Lionel Signal Lock Criteria?

Yep, it does indeed have modulation, a simple carrier won't get the job done.  It's actually an FSK signal centered around 455khz.   The base continually sends idle commands when it has nothing to say.  Your best bet is to use an old TMCC command base and if you want to tinker with the amplitude, a TMCC buffer, I know where you can get these.

The commands are detailed in the back pages of the Lionel - Complete Guide to Command Control 71-2911-250.pdf

You can actually 'scope the track signal and see the commands, the bit rate is about 3,000 BPS.  I'm sure there was a good reason that bit rate was selected, Jon Z. told me once, but I forget the details.

The late Dale Manquen had some great information on the TMCC system on his now defunct website.   The site is sadly gone now.  However, thinking ahead, I use a web site capture program to grab the whole site before it disappeared after his death.  The web archive is about 650mb, if you have a way for me to FTP it to you, I can send you the whole shebang.

@gunrunnerjohn posted:

Yep, it does indeed have modulation, a simple carrier won't get the job done.  It's actually an FSK signal centered around 455khz.   The base continually sends idle commands when it has nothing to say.  Your best bet is to use an old TMCC command base and if you want to tinker with the amplitude, a TMCC buffer, I know where you can get these.

The commands are detailed in the back pages of the Lionel - Complete Guide to Command Control 71-2911-250.pdf

You can actually 'scope the track signal and see the commands, the bit rate is about 3,000 BPS.  I'm sure there was a good reason that bit rate was selected, Jon Z. told me once, but I forget the details.

The late Dale Manquen had some great information on the TMCC system on his now defunct website.   The site is sadly gone now.  However, thinking ahead, I use a web site capture program to grab the whole site before it disappeared after his death.  The web archive is about 650mb, if you have a way for me to FTP it to you, I can send you the whole shebang.

Thanks GRJ and oh geez. FSK is annoying to generate with simple auto-router PCB circuits. You need an XO and PLL and have to keep everything 50 ohm traces and you need a VCO to modulate and suddenly it turns into a project. Maybe I'll take your suggestion and "extract" the board from a command base instead.

So here's the "why"

I'm thinking up some kind of lionel-o-meter (exact details are fuzzy still). We have one of the signal cars (I think Dale designed it actually) that measures how much carrier is on the track, but we're finding it's not super helpful. It does a good job of making sure the layout signal is happy, but even still there is such a big diversity in locomotives. Some models have really solid antenna coupling while others just blow.

So I'm envisioning some kind of box ... say 6" X 6" and 24" long with a track on the bottom... like a square "train tube". You put the train in the tube and close the ends and push a button. The train tube would be coated with metal on the inside and makes sure the surrounding E-field isn't influenced by nearby things or the quality of the building wiring. So then once the button is pushed... some electronics slowly ramp the amplitude up of the 455 KHz signal until the locomotive indicates lock (how to detect this I'm still thinking about, maybe just a photo sensor pointed at the headlamps). The electronics record what amplitude lock was achieved at, and we have a display on top that reads out "antenna quality" on some arbitrary scale from 0 to 99 or something.

Then we tell the club members we only listen to their signal performance complaints if the antenna level is above X.

I love it, that's a cool idea, especially for a big club!  I look forward to build details, I might want one of these as well!   I think the command base is the right way to go, it's already working hardware

You can make the test even easier.  Just step the signal up in small increments and generate a horn/whistle command, if the horn blows, the engine is receiving.  Probably a whole lot easier to detect than the flickering light, that might be a bit tricky to interpret.  You will want to wait a couple seconds between each test amplitude anyway as the TMCC logic takes some time to react.  There is a dead space of around a second between commands where additional commands are ignored.  This is because TMCC sends multiple commands to maintain reliability, so there has to be a pause between different commands.  It's also why when you blow the horn, it doesn't stop right when you let go of the button.

The signal car is easy to do, you just tap into the R2LC receiver,there's a signal strength DC output.

At NJ-Hi railers we build the TMCC signal car with a bluetooth meter and took readings of all our lines and ran diesel & steam engines to find out what reading the majority of our engines need without running into weak signal/blinking head light issue.  We came up with a meter reading of low to mid 40 ua for steam engines to run correctly.  Most diesels needed less signal due to non metals bodies.   With that information the team used a buffer and ran ground wires where needed to get signal readings in the 40'S.  If there were non metallic engines with poorly designed antennas, we updated the engines antenna by replacing the 2" factory antenna with a 12-14" copper strip.  These efforts have resolved the vast majority of our TMCC signal issues with club members.  Hopefully this helps.

Bob D

Can you further explain a bluetooth meter.

Bob has a meter that talks BT to a smart device, it measures the output of the TMCC receiver signal strength pin on the R2LC.

I would like to see a diagram or picture of this bluetooth monitoring setup. This would be very useful in my work with bluetooth based systems.

We used a Southwire 16040T bluetooth DVM and connected it to the TMCC signal strength circuit located in the body of a piece of rolling stock which has pickups to power the circuit.  Installed the Soutwire APP on a smart device and now we were able to see and record all the TMCC measurements regardless of the location on our 30' X 200" multi level layout.  See below diagram for TMCC signal strength circuit & Southwire meter picture.

Bob D

TMCC signal strength circuit

Bob D

Bob, how tall is that sucker?  Looks like it might have clearance issues!

Thanks for the diagram and the pictures. After having worked with bluetooth for over 5 years, this setup will come in handy and I plan to implement it soon. Of the various wireless schemes now available, bluetooth is the most prevalent, so improved testing is useful and welcome.

@gunrunnerjohn posted:

Bob, how tall is that sucker?  Looks like it might have clearance issues!

John -  the detentions of the meter are 4.8"X2.6"X1.4".   I had to cut out the back of the engine so we are able to lay the meter on its side, as it won't fit through tunnels and under some bridges standing up.   Being bluetooth, you don't care if you can't see the meter display, you just read the numbers off your cell phone.

Bob D

@rad400 posted:

John -  the detentions of the meter are 4.8"X2.6"X1.4".   I had to cut out the back of the engine so we are able to lay the meter on its side, as it won't fit through tunnels and under some bridges standing up

I thought it looked too tall in the picture.

Using bluetooth to relay the track signal strength to a smart device is neat. My current setup reads track signal level on the monitoring car (which contains an R2LC), so it it not as convenient. When I run the monitoring car, I use a battery powered loco so as to eliminate any loco induced effects on the readout. If I use bluetooth to relay the readings, I will then have to switch the loco pulling the test car to a WiFi based control system, no major issue.