After the development of a small portable radio set operating in the decimetric wave range, there has been a call for the development of duplex and multi-channel microwave communication equipment to replace landline transmission paths in the case of destruction by enemy or natural forces.
In 1942, Brown Boveri began developing a directional VHF station in 1942, it becam the the „Portable Lightweight Decimeter Station“ TLD. Since the Wehrmacht valves of the initial circuit design were no longer available in the war years, the three valve types required for the station were rebuilt by Brown Boveri. Unfortunately due to oxidation of the valve pins, there were frequent station failures. This unreliability gave the impression, that microwave communication technique itself was considered as unreliable by the commanders of troops, so the capabilities of this technology has been overseen for years.
In around 1955/57, the construction of a microwave communication network between high - altitude stations on Swiss mountain tops was started. To be used in this network, the microwave station UKR was used, partly installed in mountain station locations, partly installed on microwave communication trucks.
The UKR system equipped with an encryption system was housed in five man-sized equipment racks.
In the 1970s, these valve technology „dinosaurs“ were replaced by the much easier portable transistorised microwave system R-902.
In the early years, the microwave equipment got simple abbreviations usually from letters, so is TLD stands for Tragbar Leichte Dezimeterstation („Lightweight portable decimetric wave station“). According to the new nomenclature used from 1951, microwave communication systems were given designations R-9xx, followed by a two-digit number.
The information about microwave communication and the military background is still relatively sparse. I am thankful for more information, technical documentation and manuals and station images.
With the earliest decimetric stations, only point-to-point operation was possible. Because multi-channel equipment was usually not available, only simplex connections were made.