

Should I be worried about ground loops? i.e. "ground" at one plugin might not be "ground" at another.

Although my guess it it's OK within the same house, assuming it's up to the latest wiring codes.