AIS Range: Reception Report
Posted: Fri Jun 07, 2024 2:57 pm
Description of AIS Receiving Station
During non-boating season I usually have my VHF Marine Band radio (Standard-Horizon GX2150) with integral AIS receiver and my chart plotter (an ancient first-generation Lowrance HDS-8) on my desk indoors. The radio and chart plotter are interconnected using two NMEA-0183 connections; one for radio to chart plotter and a second for chart plotter to radio.
The two devices consume just little enough power (when the 25-Watt transmitter is not used, which would be illegal anyway) to be powered from a 12-Volt power supply that I build so many years ago I have no idea exactly when, but it was probably in the late 1970's or early 1980's at the latest, making the power supply about 45 to 50-years old. But it still works and can deliver about 3.5-Amperes, which is just enough to run the plotter and radio as long as the radio is in receive-only use.
The antenna for the radio is located in the attic of my cabin in northern Lake Michigan's Grand Traverse Bay, right on the eastern shore of the Leelanau Peninsula. The antenna is a Yagi with a reflector, a loop-driven element, and one director. The main lobe is aimed more or less due east. The gain of this antenna is probably about 5-dB compared to a half-wavelength dipole, or in terms of "marine antenna" gain perhaps 7-dB or more,
The principal use of this set up is to read the mail on VHF Maine Band traffic on Channel 16, to listen to USCG alerts on Channel 22, and to receive NOAA Weather Radio broadcasts. And thanks to the integrated AIS receiver in the radio, the AIS1 and AIS2 channels at 162-MHz are also monitored, allowing me to know of any boats equipped with AIS transmitters in the local area.
With that background on the gear in use, I now turn to the topic of this short article:
AIS Range and Reception Reports
With the radio NMEA-0183 output connected to the chart plotter, the chart display shows AIS targets received by the radio. This is quite interesting because it gives a nice indication of the range at which AIS signals can be received. At the moment the motor vessel CAROLINE MCKEE (a 135-foot length, 36.1-foot beam tug) is being received at a range of 20.6-miles from my location. The tug is northeast of me near Charlevoix, Michigan, probably at the Saint Mary's Cement plant with a barge in the notch. That is quite a satisfactory range.
Simultaneously a second vessel heading southwest in open Lake Michigan at a range of 18.4-miles and bearing 008-degress is also being received. It is another tug, the motor vessel CANDACE ELISE. With the heading almost due north, this signal is off the main lobe of the antenna, so the gain from the Yagi is minimal, if any, and perhaps even a loss compared to an omnidirectional antenna.
I also often hear calls from larger vessels that are approaching Charlevoix to alert other boaters they are proceeding inbound--the channel is not particularly wide and a large vessel may take up most of its width. The Beaver Island Boat Company ferry EMERALD ISLE is often heard making SECURITY calls when it approaches or departs Charlevoix.
When boating season really gets going, the chart plotter and radio are moved to my boat, so I miss having them on the desk. I have to resort to a small handheld radio to keep up with local marine traffic.
During non-boating season I usually have my VHF Marine Band radio (Standard-Horizon GX2150) with integral AIS receiver and my chart plotter (an ancient first-generation Lowrance HDS-8) on my desk indoors. The radio and chart plotter are interconnected using two NMEA-0183 connections; one for radio to chart plotter and a second for chart plotter to radio.
The two devices consume just little enough power (when the 25-Watt transmitter is not used, which would be illegal anyway) to be powered from a 12-Volt power supply that I build so many years ago I have no idea exactly when, but it was probably in the late 1970's or early 1980's at the latest, making the power supply about 45 to 50-years old. But it still works and can deliver about 3.5-Amperes, which is just enough to run the plotter and radio as long as the radio is in receive-only use.
The antenna for the radio is located in the attic of my cabin in northern Lake Michigan's Grand Traverse Bay, right on the eastern shore of the Leelanau Peninsula. The antenna is a Yagi with a reflector, a loop-driven element, and one director. The main lobe is aimed more or less due east. The gain of this antenna is probably about 5-dB compared to a half-wavelength dipole, or in terms of "marine antenna" gain perhaps 7-dB or more,
The principal use of this set up is to read the mail on VHF Maine Band traffic on Channel 16, to listen to USCG alerts on Channel 22, and to receive NOAA Weather Radio broadcasts. And thanks to the integrated AIS receiver in the radio, the AIS1 and AIS2 channels at 162-MHz are also monitored, allowing me to know of any boats equipped with AIS transmitters in the local area.
With that background on the gear in use, I now turn to the topic of this short article:
AIS Range and Reception Reports
With the radio NMEA-0183 output connected to the chart plotter, the chart display shows AIS targets received by the radio. This is quite interesting because it gives a nice indication of the range at which AIS signals can be received. At the moment the motor vessel CAROLINE MCKEE (a 135-foot length, 36.1-foot beam tug) is being received at a range of 20.6-miles from my location. The tug is northeast of me near Charlevoix, Michigan, probably at the Saint Mary's Cement plant with a barge in the notch. That is quite a satisfactory range.
Simultaneously a second vessel heading southwest in open Lake Michigan at a range of 18.4-miles and bearing 008-degress is also being received. It is another tug, the motor vessel CANDACE ELISE. With the heading almost due north, this signal is off the main lobe of the antenna, so the gain from the Yagi is minimal, if any, and perhaps even a loss compared to an omnidirectional antenna.
I also often hear calls from larger vessels that are approaching Charlevoix to alert other boaters they are proceeding inbound--the channel is not particularly wide and a large vessel may take up most of its width. The Beaver Island Boat Company ferry EMERALD ISLE is often heard making SECURITY calls when it approaches or departs Charlevoix.
When boating season really gets going, the chart plotter and radio are moved to my boat, so I miss having them on the desk. I have to resort to a small handheld radio to keep up with local marine traffic.