TMCC 'rule': Just ONE wire

I'm not sure of the specifics, but remember the wire from the base to the track basically turns the track into a transmitting antenna for the loco's receivers.

No matter how large or small a layout I've created for TMCC, I've always used just one wire from the command base.

It's not a rule.  You can drop and extra feed to the track.  In reality if like me you hook the 1 wire to your common on the transformer, then every time you run a power jumper you effectively add a TMCC drop. 

That being said if you are having issues in an area, I would probably try the ground solution first.

The rule isn't one wire, but one command base.  You can have as many wires to the outside rail as you like.  The signal is going to be the same in most cases unless you have something funky going on with your track.  I'm not aware of too many situations where anyone has had better results by using multiple track feeds from one command base, but it's a simple potential fix to try if you are having signal strength problems at a distant location on a layout.

As said, it's usually a ground plane problem of some sort that causes signal attenuation

or a poor antenna on a particular loco.  Trouble shooting TMCC is quite simple 95% of the time.

Cool..

  I do exactly as MartyE describes.  The wire from my command base goes to my transformer's "U" terminal.  So, by default, it feeds the the track in multiple locations.

The only issue I ever had at all with a TMCC signal was in a tunnel a made where a Bascule bridge sat up top.  I simply ran a wire from the bridge base to an outside rail in the tunnel.   Cleared it right up.   This was about 5 years ago.   No issue since.

On a larger layout, you almost have to use more than one wire at some point. The most efficient way to do this is to connect the command base to the track common back at the power supplies.

TMCC uses the common rail as a radio antenna. In a perfect world, both outside rails are tied to common, but in some instances like insulated track for block signals and across some turnouts, only one rail may be connected to common. In these cases, a wire running next to the track connected back to the command base puts the radio signal on both sides. If you check Carl Tuveson's site (http://www.tuveson.com), he also shows how you can put the TMCC signal on the hot rail as well (he runs S scale with TMCC).

In cases where you have one track over another, you need to add some type of "earth ground" in between the two tracks if there's a signal drop-off (the upper track and the lower track cancel each other out). We had to put metal screen tied to earth ground underneath the upper staging loop as it was cancelling out the lower loop.

I also use the ground terminal and have very consistent connections to all locos. 

However, if I could add to the thread - What about signal between the hand held remote and the command base.  I have some areas in my layout room where there is a very weak connection to the base even when only 8 feet away from the command base.  If I move or hold the antenna more vertical I get a connection.  Perhaps this has been dealt with in another thread.  Would you post a link.

Wood, the communication between the remote and base is totally different than the TMCC track signal.  For the CAB1, it's 27mhz, for Legacy it.s 2.4ghz.  If you have a problem 8 foot from the base, I'd look for source of interference.  For Legacy try changing the channel of the base and remote to see if you can improve the situation.

Thanks John, 

I have the original TMCC command base with a CAB1 remote.  Their is no obvious way to change the channels.  

My layout is in the basement, with a plethora of steel and copper piping, used for the radiant heat up stairs - that could easily provide interference.  One of my electronic junky friends told me to elevate the command base and my signal would improve. 

I have delayed on getting Legacy.  Would that be "less" subject to interference?

I run my Cab 1 wire not to the track, but the ground bus for the system.  Advantages:  if there is a week connection at a lockon to ground/"U", then another lockon can carry the signal.  And in some cases, like where there is a case where the straight path of an O-27, O-22 or O-72 meets up aginst the curved path, then you have BOTH outside rails with fiber pins!  Hence a good idea to have muti drops!

The CAB1 can only change channels by buying a set of crystals.  Legacy has nine channels available.  Relocating the base is the first step in seeing if you can change the interference.

TMCC uses special remote control channels in the CB band.  L uses Microwave freqs.

And a quick reminder, TMCC doesn't use the rail as the antenna, it uses the house wiring as the antenna.  So the locomotives get their signal from the house, not the track, which is why you can have problems with a multi layer layout, the upper layers block the signal from getting to the lower layers.  The track is only a ground plane for the signal.

If you are using TMCC and DCS on the same tracks do not connect to the transformer common.  The TMCC wire should go on the TIU outputs

Actually, TMCC uses BOTH the outside rails and the house wiring as the antenna!  Cab-1 is producing a radio signal which is really, really long! Due to the math and electronics or the radio signal, it needs BOTH parts to work.

Lets all not forget the plug you plug your base into has to be a grounded outlet  .. That means the outlet ground not the white wire has to be grounded to the outlet and the fuse box . Failure to have this right is nothing but ground issiues .Even if you have engines that run right some won't..

Thanks, folks!  I DID forget that the RULE is: ONE CB; NOT one wire.  Yes, I now DO realize that I already HAVE multiple connections....one from each of my 20 Lionel 'bricks'.

Related, tho':  As Dale Manquen has explained, and both Jim Rohde and JonZ at Lionel have agreed, the portion of the TMCC signal that flows thru the outside rails to one side of the radio board is NOT a RADIATED signal.  Rather, it's a CONDUCTED signal.  The other 'half', which flows from the CB into the house wires, IS radiated....to the other side of the radio board thru the engine's antenna..

Phil, you should say that again.  

I've tried a couple of times to state that the track signal is conducted to the TMCC receiver and the antenna signal was radiated, but I was contradicted.  In truth, the track signal can be radiated a short distance, just as the antenna signal can.  However, I'm sure the intention and the design by Lionel is that it's a conducted signal.

Yes, gun....Dale has even discussed this with JonZ and wondered WHY Lionel continues to promulgate that 'old wives tale' is beyond 'all' of us!

"Yes, I now DO realize that I already HAVE multiple connections....one from each of my 20 Lionel 'bricks'."

Did I REALLY say this?  What Kool-aid was i drinking?  My bricks do NOT carry that 'U'-wire signal.  But I've learned how I CAN get what I said I had [ thx, blueline]:  Connect that wire to each of my 5 TIU outputs!  Each of these controls 4 of my Lionel 180 watt brick outputs.   This I may try....

I agree.  It's frustrating that Lionel continues to spread an inaccurate view of Tracklink (apparently the official word for the TMCC/Legacy signal).  Rudy's LCS diagram shows it wrong.  Mike Reagan's videos tell it wrong.  Even a short piece in this month's OGR has it wrong!

It’s pretty straight forward.   The two sides of the Tracklink antenna are the ground wiring, etc. in the building and the outer track wire to the U terminal on the base.  Primarily two things can go wrong.

• The ground signal can be blocked or weak to the locomotive receiver.  That's when a ground wire 4-6 inches from the outside line of a track can work.  We've had great results running them along the track on telephone poles.
• The outer track signal to the Base U Terminal can get "blocked" by capacitance set up in the wire by running it in a bundle with ground or hot wire.  This can be cured by running the outer track wire to the base away from any other wires. 

The following is from a series of conversations I had with a Lionel Sr. Electronics Engineer regarding wiring for Tracklink.  Emphasis is mine.  I’m going to post this in the TMCC info thread if I ever get around to it.   

Any power or signal supply must have two connections, a source and a return.  For the Command Base the source is the earth ground and the return is the U terminal on the Base that is connected to the outside rail.  This means that the earth ground is acting as the transmitting antenna for the Base.  This also explains why putting earth ground wires on the layout helps.  The idea that the earth ground is the signal source is what normally confuses most people.  For most radios the earth ground is the return.

What causes problems is when the wires from the Base U terminal are run close to the earth ground or track power wires.  When two wires are close together there is a property called capacitance between the wires.  This capacitance acts as a path for radio frequency signals.  The closer the distance between the wires and the longer the wires run together the more the capacitance.  This capacitance can effectively short out the signal from the Base.

To prevent this, do not run the Base U terminal wires in the same wire bundle as the ground or run them over a ground plane.  Do not run the ground wires directly under the track.  The outside rail is connected to the Base U terminal so a ground wire under the track is the same as running the wires together in a bundle. A separation of a couple of inches should be adequate but more is better.   To be really careful treat track power wires just like you would ground wires with respect to the Base U terminal wires.  The track power terminal on the power supply is capacitively coupled back to earth ground through the power lines.

Steam engines use the handrails for the antenna which run close to the die cast shell.  The shell is connected to the outside rail which is the return for the TMCC signal.  This creates a capacitor between the antenna and the shell that loads down the signal and reduces reception.  The effect is similar to that caused by running the BASE U wire next to the earth ground I described earlier.  Diesel engines with plastic shells do not have this problem so they will always perform better than steam engines. 

The gauge of the wire used for the TMCC signal should not be critical.  There is no significant current in the wire so anything from 22 AWG to 14 AWG should be fine.