Installing an iMux aboard "Lady Jane"

My Fischer 37 " Lady Jane " Is basically featured with conventional Raymarine network and GPS antenna , the trio wind, depth, speed instruments, and a multi chartplotter / Radar C70 :

reseau Sea Talk

In November 2010, Reading this blog has strongly urged me get a multiplexer. Control its navigation and see instruments displayed with iPhone is really a challenging project. The navigation software iNavX is very attractive for its price and will be an excellent investment in view of continued improvement by its developer.

raccordement SeaTalkPurchased in December, the iMux is arrived with the new year. No problem for installation with SeaTalk. Just create a derivation from Seatalk wire. As indicated in the following diagram, you plug the red wire on the (+), negative on (-) and the yellow wire that send data on Seatalk connector (S) .. This works well of course and iPad tablet is fast becoming an indispensable.

Vue d'ensemble

The complete configuration connected to the IMUX

The VHF radio on board will celebrate its thirtieth anniversary. Tremendous receiver, ST-144 is no longer on top of technology. Acquiring a DSC VHF / AIS has been programmed replacement. The model chosen RO4800 is now a classic, sold under three different brands (Radio Ocean, Geonav and Navicom), it comes from the same Asian supplier that has had some software problems at begining, now been resolved versions 2.02 and upper. Geonav model was chosen for its availability in stock.

The IMUX should make life easier to set up the information that must travel on the WiFi network destined for the iPhone or the iPad.

Step one : analysis of the wiring project

  • VHF AIS transmits information to 38400 bps, the iMux has an input specifically designed for this. So AIS VHF OUT connector on the CH4 AIS.
  • The information from the ASN out of the VHF are received by the iMux CH2.
  • The radio needs information from the GPS to work properly, required information is available on the iMux RS422 NMEA OUT. This output is also connected to the NMEA IN Driver to communicate to him the info iNavX transmits the active Waypoint via WIFI.

Step two : completion of the preparatory document to wiring

Schéma de câblage

Principle of wiring IMUX

Information from Seatalk send to iMux:

  • Black wire (-) ST to IMUX ST SHLD
  • Red wire (+) ST to IMUX Red
  • Yellow Wire (data) ST to IMUX S

Information from DSC VHF

  • Orange (+) to iMux CH2 A
  • Black (-) to iMux CH2 B

AIS information coming from VHF radio

  • Blue (+) to iMux CH4 A
  • Gray (-) to iMux CH4 B

Warning : Given that suppliers taking liberties with NMEA standard, it may be necessary, either to connect the white wire (for this purpose) out of the connector on the iMux A CH4, either by inserting a resistor 1200 2000Ω for on the same white wire (see picture below).

GPS information from IMUX send to VHF radio

  • Green (-) to iMux NMEA OUT B
  • Yellow (+) to iMux NMEA OUT A

Problem to be fixed

In this configuration C70 chartplotter, receives no information about the AIS. Solution : also send information from the VHF NMEA input C70. The signal can feed four receivers following NMEA standards.

  • C70 IN White (+) to AIS VHF-OUT (+) Blue
  • C70 IN Green (-) AIS VHF-OUT (-) gray

With this wiring system, C70 can be switched off, all information from instruments and GPS are working on Seatalk network. iPad can also transmit route to pilot. For the same service the power consumption is greatly reduced and the readability much better. The C70 is still available including the use of radar in more difficult circumstances.

That's the theory, move on to practical work !


Few hours DIY to wire correctly ...

AIS cablage

AIS Optional Wiring

After completion of the wiring by following the wiring document step by step, the first test confirms the proper operation of the transfer of GPS data on the VHF, however iPad does not receive AIS information.

According to the iMux documentation providing by Brookhouse, the white wire (optional) is stripped and connected to the connector A CH4 In. No problem, Ships within 25 miles shown on the iPad (VHF antenna is placed mizzen). Note that it can insert a resistor 1200 to 2000 Ω between the white wire and the connector A from the entrance of CH4 from the IMUX.

Being careful, this installation can now be done without too much trouble.

The end result :

Les données affichées sur l'iPad

And here are some iPad screenshots :


A ferry 30 knots in the Channel !


AIS targets with iNavX on my iPad


Installation, texts, photos and screenshots of the author.

Note Francis :

The IMUX experienced disruptions in deliveries for several months. The unexpected volume of world orders added to the component supply problems have penalized the production of this company. Deliveries are scheduled to resume in early July, focusing first orders pending. It will probably wait a few weeks before they get back this great product.

Related article :
iMux, a multiplexer WiFi for iPad


7 Replies to "Installation of an iMux aboard" Lady Jane "”

  1. Faced with the unavailability of chronic IMUX, I opted for the WLN10 Digital Yacht (the same as the IAIS without the issuer AIS, NMEA-only adapter WIFI) ordered from iPadNav (also very good contact).
    I plug in the famous RT650. At first it seems simple : the blue and gray of the AIS output to corresponding inputs of WLN10 and it rolls.
    Except that I see no NMEA sentence with transit iNavX.
    The GPS input is wired to the radio and it works perfectly in AIS on its internal screen.
    I made various attempts and various wiring / interface : 422 by the blue and gray (in 38400 or 4800 baud and reconfiguring the WLN10 to accept this change in frequency), RS232 via the orange wire and the braid, by the blue and the braid, braid to ground or not ….
    Short, I give my tongue to the cat.
    The IMUX, the famous "white wire" seems to allow correct operation of the RT650 on iMux. But nothing like (not that kind of thread) sur le WLN10. So ?
    If someone has an idea I'm interested.

  2. The installation of external gps, raymarine gps is necessary or is compatible with any GPS NMEA protocol example: Garmin, Magellan,etc.

    1. Any GPS with a NMEA data output can be connected to a multiplexer. In this case (Central Raymarine) could connect an external GPS connector CH1.

  3. Hello,
    a big thank you for the explanation of text and images on the bonding between our navigation instruments and the tablet will be very present on the boats now.
    Being in the preparatory phase of equipment for a new boat, used cruising / racing, I ask myself the question of the return information Distance To Waypoint, WVMG, XTE, iNavX available with the Iphone that will stay dry on the chart table, for recovery of the cockpit displays.
    The information comes from the instruments to the IMUX, and redistributed to the Iphone, the reverse is achievable ?
    In your Montange around a SeaTalk, the port (yellow wire)and therefore must be biderctionnel IMUX integrate as part of the network.
    For use with other type of network, it seems that the IMUX must be wired only NMEA, In this case the information sought they can be displayed ?
    Thank you for your advice and technical information provided in your blog,

    1. In the TCP / IP settings of iNavX, if you activate "Repeat to AP", The’iNavX Help you said :

      When a waypoint is active, NMEA sentences $ GPAPB, $GPBOD, $GPBWC, $GPRMB, $GPRMC, $GPWPL, $GPXTE, $GPVTG are sent to the server TCP / IP (iPad only).

      It will suffice to connect, in addition to the pilot, a multi repeaters to output NMEA RS422 Differential of the IMUX order to display all the desired data.
      With Standard IMUX, we use the RS232 port (Rx/TX/Gnd), to perform the same functions as the port SeaTalk, to connect a navigation. For example, the Central de Silva NX2 (or equivalent Furuno FI30) has a RS232 port that works with multiplexers. However, it is difficult to say for all brands not yet tested, NMEA protocol are not always properly implemented by manufacturers. See my related subject.

  4. The Raymarine chartplotter NMEA input can also be connected to the iMux RS232 output (38400 bps) .. This has the advantage that both AIS and DSC are available in the chart plotter. Many people also install a fast heading sensor (i.e.fluxgate), or take the 10Hz NMEA output of the auto pilot, and connect to a free iMux input port, to provide highly accurate heading data. This way the chartplotter performs better for Marpa and radar-overlay. iNavX can also handle the 10Hz heading without problems. Connected in this way, of course, the charplotter now also receives instrument data via NMEA, but this is not a problem as Seatalk is given priority if the same data is abvailable on the Seatalk bus.

    1. Thanks to Brookhouse for these important technical details. And also for informing us that orders would be served in France in the next few weeks.

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