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Setting up a simple, fault free NMEA 2000 network

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The Actisense QNB-1 is designed to make NMEA 2000 networking easier, simpler and safer. With how simple the product is, it’s super easy to achieve a fault free network.

Sometimes known as an NMEA junction box, in simply terms the device is a multi-drop NMEA 2000 network backbone connection block, which utilises a barrier strip connection block in the center that adheres to the NMEA 2000 specifications. Power can easily be added to the QNB-1, allowing it to be the power insertion point for your NMEA 2000 network, thanks to the BATT connection on the product.

Two fuses are present, one for each ‘side’ (left and right) of your network. This means that if one of the fuses blows, you don’t lose your whole network in one go. Instead, you will only lose the devices connected to the side of the block that the fuse has blown on. The other devices will remain powered and operating.

These fuses can be 8/16A (rated 4 or 8A individually) depending on cable and provide current protection on the network, which regulate the amount of current on the network to safe levels.

Simple Diagnostic LEDs are found on the QNB-1 NMEA network block, providing you with a clear and easy way of identifying any issues at a very basic fault finding level. The 5 LEDs are for Power Status, Reverse Polarity Indication, Fuse State and Data, which work in the following way:

  • Power LED: Illuminated when device is correctly powered
  • Polarity LED: Will illuminate RED when polarity is incorrect. Swap the battery connections if this happens
  • Data LED: Illuminates to indicate data is present
  •  Fuse LED: Each LED will be illuminated when the individual fuse is intact. If one or both are out then a fuse(s) has gone.

Variants of the QNB-1

The Actisense QNB is available in 2 variants, the standard QNB-1 and the QNB-1-PMW. Operationally, the devices both behave exactly the same way, with the only difference being the connectors. The PMW variant comes with six NMEA 2000 standard M12 female connectors, allowing for maximum ‘plug and play’ capability when using NMEA 2000 devices.

The standard version offers more flexibility with cables and connected devices, but does require the devices to be wired in which would involve stripping cables. Whilst this isn’t a difficult task and a certified installer or experienced marine electronics technician can do it in a matter of minutes, it isn’t as convenient. In a scenario where you have half NMEA 2000 Device net, and half Raymarine STNG backbone, the QNB allows you to connect them together seamlessly, removing the need for adapter cables.

Here is an example of how a QNB-1 can be implemented into an NMEA 2000 network to easily connect multiple devices together, without the need for individual T-Pieces:

Actisense Network Diagram

Did you know?

The QNB-1 can also operate with NMEA 0183 data! This is a topic which isn’t discussed much, as it is primarily used for NMEA 2000 networking. However, the device can receive and distribute NMEA 0183, acting like a simple non-intelligent ‘buffer’ of sorts.

The QNB-1 can have 1 NMEA Talker inputting data, and up to 5 NMEA 0183 Listeners connected which receive the data. The number of connected devices varies on the current drive from the talker, as some devices have a lower drive which means less Listeners can be driven.

QNB-1 NMEA 0183 Connection Diagram

NMEA Talk Banner