Re: TMCC signal doubler

["Ira Schneider" <ira_schneider@iname.com>]

I agree with Scott that we have problems using TMCC on our layout.

I don't know how to fix the problem, or even what is causing the problem.  My best guesses are:

- The K-Line shadow rail we are using on many modules have isolated outside rails.  The
   TMCC signal, which is carried by the outside rails, might not carry across the track pins
   from track to track.  We should inspect all modules using insulated tracks to ensure that
   both rails are connected to the common wire on all four tracks.  For example, the newer
   corner modules only have one rail connected to ground on each track.

- The Lionel Command Base could be transmitting a weak signal.  Our equipment is old
   and may be wearing out.  For example, the Lionel PowerMaster for track 4 no longer
   resets the track voltage to zero.  Also, the transformers appear to be putting out less
   than 18 volts.  It is possible that the Command Base is also wearing out.

- The wires we used on the module harnesses are varying gauges.  I don't know whether
   or not an undersized wire would affect the TMCC signal.  It certainly would affect the
   power that could be sent through the wire.

- The main power plug (the connectors used to connect the power box to the layout) might
   be defective.  We know that the casing around the ground pin melted due to being
   overloaded.  We added a second ground wire to the cable to double the power
   capacity.  However, the damage may have already been done to the plugs.  We might
   consider replacing the plug on the cable from the power box and the connector on the
   main power corner module.

The Train America Studios Signal Doubler might help.  We can't use it as designed, since we
don't have access to the ground wires going to each rail in the power box.  However, the Signal Doubler
transmits the TMCC signal along both the ground and hot wires.  We could probably connect
the output from the Signal Doubler to the hot wire going to a track and the common ground bus
(ignoring the second ground output wire).
This might increase the signal strength going to the track.  We would need four of them, one for
each track.  We could buy one of these units and connect it to one track to see if it helps.
I do have a concern that it is sending the TMCC signal down the center rail, which is where the
MTH DCS system sends its signal.  I don't know if this would cause any problems, but we
could certainly experiment with one and see.

I don't believe the MTH DCS system interferes with the TMCC signals.  The MTH Track Interface
Unit is only connected to tracks 2 and 3.  The TIU transmits its signals on the center rail, not the
outside rails.  The TMCC system transmits its signals on the outside rails.  I don't see how they
could interfere with each other, especially since MTH specifically states that you can control
your TMCC engines via the DCS system through the Lionel Command Base.

I also don't believe that a bad PowerMaster (or Track Power Controller) could affect the TMCC
signals.  The Command Base is connected directly to the ground bus, after the PowerMaster.
The only way the PowerMaster could affect the TMCC signal is if it was to impress its own
erroneous signal on the ground bus, which is unlikely.

It appears to me that the TMCC problem is engine-specific.  Some TMCC engines work with no
problems on our layout, while others experience signal problems.  We have the same situation with
ProtoSound 2 engines.  I recently performed a signal test on my Chessie ProtoSound 2 engines
which were double-headed.  They were running together around the layout.  The signals reported
back to the TIU were significantly different between the two engines.  One reported signal strengths
varying from 8 to 10, while the other engine reported signal strengths of 3 to 5.

There isn't really anything we can do about engines which are more sensitive to signal quality
other than try to improve the overall signals.

There is one other alternative, which has been previously suggested.  We could disable
TMCC operation entirely on the layout.  If we disconnect the Command Base, all TMCC engines
would power up and run in conventional mode.  Unfortunately, there is no way to temporarily disable
the TMCC signal on a track by track basis to allow a balky engine to run in conventional mode.




Ira