Yes... RG-62 has a different impedance, and a different velocity of propagation. With both sifferent Z and Vp, the cable can cause signals to become so distorted that station on the other cable runs may see either noise, garbage (illegible data), or an apparent collision. If reflections from the Z mismatch don't get ya, the changed Vp will... Phase errors and ghosts or ringing are the most common insults. Some NICs will fail to transmit if they detect improper Z. A functional thinnet system should never show less than 25 ohms DC resistance (R), there being two 50 ohm terminators in parallel. Adding the DC resistance of cable, you can only increase the R. Above about 100 ohms, thinnet peters out. Excessive R or Z cause signal loss and failure. Chances are, if you pursued this a little further, you would have found performance problems with the other stations. Excessive collisions would be one hint. A good sniffer should have pointed out errors, particularly physical (MAC or PHY or Layer 1) errors. As an aside, the max length of a thinnet segment is determined not just by R or Z of the long cable, etc, but by the transit time of a signal from one end to the other. If the transit time exceeds the wait time for collision detection, two stations at maximum distance may try to transmit concurrently, unaware the other already has. Collisions abound, since the stations never wait long enough to hear the other talk. In the extreme, they go into constant contention... Ick. the station limit of 30 is fairly arbitrary, based on real-world assumptions about connector quality, various losses, and the desire of manufacturers to sell a few repeaters. Obviously, I'm bored this morning... Pardon the digression. Diagnosing 10Base-2, 10Base-5, and Thinnet systems is a lost art... God help me, I love it so... If any of you need tips on troubleshooting this stuff, write me. Rick - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org
