Continuous outside rail for TMCC

Its best not to have any gaps, but if you need gaps in the outside rail for signaling or accessory operation the you can add a 0.1 yf 50v ceramic capacitor across the gaps.

Bill

Won't any/all axles riding on sections with "gaps" eliminate the gaps, electrically? 

As long as there is a TMCC signal on the "continuous" common rail, there wouldn't be a need for a TMCC signal on an unoccupied, isolated/signalling section would there?

Did Lionel ever issue a TMCC Installation  Manual?

I know from personal experience that having only one rail hot and the other not connected to power will affect the reliability of small units like the Lionel Speeder and Early Era Inspection cars.  However, I believe this is as much a power issue as a TMCC issue.

"One wire installation"... CB "U" to layout common.

From page 5 HERE.

I only use a single outside rail to connect the TMCC/Legacy system to my layout. The other outside rail has insulated pins in each section of my Ross track. This was to allow me to use the insulated rails to operate accessories in the future.

Have been using this method since TMCC was first introduced. Never  I repeat never had an issue and never had to install a capacitor or anything else.

Just as a side note. We were doing a TMCC Demo at a Greenberg show a couple of years ago and forgot to connect the ground wire from the Command Base to an outside rail. The TMCC signal was so strong that the engines responded and received the command signal from the Command Base. Of course once we found out that the wire was not connected we corrected the situation.

The current best answer is watch the video,

http://www.lionel.com/Customer....cfm?documentID=6355

Bill

Your question is a little vague,why would you have "gaps" in the outside rail anyway. When creating "blocks"  for instance only the center rail needs a break or gap.

Hmmmmm. I was sitting here wondering the same thing as I was reading. 

One would have gaps in the outside rail if using an insulated rail section to control a signal.

B&OBill

With all due respect, Boxcar Bill, that video by Mike R. is full of bullcrap.

1.  The outer rails do not produce a halo of signal that is picked up by the antenna.  The track signal is conducted directly to one side of the receiver by the wheels and chassis.  The antenna is picking up the earth-referenced signal that is traveling from the Base through the wallwart's power cord to the house safetly ground wiring and to earth.

2.  A millisecond error in sync signal would require a distance difference of 186000/1000 or 186 miles since electricity travels at nearly the speed of light.

3.  The circuit that generates the sync signal by looking at zero crossings is not a precision circuit.

4.  You cannot create a reflective shield with a small metal plate at 455KHz.  The signal wavelengths are thousands of feet long and go around any obstacle of that size.  And you wouldn't want to create a shield.  You want to add in a radiator for the earth-ground component of the signal.

It is too bad that Lionel has not corrected this video.  When I asked John Z., Lionel's Chief Technical Officer, why he allowed this wrong information to persist, he admitted that Mike R. apparently did not understand the true nature of the TMCC signal.  But they didn't fix anything....

My explanation is available at http://www.trainfacts.com/trainfacts/?p=317

There are two outside rails, only one (1) needs to be used to control a signal.

If hard pressed a relay can always be used.

The problem is not signal radiance from the outside rails. As long as you have good power pickup you have good signal. The problem is with traction tires and dirty track. If one rail is insulated for what ever reason and the traction tire is on the other rail you run the risk of having poor electrical pickup if there are a limited number of wheels to pick up power such as on small vehicles. Poor electrical pickup will add a lot of noise to the signal causing poor reception. If you use an insulated outside rail clean track and wheels are a must.

Al

My point exactly.  Now only do you have a flaky TMCC signal, you also have a flaky power connection!

Oh, I don't know about that. 

Couple of years ago, I set up two loops of S gauge track.  I hooked the outer loop to TMCC (via TIU and Z4000) and conventional on the inside loop and the inside loop to a variable AC throttle output on the Z4000.

I went to try to run one of my Flyer TMCC Mikado's on the inside loop under conventional and it wouldn't run, but would run when selected under TMCC as long as I had an adequet conventional AC voltage present. 

Any conventional AC locomotive otherwise had no problems running on the inside loop by the Z4000's throttle regardless if I was running a TMCC equipped locomotive on the outside loop or not. 

I can only assume the TMCC signal was radiating enough from the outside loop to convince a command equipeed locomotive on the inside loop that TMCC was present.

Rusty

Rusty,

I don't think your example doesn't proves or disproves anything about what Dale said. I too have had an engine receive the TMCC signal on the work bench with no intended connection of the outside rails. I suppose it's possible for the outside rail to be picked up by the workbench outside rail which by some capacitive coupling, etc., but it's intended role in the scheme is to conduct directly to one side of the receiver in the loco and not provide a halo to be picked up by the antenna.

Rusty, if I read your post correctly, you had both loops connected to the same Z4000, and that would mean that the Commons were tied together.  If you put a TMCC signal on one loop, it will flow back through the Z4000's common to the other loop.

Well, after reading all of these replies, I'm STILL not sure what to do!

To those who questioned the need for outside rail gaps:  In my case, it will be the use of the non-derail wiring of DZ-1ooo's.

Dale;  what's YOUR suggestion?

Hi Phil,

I use gargraves, so the outside rails are isolated from each other. I connected my signal wire to the inside rail with no gaps and used the outside with gaps for signal detection and I have had no problems.

Hope this helps you,  Doug

Gaps in one outer rail shouldn't  be a problem if the other rail is continuous.  If you need to swap sides at a switch, just use a jumper prior to the sensor rail.  The TMCC signal will be fine.

Doug

   This is how I have mine wired. Been doing it that way since I purchased tmcc in 1998. Haven't had any problems.

Bill

Many thanks to ALL!  I now know just what to do:  As long as there's continuity 'all-around' it needn't be confined to 1 of the 2 outside rails; jumpers where required.

I have my TMCC connected to the track, a few feet away I have my engine cradle.  I was working on my engine and needed to run it in the cradle, I hooked it up to a different transformer with alligator clips.  It wouldn't run... it lit up... so I finally tried my cab-1 remote and she started rolling!  My thought was that TMCC travels though the house ground. 

Now my dishwasher has 128 wash cycles!! lol...  no but the above is true!

If anyone wants to come to my club and see what TMCC tricks are going on, please come by and solve them!

Dave- I read your discussion on radio signals. impressive. However, as a commercial class general radiotelephone operator license holder, I to have an understanding on RF. I guess what is bothering me most about your discussion is where you say that signal is somehow emitting from ground. earth ground? sorry, just cant get my mind around that one. true, the RF transmission and receiving wont work without a reference ground plane (house wiring in the case of TMCC) signal doesn't emanate from it. I guess I can accept the general theory of hole flow vs electron flow when talking RF and where the "signal" is actually coming from however. so if I look at it that way, it works. by definition though, earth ground has always had, does have and will alway have "ground potential (zero volts) That is why you cannot connect the common to earth when using tmcc. you have explained that well. but signal coming from "ground"... obviously I must have missed something. 

actually, my last post was responding to Dale- not Dave. sorry!

1.  What is the receiver in the locomotive sensing?  It senses the voltage gradient between the signal on the outside rail that is conducted through the wheels and frame to one side of the receiver's input circuit and the "signal" picked up by the locomotive's antenna and applied to the other side of the receiver's input circuit.  That antenna won't just float there at zero volts with current actually flowing back and forth through the receiver's input circuit; rather, the antenna is coupled to ground through an electromagnetic wave.

2.  If I have any vertical monopole antenna, including an AM transmitter tower, the tower acts as half of a dipole.  The other half of the dipole is an implied image of a similar half dipole that is buried vertically into the ground.  The ground is the surface at which this image reflection occurs.  The ground is absorbing lots of signal, and there is a substantial voltage gradient around the base (think tuned ground radials.)  Electromagnetic waves are produced by current flow, and the current flowing into and out of the earth must create an electromagnetic wave component.

We had a "contest" a while back to figure out the best name for the elusive other half of the TMCC "wave".  Our final choice was earth-ground-referenced component.

In a practical home installation, much of this component may be radiated from the house wiring by the current flowing from the base through the U-ground pin through the house wiring to ground.  At 455 KHz it doesn't take a very long wire to create significant inductance, and that means that there is a significant voltage drop from the Base to true zero-potential earth.  We can also distribute this earth-ground-referenced component directly by attaching a wire to Pin 5 of the 9-pin connector since this is the "ground" side of the power supply that drives the output stage.

3.  If I hold my hand over a misbehaving locomotive, I can improve the strength of the signal received by the locomotive.  Since I am not touching anything, any induced coupling between my hand and the locomotive's antenna must be electromagnetic.

That is my explanation.  I solicit your version of how this all works, including what the antenna in the locomotive is sensing.

The easiest way to prove Dale's position is to connect the antenna in any TMCC engine to the outside rail. If the antenna is picking up the signal from the outside rail this should allow for max signal. Go ahead, try it and see what hapens and then explain it. One cannot receive a signal from the ground of the receiver.

Al

Going back to the original question posed you don't need to worry about isolation pins or whether the outside rails are tied together.  Once the signal gets out of the command base, it pretty much goes everywhere.  

Lionel advertises TMCC as a "one wire hook up", they never said it was a one wire system.  As Dale has pointed out, they use the ground wires (aka third prong of a three prong plug) of the house as the other half of the rf signal.  I'm not sure that it matters that these wires do go to earth ground (or are at least supposed to).  Those ground wires run all over the house.  If the house is wired properly they can completely envelope the layout.  Since they are supposed to be tied to earth ground that makes it easier to add aux ground feeds (like cold water pipes) to "fix" reception issues on the layout.  I think Dale's suggestion that using the ground pin on the serial port for the aux ground is actually the best way to handle this.  No issues with surge suppressors, bad house wiring, bad earth ground.   You are directly access the "other side".

The main issues with TMCC reception is that the receiver needs to be able to see both the track signal AND the reference plane to work properly.  If there is so much track signal it overwhelms the receiver and the unit won't work. If there is too much induced signal from large ungrounded metal objects these can interfere with access to the reference signal and the receiver won't work.  In both cases you supply an auxiliary source for the reference plane and the receivers can see the signal and the system works as intended.  The system works deep in the "near field" and the magnetic component can easily interact with any ungrounded metal objects in the area and generate induced RF that can be stronger than the original signal and their shape/orientation may be setting up interference patterns that could affect the receivers ability to "see" the track signal.

If you want to test this out pull all locos off the track and only have accessories or sound cars active.  The following assumes you are not using the ground pin on the command base for the reference plane.  Put a cheater (two to three prong converter) between the wall wart for the command base and the power outlet.   You should have little or no TMCC signal (note, wire from CB to wall wart can act as an antenna so you might get some signal).   You've just removed (or removed most) of one side of the signal.  Pull the cheater and plug the base back into the house wiring.   Now disconnect the wire from the command base to the track AT THE COMMAND BASE side.  Make sure there is a couple of inches of separation.  Again,  no signal.  You just removed the other half/side.  I've used this method to test TMCC engines in "conventional" mode using a TPC as a controller.  I can still "talk" to the TPC via the serial cable.  I'm using the CAB to control the TPC but the loco is running in conventional mode (I could take the engine apart and disconnect the antenna on the receiver but this seemed easier).

OK, take about two to three feet of bell wire and attach that to the antenna terminal on the command base but don't attach it to anything else.  Just leave it so it doesn't make contact with anything.  You should now be getting TMCC signal.  Maybe not great, but it should be there.  (This is the flip side of the TPC test.  I tried disconnecting the wire on the track side and loco's were still seeing the command signal.  The 18" of hookup wire was enough for the signal to break out).

Hijacking but it's pertinent...

I have seen more than one Legacy base with a very much reduced U terminal track signal. About 1/6 th or less than a properly working one. The problem with this is that the Lionel Service department has pronounced this base as working properly. But in the owners layout, it is very iffy...works and doesn't work. As you might guess, they didn't measure the level of the track signal but just that it worked on their test layout. It also worked on the owners test layout, but not well on his big layout. The base was clearly "broken" but there was enough track signal to confuse the issue.

On my recent trip across country to visit train layouts, I measured the track signal on maybe eight layouts with my oscilloscope.  Of these, one had half the sinewave missing, and another had 1/4 of the sinewave missing.  When we substituted properly working units, performance did improve.

Dale, any chance the misbehaving units were "out of tune"?

No, this was abrupt clipping like you would see from an improper bias point.  I suspect lightning damage.

"I suspect lightning damage."

Ouch! 

If you had a simple oval with switches on the straight for a siding or four of them to make a figure eight you now have gaps all over in the outer rail simply because of the non derailing feature. Outer rail gaps have never changed the TMCC signal in any layout we have seen.

chuck:  You said 2 things that warrant a reply from me:

1."The system works deep in the "near field" and the magnetic component can easily interact with any ungrounded metal objects in the area and generate induced RF .... " This makes me wonder if you're referring to Maxwell's E & M equations....

2.   " you don't need to worry about isolation pins or whether the outside rails are tied together",    which seems to 'fly in the face' of most of the other guy's opinions.....????

I'm referring to observed behavior in both cases.  I saw odd behavior in floor layouts at my mom's house when visiting for Christmas.  We identified the sources of the signal "scrambling".  I discussed what I observed with some of my former colleagues in my old department (EE).  They were the ones that pointed me in the direction of looking at the near field for effects/issues.  

This is an odd use of radio.  We are using an extremely low power signal that would have a short range because of the power.  It's also a fairly long wavelength (a single sine wave is almost a half mile long).  Because of the wavelength we are working deep in the near field and near field effects can cause issues with reception because the signal sources may not always be the intended antenna(s), aka the track and house wiring.

The track gap issues was settled for me when I was trying to run the TPC's to test command loco's in non command mode (specifically to test Odyssey issues) and to find out much difference there is in pulse vrs non pulse supplies and differences in absolute vrs relative speed steps.  If I disconnected the "one wire" from the track side (two-three feet of wire) the command signal was still present.  I tried moving the wire as far away from the track as possible.  It didn't matter.  If I disconnected the wire at the command base side, no signal.  If the signal can propagate across a gap of several feet a couple of millimeters shouldn't be a problem.  

1.  The outer rails do not produce a halo of signal that is picked up by the antenna.  The track signal is conducted directly to one side of the receiver by the wheels and chassis.  The antenna is picking up the earth-referenced signal that is traveling from the Base through the wallwart's power cord to the house safetly ground wiring and to earth.

I'm lost as usual, How does an engine's  receiver  pick up the TMCC signal (via the wheels & chassis) if the "U" connection from the command base is NOT connected to the track. Some say it does, others say it can't. 

Regardless , it seems  the not so accurate info  did wonders for some layouts.  Wrong terms I guess but the method seemed to work.

They're just saying that the U connection can be from radiation over a short distance from the U terminal with a short wire on it to the outside rail or over a short gap in the outside rail. It's better to have a solid connection of course, but an iffy connection without a wire over a short distance can be explained by the field theory.

It would be interesting if an aerosol spray could make visible all the electromagnetic fields present in our house, or environment...and disconcerting for some too. And who knows, maybe some of it is beneficial in ways we don't suspect.

Yes, this would be an amazing aerosol spray can!!!  Anyone ever try to shoot your layout with a video camera in the "Infra-red" mode?  I wondering if anything shows up? I know my TV Remotes did! But my camera is broken now