The iMux

The Brookhouse WiFi NMEA 0183 multiplexer for the iPad, iPhone and iPod touch.  

The Apple iPad with iNavx application offers powerful marine navigation capabilities, using Navionics charts, at a fraction of the cost of a chart plotter. Features include AIS target plotting and full marine instrument support. However, the only way NMEA 0183 data from AIS, external GPS and instruments can be input by the iPad is via WiFi (wireless LAN). To unlock the full potential of the iPad for navigation, Brookhouse now offers the iMux, the NMEA 0183 multiplexer with WiFi output. With its large screen, the iPad is the first choice for navigation, but the iPhone and iPod touch are also supported. 
Update August 2013: iMux Mk3 supports simultaneous wifi TCP/IP communication with up to 16 i-devices , computers and/or androids using  infrastructure mode, DHCP and WPA2 security.

Two iMux models are available:

  1. The standard NMEA 0183 iMux

  2. The iMux-ST for Raymarine Seatalk installations.

The standard iMux combines AIS data from any AIS receiver or transponder with GPS and NMEA instrument data and transmits the combined data stream via WiFi to the iPad or a computer. The iMux also has a serial output port for hard-wired connection to a chart plotter and/or a computer. All of the functions of the Brookhouse multiplexer model AIS are included, so application of this model is not limited to WiFi only. 

The iMux-ST converts Seatalk GPS and instrument data to NMEA 0183 and combines this data with AIS and data from other NMEA 0183 sources. The single  data stream is transmitted via WiFi for input by the iPad. In addition, the iMux-ST offers most of the features of multiplexer model AISC, for integration of AIS and other NMEA talkers with Raymarine chart plotters. The Seatalk GPS position is output as NMEA at 4800 baud and can be used as input by DSC VHF or SSB radios. 

The iMux is easy to install, no configuration is necessary unless the advanced features need to be enabled.

The WiFi capability of the iMux is not limited to wireless communication with the iPad. The iMux is also perfect for reliable wireless transmission of NMEA data to a laptop or other on-board navigation computer with wireless Lan adapter. All navigation programs that receive NMEA 0183  via a serial port,  USB or bluetooth can also work with the iMux.

For more about wifi and the capabilities of the iMux, click the following link: Brookhouse WIFI

In contrast to the other Brookhouse multiplexers, these 2 new multiplexers are “all-in” models without optional extras. Although most of the advanced features of the other models are available, including filtering and NMEA conversion, the aim has been to provide easy to install solutions that require minimal preparation and offer maximum features.

iPad models and prerequisites

The iPad 3G has an internal GPS, the WiFi only model does not have a real GPS and uses WiFi for “location services”. Both iPad models are suitable for use with the Brookhouse iMux, because external GPS, AIS and instrument data is received via WiFi. The vessel’s own accurate on-board GPS or DGPS is used for determining the position, not the internal iPad 3G GPS. The iMux-ST also transmits data from a Raymarine Seatalk GPS and Seatalk instruments. This means the iPad can be used for navigation anywhere on the boat without compromising GPS accuracy due to a blocked view of the sky. The internal GPS of the iPad 3G is a good back-up, but it is not a requirement.

Program iNavx for the iPad is a requirement. This excellent low-cost navigation program with AIS and instrument support and many other functions can be be purchased online:

Navionics charts for the iPad are available from X-traverse.

Functionality offered by the standard iMux

  1. Combines NMEA data from 3 standard 4800baud NMEA talkers plus AIS at 38400 baud to a single data stream which is transmitted via WiFi.

  2. The combined data stream is also available at a 38400 baud serial output port to feed a chart plotter and/or computer.

  3. Baudrate conversion allows feeding a DSC VHF or SSB radio with position data from a chart plotter at 4800 baud if the chart plotter has a single NMEA output port that follows the baudrate of the NMEA input.

  4. An auto-pilot can be controlled by the iPad or chart plotter in “track-mode” (GPS mode) via the same port. This function is not available for iPhone and iPod touch.

  5. Waypoints can be created in iNavX on the iPad and transferred via Wifi to a computer or chartplotter (iPad only). 

Functionality offered by the iMux-ST

  1. Translates Seatalk instrument and GPS data to NMEA 0183 and transmits all data in a single WiFi data stream for use by the iPad (or a computer) at 38400 baud.

  2. Transmits AIS output of an AIS receiver or transponder connected to the iMux via NMEA, combined with the instrument/GPS data of (1) above.

  3. Apart from the Seatalk and AIS ports, 2 more NMEA input ports are available for connection of extra NMEA talkers, e.g. a fast heading sensor and DSC/DSE output of a DSC radio or a backup NMEA GPS.

  4. Besides WiFi output, the combined data stream is also available at a 38400 baud output port for connection to the NMEA IN port of a chart plotter, such as a Raymarine C/E series.

  5. Converted Seatalk GPS data is also made available on a 4800 baud NMEA out port and can be used as lat/long input for a VHF radio.

  6. Baudrate conversion of chart plotter NMEA output from 38400 to 4800 is available. Since the multiplexer outputs GPS data, obtained directly from Seatalk, chart plotter NMEA output will only be required in special cases and the plotter’s NMEA output usually does not need to be connected. 

  7. Waypoint transfer from iNavX to the iPad. This function is not available for iPhone or iPod touch.

    All of the above functionality is available with factory settings.

How we see the role of the iPad on boats with Seatalk instruments.

Many production boats are delivered with a standard Raymarine instrument pack (speed/log, depth, wind) and a Raymarine chart plotter with GPS at the helm as an optional extra.
The iPad, paired with a Brookhouse iMux can be a low-cost alternative for a chart plotter. Naturally,  the iPad does not offer the same level of ruggedness as a purpose-built chart plotter. However, much can be done to protect the iPad against the elements and other risks of damage on board a boat. Waterproof covers and mounting brackets are widely available.

While the iPad’s function as the main chart plotter on a sea-going vessel is debatable, its powerful features can also be a tremendous complement to a fixed chart plotter at the helm: 

  • When sailing under difficult circumstances, when the helmsman has to concentrate on steering the boat, another crew member can be given the task of checking AIS targets and other navigational data on an iPad in any convenient position.

  • An iPad, semi-permanently fixed at the chart table makes a great repeater for Seatalk instruments.

  • Because the iPad receives GPS, AIS and instrument data independently from the iMux, it is an excellent backup for the C- or E-series or any other model chart plotter.

  • If the boat has an older generation chart plotter without AIS support, such as the Raymarine Pathfinder series, instead of buying a new chart plotter with AIS, an iPad with Brookhouse iMux will offer the additional functionality.

  • Since the iPad has powerful email and net-browsing capabilities, in many cases it can be used instead of an onboard computer. To improve the 3G range, a small 3G router installed in an elevated position can be considered. 

General specifications
standard iMux

  • · 4 opto-isolated “NMEA Listener” (Input) ports, 3 at 4800 bps, 1 at 38400 bps for AIS.

  • 1  RS232 output port  for connection to a chart plotter or computer

  • 1 RS232 input port 
    (baudrate conversion input).

  • 1 Output RS422 port (differential NMEA talker port) 4800bps
    (baudrate conversion output)

  • Baudrate conversion 38400bps-4800bps.

  • Indicators: red LED for power, green LED for data-transmission.

  • Supply Voltage: DC 9-35 Volts.

  • Reversed polarity protection.

  • Physical size: 110x65x37mm (hxwxd)

  • Weight: 140 grams

  • Mounting: bulkhead mounting with screws.

  • NMEA management and control:

    • NMEA Sentence Filtering

    • NMEA Sentence editing “on the fly” for NMEA protocol conversion.

    • Automatic port switching.

General specifications

Specifications are the same as for the standard model with 2 exceptions:

  • Instead of 3 NMEA 4800 input ports the iMux-ST has 1 Seatalk port and 2 NMEA 4800 baud input ports. If the Seatalk port is disabled, a 3rd NMEA input @ 4800 is available.

  • Seatalk GPS data, if available, is always sent to the 4800 output port as input for a DSC radio.

    *All popular AIS receivers and transponders are supported.

WiFi specs

  • Up to 16 TCP/IP sessions

  • DHCP

  • WPA2 security

  •  2.4 GHz 802.11 b/g transceiver

  •  low power

  •  internal chip antenna

  •  FCC/CE/ ICS certified

The iMux WiFi range has been tested on several types of boats. Installed in a cabinet or behind an instrument panel, a range of 10 meters is not a problem for the internal chip antenna. For most installations this is adequate. This is only an indication, circumstances differ from boat to boat. In some cases it may be necessary to experiment with the location to achieve the best performance.

An optional external antenna connection is available if required. 

More reading about multiplexers:

Please click this link: What to look for:



Pricing, ordering and payment 



Note: Seatalk is a trade-mark of RayMarine.




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