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This device is used to better couple the TMCC and Legacy base output to the railroad. It improves coupling to the track, cleans up the track signal, and filters out other frequencies that are picked up by the track because it acts like a giant antenna. It also boosts the signal. Including me ( as the designer ) there have been two other railroad clubs that have built this device. All of us were experiencing signal loss and blinking lights and engines flipping out of command control because of loss of signal. We had all tried all of the other TMCC fixes such as ground planes and the like. Nothing worked to the point where TMCC was not working at all and our railroads were unusable. This device solved all our problems. It is not for the faint of heart. I am an electrical engineer and grew up with vacuum tubes and ham radio. This is a 3 watt linear amplifier using 2 vacuum tubes and a custom wound coil for the output tank circuit. Some have suggested converting it to solid state but I am not a solid state amplifier designer. Another person will have to tread that road. In the mean time this works and has saved my railroad and 2 others that I know about. Note the aluminum plate between the 6AQ5 tube and the coil. I was using an existing chassis from another project and I felt the tube was to close to the coil for a remote possibility of heat and capacitance coupling. No basis for that other than a feel. Mounting the 6AQ5 and the coil further apart would have made me not even think of a shield. I buy most of my tubes and transformers and capacitors from www.tubesandmore.com.  I buy a lot of other stuff like resistors and fuse holder from Mouser. Parts should not be a problem. I actually had all of this stuff in my parts bins but I am 64 and have been in the electronics game since I was 5 years old. The tank coil is wound on a piece of 1 inch PVC pipe using 28 gauge enameled magnet wire. The primary with the most turns is wound first in a single layer. Drill a small hole to stuff the starting end through and start winding in close spaced single layer until done. Then you wrap the whole thing with electrical tape, about 2 layers of Skotch 33, and then wind the secondary over the tape starting at the same end and winding in the same direction. You will have a much shorter winding for the secondary. The primary and secondary ends that start even with each other will be the plate wire and the track wire respectively. The other primary end is the B+ and the other secondary end is ground. You must use a grounded power cord and ground the metal chassis and this secondary wire also. You can add more turns to the secondary to increase the output. I believe one club did that.  

Attachments

Images (4)
  • IMG_3728: View under Chassis
  • IMG_3729: Front view
  • IMG_3730: Back view
  • IMG_3731: Top view
Files (1)
Schematic Diagram with parts values
Last edited by Jim LeFevre
Original Post

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The original TMCC base puts out a 7 volt PP signal but excessive track loading and poor coupling and the inability to filter all frequencies except 455 kHz make it problematic in demanding layouts. My device also puts out 7 volts PP but does it cleanly.  If Lionel can put 7 v PP into a large metal structure and not have FCC problems then my device is nothing different. I have never detected any trouble with AM radios in the train room with TMCC with or without my device. 

Is this the one that the NJ-HR's were trying and/or using?

 

From personal experience, I can tell you that normally the FCC only comes after you if there's a complaint.  With that said, Rich is right, I'm sure that 3 watts of RF in that band is well beyond the legal limit.  That's not to say it'll cause any issues, but it's not technically legal.

 

Note that in the heyday of assembling your own computers, most of them would not be technically legal either.  The FCC only certifies the complete assembly, not something assembled from component parts.

 

 

Interesting.  But once published, whether issues are being have or not, do you think the FCC will cause any problems?
 
Originally Posted by Jim D:

We did it at the NJHirailers and it works great. The member who built it, is writing an artical for OGR and will post something here as soon as the I's are dotted and the T's are crossed.

Jim D.

 

Originally Posted by Jim D:

...The member who built it, is writing an artical for OGR and will post something here as soon as the I's are dotted and the T's are crossed.

Jim D.

I don't mean to rain on anyone's parade here, but we cannot publish an article about building this amplifier because it is illegal to use this! FCC rules clearly state that unlicensed transmitters (which this is) cannot exceed 100 milliwatts (1/10 of a watt) input power to the final amplifier stage. At 3 watts, this one far exceeds that power level.

 

I'm sure this amp has been a big help for the NJ Hi-Railers and other layouts in huge rooms where RF signal prorogation may be a problem.  However we will not publish an article advocating illegal behavior.

Here's the parts list tracking sheet I put together as we collected the components.  Please take this for what it is.....a sheet I used to keep track of what I ordered, not necessarily a comprehensive lists of parts.  The PDF diagram attached to Jim's first post lists the part number for each component.  

 

 

This is the Yahoo Groups thread that Jim posted several years ago that got us interested in the amp.  It's a interesting read on its history

 

starting to design linear RF amplifier for TMCC

 

 

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Last edited by Chris Lord
Originally Posted by Jim LeFevre:

The original TMCC base puts out a 7 volt PP signal but excessive track loading and poor coupling and the inability to filter all frequencies except 455 kHz make it problematic in demanding layouts. My device also puts out 7 volts PP but does it cleanly.  If Lionel can put 7 v PP into a large metal structure and not have FCC problems then my device is nothing different. I have never detected any trouble with AM radios in the train room with TMCC with or without my device. 

Legal or not, I dont see a problem with this setup.

Very few people use AM receivers anymore and those that do wouldn't notice.

I know of nothing else operating in that freq and unless someone else was actively sniffing around any activity would go unnoticed.

 

Ham operators (and the FCC) know that there a pirates operating across the entire spectrum but rarely are any ever caught.

Originally Posted by Flash:
Legal or not, I dont see a problem with this setup.

The fact that is ILLEGAL TO OPERATE THIS AMPLIFIER is not a problem for you?  Wow.

 

There is so much outright WRONG information on line about this it is amazing. For example, here is a quote from the Yahoo groups post linked to above:

 

"...Another thought comes to mind on a source of interference. I am less than a 1/2 mile from a large cell tower. And guess what the X2 frequency of 455 is, 910. And guess what a common cell frequency is, 900. Just a thought..."

 

The "455" frequency used within the TMCC system is 455 KILO hertz. In other words, .455 MEGA hertz. The "910" mentioned above is 910 MEGA hertz. It's a long way from .455 Mhz to 900+ Mhz and if the poster does not understand this, there are many other fundamental principles of electronics he does not know about.

 

This project is rife with problems, many of them serious and all of them illegal. I'm going to close this thread now.

Last edited by Rich Melvin
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