Home and News

Battery Power
Radio Control
and Sound

Changes Log

Club Information

Events

Guest Book

Items For Sale

Links

Miniature Power
Web Site

Modeling Projects

Modeling Tips

Photo Gallery

Trackwork

Videos

Web Site Index

Web Site Search

Radio Control - Radio Noise Suppression

by Paul Norton

---

INTRODUCTION

Since 1995 our club has successfully run the Aristo-Craft, 27 MHz Train Engineer receiver with battery packs in a trailing power car, tender or B unit. The trailing power car always provided a reliable radio range of thirty to forty feet which was adequate for our busy club railway.

When the 75 MHz receiver was introduced several of our members began installing the receiver and batteries in various diesel locomotives. Unfortunately radio range was not always dependable and sometimes not adequate. The most noticeable problem was poor response to the slow button. As running trains without brakes on a busy club railway was not acceptable, the problem was discussed with members of the Aristo-Craft and My Large Scale Forums.

The problem was identified as Radio Frequency Interference (RFI) generated by the motors. The solution was to install radio noise suppression components.

These included a 0.1uf capacitor across the terminals of each motor.

My Aristo-Craft, Plug and Play, FA-1 already had noise suppression components soldered across the motor terminals, but I found that the 0.1uf capacitor worked better.

If you are installing capacitors in the motor blocks of a USA Trains diesel, I suggest removing the brass rods and slip on connectors and replacing them with wires soldered directly to the motor terminals. Every mechanical connection has the capacity to radiate noise.

The capacitors are available from All Electronics under part number 104D50.

The second component was 22uH, 4 amp chokes in the motor leads to the receiver. A small piece of perf board was cut to hold the chokes and screw terminal blocks for the motor wires.

The chokes and perf board are available from All Electronics under part numbers CR-224 and ECS-4 respectively. The four-position, terminal blocks are manufactured by Phoenix Contact and available from DigiKey Canada, or Digikey USA under the manufacturer’s part number 1725672.

The board was placed in the fuel tank of my NW-2, and the wires from the motor blocks and receiver were attached to it. The results were amazing! My NW-2 went from zero range to a reliable range of one hundred feet when using a 75 MHz transmitter with the telescoping antenna.

ASSEMBLING THE CIRCUIT BOARD

Use a razor saw to cut the small circuit board, 17 columns across and 10 rows deep, out of the larger perf board. Sand the edges smooth.

Drill a 1/2 inch hole in the middle of the board with a spade bit. This opens the traces and eliminates short circuits.

Superglue (CA) the four position terminal strips to the top of the board with the pins in the holes at:

• column 2, rows 4, 5, 6 and 7;



• column 16, rows 4, 5, 6 and 7.

Make sure the adjustable openings for the motor wires face out.

Push the leads of the four chokes through the holes in the board at:

• column 6, rows 1 and 4;



• column 6, rows 7 and 10;



• column 12, rows 1 and 4;



• column 12, rows 7 and 10.

Turn the board over and solder the two outside pins of the terminal strips to the board. The two outside positions of the terminal strip will be used to attach the motor block wires to the circuit board. The center positions are not used but provide the proper spacing for the outside ones.

Solder the eight leads of the chokes to the board and trim them flush.

Cut a piece of red and a piece of black wire long enough to reach from the noise suppression board to the receiver. Trim a small piece of the insulation off one end of each wire.

Place one end of the red wire through the hole in the board at column 9, row 1 and solder it in place.

Place one end of the black wire through the hole in the board at column 9, row 10 and solder it in place.

When mounting the board, these wires should pass through the hole in the center of the board to keep them away from the motor block wires.

I hot glued this noise suppression board to the bottom of the frame, in the fuel tank of my NW-2. The hole in the board was aligned with the hole in the center of the frame. The wires passed through the holes to the receiver mounted on top of the frame under the hood.

The black wire is attached to grey wire of the Aristo-Craft connector or pin 3 of the receiver.

The red wire is attached to orange wire of the Aristo-Craft connector or pin 10 of the receiver.

I filed a slot in the flange on both ends of the fuel tank of my NW-2 to allow the motor wires to pass through without binding. The wires should be kept as short as possible, but allow free movement of the trucks.

The wires from the motor block are attached to the outside positions of the terminal strips. The wires may be a different colour than those shown.

There are several reasons for placing the noise suppression circuit board in the fuel tank:

• It minimizes the length of the motor block wires and amount of noise radiated,



• It keeps the motor wires away from the receiver, minimizing RFI, and



• It allows the motor blocks to be removed by removing the fuel tank instead of the diesel hood.

Note the opposing colour of the motor wires attached to the terminal strips. This allows two motors mounted in opposite directions, to operate in the same direction.

Congratulations! You have made your first RFI Suppression circuit board. You should be able to obtain about 100 feet of radio range if you are using a 75 MHz transmitter with the telescoping antenna.

PROBLEM SOLVING

If you do not obtain the expected range, check the following:

• Are the batteries in your transmitter fairly new? Aristo-Craft recommends using Coppertops or similar batteries. Rechargeable batteries do not have the same voltage and decay when left sitting.



• Are the batteries for your locomotive fully charged to at least 18 volts? According to rumor, the receiver responds better at higher voltages.



• Are you holding the transmitter antenna straight up?



• Is the receiver antenna unwrapped and properly placed as high in the locomotive as possible? The antenna should not cross over itself.

Have you tried a Black Kat antenna? I have used them in all my 75 MHz receiver installations. It is mounted just above the receiver in my NW-2. The manufacturer recommends that the receiver's antenna be trimmed to about 1 inch in length and soldered to the Black Kat.

The Black Kat antenna is available from E Cubed R/C.

UPDATE

After the success of this RFI Suppression board, I later assembled a Super Socket. It not only contains the RFI chokes, but a socket for the 75 MHz receiver, resistors for LED lighting and longer terminal blocks for all the wiring.

The socket is easy to assemble and there are many advantages to using it.

• Wiring the battery, motor blocks, and lights is easy.



• The chokes on the board suppress radio noise generated by the motors and greatly improve radio range.



• Resistors mounted on the board allow the use of efficient LED lighting.



• The socket and a lithium-ion battery can be used to convert most USA Trains and Aristo-Craft, 4-axle diesels to on-board, battery power and radio control. The socket can also be used for track power and radio control, by connecting the track power wires to the board instead of battery wires.

If you are interested in how the Super Socket for the 75 MHz receiver was assembled, just click on the link.