Serial cable length

[stargategfx]

Does anybody know how long a serial cable I can use on a new prt96 before problems arise?

[kaaboom_99]

I presently have the original cable sent with my PRT and I added a 30 ft extension to it without any problems

[kaaboom_99]

Also have a 10 ft cable on my keyboard as well.

[m. holm (Unregistered Guest)]

The RS-232 specification states that the signal should not be expected to pass beyond 50 feet. That said, I have seen it successfully travel up to 250 feet. Additionally, you can buffer the signal with an outboard device and send it thousands of feet.

[stargategfx]

Thanks guys!

[kerrazy]

But those excessive lengths are only reched with the new generation Flux Capicitor, formerly found on Deloreans

[stargategfx]

I didn't think an over-length shielded serial cable would be this difficult to find.
Can you suggest any on-line sources?

[bill_thorpe]

Boyd, You can find serial cables at MCMINONE.COM or 800-543-4330. Their cables run from 3 to 50ft. A 25ft DB9 female to male cable sells for $8.35. The part number is 83-942. Hope it helps.

[richards]

The following is quoted directly from www.lammertbies.nl/comm/info/RS-232_specs.html (http://www.lammertbies.nl/comm/info/RS-232_specs.html)

"Maximum cable lengths

Cable length is one of the most discussed items in RS232 world. The standard has a clear answer, the maximum cable length is 50 feet, or the cable length equal to a capacitance of 2500 pF. The latter rule is often forgotten. This means that using a cable with low capacitance allows you to span longer distances without going beyond the limitations of the standard. If for example UTP CAT-5 cable is used with a typical capacitance of 17 pF/ft, the maximum allowed cable length is 147 feet.

The cable length mentioned in the standard allows maximum communication speed to occur. If speed is reduced by a factor 2 or 4, the maximum length increases dramatically. Texas Instruments has done some practical experiments years ago at different baud rates to test the maximum allowed cable lengths. Keep in mind, that the RS232 standard was originally developed for 20 kbps. By halving the maximum communication speed, the allowed cable length increases a factor ten!

RS232 cable length according to Texas Instruments Baud rate

[stargategfx]

THIS is why I bought a Shopbot.
Thanks again for the help guys!

[Lawrence H. Smith (Unregistered Guest)]

I did experience a problem when I first set up my PR (no T) 96 (circa 1997). I was using a 25 or 50 foot cable, of perhaps the worst possible design for a long cable - flat ribbon cable. It was what I had in the junkbox, and turned out to be a poor choice. The maximum move speed was cut way down, presumably from communication errors. A properly sheilded cable should be more tolerant of long lengths. I do recall using special low-capacitance cable (fat insulation) back when I used to run a lot of terminal lines for mainframe computers...