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Choosing the Right Mobile Decoder

For a simple installation, many decoders will work.

©2010 Ryan C Kunkle, licensed to About.com, Inc.

For locomotives, you'll want to choose from the extensive array of mobile decoders on the market. With so many out there, the selection can be as daunting as the installation.

So what should you look for when narrowing your search? Here is a basic checklist to help you on your way.

  1. Size: The decoder won't work if it won't fit! Many manufacturers market decoders for a specific gauge but there is no guarantee that an "HO" decoder will fit in any "HO" locomotive. At the same time, it is possible that you may be able to use a smaller "N" scale decoder in an HO model if the current draw is small enough.
    Manufacturers will also list dimensions for their decoders. This is much more telling of whether or not the decoder will actually fit. Unfortunately, measuring the available space inside your model may be difficult. A good estimate may be the best you'll be able to do.
    With manufacturers packing every available space with weight and older models not designed with decoders in mind, some jobs can be more challenging than others. Creative thinking can put decoders in cabs, fuel tanks, tenders or more. In the end, you may have to mill the frame to make room. With sound decoders and speakers, the project can be even more challenging.
    Especially with newer models, there may be a decoder specifically designed for your locomotive. This is almost always the best choice at any cost!
  2. Power: In addition to the physical size of the decoder, its power rating is also important. In addition to the motor itself, your decoder will be controlling the load of lights and possibly sounds. It is important to have a decoder that is rated for the amperage draw of the model. Again, the scale designations of the decoder can be a good clue. Older and open-frame motors will have a higher current draw than today's can motors, and some models may have more than one motor. All of these will have an impact on which decoder you may choose.
  3. Plug or Hardwire: With DCC becoming a standard today, most new locomotives come pre-wired with a plug for easily decoder installation. This can save a lot of time. Of course with our without the plug, you can also hardwire the decoder directly to the trucks, motor, lights, etc.
  4. 2 or 4 Digit Addressing: Earlier and some starter systems only support 2 digit addresses for decoders. That is, only addresses 01-99 can be used. Later systems allowed 4 digits, 0001-9999, for more options and easier programming. Most decoders on the market today can support either, with an option to use 2 or 4 digit addresses available in programming. Decoders are preset to address 03.
  5. Silent Running: Today "silent running" decoders, which help eliminate motor noise or "hum" are pretty much a standard. But it is something to look for if you are shopping for used or older decoders.
  6. Lights: Even basic decoders will give you options to install a headlight and back up light. For additional functions like a Mars light, ditch lights, cab lights, etc. you'll want to choose a decoder with more functions. You'll pay a little more, but the results can be well worth it on a finished model.
  7. Sound: Adding sound to models adds a whole new dimension to your layout. Today, sound can be added to a typical model for around $60 to $150 dollars depending on the quality and size of the decoder. Some come preprogrammed for specific models, some offer generic sounds, others can be programmed with files downloaded from the internet. The quality and specificity of sounds you want will determine the cost of the decoder.
  8. Transponding: Transponding is a feature that allows the decoder to talk back to the command station. This is useful if you intend to hook up a computer to control the layout to track specific trains or create other scenarios like refueling or maintenance schedules for the locomotives.
  9. Price: All other things being equal, price is often the final factor in determining the decoder you buy. It may be finding the cheapest option for the features you want, or it may mean limiting the features for the price you are willing to pay. A basic decoder may cost around $12-15. A delux sound installation may be over $150.
    You can always upgrade to a newer or more advanced decoder later, often without any significant changes to the rest of the wiring.
  10. Manufacturer: With most manufacturers following standards adopted by the NMRA, you can use decoders from different makers on the same layout and with different systems. Some modelers do prefer to standardize on one brand. Shopping around can often yield better prices and can help you learn about features you may have missed on your "standard" brand.
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