Getting Maximum VHF/AIS Reception

AIS Antenna on Roof

We are often asked about the best antenna to use with our AISNet Base Station Receiver, which is used by many customers to send AIS data to online AIS websites like Marine Traffic, Pinkfroot, AIS Live, Boat Beacon, Shipfinder, etc. We usually suggest a good quality, AIS tuned antenna, with at least 3dB gain and in most cases this gives a good reception range – up to 20-25miles or more. You can get greater range by going to a more expensive directional Yagi antenna, but these often have a limited beam width and may only receive strong signals from vessels within a 120deg arc of the antenna.

Generally speaking a 1/2 dipole, omni-directional whip antenna is probably the best choice for most installations, as they are generally not too expensive, give a good 3dB of gain and will receive targets through a full 360 degrees. In our opinion, it is better to spend time and money on getting the antenna mounted as high as possible than to spend more money on a higher gain directional antenna.

This week, however, we were contacted by a customer who had bought a well known brand of AIS whip antenna but was only seeing targets out to about 12-15 miles. Looking at the spec of the antenna, everything seemed OK but then we noticed that it came with 20m of RG58 coax cable which, according to the attenuation table below, would lose over -3.6dB negating the benefits of using a 3dB antenna.

Attenuation figures of different types/lengths of Coax Cable
Coax Type 20′ (6m) 40′ (12m) 60′ (18m) 80′ (24m) 100′ (30m)
RG-58 -1.2dB -2.4dB -3.6dB -4.9dB -6.1dB
RG-8X -0.9dB -1.8dB -2.7dB -3.6dB -4.5dB
RG-213 -0.5dB -1.0dB -1.6dB -2.1dB -2.7dB

When selecting antennas, the coax cable is often overlooked and, as we discovered, this can have a significant impact on reception range. We suggested that they looked at an alternative whip antenna that came with no cable but had an N-Type or PL259 type connector on the base of the antenna. This would then allow them to make up their own coax cable, using the minimum possible length of low loss RG-213 coax cable.

Even with RG-213, you can lose approximately 1dB for every 10m of cable that you use and as the AISNet is fairly portable, it is always better to move the AISNet closer to the antenna and reduce the coax cable length. You can always run longer lengths of RJ45 network cable inside the building (which does not suffer the same attenuation as coax cable), or better still use a wireless access point or repeater to wirelessly connect the AISNet to the main router in the building.

For more information on our AISNet Base Station receiver, click here.

 

AIT3000 Nucleus AIS Transponder transponder debuts at Southampton Boatshow

Wow! New AIT3000 Nucleus Class B AIS transponder with built in antenna splitter and WiFi interface

Class B AIS transponders have made a remarkable impact on small craft navigation but many potential users or installers are put off by the requirement for yet another VHF antenna.

The new AIT3000 “Nucleus” Class B AIS  changes that and incorporates not only a full function Class B transponder but also an antenna splitter allowing the main VHF antenna on the boat to be shared with the AIS and VHF.

ait3000 mq jpeg

It’s also been designed with the latest interfacing capability including NMEA 0183, NMEA 2000, USB and a WiFi server to allow tablets and iPads to connect – hence the name Nucleus as it becomes the hub for on board navigation.  NMEA data from other on board systems can be multiplexed by the Nucleus and combined on the WiFi link.

The Nucleus transponder is the World’s first to include patented ZeroLossTM technology for the antenna sharing and a wireless interface for iPad connectivity.  More and more boat owners are utilising an iPad or tablet as either a primary navigation display or as a touch screen repeater for their existing navigation system.  Digital Yacht also offer a free AIS viewing app called iAIS as well as more sophisticated charting apps like NavLink. If you’re an Android user, AISView is also compatible.  The NMEA interface allows connection to any AIS compatible chart plotter and USB is available for MAC or PC users as well as allowing programming of the unit with your boat details.

ait3000 main mq

Other features include a silence switch option allowing the unit’s transmissions to be stopped while continuing to receive AIS transmissions.  It also has an output for a FM stereo radio.  The AIT3000 will have a UK list price of £825 plus vat.

A dealer preview pack is available here

See it first from Friday 12th September at the  Southampton Boatshow Stand G147 with our UK Distributor CA Clase – check out the 2 minute video below to:

The Non-Idiot’s Guide to AIS

Non Idiots

We had an enquiry today from a US Dealer about why some chart plotters do not display all of the 26 different AIS Messages that are transmitted by Ships, AtoNs, AIS MOB systems and other AIS equipment. This is quite a complex issue as there are three variables at play….

1) The AIS transponder or Receiver

Most AIS receivers and transponders support all AIS messages, however it is true that early Class A and some receiver only units do not support all AIS messages. It is always best for the owner of older AIS units to check that they have the latest firmware in their units and to even contact the manufacturer to see if their unit supports the more recent AIS messages like AtoNs and AIS SARTs (MOB) systems.

The good news for Digital Yacht customers is that every AIS unit we have ever sold supports all of the 26 AIS messages currently defined.

2) The Chart Plotter or Software Application

Even if the AIS transponder or receiver is compatible with all 26 messages, it does not necessarily mean that the chart plotter or software application (running on PC, iPad, etc.) knows how to read and display the AIS messages.

When AIS was first released, many manufacturers and software developers just did a partial AIS implementation, only supporting what they considered to be the most important AIS messages. Also due to delays in the definition of Class B transponder messages, some of the manufacturers only supported the display of Class B targets but not the reading of the Class B static data (boat name, boat type, etc.). Even large manufacturers like Raymarine, Navico and Garmin took a few years to release new firmware for their plotters to improve the number of AIS messages that they supported.

3) NMEA2000 PGNs for AIS

Due to delays in the NMEA committee defining PGNs for AIS, some plotters only support some of the 26 AIS messages when connected via NMEA2000, even if they support all 26 messages via NMEA0183. This Panbo article provides more info on this issue.

http://www.panbo.com/archives/2012/06/ais_over_nmea_2000_the_shame_sheet.html

To help the dealer better understand some of these finer points of the AIS system, we sent him a copy of our Non-Idiot’s Guide to AIS that we produced for the British Marine Electronics Association.  The 26 AIS messages are detailed on page 12 of this document and the NMEA2000 PGNs are on page 13.

This presentation is a few years old now but is still a useful reference for anyone wanting to learn a bit more about AIS technology. To download a copy click here.

European Space Agency and the International Space Station have AIS on board

Since 2010, the International Space Station has been equipped with a space-based AIS System receiver that allows it to track ships at sea from space. Since then, the system aboard the ISS has been receiving as many as 400,000 ship’s position reports from more than 22,000 different ships every day.

This video shows how this experimental system was used in 2012 to rescue a sole surviving crew member of a Norwegian vessel after it overturned in the North Atlantic during a storm.

For the technical, there’s details here on the scientific projects that the ISS is carrying out right now – click HERE.  We say get a Digital Yacht or Digital Deep Sea AIS Transponder on board today – and an AIS SART too!

dds family

 

 

Digital Deep Sea – Solutions for the professional market

Digital Deep Sea design and manufacture products for the commercial, fishing, workboat, naval and superyacht markets.  Here’s a guide for pro-market installers, users and dealers on our product line up which includes Class A AIS, wireless navigation solutions for Pilots and Captains and  a range of sensors.  Download it from here Digital Deep Sea Innovative Solutions

class a ais

New SmarterTrack Lite V1.04

SmarterTrackLITE_V1_04

Today we have released an update to our popular, free SmarterTrack LITE software. Version 1.04 has improved cursor Lat/Lon display in the Status Bar at the bottom of the screen and support for the AIS transponder VDO message which allows SmarterTrack LITE to take the boat’s position from the AIS transponder even if it is not outputting traditional NMEA0183 GPS messages like GGL, GGA or RMC.

A number of people have wanted to use SmarterTrack LITE with the Pilot Plug connection of a Class A AIS Transponder and the new version now supports this allowing you to plot the boat’s position and all of the AIS targets around the boat, via one of our Pilot Plug adaptor cables or wirelessly using our PilotLink product.

Other popular applications for SmarterTrack LITE are; testing a USB or Wireless enabled AIS unit on a Windows PC or for monitoring the local AIS traffic that our AISNet product is sending to Marine Traffic, AIS Live or any of the other internet AIS services. To download a copy of the latest V1.04 please click here.

Interesting AIS Applications – Tender Tracking

Most yachts above 50ft are now equipped with either a Class A or Class B AIS transponder.  Any superyacht carrying more than 12 passengers or over 300GRT is mandated to carry a Class A transponder like our CLA1000 – details here

But how about the yacht’s tenders or jetskis?

Adding a low cost Class B transponder to a yacht tender or jetski allows it to be easily tracked for safety and security. The Digital Yacht AIT2000 Class B transponder will provide regular 30 second transmissions of the tender’s position, course and speed and allow positive identification of the tender from the mother ship.  What’s more there’s no running costs or internet connectivity required for tender tracking with AIS unlike cellular based solutions.

The AIT2000 can also connect to a compatible plotter fitted on the tender to allow an AIS overlay of targets as well as making it easy for the helmsman to locate the mother ship.

Our new GV30 combo GPS-VHF antenna is ideal too for an unobtrusive installation.

 

jetski_ait2000VR 2

 

Here’s a reminder of some of the features of our AIT2000

  • AIT2000 – ultra compact Class B AIS transponder
  • Fit and forget solution – Waterproof to IP65
  • Supplied with GPS antenna – requires connection to VHF antenna or suitable splitter such as SPL2000 or can be supplied with our new GV30 combo GPS-VHF antenna
  • Features dual NMEA 0183, NMEA 2000 and USB interfaces for maximum flexibility
  • Remote silence/transmit inhibit feature
  • Class B AIS transmissions every 30 seconds for real time tracking

On board the mother ship, our  WLN10HS NMEA to WiFi server can be fitted to yacht’s main AIS system to allow wirelss tender tracking on crew or guest’s iPad/Phone – neat eh?  The WLN10 will typically footprint NMEA data over a boat up to 35m in length so crew can use an iPad or iPhone for navigation and tender tracking with apps like NavLink, iNavX and iAIS.

ait2000 plus wln10 for class a