Standard-Horizon GX1850 VHF Marine Band DSC Radio

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
Posts: 11862
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Standard-Horizon GX1850 VHF Marine Band DSC Radio

Postby jimh » Wed Feb 06, 2019 10:32 am

Standard-Horizon has added six VHF Marine Band radios with Digital Selective Calling to their line of fixed mount 25-Watt radios. The retail pricing seems very attractive for these new radios, and I expect they will be in high demand once actually in the retail channel and shipping.

Fig. 1. GX1850 VHF Marine Band DSC radio
GX1850.png (178.38 KiB) Viewed 16696 times

Models with NMEA-2000 and integral GPS receivers are available, and special models with ATIS features for use in Europe are also available. There are six model variations in this series:

  • GX1800 is the base model and omits the NMEA-2000 interface and the GPS receiver
  • GX1800GPS includes an integral GPS receiver but omits NMEA-2000.
  • GX180GPS/E includes an integral GPS receiver, omits NMEA-2000, and is a European-only model with ATIS features.
  • GX1850 includes the NMEA-2000 interface but omits the GPS receiver
  • GX1850GPS includes the NMEA-2000 and the GPS receiver
  • GX1850GPS/E includes the NMEA-2000 interface and the GPS receiver, and is a European-only model with ATIS features.

Note that all VHF Marine Band radios to be sold in Europe are now required to have an integral GPS or GNSS receiver. The /E versions of the radios thus are all models with an integral GPS or GNSS receiver. Models with the 50 suffix have NMEA-2000. Models with GPS suffix have an integral GPS receiver. Standard-Horizon also uses the name "EXPLORER" to refer to this series, and appends NMEA2000 and GPS to further identify the model family.

We look more closely at the GX1850 model or EXPLORER NMEA2000, that is, a USA radio with NMEA-2000 but without integral GPS receiver:

The most significant features of the GX1850 are:
  • NMEA-2000 interface
  • NMEA-0183 interface
  • compact size; only 3.7-inch depth
  • three front panel soft keys for user interface
  • supports optional second station with intercom
  • three-year warranty
  • permits reset of MMSI in the field by the user with appropriate code supplied by manufacturer

The GX1850 and variant model radios were granted approval for sale in the USA on December 2, 2018, and given FCC ID K6630643X3D.

A discount retailer lists the GX1850 at $220.

NMEA 2000
The NMEA 2000 interface supports the follow parameter groups:
    059392 ISO Acknowledgement
    059904 ISO Request
    060928 ISO Address Claim
    065240 ISO Commanded Address
    126464 Receive/Transmit PGN's group function
    128993 Heartbeat
    126996 Product Information
    127237 Heading/Tracking Control
    127250 Vessel Heading
    127258 Magnetic Variation
    128259 Speed
    129025 Position, Rapid Update
    129026 COG and SOG, Rapid Update
    129029 GNSS Position Data
    129033 Local Time Offset
    129540 GNSS Sats in View

    059392 ISO Acknowledgement
    059904 ISO Request
    060928 ISO Address Claim
    126464 Receive/Transmit PGN's group function
    128993 Heartbeat
    126996 Product Information
    129029 GNSS Position Data
    129799 Radio Frequency/Mode/Power
    129808 DSC Call Information
    129540 GNSS Sats in View

The NMEA-0183 interface is supplied with the following signals:
The signals use the standard NMEA color code for wire insulation, but the manual still refers to the signal names using non-standard nomenclature with terms output and input and polarity markings of plus and minus. The lack of proper signal name designation continues to confuse me. I don't understand why manufacturers of NMEA-0183 devices will not follow the standard naming conventions for the signals.

The NMEA-0183 sentences supported are:
    TALKER = DSC, DSE; GSA, GSV, GLL, and RMC can also be sent from the GX1850GPS model

The compact radio is 5.9 x 3.4 x 3.7-inches (W x H x D). If flush-mounted the radio extends only 2.2-inches behind the front panel.

A push-to-talk (PTT) microphone with a captivated coiled cord is attached to the front panel. The microphone element is a noise-cancelling design. In addition to the PTT button, there are four other buttons on the microphone housing. A pair of up-arrow and down-arrow buttons controls channel selection. An H/L button toggles transmitter power level. A red 16/S button switches the radio to channel 16 (the PRIORITY channel) or if held to the SUB channel. The default SUB channel setting is Channel 9, but the radio permits the user to change the configuration of both the PRIORITY and SUB channels, if desired.

Fig. 2 GX1800/GX1850 with white housing; front panel controls shown.
GX1800WhiteFrontPanel.png (54.93 KiB) Viewed 16661 times

The GX1850 radio has extensive operator controls on the front panel. The on-off power is controlled by a dedicated red ON-OFF button, not part of any other control function. Volume and Squelch are provided on separate rotary knobs rather than concentric knobs. The volume knob is at the upper right corner of the enclosure, where it is easily reached. The squelch knob is at the lower right corner, and is unlikely to be confused with volume.

To give the operator further awareness of a channel in use condition, an annunciator lamp in the upper left illuminates when the receiver squelch has opened. Curiously the lamp indicator is green, which usually indicates a safe condition. This seems inappropriate.

Channel selection is accomplished with two pushbuttons, arranged vertically with up-arrow and down-arrow indicators.

A large 2.6 x 1.4-inch 222 x 122-pixel dot-matrix display has five pushbuttons associated with it arranged in a row below the display; the outer pair are for scrolling horizontally on the display or changing the soft key functions. The inner three are for selecting one of the soft key choices shown on the display. A further enhancement permits the user to custom program three soft key functions to his own liking.

A second row of buttons below the display provides a H/L button for toggling transmit power; a MENU/SET button for accessing the menus or when held to move to the setup menu; a CLEAR button to cancel selections; and a red 16/S button for switching the radio to Channel 16 or when held to the SUB channel.

As required for all DSC radios, a red DISTRESS ALERT button is provided under a hinged access cover.

The rear panel contains five connectors and one integrated cable assembly. A terminal post allows connection to GROUND. An SO-239 receptacle allows connection of the ANTENNA with a mating PL-259 plug. A DeviceNET Micro C male connector allows a NMEA-2000 drop cable to connect. An SMA connector permits the external SCU-38 GPS ANTENNA to be connected. A specialized multi-pin connector permits an extension cable for a RAM-4 remote microphone to be connected.

The cable assembly contains the 12-volt DC power cables, the NMEA-0183 TALKER and LISTENER pairs, and an audio amplifier output for connection to an external speaker.

The owner's manual mentions that the MMSI of the DSC radio can be reset by the user after contacting the factory to obtain a reset code. Standard-Horizon has already used this method on the HX870 hand held radio. This is a significant improvement over the usual situation where the radio was required to be shipped to the factory or an authorized service center for any change of the maritime mobile service identity.

The GX1850 radio provides the user with extensive configuration and option choices. Much of the 125-page user manual is dedicated to explaining the many configurable options available in the radio. The user manual is available from the manufacturer's website.

Posts: 11862
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: Standard-Horizon GX1850 VHF Marine Band DSC Radio

Postby jimh » Wed Feb 06, 2019 3:56 pm

Some other notable features of the GX1800 series radios:

  • USA models comply with ITU-R M.493-13 Class D DSC
  • European models comply with ITU-R M.491-14 Class D DSC
  • rated to IPX8 submerged 5-feet for 30-minutes
  • described as NMEA-2000 "compatible" so perhaps not NMEA certified
  • has internal navigation computer, stores waypoints, stores Man Over Board position
  • display illumination has a night mode lighting setting which inverts black and white
  • available in either black or white body and microphone color
  • three modes of channel scanning possible
  • includes NOAA Weather Radio channels and NOAA Weather Alert monitoring
  • flush mount kit available as optional accessory
  • white dust cover available as optional accessory
  • supports optional SCU-31 external GPS receiver with 49-foot cable
  • models with internal GPS support optional SCU-38 external antenna with 15-foot cable

The optional SCU-31 external GPS "antenna" is not just an antenna but a complete GPS receiver with NMEA-0183 output. Unfortunately this receiver appears to be designed only for reception of the US Air Force NavStar Global Positioning System L1 C/A signal, and apparently it is not useful with other GNSS systems such as GALILEO, GLONASS, or BEIDOU. And, yes, the cable is really 49-feet long. The SCU-31 user guide explains more details. To use the SCU-31 with the GX1800-series radios, the integral connector has to be cut off the cable, and the individual conductors in the cable must be mated to power and to the NMEA-0183 interface on the radio. This GPS receiver works with all six model of the GX1850.

The SCU-31 external Smart GPS receiver sometimes called an "antenna" in Standard-Horizon literature.
This receiver retails for about $100.

The optional SCU-38 external GPS antenna is exactly that, just an antenna. When connected to the rear panel SMA connector, the GX1800 radio's internal GPS receiver will prefer to use the external antenna rather than the internal antenna in the radio. The SCU-38 has a 15-foot cable. This antenna only works with the GX1800GPS, GX1800GPS/E, GX1850GPS, and GX1850GLS/E models, that is, the models with an internal GPS receiver.

Fig. 2. The Standard-Horizon SCU-38 external antenna with 15-foot cord and SMA connector.
This antenna retails for about $50.
SCU-38.png (99.56 KiB) Viewed 16019 times

Posts: 11862
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: Standard-Horizon GX1850 VHF Marine Band DSC Radio

Postby jimh » Fri Jul 05, 2019 7:33 pm

UPDATE: added more information about the two options available for an external GPS antenna (SCU-38) or an external GPS receiver (SCU-31), included photos. In the prior version there was some confusion between these two products.

Posts: 72
Joined: Sat Dec 15, 2018 10:37 pm

Re: Standard-Horizon GX1850 VHF Marine Band DSC Radio

Postby B.E.Coyote » Tue Sep 10, 2019 9:39 pm

If you buy the GX1800GPS model with integral GPS receiver, what would be the benefit of also having an NMEA-2000 connection [as in the GX1850GPS model] ?
2001 Dauntless 160
Virginia Beach

Posts: 11862
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: Standard-Horizon GX1850 VHF Marine Band DSC Radio

Postby jimh » Wed Sep 11, 2019 9:26 am

The benefit of a NMEA-2000 connection to the radio is realized in simpler wiring between the radio and other devices. NMEA-2000 is a network bus. The alternative is NMEA-0183, but that is a point-to-point circuit interconnection.

The notion that the presence of an internal GNSS receiver obviated the need for the radio to be connected to other devices ignores the extremely important connection of the radio data output to associated navigation devices such as chart plotters.

A digital selective calling (DSC) radio will be creating data output from DSC calls it receives. See more about data output from DSC radios at ... sTest.html

Part 4 of the four-part article show how some chart plotters display data from some radios: ... otter.html