Radio Beacons in 1949
The following map shows the former location of Radio Beacon Stations that were used for distance finding.  During fog conditions
they transmitted near the end of the operating minute a one second dash followed by a one second silence and a long dash of
either three or five seconds duration.  These two dashes were synchronized with the blasts of the same duration from the sound
fog signal.  The number of seconds elapsing between the termination of the long radio dash and the termination of the long
blast of sound divided by five gave an approximate distance in statute miles from the light station.
 

source:  Radio Aids to Navigation Great Lakes 1948 - US Navy Department, Hydrographic Office
 

                 Radio Frequencies used on the Great Lakes

Algoma 156.875 Channel 77
Algoma 156.925 Channel 78
Algoma 157.425 Channel 88
American Steamship 156.900 Channel 18
Andrie Towing 156.950 Channel 19
Andrie Towing 156.475 Channel 69
Carferry Badger 156.475 Channel 69
Bethlehem Steel 156.325 Channel 66
Columbia Transportation 156.950 Channel 19 (Columbia Star, Middletown)
Columbia Transportation 156.275 Channel 65 (Varies according to boat.)
Columbia Transportation 156.325 Channel 66 (Joe Frantz)
Columbia Transportation 156.875 Channel 77 (Reserve)
Columbia Transportation 156.925 Channel 78 (Middletown)
Columbia Transportation 156.975 Channel 79 (Armco)
Desgagnes 156.375 Channel 67
Great Lakes Towing 156.300 Channel 06
Great Lakes Towing 156.500 Channel 10
Great Lakes Towing 156.900 Channel 18
Hanna Towing 156.725 Channel 74
Inland Steel 156.275 Channel 65
Inland Steel 156.325 Channel 66
Inland Steel 156.375 Channel 67
Interlake 156.350 Channel 07 (George A. Stinson)
Interlake 156.950 Channel 19 (Varies according to boat.)
Interlake 156.275 Channel 65
Interlake 156.375 Channel 67
Interlake 156.575 Channel 71 (Paul Tregurtha)
Interlake 156.925 Channel 78
Interlake 156.975 Channel 79 (Charles M. Beegley)
LaFarge Cement 156.875 Channel 77
Medusa Cement 156.250 Channel 05 (Medusa Challenger)
Medusa Cement 156.725 Channel 74 (Medusa Conquest)
Paterson 156.375 Channel 67
P&H 156.325 Channel 66
P&H 156.525 Channel 70
P&H 156.575 Channel 71
P&H 156.875 Channel 77
Presque Isle 154.600
St. Marys Cement 156.375 Channel 67
Selvick Towing 156.500 Channel 10
Selvick Towing 156.875 Channel 77
Selvick Towing 156.725 Channel 74 (Used when towing the Harriman)
Upper Lakes Shipping 156.275 Channel 65
Upper Lakes Shipping 156.325 Channel 66
U.S.X. Great Lakes Fleet 467.775 USX "Ch. 1"
U.S.X. Great Lakes Fleet 467.800 USX "Ch. 2"
U.S.X. Great Lakes Fleet 467.400 USX "Ch. 3"
Upper Lakes Towing 156.675 Channel 73 (Joe Thompson)
BN Ore Dock, Superior, WI* 160.515 (RR frequency)
Taconite Harbor Ore Dock* 451.975 (RR frequency)
*Docks use ships walkie-talkie frequency when actual loading is taking place.