Fall 2002 Issue

Predicting VHF/UHF Conditions

If you live along the coastline of the U.S., here is a simple way to predict how far you can talk on VHF/UHF.

By Van R. Field, W2OQI

.Undoubtedly, there are some exotic computer programs which when fed with the proper information can predict, at least short term, how far one can talk on VHF/UHF.

I offer a simple system, particularly for those who live along the coastlines of the U.S. The equipment consists of a VHF scanner. If Marine Channel 16 (156.8 MHz) is programmed, then with a simple outside antenna the Coast Guard stations up and down the coast can be monitored. The Coast Guard uses its location for a callsign and repeats it frequently, so you know right away where the station you are hearing is located. Channel 22 (157.10 MHz) is used for weather broadcasts and to talk to pleasure boaters.

You should be alert for not hearing a distant station as well as hearing it. Sometimes conditions change rapidly, and a full-quieting signal one moment may be gone the next.

The Coast Guard operates from “groups” of stations. Large groups are called Activities—i.e., Activities New York. Group Long Island Sound is at New Haven, Connecticut. Stations usually use 25-watt radios with antennas no higher than 90 feet. Groups use 100-watt stations in several locations, which are keyed by the same operator, sometimes simultaneously. The Group/Activities location may have a local 25-watt radio as well. This makes a difference when listening for changes in local conditions, but when I hear Group Cape Hatteras at my QTH on Long Island, I get the idea that the band is open at that moment to North Carolina. On the other hand, tuning 2-meter sideband may produce only a few over-the-horizon stations. After a while, you catch on to the condition of the band, even if you don’t hear anyone.

Sometimes you may hear the vessels with which the Coast Guard is communicating, indicating a good opening, because antennas on small vessels aren’t more than 20 feet off the surface of the water and all vessel stations are 25 watts.

 

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