Signal issues

It sounds like the metal parts of the accessories (which I believe are tied to track Common/outer rail) are causing the signal problem.  The earth ground wire is the solution.  Wrapping the wire around the metal may put the wire too close to the problem.  Try other placements along the track or under the track.  You might also try an earthh-grounded sheet of aluminum foil or a cut-up aluminum plate adjacent to the accessories, but not electrically touching the accessories - above or below deck as your layout permits.

Your finger on the antenna injects a strong earth-ground signal, giving you the good results.

See http://www.trainfacts.com/trainfacts/?p=317 for a better explanation.

Thanks Dale!  

A sheet of aluminum foil under the layout seems to work - at least when I tested it tonight.  Interestingly enough the problem does not start until the train makes a few laps after I turn the power on - I'm not sure why that is.  I ran a bare copper 14 gauge earth ground underneath my layout over the weekend so I could easily tap into it anywhere on the layout.

Which is better - a bigger piece of thin aluminum foil, or a smaller piece of thicker aluminum metal?

Don, I am actually in the middle of some testing of TMCC Bases to characterize the frequency drift of the Track command signal as the Base warms up.  I am trying different types of capacitors in the tuning circuit that reduce the drift considerably.

I wonder if your problem is related to this frequency drift during warmup.

There is no significant current in the foil, and therefore the resistance of the sheet as a function of thickness is unimportant.  I suggested the metal plate just because it won't tear.

Dale,

Could you explain "frequency drift" and why it would cause the signal to go from strong to weak without the earth ground changing.

Dale's alot better at explaining this but heat is the culprit. It expands every thing and causes it to go slightly off frequency . This happens in the hand held and the engines .
My legacy hand held heats up a little with use and these new fangled engines with dual smoke units and not to mention just the motor itself create heat.

I use to have a ham radio that had an external cooling fan on a switch . If I was on a certain frequency and didn't turn the fan on people would start to sound like Mickey Mouse. Turn on the fan and they were back to normal(Swan 350)

Best thing to help it what you can is get the hand held out of that form fitting cradle when running your trains and let some air get around it. One of these days these engines they're packing with goodies are gonna need a cooling fan on the flywheel to keep them from melting.

David

The transmitter (Command Base) and receiver (in the locomotive) need to be on the same frequency to get the strongest reception of the transmitted signal. 

Considering the Base only here, the Track output frequency is determined by a tuned circuit consisting of a variable coil (inductor) and a fixed capacitor.  As these components warm up, their values change slightly, causing the frequency to shift slightly.  If the frequency shifts away from the "sweet spot" of the receiver, the received signal may get too weak to be properly detected everywhere on your layout.

One of the design tricks is to use component pairs that drift in opposite directions by an equal amount, thereby cancelling out any change in frequency.  The other method is to find components that drift very little with temperature.  There are a number of different materials used to make capacitors (ceramic, Mylar, polypropylene, mica, etc.), and they all have different temperature drift characteristics.

The TMCC receiver in the locomotive is somewhat "frequency agile", meaning that it has a range of useful frequencies, but there is a sweet spot.

I don't know what the Lionel specifications are if/when they test the Base and loco receiver, but I do know that adjusting the Base when it is cold will not guarantee you will have the correct frequency when things warm up!

I will know more when I complete my testing.

This sounds really interesting Dale, perhaps a simple component change could make a big difference in reliability.

Dale - you may have something with the signal shift. I ran my J for 25 minutes tonight armed with a piece of commercial grade aluminum foil and it didn't fail once. It has always been intermittent. It then occurred to me that I have two remotes and I was using the one from the Legacy Base unit.  So I put the remote back in the base unit and it failed within 2 laps of the track.  Unfortunately, removing the remote from the base unit doesn't seem to stop it from failing once it starts. I stapled the foil in place and the headlight no longer flashes by the icing station.  I'll give it a 2 or 3 hour test this weekend just to make sure it works. After that I'll start strategically placing foil in other spots around the layout. 

If you are running a Legacy Base,  there shouldn't be any frequency shifting at the transmitter.  In that design the Track signal's frequency is derived from a logic chip clocked by a crystal. 

There still could be heating in the receivers since the inside of a locomotive can get very hot.

Sounds like you are making progress!  Keep the reports coming.

Dale you could be on to something. I find that when I run my engines at a show for a few hours they start giving me signal problems. They start stopping in places they didn't stop before. I have to shut them down and let them cool off.

Jim D.

If that hand held is sitting in the base in the charging mode and your using it, it can get pretty darn hot. Would that not affect it?
Mine got hot as the daylights till I sent it off to get it repaired. Now I keep the charging circuit off unless I'm charging the batteries(about 45 minutes) and only when I'm not running trains.


David