Dead-Rail Transmitter/Receiver Options and Installation

Numerous wireless RF transmitter/receiver (Tx/Rx) options for locomotive control are available in the US and abroad. My discussion is confined to wireless RF transmitter/receiver options that are DCC compatible, which means that the transmitter sends “logic-level” DCC packets. The receiver converts the “logic-level” DCC packets back to “bipolar” DCC packets, as would be transmitted on tracks, that an onboard DCC decoder can “understand.”

Schematic of representative application

Why am I limiting my discussion? Because DCC is a standard, and if you don’t go with solutions that have standards behind them, then you are likely to suffer “vendor lock,” where a single vendor holds you “hostage” with “their” solution. Perhaps that attitude is a bit overblown, but vendors with proprietary solutions tend to lag in innovation for lack of competition, and what happens if the vendor goes out of business?

I know that the NMRA DCC standards have some problems, including the following issues: pending issues under consideration for years; vendors ignoring some parts of the standards; some vagueness in places; and lack of standards for wireless. The DCC standard is imperfect but far better than no standard. Plus, the DCC decoder market is competitive and feature-rich – you can almost assuredly find a DCC decoder that will satisfy your needs.

As a further limitation of this post, I will mostly confine my discussion on DCC-compatible wireless Tx/Rx options to the 902-928 MHz ISM (Industrial, Scientific, and Medical) band because this is where I have direct experience. There is significant and exciting activity in the DCC-compatible 2.4 GHz ISM band (using Bluetooth technology) as well (see BlueRailDCC), but I have no personal experience with this band. Another advantage of the 902-928 MHz ISM band is some interoperability between transmitters and receivers, although there is currently no firm standard behind this interoperability.

DCC-compatible Tx/Rx options are a vast topic that I cannot fully cover in this blog. These options are well-covered in the following links:

  • Dead Rail Society: This should always be your first stop when looking at topics related to dead-rail. This site is the epicenter of dead-rail. In particular, this page discusses vendors for dead-rail Tx/Rx.
  • Facebook Dead Rail page: This social media page is a valuable source for the latest announcements and discussions for dead-rail, including Tx/Rx options.

Receivers

Below is my personal experience with 902-928 MHz ISM DCC-compatible receivers.

General Comments

How each of these DCC-compatible wireless receivers handles the loss of valid RF signal from the transmitter is discussed here.

CVP Airwire

A CVP Airwire CONVRTR-60X wireless DCC-compatible RF receiver is mounted to the tender hull’s side using Velcro. The U.FL antenna cable was later connected. The DCC “A/B” output of the CONVTR-60X connects to the “Track Right/Left” inputs of a wiring harness for a LokSound L V4.0 DCC decoder (not yet inserted) on the opposite side of the tender hull.

The company CVP manufactures and supports its Airwire series of products, including hand-held wireless DCC-compliant throttles (such as the T5000 and T1300) and receivers, such as the CONVRTR series that seamlessly connect to DCC decoders onboard the locomotive. As a general comment, CVP provides excellent, detailed installation and operation documentation, partly because they are dominant in some segments of wireless model railroad control. The CONVRTR receiver has some sophisticated features, such as setting its Airwire RF channel purely in software, described in its User Guide.

However, the CONVRTR interacts with the Airwire wireless throttles in ways that make it difficult to impossible​ to transmit just “garden variety” DCC wirelessly to the CONVRTR for proper operation. The Airwire throttles transmit numerous DCC “Idle” packets as a “keep-alive” message for the CONVRTR. A red LED on the CONVRTR board indicates received signal quality and flickers least when receiving many DCC Idle packets, and the brightness of the LED indicates the received RF power. Typical DCC throttles are not designed with these “keep-alive” concerns in mind and do not output DCC Idle packets often enough to keep the CONVRTR “happy.”

Other than the CVP Airwire transmitters (the T5000 and T1300), the only currently available (the no longer manufactured NCE GWire Cab was also Airwire-compatible) RF transmitter that I am aware of that is capable of communicating with the Airwire CONVRTR is the ProMiniAir, whose open-source software (at GitHub AirMiniTransmitter) intercepts “garden variety” DCC from the throttle and interleaves a sufficient number of DCC Idle packets to communicate correctly with the CONVRTR. This “keep-alive” requirement for the Airwire CONVRTR is challenging to produce, so sometimes a reset of the DCC throttle ​or the ProMiniAir is required to initially send enough DCC Idle packets to initiate communication with the CONVRTR.

Like the Gwire receiver below, the Airwire CONVRTR “X” versions have a ​U.FL connector for connecting a shielded antenna cable from the receiver to an externally-mounted antenna. An internal antenna option is also available for CONVRTR mountings that are not surrounded by metal.

QSI Solutions Gwire

Gwire U.FL connector. If using the U.FL connector, detach the wire antenna.

The Gwire receiver operates on Airwire RF channels 0-7 ​that the user must select from a dial on the device itself. A nice feature of this receiver is an onboard U.FL connector (see the Figure above) that allows the user to connect a shielded antenna cable from the receiver to an externally-mounted antenna – useful when the antenna needs to be on the exterior of a metal locomotive or tender shell. See Blueridge Engineering’s website for details on how to interface the Gwire to any onboard DCC decoder. The Gwire presents no difficulties for wireless 902-914 MHz ISM band DCC-compatible transmitters, and you can find it on eBay at relatively low ($20 US or less) prices.

Tam Valley Depot DRS1, MkIII

Tam Valley Depot DRS1, MKIII in an open-cavity install. Note the built-in long-wire antenna.

The Tam Valley Depot DRS1, MkIII receiver operates only on Airwire RF channel 16 (actually 916.49 MHz, which is close enough to Airwire channel 16 at 916.37 MHz) and makes a suitable wireless DCC receiver. This receiver has a long, single-wire antenna that provides efficient RF reception (see the Figure above). However, placing this wire outside any metal shell would be best, which may be inconvenient in some mounting applications. The DRS1, MkIII, presents no difficulties for the 902-914 MHz ISM DCC-compatible transmitters as long as they transmit near 916.49 MHz. The DRS1, MkIV described in the next section supersedes this receiver.

Tam Valley Depot DRS1, MkIV

The recently-released Tam Valley Depot DRS1, MkIV receiver. Note the internal antenna on the right side of the board.

The Tam Valley Depot DRS1, MkIV receiver is a significant upgrade from the DRS1, MkIII, and operates at the original Tam Valley 916.49 MHz frequency, Airwire Channels 0-16, and at 869.85 MHz (for European operation). The DRS1, MkIV presents no difficulties for the 902-928 MHz ISM DCC-compatible transmitters. It is an interesting choice because it changes channels automatically until it finds a sufficient RF signal carrying DCC packets. See the Figure above for the version that employs an internal antenna that is useful when the receiver is not mounted inside a metal shell.

The DRS1, MkIV with a U.FL antenna connector (and a heatsink update) is now available (see picture below), making it very useful for connecting external antennas outside metal shells. This version of the DRS1 makes it highly competitive in capability and quality with the Airwire CONVTR. Perhaps a future version will provide DC output to the onboard DCC decoder when no valid RF signals carrying DCC packets are available, making it possible to program the DCC decoder’s behavior when no DCC signal is available.

Tam Valley Depot DRS1, MkIV receiver with U.FL connector.

OScaleDeadRail ProMiniAir Receiver

ProMiniAir receiver/transmitter

The inexpensive ProMiniAir receiver presents no issues when used with 902-928 MHz ISM DCC-compatible transmitters. It operates on Airwire RF channels 0–16. It requires a separate, low-cost amplifier (e.g., the Cytron MD13S) to convert the ProMiniAir’s unipolar 5V DCC to bipolar DCC that provides sufficient power to the decoder.

The ProMiniAir’s open-source software is available for download at the GitHub site AirMiniTransmitter.

Transmitters

So far as I’m aware, there are four 902-928 MHz ISM DCC-compatible transmitters: the CVP Airwire T5000 and T1300, the Tam Valley Depot DRS1 transmitter, and the OScaleDeadRail ProMiniAir transmitter.

CVP Airwire Transmitters

The CVP Airwire T5000 and T1300 transmitters are excellent choices for operating with 902-928 MHz ISM DCC-compatible receivers, which will properly communicate with these two transmitters. When I am testing wireless receivers, the T5000 is my “go-to” because, in addition to serving as a DCC-compatible throttle, it can program onboard DCC decoders, via the wireless receiver, in either “OPS” (or Programing-on-the-Main, PoM) or “Service” mode. While the T1300 cannot program the onboard DCC decoders, it serves as a typical DCC throttle.

Of course, the Airwire transmitters send sufficient DCC “Idle” packets to keep the Airwire CONVRTR receivers “happy.”

Tam Valley Depot DRS1 Transmitter

The Tam Valley Depot DRS1 transmitter uses DCC packets produced by any DCC throttle or command station that outputs “bipolar” DCC to tracks. The DRS1 transmitter converts the “bipolar” DCC to “logic-level” DCC and transmits it at only 916.49 MHz, which is close enough to Airwire Channel 16 at 916.36 MHz to be received. This frequency limitation means that only the Tam Valley Depot DRS1, MkIII, and MKIV, and the OScaleDeadRail ProMiniAir receivers can operate with this transmitter if they are receiving on 916.48 MHz or Airwire Channel 16.

While the Airwire CONVRTR can operate on Airwire Channel 16, the DRS1 transmitter is not designed to transmit sufficient “Idle” DCC packets to keep the CONVRTR “happy” since it passively sends along only the DCC packets it receives from the DCC throttle or command station.

OScaleDeadRail ProMiniAir Transmitter

The ProMiniAir transmitter with optional LCD. The antenna in the picture was replaced with a high-quality 1/2-wave Linx ANT-916-OC-LG-SMA antenna from either Mouser or Digi-Key for improved transmission.

OScaleDeadRail provides the ProMiniAir transmitter/receiver that uses open-source software at the Github AirMiniTransmitter site. Like the DRS1 transmitter, it is designed to take inputs from any DCC throttle or command station’s “bipolar” DCC output to tracks (via a simple, low-cost optocoupler provided by OScaleDeadRail) and transmit the “logic-level” DCC on Airwire channels 0-16.

The ProMiniAir transmitter inserts a sufficient number of DCC “Idle” packets into the original throttle-produced DCC to keep the Airwire CONVRTR “happy.” This keep-alive capability, coupled with the transmission on Airwire channels 0-16, ensures that the ProMiniAir transmitter can communicate with any of the 902-928 MHz ISM DCC-compatible receivers discussed in this blog.

This transmitter’s settings, like channel number and output power, can be controlled by the DCC throttle or command station in the “OPS” mode by setting the throttle address to that of the ProMiniAir, which is 9000 by default. An optional LDC display can be attached to the ProMiniAir transmitter for status display. More configuration information is available at the GitHub AirMiniTransmitter site.

Author: Darrell Lamm

I earned my Doctorate in Physics from the Georgia Institute of Technology in 1982, and before retiring in 2019 I worked for 37 years at the Georgia Tech Research Institute. My last position was Chief Scientist of the Electro-Optical Systems Laboratory. Like many people, my love for model railroading began at an early age, and I rekindled that interest starting in 2017.

4 thoughts on “Dead-Rail Transmitter/Receiver Options and Installation”

  1. Ok good topic. Any hope for us that still run postwar locomotives with armature motors, not newer can style motors?

    1. Hi Matthew,
      Thanks for dropping by. I hope you’ll have a look around. That particular post needs to be updated.

      I have tried to use the original open-frame motor in several Dead Rail conversions, but the DCC decoders did a poor job controlling the motor in all cases. Also, these motors are inefficient power hogs compared to more modern motors with powerful rare-earth magnets. However, there is good news: the locations of the mounting screws in the motor mount brackets matched up precisely with the newer replacement Pittman motors. Depending on your chosen replacement motor, the length between the mounting brackets may need some adjustment. Replacement Pittman motors are frequently offered on eBay for around $50 or so, or you can buy them at the Lionel Parts web pages. If you decide to “make the plunge,” I’ll gladly help you in detail.

    1. Here are some Pittman motor numbers I have used or were resident in O-scale locomotives: 9234K350-R2, 9234F003, 9234A105-R1, 9234S004-R1, 9413C698, 9233C377 (Sunset), 9233C196 (Sunset), 9433L187 (Lionel), 9433L177, 9434F827-R1, 9234E066, 9434J434. Try the Lionel site here.

      Lengths: 9XX2 = 1.828″, 9XX3 = 2.203″, 9XX4 = 2.403″.
      Diameters: 1.580″

      If you provide the length between your mounts, we can make some progress in finding the right one for you.

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