Legacy interference

The system is working as designed. Changing frequencies will not have an effect on the problem you are experiencing... the command locos will look for a signal on power-up and default to conventional if there is not one.

Thank you Rob.

The issue is that even without a connection between layouts, you can have the TMCC carrier affect you.  I can occasionally get a TMCC signal on my workbench which is totally isolated from the layout.

Is there something about the nature of the TMCC signal that would let us figure out a way to block it?  I don't know a lot about tmcc... I think the engines have an antenna... can that be disconnected?   If need be, they could be reconnected.

There's not a problem with starting the S layout first, but if there is a problem on the S layout, we'd have to shut down our large O layout, just to get the S layout back to working conventionally?

One side of the signal is transmitted via the base through the ground lug of the wall wart and broadcast from the ground wiring in the walls of your layout room/ building.

The S guage engines are "seeing "this signal and are waiting for the track signal to respond to Legacy commands.

Just wire the outside rail to the earth ground (3rd prong of an outlet), that will kill off any TMCC signal on that layout.

Rick, I don't have it here but I thought the wall wart didn't have a ground pin... I'll look!  The wall wart plugs into the TMCC with a co-axial plug I think it's only 2 conductor.  EDIT: looks like the Legacy base has a grounding wall wart... but we need THAT to keep the O gauge layout working well on Legacy.

GRJ... that will work on a 2 rail S layout?  Just ground one rail?  Seems like the TMCC signal is traveling around the room on the building ground wire... wouldn't grounding one side boost the signal?

Obviously, I have no expertise in tmcc/legacy...

Another thought... it looks like the Loco we have has a "radio receiver board" (at least according to the parts list.)  Can it be unplugged and just left in place?  Seems like that would kill the TMCC reception...

John's grounding solution will work on a 2 rail S gauge layout without reverse loops. Just make sure the Base Posts of all transformers are "in phase" and then ground them. With reverse loops make sure the only ground connection is from the transformer Base Post, no connections from the track feeders since some of those feeders will be wired through the reverse loop controllers.

You can also use a .1uf capacitor to short out the signal, that will solve the problem of reversing loops.  However, if you're running AC with Legacy, do you have reversing loops?

John, yes, I have 5 reversing loops on my AC powered, Legacy operated S gauge layout. Works perfect with the addition of your Buffer/amplifier. I have .1mfd capacitors between the two rails in each block to put the Legacy signal on both rails for better reception. As we discussed before, this would kill a DCS signal, but in S gauge that does not matter. The .1mfd cap to ground will definitely work for a non-Legacy layout to kill the Legacy signal.

John, I may have talked past your question. Even with Legacy, a reverser board such as a PSX-AR-AC is needed to flip the track power connections within the reverse loop when the train crosses the boundary. Otherwise, short circuit.

The .1uf capacitor I'm talking about is connected from earth ground to the track, that's what will short out the TMCC signal that is being radiated by the other layout.  It's not the same as your cap between the rails.

No reverse loops, just 2 tracks, 2 transformers, 2 legacy engines...

So, it sounds like a 0.1uf capacitor from each rail to AC ground should work?  That would be easy!

Agree, John but it is good to state it clearly.

One rail to ground should work, but it would not hurt to tie both rails to ground through a .1mfd capacitor. I use ceramic disc capacitors rated for 50V.

I'm really confused as to why you thought a Legacy locomotive should run conventionally with the Legacy command base active on the rails???  Of course, one has to wonder why run a Legacy locomotive conventionally at all if you have the Legacy command system.

FYI, for Legacy locomotives with a plastic shell, you're going to find that unplugging the antenna is not a sure fix, many will run fine without the antenna connected.

If you really don't want it to run in Legacy mode, add a switch to short the antenna to the frame, that will kill the Legacy signal to the engine.