FYI - found an interesting write up that has a lot of information dealing with this topic.
Here is part of the write up.
Problems and Solutions
Now that we know how the TMCC Track signal is transmitted and received, we can look at some common problems and their solutions.
- We must establish a good connection between the Command Base and the AC wiring in the house.
- Our house wiring must have proper safety ground wiring with U-ground receptacles. Do not use a 3-pin to 2-pin adapter plug on the Base wallwart.
- We must use the Lionel wallwart so that we have the jumper between the Base ground and the house safety ground. Check for continuity between the outer barrel of the coaxial power connector and the U-ground pin on the wallwart.
- If you use an outlet strip, verify that the U-ground receptacles are connected to the U-ground pin on the plug.
- Do not connect the Base wallwart to a coiled up extension cord. The coiling of the cord can create an inductor that hinders the flow of the Track signal to the house wiring.
- Use only proper 3-wire extension cords with safety ground pins.
- I don’t think surge suppressors in an outlet strip should degrade the signal. At worst, the suppressors will capacitively couple the safety ground TMCC signal to the hot and neutral, but the wiring capacitance throughout the house wiring also does that without ill effect.
- Eliminate any electrical noise sources.
- Use a portable AM radio to “sniff” for noise sources. Tune the radio to an unused frequency. Common problems are faulty fluorescent lamps, arcing capacitors in the AC line filter for most electronic devices, faulty aquarium thermostats, failing power supplies, arcing power supplies in TVs or computer monitors and DC motors.
- Add capacitors to the brushes of Pullmor motors in older locomotives and motorized accessories.
- Keep your track and pickup rollers clean.
- Check the integrity of the locomotive’s antenna
- If the antenna is metal handrails, there must be no resistive path between the handrails and the boiler casting.
- Verify that the antenna is securely connected to the TMCC receiver board.
- Some diesels will benefit from extending the antenna by adding foil tape or just wires.
- An antenna inside a closed metal box is blind. If the receiver and antenna are inside a tender shell:
1) Insulate the top part of the tender shell from the frame with tape and connect the antenna to the insulated portion.
2) Poke a hole in the shell and route a section of antenna wire outside the shell.
We must avoid configurations that block out the airborne Track signal by having too much outer rail Track signal. Imagine what would happen if you put your locomotive inside a metal box that was connected to the outer rail. You would have lots of Track signal conducted through the wheels, but there would be not airborne signal on the antenna to cause current to flow back and forth through the input stage of the receiver. This is the situation you create if you have overhead bridges and/or trackside metal structures connected to the outer rails of the track, or many parallel tracks.
Now imagine that we drill a hole in the metal box containing our locomotive, and we insert a wire connected to the earth ground signal. Now the locomotive’s antenna can pick up some of the earth ground signal and create a voltage differential across the receiver’s input. We can pick up the earth ground signal from the center screw on a grounded wall receptacle, a metal water pipe or electrical conduit, or Pin 5 of the 9-pin connector on the back of the Command Base.
- Avoid overwhelming the airborne signal with too much conducted Track signal
- Do not connect tubular track ties directly to metal bridges with metal mounting screws. Alternatives are nylon screws or using insulating shims and plastic shoulder washers.
- Beware of trackside accessories with metal parts that are tied to the layout’s common bus. This will put the conducted Track signal onto the metalwork. One solution is to use a separate transformer and wiring for accessories that are not tied to the track common.
- If necessary, add some earth ground antennas in the region where there is too much conducted Track signal. Run a wire connected to earth ground on the underside of the bridge or between the parallel tracks, or string some fine wire as power lines on power poles.
- We can temporarily augment the airborne signal by using our body as a secondary antenna, and placing our hand near the locomotive. This brings more earth ground signal to the locomotive. If this helps the locomotive, the permanent fix is to add an earth ground antenna to that area.
Note that this overwhelming is not what we would normally consider to be interference or cancellation. The multiple Track signals are not interfering and reducing anything. They are all adding up quite nicely, too nicely in fact. (There is no “interference” because a wavelength .4 mile long is much too long to create cancellations in a space the size of a layout. We are dealing with a simple imbalance.)
The full article can be read here http://www.trainfacts.com/trainfacts/?p=317
