I know this issue comes up form time to time and I figure it woudlnt be a bad idea to reprot on any locomotives or rolling stock that may negatively effect the DCS signal. Has anybody found a piece in their collection that has dropped your DCS signal?
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Where's Marty F's list???
Any engine or stock that has caps needs a inductor I believe.
I forget the name of the board that keeps constant voltage for lighting? CV boards?
Matt,
From page 157 of The DCS Companion 3rd Edition:
Some, but not all, TMCC engines will degrade the DCS signal of any DCS engine with which they are in close proximity. This effect varies both by individual TMCC engine and by the distance between the TMCC and DCS engines. In many cases, an RF choke inserted in the Hot wire between the pickup rollers and the TMCC engine's circuit board will correct this problem.
Some lighted cabooses, most notably those manufactured by Atlas O, may degrade the DCS signal, as may some engines or passenger cars with constant voltage (CV) lighting boards.
Older GGD passenger cars are often offenders.
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Off the top of my head. Most Lionel passenger cars until Lionel recently went to LED lighting. Atlas passenger cars, Weaver passenger cars, MTH rotary snow plow, older GGD cars before LED lighting. The worst is the Atlas caboose until LED lighting. Scott Mann was the first to react on the issue and went all LED. I was buying RF chokes by the hundreds. I have many hundreds of passenger cars.
Before Lionel recently started making the 21 inch cars I had occasion to test the board that was going to be used. Mike Reagan had a great board built and it plays well with DCS equipment.
I did a post on this in the past with all the offenders. I may have it on my older lap top. I will add it here when I find it.
Guys/Gals, here is an older post I made with a list.
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Bil, off the top of my head, here are the big violators. I have all my test results on my laptop that is not with me today.
1. Recent high end Lionel aluminum cars.
2. Atlas passenger cars.
3. Weaver passenger cars.
4. Atlas caboose--The worst.
5. MTH Rotary snow plow.
6. GGD passenger cars.--Scott Mann was the first to resolve the problem.
7. Third Rail RDC.
8. Smoking caboose from Lionel, K-Line and MTH.
This testing was done with rolling stock. Every car listed above with a choke would restore a 10 signal.
All the above would bring DCS signal from a 10 to 3-4. In testing the rev L TIU, Jason let me keep it a bit longer and all the above trains came up with 10 signal with no choke or light bulbs on the TIU output.
MTH and K-Line passenger cars did not cause any problem as the lighting was powered directly from track voltage.
When we see the next version of DCS, this will all be ancient history. When the choke fix was first used, Scott Mann contacted me as he felt it was very important for him to change his lighting boards as the 3 rail DCS guys were buying his products. He did so and has a great LED lighting board in all his passenger cars now. Very DCS friendly with any TIU.
Hi Marty, thanks for publishing that list again. Can you expand on what you meant by "When we see the next version of DCS, this will all be ancient history."
Thanks Marty, our best to Dottie and Ralph 
Paul
Thanks for republishing the list. I have about 28 Lionel aluminum passenger cars and whole bunch of Lionel and K-Line smoking cabeese. I thought it might not be a bad idea to revisit this one since I think people forget about it.
Matt,
I own about a dozen K-Line smoking cabooses. They are not an issue regarding the DCS signal.
Thanks Barry, this project is yet another on a long list of things that need doing so the shorter the list the easier it will be to get done. I dont have very many TMCC locos so that will make the list shorter. Ive got a Digikey order coming up I will have to get about 100 chokes
Remember, the locomotives will need around a 3-4 amp rated choke, obviously passenger cars will need a smaller one. No reason to spend the money for the big choke for cars that don't need the current capacity. 
Guys, any particular chokes that you prefer?
I just look on Digikey for 22uh chokes and then match my current requirements.
Thanks John, im pretty familiar with Digikey, I was just wondering if you found any you liked more than others. Its o gauge so there is plenty of room inside so I can imagine it matters all that much. Ill check mouser too and see if they have any. I imagine a thru hole axial type would work best
Chokes are cheap. No polarity or heat to worry about.
So, do I understand correctly that the rev L TIU eliminates the signal loss issue from the aforementioned rolling stock? Or do the chokes still need to be installed, even with the rev. L TIU? I have a rev. L TIU and want to make sure that I do or do not have a problem.
Tom,
do I understand correctly that the rev L TIU eliminates the signal loss issue from the aforementioned rolling stock?
No, you do not understand correctly.
The Rev. L TIU does not prevent degradation of the DCS signal by offending TMCC/Legacy engines or some illuminated cars with CV boards.
do the chokes still need to be installed, even with the rev. L TIU?
Yes, the chokes still need to be installed.
GRJ, other than a CV board, what in a loco would require a choke to save DCS signal?
Potentially, any board that uses capacitive filtering can damp the signal, the amount depends on the design. I've never done an exhaustive test, when I design a board for use on track power, I include the 22uh choke, problem solved.
With so many factors that degrade DCS signal strength , I had planned to set aside some time to focus on solving the issues on my new layout. I just didn't know exactly where to start....that is until I read this post this afternoon. After dinner I pulled every TMCC equipped engine and lit car from the track and am pleased to say I now get solid 10's everywhere. This topic just saved me a pant load of unnecessary tracing. Thanks all!
Bruce
Ive known that this can happen but i figured its the DCS issue that gets overlooked. Glad this thread could point you in the right direction
brwebster posted:After dinner I pulled every TMCC equipped engine and lit car from the track and am pleased to say I now get solid 10's everywhere. This topic just saved me a pant load of unnecessary tracing. Thanks all!
Now you just need a buttload of RF chokes and some time to fix them all! 
Put them on one at a time to see which ones effect DCS and which do not. May not be a butt load... G
Right, could just be the right cheek. 
Yes, testing individually and adding chokes where needed is the logical next step. Fortunately there's no hurry and they can be upgraded in dribs and drabs, whenever the mood strikes. A lot of the offending culprits need LED upgrades anyhow, so they'll get the ol' 2 birds with one stone treatment.
I had initially thought the track wiring method used was causing the signal issues. I purposely avoided home run wiring, using solid core Romex in a buss configuration for simplicity and economy. DCS was taken into consideration by using one drop per block to avoid electrical loops.
I want to complete the basic track wiring and add a couple of local control panels so that any unforeseen problems can be easily traced and repaired. Then I'll move on to the more complicated wiring of switches, signals and accessories. I'm 99% certain I'll be adding powered catenary as well. Frankly, my wiring goals are way more ambitious than I'm comfortable with, but it's encouraging to find that the already completed wiring won't need to be ripped out.
Bruce
Bruce,
using solid core Romex
Not the best choice for DCS.
I've got 16 ga stranded speaker wire for my layout. 2 500 ft spools was like $96. I was using 14 ga speaker wire but that was temporary wiring for 3 1/2 years. I finally got ashamed of the rats nest. No my methodology is, run a wire test the heck out of it, run a wire test the heck out of it. It takes longer but will save me on troubleshooting later
Against better judgement the Romex was used but now doesn't seem to cause any ill effects concerning DCS. All drops are of stranded 14 gauge speaker wire. All drops were fed by 3 wires to power GarGraves track, with future intentions of using the 3rd wire to trigger accessories, signals or train detection from isolated sections. Adding a fourth wire from the catenary into the equation could really make for some interesting circuitry.
Bruce
IMO, the benefits of stranded vs. solid wire are not significant, and I don't believe they exist at all. Unless you're using Litz wire, stranded wire acts the same as solid wire at RF frequencies. The argument here is that skin effect of the stranded wire offers lower impedance to the RF signal due to the multiple conductors. However, that argument falls apart because the strands are not insulated from each other, so for the purposes of RF, they act like a solid conductor. Use whatever you like.
Thank you Matt for posting this topic, and thank you to everyone who has contributed!! I will take all of this into consideration while planning my first real layout using command control. These are some of the most important issues to learn after running trains conventional since the late 1960s.
John,
However, that argument falls apart because the strands are not insulated from each other, so for the purposes of RF, they act like a solid conductor.
Not exactly.
I have absolutely no intention of debating your opinion, however, the surface area of a bundled set of wires is greater than a solid wire of the same gauge. You can see this if you grasp a handful of uncooked spaghetti.
Your mileage (and choice of pasta) may vary.
Barry, you'd argue if I said the sun rises in the East and sets in the West, so you're right, no point in arguing it.
Suffice to say that I'll put my experience and education on the topic over your pot of spaghetti. We won't bother to mention countless other references to the RF propagation on solid and stranded wire that can be readily obtained if you choose to look.
You can consider this my last word in this topic, feel free to add more spaghetti to your pot. 
John,
you'd argue if I said the sun rises in the East and sets in the West
No, I would not, since the sun does, indeed, rise in the East and set in the West on planet Earth. It's good to know that it also does so on your planet.
Just curious: what frequency range does DCS operate within?
For those that care, here is an article from Belden. Be certain to read the comments.
Belden: Understanding the Skin Effect.
The DCS carrier is at 3.27mhz.
In particular, this exchange pretty much spells it out, even though some refuse to believe it. One should take a cue from the fact that network cable has better characteristics with solid conductors.
Phillip replies: What about stranded wire vs solid conductors? is the internal surface area used to carry the high frequency or just the OD of the bundle? ANSWER: It's just the OD (outer diameter) of the bundle. The network cable standard (cat5, 5e and 6) specify solid conductors for longer runs, wouldn't a stranded wire have more surface area for skin effect and therefore lower attenuation at the higher throughput frequencies of modern networks. Even if the DC resistance of a solid conductor is lower. ANSWER: No, the resistance of a stranded wire is always worse than a solid wires because of all those employ spaces between the conductors (called "interstices"). The surface of the stranded wire is equally chaotic, making it a poor choice to carry high frequencies. This is one reason, when we are forced to use stranded wire at high frequencies (such as Belden 1694F or 1505F) that we run the group of strands through a die. This is known as a "compacted center" and gets the whole conductor closer to a solid in shape but stranded in flexibility.
So then, would the increased resistance of the stranded wire have any significant negative effects on the DCS signal? And would the increased resistance of the wire be additive? So lets say I have a 100 foot long loop of track fed by 4 - 50 foot wire runs. Now lets say each wire run has a resistance of 10 ohms for a is the signal pushing against 10 ohms or resistance or is it pushing against 40 ohms or 4/10's of an ohm? Now I am quite aware that in terms of electricity resistance in parallel circuits is not additive but this is not just electricity
Marty Fitzhenry posted:Guys/Gals, here is an older post I made with a list.
=================================================================================================
Bil, off the top of my head, here are the big violators. I have all my test results on my laptop that is not with me today.
1. Recent high end Lionel aluminum cars.
2. Atlas passenger cars.
3. Weaver passenger cars.
4. Atlas caboose--The worst.
5. MTH Rotary snow plow.
6. GGD passenger cars.--Scott Mann was the first to resolve the problem.
7. Third Rail RDC.
8. Smoking caboose from Lionel, K-Line and MTH.
This testing was done with rolling stock. Every car listed above with a choke would restore a 10 signal.
All the above would bring DCS signal from a 10 to 3-4. In testing the rev L TIU, Jason let me keep it a bit longer and all the above trains came up with 10 signal with no choke or light bulbs on the TIU output.
MTH and K-Line passenger cars did not cause any problem as the lighting was powered directly from track voltage.
When we see the next version of DCS, this will all be ancient history. When the choke fix was first used, Scott Mann contacted me as he felt it was very important for him to change his lighting boards as the 3 rail DCS guys were buying his products. He did so and has a great LED lighting board in all his passenger cars now. Very DCS friendly with any TIU.
Guess I've been lucky. I run a lot of these on the list, and the blinking Atlas caboose as well, and have yet to experience any problems which I could link to any of these.
Matt Makens posted:So then, would the increased resistance of the stranded wire have any significant negative effects on the DCS signal? And would the increased resistance of the wire be additive? So lets say I have a 100 foot long loop of track fed by 4 - 50 foot wire runs. Now lets say each wire run has a resistance of 10 ohms for a is the signal pushing against 10 ohms or resistance or is it pushing against 40 ohms or 4/10's of an ohm? Now I am quite aware that in terms of electricity resistance in parallel circuits is not additive but this is not just electricity
Matt, it's more likely the difference between 10 ohms and 10.1 ohms. I can't imagine it making a measurable difference.
Thats what I figured, nothing youd notice.
I actually have the Lionel Powhatan arrow cars on the layout right now with a Williams Class J ps2 upgrade and i havent noticed any DCS signal issues but Ill check this weekend. I do have 4 sets of those Lionel Aluminum passenger cars but I hardly ever run them
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