separation

I recall reading somewhere 6 inches or so was fine.  If the track bus is lightly twisted, 3-4 turns per foot, you might even get by with less.  Basically just don't zip tie them together.

Most anything DCC is really designed to put up with some really "creative" installation.  It's only when you do something really wierd or end up with some odd environmental issues that you really HAVE to start paying attention to things like twisting the track bus or applying the RC terminations on the buses.  These are really your EDGE cases and usually will only show up on the larger basement empires or the modular get togethers.  Some of it can be helped by using a simple computer desktop style UPS that you plug the DCC system into.  In all reality, don't zip tie your busses together and you're probably ok. 

If you think you need to do more or just want some peace of mind, keep them 6 inches apart or more and that'd be better.  Twist the track bus and keep it 6+ inches away from the throttle bus is better still.  For a "premium" assurance, twist the track bus, keep them 12 inches or more apart, keep your track feeders 6-12 inches or less, and apply RC terminators to the ends of the busses, make sure you add additional power to your throttle bus, AND finally plug all your DCC power supplies into a computer/Home Theater power conditioner/UPS.  How nuts you want to go with it is up to you.  The "premium" takes some time and effort, and the parts cost can be significant.

Were it me, I would probably twist the track bus, keep the track feeders short, and separate the track/throttle bus by 12 inches or so.  That's probably your best insurance for the least amount of effort and cost.  It will cost you very little in parts or time compared to not twisting and putting the busses next to each other.  Most likely you won't even really need all that.  You can do all that and never have a problem.  The annoying bit is that you'll never really know if you needed to do all that in the first place so it's a case of go overboard in the beginning and then never worry about it again, or possibly skimp and then wonder if that occasional glitch is caused by bus separation or some other issue.

Hope that helps.

-

S

Alan Gartner says..

Alan Gartner's website is my "book" on DCC. Its why I have endless books on everything except DCC..

http://www.wiringfordcc.com/wirefordcc_toc.htm

His section on excessive inductance has this blurb:

The problem - interference:

Some modelers who have long bus are experiencing interference being caused by their DCC systems. This interference may be interfering with the operation of throttles.

The interference isn't too hard to understand. The relatively sharp rise and fall times of the DCC squarewave generates radio waves. Your booster is in effect, a radio transmitter. Your bus wiring is an antenna.

What to do about interference:

Keep your throttle and booster network wiring as far as possible from your bus wires. I don't mean they have to be on the opposite side of the room. But if you can separate them by just 6" (154mm), will make a huge difference. If you can separate them 12" (308mm), that will be four times better. Why is twice as far, four times better? I could tell you, but I promised not to give you a headache. Just take my word for it that for every little bit further you can reasonably separate them will be very significant.

While not the prettiest site on the web, I cannot say enough about how useful I have found the information here.

Chris

Thanks, guys

I posed this question to a friend of mine who is an electrical engineer and he pretty much echoed what you guys said.  I appreciate the input very much.

As for the difference between 6" and 12", I would imagine it is one of those physics things where the effect varies with the square of the distance, like gravity.  See, even an old bean-counter like me remembers some of that stuff!

Happy railroading!

Dave

Keeping the buses separate

 I run all my Lenz Xpressnet busses using screened two pair cable, making sure the screens are grounded back to the control unit. I've never had any trouble with interference. Some of my cables run in with power cables.

Mike Ruby

+

The NCE cab bus and Xpressnet  use RS-485.  Shielding is debatable in RS-485 plus it  would  add to the cost of the cabling.  They  recommand cab bus in front,  control bus in back to limit or illiminate crosstalk potential.  Twisting the leads helps illiminate crosstalk and EMI/RFI.  Shielding could also cause ground loops if not done properly.  IF they did not use shielding, they probably had a good reason not to use or recommend it.

Dave,  If you go to the NCE web site you can download the ' System reference manual '.  It  answers your questions.  They recommend power cab wires at the rear and cab bus wires to the front of layout.   Plenty of good info to be found.  

http://www.ncedcc.com/pdf/Sysman07.pdf

Marc F