Introduction
NCE recently released D13DRJ, a new version of its popular D13 series HO decoders, which is intended for use in battery powered, radio controlled models. "DR" is derived from "direct radio" and "J" means it has an NMRA standard 9-pin JST socket and wire harness. The radio is compatible with S-CAB and battery power can be a BPS battery power supply or a series-connected, multi-cell (typically 11.1 or 14.4 volt) battery pack. One side of the circuit board is the decoder, which has been simplified and reduced in size by removing rectifiers that are required for DCC track input, but unnecessary with battery power. A Linx Technologies radio receiver, mounted on the second side of the board, provides DCC commands directly to the decoder microprocessor; the same method as used by S-CAB. The remaining radio-side components form an electronic on/off battery switch. The blue wire is an antenna. (A 3 inch length of wire makes a simple antenna.)
 Decoder side |  Radio side |
Using D13DRJ with S-CAB
The decoder is "plug and play" when used with S-CAB radio and a battery pack. However, decoder red and black leads are no longer DCC track input. Red is battery positive and black is battery negative. Correct polarity is critical.
Simple modifications are required when used with BPS battery power. The battery switch included in the decoder is convenient when using a battery pack, since it eliminates the need to mount a separate switch somewhere in the loco. Battery power is turned on with a magnetic wand and turned off with a command to the decoder. However, this duplicates functionality already included in the BPS and would not prevent BPS battery discharge, since the BPS battery connects internally to a step-up converter, which produces the 12 volt output.
There a two ways to eliminate the confusion of duplicate switches. Either disable the electronic switch by putting it in a permanently 'on-state' when there is battery power, or remove the switch and replace it with a wire connection.
I'll illustrate removal for this blog. It's simple, but not reversible. All components except the radio are removed and the chip that forms the electronic switch is replaced with a wire.
The always-on modification suggested by NCE is slightly more complicated, but is a reversible procedure.
Availability
S-CAB users can order the D13DRJ decoder now at the same price as an S-CAB-compatible D13SR or D13SRJ. I'll add it to the price list page once I decide whether or not it replaces D13SRJs. It's a neater, smaller, easier to install solution for users who prefer non-sound decoders or are working with restricted space in small locos.
For S-CAB use, I've added a ceramic antenna with a healthy dab of epoxy to reinforce the very weak solder connection. Horizontal or vertical mounting is available and both orientations provide excellent radio reception.
NCE decoders sold by me for S-CAB use now include a firmware version that supports use of function F5 for turning off battery power and eliminates the requirement to use a separate switch or sensor for this purpose. This is part of an effort to "standardize" F5 as a battery-off command. However a switch can still be used if that is the user's preference.
Acknowledgement
I thank NCE for cooperation during this development and willingness to bring what may remain a niche product to market. As always, NCE's proprietary rights are acknowledged.