Foil Ground Plane 0.5" Below Track for Improved TMCC Signal - Yes or No??

Carl,

I would tend to say no, definitely not.

Remember that TMCC/Legacy was designed such that its broadcast "antenna" has two components, the first is at least one outside rail all the way around the layout, and the second is the earth ground beneath and/or around you.

This works best if the two have some separation between them, usually several feet.  The layout is most frequently on a table and the earth ground is in the ground.  If you add conductive tape tied to earth ground and place it immediately under the track you're bringing the two components much too close together.

The only time you should need to use this kind of "special ground" is when you have two tracks, with one above and largely parallel to the other.  In this case placing foil tape under the upper track might help improve clear reception of the TMCC/Legacy signal.  But this is the really only case.

Mike

Another no vote here. If you want to add a ground plane its best placed 4-6” above the track. Some use telephone poles to do this with actual wire. As Mike points out the trouble spots are where metal is over the track like a bridge.

Pete

A definite no.  It's the worst place for it.  The antennas on the engines are either handrails on steamers or a metal plate in the top inside of a diesel shell (on the the rare case of a diecast diesel a metal plate on the top of the shell.).  Putting the ground signal under the track allows the outside rail signal to weaken it and in the case of a diecast engine the shell blocks the signal from the antenna.  The best place is on a telephone pole next to the track or not as good but better than below is a wire laid parallel to the track about 2-3 inches away.  The "ground plane" under the track is an ancient history erroneous idea.  This information came to me directly from a Lionel electronics engineer.

The NO's carry the day, the antenna should be above the track, not below it!  For a single level, a good place is telephone poles with fine wire.

Carl, since you are an OGR Digital Subscriber, you can view all of the old OGR magazines.  Look at the December, 2006 edition.  I have an article in there called "Overcoming TMCC Gremlins" that should be of help to you.  Also feel free to e-mail me (address in my profile) with any questions.

No here too. It's unfortunate that the word "plane" got attached to the words "ground wire". The ground wire (the third wire which is the ground in your electrical system) is the antenna and generally is above the layout in most rooms. You can add to this, as others have said, by running a wire, connected to the house ground, over the track. It's simply a thin wire that's all that is required. The connection can also be made at the Legacy base, pin #5 of the 9 pin connector.

I have a layout with foil tape under all the track. The layout was built using the tape by a professional layout builder based on their experience with over 100 layouts. They provide a one year full unconditional warranty and 5 year limited warranty so when the layout leaves the factory and is reassembled in the owners train room it has to work. They do not have the time to custom route wires above the plywood holding the track.

I can tell you it works. I will also tell you it is not necessary with a home built layout. My layout has 700’ of track, some is two levels, some three and some areas are 4 levels. I estimate about 1/3 of the track would require a supplemental wire along the track if the tape were not present.

Some of these ideas that are flawed in theory may work. Yours sounds like the lower layer benefits from the foil under the upper track. Having the ground wire over the lower track in the form of foil under the upper track is not a good idea since it greatly increases the capacitance between the outside rail and the ground antenna wire. Generally, not good but maybe not killing enough of the signal to matter.

@Bob posted:

Carl, since you are an OGR Digital Subscriber, you can view all of the old OGR magazines.  Look at the December, 2006 edition.  I have an article in there called "Overcoming TMCC Gremlins" that should be of help to you.  Also feel free to e-mail me (address in my profile) with any questions.

This article, which I have kept, is the gold standard.

Bob does an excellent job of identifying the very few issues with TMCC and documenting their solutions.

George

My most intense challenge layout for TMCC signal reception has multiple levels with some elevated tracks parallel to and generally running above the base level tracks.  The layout has lots of bridges, accessories, building, and scenery that limited access for installing a ground plane enhancement.  I chose to use a single strip of 2" wide aluminized tape on the underside of the upper level plywood because it could be applied easily to the existing finished layout - particularly in tunnels.  It works fine.  I also used a single wire for some of the installation.

I would not try to coat the entire underside of an upper platform with a ground plane.  As previously described, the TMCC receiver measures the voltage differential between the track (outside rails) and the antenna.  Too much of either signal component can swamp the receiver as is the case of multiple adjoining tracks or overhead tracks without a ground plane enhancement.  Its a matter of balance.

When building a layout, using a wire on the underside of upper levels over track works fine - it can be installed during construction.  For existing layouts, access around a multitude of accessories and scenery items becomes a challenge to attach a wire.  Copper foil tapes may be a most suitable solution as they come is widths from 1/8" and up.  Aluminum foil tape is less expensive and readily available at local hardware stores.  I found that it sticks nicely to the underside of plywood in tunnels where access is a long reach.

Other TMCC gremlins are metal accessories that use the "common" ground of the track as is common practice on conventional layouts.  Metal signals cause a signal loss near the signal when the accessory ground is shared with the track.

Metal truss bridges should be isolated from the track ground rails.  A ground plane wire is then run through the bridge, or the bridge can then be connected to the ground plane.  I had concerns that a metal bridge, that is connected to the ground plane and completely surrounds the locomotive as is passes through would swamp the TMCC signal reception, but found that operation through the bridges was flawless.

A single-level layout does not generally need ground plane enhancements.  The ground plane signal emanating from the house wiring in the walls and ceiling of the layout room will be strong enough.  Adding ground plane signal under the single level track is probably unnecessary.   Exceptions are track-dense yards and turntable whisker tracks.

A multiple level layout will broadcast the rail signal component from the upper tracks and swamp the weaker ground plane signal coming from the house wiring.  These areas need to boost the ground plane signal with a wire or metal tape ABOVE the tracks.  A single wire/tape will probably suffice for several of the lower level tracks.  YMMV and you may need to use more wire/tape.  Test, rinse and repeat.

Always test the ground plane wire/tape with a multimeter to ensure it is not cross connected with the track rails.