Propogation Delay of DCC Signalsgreenspun.com : LUSENET : Wiring for DCC : One Thread
I have seen a number of discussions on European forums talking about the problems of propogation delay of the DCC bi-polar signal in a large Garden Railroad. The description is typically that there is a large loop of several hundred feet out from the booster location and back and then possibly out again and back. To counter the voltage drops on such a long run (mostly caused by the railjoiners), people run a heavy (say 16 gauge) feeder wire from the booster to the loop return section of track that has returned and is close to the booster but about half way on the total run. Adding this extra feed helps with the voltage drop but apparently causes problems with the DCC signal and its proper recognition by the decoder due to the difference in propogation delay down the track and back vs. the propogation delay along the short piece of feeder wire. I wonder if anyone here has experienced that or if this is even a possibility. I don't think there is anything in the NMRA spec. to cover this.
-- Knut Schartmann (firstname.lastname@example.org), October 19, 2004
I have what definitely qualifies as a large garden RR. My longest bus run is about 125 feet (42m). I buried a pair of #10 AWG wires under my track as my bus. I ran feeders to the track every 6 feet (2m) using #14 AWG wires. While the track forms a loop, I did not connect it at both ends of the track or the bus. Everything works fine.
-- Allan Gartner (email@example.com), October 19, 2004.