An Introduction to Scanner Marine Radios

Table of Contents

Title Page
The Editor's Notebook
Marine News
An Introduction to Scanner Marine Radios
Ship of the Month No. 87 William C. Warren
Answers to our "Turret Pilothouse" Quiz
Questions from Florida
Additional Marine News
Table of Illustrations

by Larry D. Morrill of Collingwood, Ontario

How often have we been working at home but wishing we were at the Welland Canal and wondering what ships we were missing? How many times have we been at the Canal or the Soo when it seemed as if the next boat would never arrive? By tuning in the V.H.F. marine radio, we can find out what is going on without being there and, if there, have all the information on the ships that may be coming our way.

The V.H.F. marine band is just one of several bands of the electromagnetic frequency spectrum allocated for public service use. The public service bands are V.H.F.-Lo (30-50 MHz), V.H.F.-Hi (150-174 MHz) and U.H.F. (450-470 MHz). "MHz" stands for megahertz, or millions of cycles per second. "V.H.F." stands for Very High Frequency, whereas "U.H.F." designates Ultra High Frequency.

Marine communications are carried on two narrow portions (156.275-157.425 MHz and 161.000-162.025 MHz) of the V.H.F.-Hi band. At these frequencies, radio transmissions are of the F.M. (frequency modulation) type. This results in a clear signal but one with a rather limited range. Consequently, V.H.F. marine signals are only reliable over a radius of about fifty miles. Also, because of the high frequency of the transmissions, signal reception is dependent to some extent upon cloud layers and other atmospheric conditions such as rain and snow. Noise from engine ignitions and other similar sources will also affect the quality of incoming signals.

There are two basic types of receivers available for the monitoring of the V.H.F.-Hi band. The least expensive is the multi-band radio sold by many department stores. This type of radio is not, however, ideally suited to the monitoring of the marine bands. A multi-band receiver allows one to monitor only one channel or frequency at a time. In addition, the set will be difficult to tune to the desired frequency because the transmissions are usually intermittent and of short duration, and the physical length of the tuning scale limits the accuracy of preset tuning.

The only receiver which allows reception of public service bands with reliable "hands-off" tuning is the fixed-tuned set. Nearly all of the receivers of this type on the market today are capable of being fixed-tuned to more than one frequency. The scanner, as it is known, is a multi-fixed-tuned receiver which is capable of automatically sampling all of its preset frequencies in a sequential fashion.

The conventional scanner is fixed-tuned by inserting a separate crystal for each frequency to be monitored. However, modern technology has now developed the frequency-synthesized, micro-processor-controlled scanner which tunes in whichever frequencies are entered into its computer memory via a keyboard. A scanning receiver is essentially identical to any F.M. radio, such as those in most homes or cars, except that an electronic switch automatically changes the "stations".

Certain important points must be considered by anyone purchasing a scanner. First of all, one must decide what one wants to receive with the set; that is, are only marine communications desired or are local transmissions also to be monitored? Depending on how many frequencies are to be monitored at any given time, many scanner channels may be required. For instance, in the Toronto area, at least 20 different marine frequencies can be monitored. The number of channels required will dictate the type and model of scanner one should purchase.

Crystal-controlled units tend to be less expensive initially but may cost more in the long run. An eight-channel crystal-tuned set, which will allow one to monitor only eight frequencies at one time, will cost approximately $200 in Canada (less in the U.S.), but by the time the eight crystals are purchased at $9 each, the cost will have reached $272 plus tax. On the other hand, a 20-channel micro-processor-controlled scanner can he bought for about $300 and will allow the monitoring of some 16,000 frequencies.

Some other specifications should also be considered when purchasing a scanning receiver. Sensitivity is a measure of a receiver's ability to extract a radio signal from the airways. Generally, the lower the rating, the better; a radio with a specified sensitivity of 0.4 microvolts (millionths of a volt) is more sensitive than one with a sensitivity of 1.0 microvolts. Greater sensitivity means that more distant stations can be received. Selectivity is a measure of the set's ability to differentiate between signals. In this case, the greater the rating, the better, a selectivity of 60 decibels being preferable to one of 40 decibels.

When purchasing any piece of electronic equipment, be it a television set or V.H.F. scanner, it pays to shop around. For the same scanner, prices may vary by as much as $200. Also to be considered are such details as manufacturer's warranty and service availability; be certain that the set can be serviced locally or, at least, within the country. Dealing with a local distributor of mobile radios may be more advantageous when information or service is desired than dealing with larger chain stores.

It would not be remiss to mention a few tips on keeping a scanner in good working order. Always make sure that the power switch is off before plugging the set into the house current or the car's power system, and before attaching or removing antenna leads. If using the scanner in the car, mount it so that it may be removed easily. When leaving the car, remove the radio and place it in the trunk or, at least, cover it with a coat or similar object so that it is not in full view. A home insurance policy may well cover the scanner but the addition to the policy of a separate rider will ensure that it is covered against such perils as fire, theft, etc. A radio receiver will not be covered by an automobile insurance policy unless it is actually attached to the vehicle. Remember that, in the care of a scanner, a little common sense goes a long way.

To ensure good reception from a scanner at home, an outside antenna mounted high above the ground will be desirable. It can be placed on a t.v. mast above the television antenna or even affixed to the chimney. Apartment residents might clamp an antenna to a balcony railing. Mobile antennas, held in place by magnets or gutter-clips, can be readily obtained to assist in the use of the set in an automobile. Remember that, with the high frequency of V.H.F. marine signals, reception is theoretically limited to the line of sight. Consequently, those living more than 50 miles from a shipping channel, or in a valley, should not count on receiving F.M. marine broadcasts .

Persons wishing to purchase scanners would be well advised to provide for the reception of at least the following channels:

06 156.300 MHz Intership Safety and Communications.
11 156.550 MHz Vessel Traffic Dispatch, notably by Seaway Newcastle (Lake Ontario) and by Sarnia Traffic Control.
12 156.600 MHz Vessel Traffic Dispatch by Soo Control on the St. Mary's River and by harbour authorities including Toronto and Hamilton.
14 156.700 MHz Canal Traffic Dispatch, notably by U.S. (WUD31) and Canadian (VDX23) Soo Canals and by Seaway Welland.
16 156.800 MHz Distress, Safety and Hailing Channel.
22 157.100 MHz Coast Guard communications, including navigational bulletins and weather forecasts.

A scanner can provide the boatwatcher with many hours of listening pleasure throughout the year. It most definitely adds that extra touch to those regular pilgrimages to the Soo, the St. Clair River, or the Welland Canal.


Previous    Next

Return to Home Port or Toronto Marine Historical Society's Scanner

Reproduced for the Web with the permission of the Toronto Marine Historical Society.