The base model in the series is the UM725 radio, but it has many excellent features:
- speaker-microphone handset
- large LCD screen
- 16 front panel controls
- separate volume and squelch controls
- compliant with latest ITU recommendations ITU-R 493-14, -15, IEC 62238
- supports remote microphone handset
- provides NMEA-0183 interface with standard wire insulation colors for interconnection to other devices
- support for external speaker
The UM725G radio includes all the features of the base radio and adds an internal GNSS receiver to GPS and for augmentation systems WAAS, SBAS, and QZSS. And perhaps most significantly a NMEA-2000 network port is provided. Typically interconnection of the radio to a chart plotter or additional GNSS receiver is greatly simplified by using NMEA-2000 for boaters who plan to self-install the radio.
The UM725GBT radio includes all UM725G features, and adds the VHF Digital Short Message Service (VDSMS) protocol. VDSMS permits the radio to transmit short text messages to other radios with VDSMS capabilities. To improve the user interface to composition and sending of text messages, the UM725GBT adds a Bluetooth interface. By using a smartphone and special application, the text message can be composed on the smartphone using a familiar touchscreen keyboard interface.
The VDSMS protocol is a recent addition to the VHF Marine Band authorization in the USA. This service was authorized in 2016. An earlier article in this forum gives more background on VDSMS. The FCC has already modified the VHF Marine Band frequency allocations (channels) to permit VDSMS operation on several channels. A prior reference article gives details of the [url=VHF Marine Band Channels]recently-changed VHF Marine Band frequencies, channel numbering, and authorized uses[/url].
While the VDSMS protocol and frequencies were authorized several years ago, implementation of these features in VHF Marine Band radios so far is a UNIDEN exclusive. In addition to the new UM725GBT radio, UNIDEN previously released a hand-held VHF Marine Band radio that supported VDSMS, their model MHS335BT.
DIGITAL SELECTIVE CALLING
The UM725 radios comply with the newest ITU recommendations for a Class-D DSC radio, which exceeds the requirement for sale in the USA. This gives the radio the best possible feature set for a Class-D DSC radio, including position polling or position polling reply. More details on DSC Class-D and position polling are given in a separate article.
The UM725 radio implements the NMEA-0183 protocol and uses the standard wire insulation colors. Unfortunately the technical documentation does not use the correct signal names. The NMEA-0183 interface is provided on a multi-pole connector. A mating connector and short cable with wires at the other engine provide the physical interface.
- TALKER A = WHITE
TALKER B = BROWN
LISTENER B = GREEN
LISTENER A = YELLOW
There are 16 front panel controls:
- Power ICON
- Send DISTRESS Alert
- Hi-Lo transmitter power
- Jump to CH 16 or PRIORITY Channel
- Menu cursor up-down or Squech
- Push to enter (part of Menu up-down)
- Menu cursor left
- Menu cursor right
- Soft Key left
- Soft key center
- Soft Key right
- Channel change UP
- Channel change DOWN
- North Up
- Course Up
- Normal Monitoring
- Favorite Position (GPS)
While all radio transmitters provide a microphone, the UN725 provides a combination speaker and microphone. Having a small speaker in the microphone that can be held close to the operator's ear can be very useful on a small open boat where the radio is being operated in an open cockpit with noise from the engines and hull. The speaker-microphone has these controls:
- Push to Transmit button
- Channel Change UP
- Channel Change DOWN
- Jump to Ch 16 or Priority channel
The operator's manual provides a detailed list of the NMEA-2000 parameter groups that the radio can transmit or receive via NMEA-2000.
The large LCD display can provide the status of many radio settings and functions. When not in a special menu selection or other special function mode, the display presents 21-different areas for text or icons to appear to the user. This is an overwhelming amount of data to take in at a glance.
TEXT MESSAGE COMPOSITION
The content of a text message can be composed using an iPhone or Android smartphone application. The smartphone is linked to the UM725GBT radio using Bluetooth communication. Use of a smartphone for composing the text message relieves the sender of having to compose the message on the radio itself and with the radio's user interface controls, which would be more awkward than componsing on a typical smartphone touch screen.
The UNIDEN UM 725-series radios are good examples of the complexity that has been incorporated into modern VHF Marine Band DSC radios. With so many controls, a large screen showing complex displays of text and icons, with comprehensive DSC settings and functions, and with the added VDSMS function, to become familiar with all aspects of this radio will require extensive study and use of the radio.