Posted on May 9, 2015 by John Hays in News, UDRC
Universal Digital Radio ControllerHere at NW Digital Radio we are always looking at ways to enhance digital communications for the radio amateur. As we have been marching forward with the development of the
UDRX440 there have been a few products that have come to market both from us and from other manufacturers.
When designing the UDRX440 we wanted to enable DSTAR voice communications and designed a daughter card to provide the AMBE vocoder. We choose the
DVSI AMBE3000™ chip which has the potential of providing superior voice reproduction on DSTAR, but also supports AMBE+2 which is used by other radio standards such as DMR, NXDN, Yaesu Fusion, APCO P25 Phase 2, … We created the DV3000, which is available as a standalone product along with the open source AMBEServer to make AMBE vocoding available over a network. This Raspberry Pi shield rapidly gained a following and hundreds are now deployed around the world. Later, we created a USB connected version of this device called the ThumbDV™, which has opened up AMBE vocoding to hundreds of additional users.
When Yaesu offered their new DR1X Fusion repeater to clubs for $500, the Northwest Digital Radio Club (not part of NW Digital Radio company) purchased one and put it on the air in Edmonds, WA as NW7DR. The half rate digital voice is very good and the full rate voice is excellent. It wasn’t long before John (K7VE) looked at the external accessory adapter and wondered if the repeater could also do DSTAR. After considerable research and experimentation using a Raspberry Pi B+/2 for control and a DVRPTR V1 GMSK modem it was discovered that the DR1X made an excellent DSTAR repeater. By comparison, John’s Kenwood based repeaters often run significant BER (bit error rate) on receive, at one location the Kenwood runs around 7+% BER, while the DR1X is at 0%. (The repeaters are co-located and both use the DVRPTR V1.)
At first, the experiments ran into a known lockup condition when using an external controller in combination with Yaesu Fusion Digital mode. To overcome this issue it is necessary to modify a single line between the receiver and transmitter inside the repeater. However, if one wants to run DSTAR and Analog (without Fusion Digital) on the DR1X, this modification is not necessary. Later, the modification was made and the DR1X is able to provide DSTAR, Analog, and Fusion Digital all on the same channel on a per transmission switched mode. Mode control is accomplished using GPIO pins on the Raspberry Pi.
NW Digital Radio looked at the Raspberry Pi control system and soon decided that a combination control board with integrated CODEC could be built as a shield and thus is born the Universal Digital Radio Controller or UDRC. The prototype board is slated for viewing at the Dayton Hamvention (Booth EH0515). The shield will sit on the 40 pin GPIO interface on the Raspberry Pi B+/2 and will have a HD15 connector with a cable to mate with the HD15 connector on the DR1X. To operate all modes, an alternate cable will be developed to replace the current RX/TX control cable inside the repeater and will use standard 3.5mm (1/8″) stereo plugs to mate to the UDRC.
With the addition of the UDRC, the DR1X will operate in 3 additional configurations:
• Mode 1: DSTAR/Analog (no internal cable modification)
• Mode 2: DSTAR/Fusion Digital (with internal cable modification)
• Mode 3: DSTAR/Analog/Fusion Digital (with internal cable modification)
The UDRC does not transcode between DSTAR and Fusion, it allows the DR1X to repeat DSTAR transmissions and use the ircDDBGateway to communicate with stations, linked reflectors and repeaters, STARnet Digital Groups, etc. Analog, Digital Fusion, and DSTAR are switched at the repeater on a per transmission basis.
The UDRC is designed as a simple to install addition to the DR1X, however, NW Digital Radio has kept the experimenter in mind by providing various headers to allow straightforward hardware modification for integration with other hardware and applications. The builtin CODEC also will be available for software developers to adapt other modes, e.g. Packet Radio, VOIP (Asterisk/IRLP/Echolink), Codec2.
Share your application ideas on the Universal Digital Radio group. Estimated price for the UDRC is $99.95.