TH-3 Medium-Haul Application: Equipment and Building Considerations

T H - 3 radio in its overall systems equipment concept for 4000-mile long-haul radio is almost identical to TD-3 radio. 1 The primary difference is in the frequency band, the circuit capacity, and the number of radio channels per route. All of the supporting equipments, such as power plants, FM terminals, radio line protection switching, entrance link and FM terminal protection switching, patching and access and emergency restoration equipment as well as test equipment, are essentially identical in their application to TD-3 and TH-3. Some of of the supporting items will handle broadband channels of both TD-3 and TH-3 on a direct intermix basis whereas others require only minor changes. The largest application of TH-3 will be in the addition of TH-3 radio at 6 GHz to already established fully loaded TD-2 and TD-3 radio routes operating at 4 GHz (overbuilding); this involves using existing buildings and common facilities, including antennas and waveguide insofar as possible. Two T H - 3 radio systems have been developed; a version for use on 4000-mile long-haul routes and a simplified version for use on medium-haul routes where only one working broadband channel is required. This capacity restriction for medium-haul usage permits the protection switching to be greatly simplified and the use of a single antenna for transmitting and receiving in each direction. This medium-haul system should have considerable application in meeting 2345