CTT TMCC article

[MartyE]

Although just breezing over it, the article on TMCC signal issues looks great. I was always thinking this would be a great subject. Good job CTT!

[Anonymous]

Personally, I can't get enough of the TMCC articles. Everytime I think I understand it, something happens and I have to resort to these forums to find the secret recipe of buttons to pu***o get it working again.

[SMSimon]

I am building my first layout in decades and thus my first for use with TMCC. I will have in some places up to four levels. I have heard of signal problems with multiple layers. In this article on TMCC in the most recent Classic Toy Trains they suggest have a grid of 1"x2" wire under the track to solve the problem.
I have a lot of excess screening (some of it copper screening). Before I lay my roadbed, why not run screening right under the roadbed with all the screening grounded to real-world ground.
Does this sound like a reasonable idea? If so, should I do it all over, or just where there are multiple layers?

Thanks,
Sandy

[nblum]

I think you are asking for trouble using metal screening all over the layout. And screening is probably overkill. A single 18 or 20 gauge wire run along the underside of the roadbed of the upper track has worked for most people when there have been problems of signal interference.

[Buckeye Riveter]

Sandy, [#welcome][#welcome][#welcome]

Before I would advocate the wire grid solution, I think some advice from my local train store went along way in keeping a strong signal when I installed TMCC. I have power connections to the track about every 6ft to 8ft. Not only do I have a strong TMCC signal, I don't have power drops. I also used spade connectors where appropriate. I have a small meter that I use to check track voltage to make sure there was power in both outside rails.

Instead of the wire mesh idea, I believe a single continuous wire beneath the track with no breaks would be easier to install. Welded wire mesh as described is heavy and does not seem to me to be easy to work with.

Also, Train America Studios has a signal booster for TMCC and that may be the easiest and best answer for a large layout. I am enlarging my layout and we will see what happens in the months ahead.

BTW, since my layout is in the room above the garage, I sometimes have had the layout turn on due to the signal from the garage door opener. [:)]

[Big_Boy_4005]

I thought the article was pretty good, but I'm not sure if some potentially useful material was overlooked. (Here I go again. [;)])

I was lucky enough to have a private audience with Jim Barrett from OGR back in May, when he visited my local hobby store. I explained my massive project to him, and he offered me a couple of tips, which the article made no mention of.

The first tip had to do with multiple parallel tracks. Appearently, if you have a number of parallel tracks, such as a yard, it is possible for the signal from each interior track to be lost. Under ideal conditions, the TMCC radio signal should form sort of a "tunnel" along the track. Too many tracks, and the signal distorts into one giant tunnel, bridging all of the tracks, resulting in poor signal on the interior tracks. The solution is simple, place a wire between each track, and tie them to the ground plane. This forces each track to have it's own signal tunnel.

The other suggestion dealt with a completely different and more obscure problem. Because of the size of my layout, I will have multiple ground rail connections. When all is said and done, I might end up with over 3000 feet of track. The wiring diagram in the TMCC manual seems overly simplistic for a large layout. There is no way to properly ground that much track from a single point. In order to keep the signal strength up, Jim suggested that each ground feed should have 1 micro Henry choke placed on it. This has caused me to rethink how I will be wiring the ground on my layout.

As for the ground plane mesh shown in the article, I haven't gone shopping for that specific material. I will keep that grid spacing in mind as a minimum effective density level. I was under the impression that any mesh would work as a shield between levels. If the mesh is fine enough, all the way down to window screen or even foil, it may provide enough protection from conflicting signals, that it doesn't necessarily have to be tied to the ground plane. That can still be done if the material alone proves ineffective.

[Buckeye Riveter]

Err..the local train store that I am referring to is:
http://www.davistrains.com/repairshop.asp And guess who gave me the advice about the power drops every 6-8 feet. [:D] [^]

[Anonymous]

can anyone tell me what I have? It is a Santa Fe 2480 engine

[Big_Boy_4005]

QUOTE: Originally posted by Buckeye Riveter

Err..the local train store that I am referring to is:
http://www.davistrains.com/repairshop.asp And guess who gave me the advice about the power drops every 6-8 feet. [:D] [^]

Hey Buck, are you talking power on the center rail, or ground on the outer rails? I had planned to have power (center rail) on every section of Gargraves track, and matching ground feeds as well. The concern on the large layout is that too many different entry points would "water down" the signal. That was my unerstanding of the function of the chokes.

Another potential problem is, if the signal has to travel down wires of different lengths, wouldn't there be something of an echo as the signal emerged from the longer wire later than from the shorter wire. If the distances are long enough, the resulting offset could cause problems.

I wonder what would happen (beside my layout becoming non-FCC compliant) if I was to try to broadcast at sufficently low power, my TMCC signals through the air. I mean I don't want to have garage doors all over the neighborhood popping open every time I blow my whistle, but the through the track signal seems to be subject to a number of complicating factors when trying to deal with a larger than normal layout.

I guess it's just the way I like to do things, bigger than normal. What can I say?[swg]

[Buckeye Riveter]

QUOTE: Originally posted by Big_Boy_4005

QUOTE: Originally posted by Buckeye Riveter

Err..the local train store that I am referring to is:
http://www.davistrains.com/repairshop.asp And guess who gave me the advice about the power drops every 6-8 feet. [:D] [^]

Hey Buck, are you talking power on the center rail, or ground on the outer rails? I had planned to have power (center rail) on every section of Gargraves track, and matching ground feeds as well. The concern on the large layout is that too many different entry points would "water down" the signal. That was my unerstanding of the function of the chokes.

Another potential problem is, if the signal has to travel down wires of different lengths, wouldn't there be something of an echo as the signal emerged from the longer wire later than from the shorter wire. If the distances are long enough, the resulting offset could cause problems.

Every 6 to 8 feet I have power to the center rail and ground to an alternating outer rail.

I'm not sure you can water down the signal with too many feeds, but I do seem to think that the signal is directly proportional to the track voltage, but when you read the Train America information that doesn't seem to be a consideration. Train America makes the signal doubler described below:
· The Signal Doubler is designed to eliminate signal strenghth problems on your TMCC layout. The Doubler infuses the Command Base Signal into both the two outside rails and the center rail without creating a short circuit. (Thank God, if would cause a fire if it did.) The Doubler is ideal for layouts that have Atlas O or Gargraves track. (I don't have a clue why.) The Doubler is also ideal for layouts that have a lot of insulated outside rails for accessory activation or block detection. The Doubler transmits the Command base signal down all 3 rails without creating a short!
· The Doubler does not draw any power from your transformer, it simply allows the AC power to pass through the doubler and infuses the Command Base signal into both the AC hot and ground leads without creating a short circuit. The Doublers are available in three different wire sizes to adapt to your existing layout wiring.
· We can almost guarantee the Signal Doubler will eliminate all your signal transmission problems. Please keep in mind that one Signal Doubler is required per each power block. For example, if you have a loop of track with two power blocks (and each power block has its own power supply) then you will need two Signal Doublers for that loop. One for each power supply. (But I think you still would only have one command base from the wiring diagrams I have seen.)

A signal echo, is more like two radio waves out of phase cancelling each other out creating a dead spot. Since it seems that the electrical current is the carrier of the TMCC signal, it would seem that the signal must be somehow realated to the 60 cycles per second for household current since Train America connects the Doubler to the power.

I'm no expert on this stuff, but if my $40 walkie talkie powered with a couple of AA Bateries can send a signal 2 miles, it seems that TMCC could send a signal through a conductor fairly far.

BTW, I have also learned the the command base needs to be in a place where the signal from the CAB-1 to the base has no interference, such as metal. In fact, I think Lionel says something about not setting a command base on a metal object.