MICROWAVE TRANSMISSION IN 1944— GENERAL DF:SCRIPTI0N 



The X- and S-baiul receivers deserve meiiiiuii be- 

 cause of their special characteristics, which were de- 

 veloped to meet the requirements of this work. They 

 are provided with AFC circuits arranged to search 

 for a lost signal automaticall}'. Having found the 

 signal, the circuit locks the receiver in tune and con- 

 tinues recording. These receivers have specially de- 

 signed automatic gain control circuits providing es- 

 sentially logarithmic response of 70- to 80-db range 

 well spread across the recorder scale. The minimum 

 detectable power for these receivers is approximately 

 110 db l:)elow 1 w for both S band and X band, and 

 the minimum signal required for satisfactory opera- 

 tion of the AFC is approximately 105 db below 1 w. 

 The latter figures are important for this particular 

 setup, since they determine the usefulness of the re- 

 ceivers in studying signal strength near or below that 

 encountered under standard refraction conditions. 



The receivers were calibrated daily by means of 

 signal generators coupled permanently to the wave 

 guide between the antenna and the receiver through 

 wave selectors with known fixed coupling losses. Very 

 close check on performance was maintained so that 

 the receivers at all times gave an accurate indication 

 of the absolute value of received signal strength. 



The arrangement of S- and K-baud receivers iu 

 the house on top of the tower was similar to that in 

 the lower house, but the K-band receiver was of a less 

 sensitive type requiring no tuning. There was a 117- 

 mc receiver in the top house but not in the bottom 

 house, and there was no receiver for the Deer Island 

 circuit in the top house. 



The oirtputs of all eight receivers were wired direct- 

 ly into an Esterline-Angus recording milliammeter. 

 With this arrangement one operator was able to keep 

 continuoiis watch on the performance of all receivers 

 and was required to climb the tower only when major 

 adjustments of the top receivers were necessary. 



The Gloucester station was the control station for 

 the radio network formed by all the stations involved 

 in the project. The transmitter station at Province- 

 town, each of the radar trucks, the fixed meteoro- 

 logical stations, the boat, and one of tlie airplanes 

 were all equipped to operate radiotelephone on 3.5 mc, 

 thus allowing rapid and efficient exchange of informa- 

 tion essential to the operation of all units involved in 

 the program. 



11-4 Meteorological Program 



The meteorological phase of our program con- 



sisted of two main parts: (1) meteorological meas- 

 urements, and (3) forecasting and analysis. 



All meteorological measurements were made with 

 varying versions of the psychrograph, earlier models 

 of which are completely descrilied in reference 2. 

 This instrument measures wet and dry bulb tempera- 

 tures as a function of height, using the electrical re- 

 sistance thermometer principle. From these measure- 

 ments the M curve is constructed. 



The meteorological soundings were made in the 

 Massachusetts Bay area with psyclirographs carried 

 by two aircraft, by captive balloons operating from a 

 boat and from two fixed land stations. The boat 

 operated in the Bay and out to about 100 miles off- 

 shore, while the aircraft operated as far as 170 miles 

 offshore. It should be mentioned that aircraft sound- 

 ings of this type are rather hazardous, since they in- 

 volve descending to altitudes of approximately 20 ft 

 at large distances from land. 



The fixed meteorological stations were located at 

 Duxbury and Eace Point. The Duxbury location was 

 chosen to place the sounding station near enough to 

 the shore to obtain a representative sample of the air 

 just leaving the land. 



The Eace Point meteorological station was located 

 at a position to allow soundings at the water's edge 

 on the westernmost extremity of the top of Cape Cod. 

 The primary purpose of this station was to measure 

 the characteristics of the air after it had been sub- 

 jected to the influence of the ocean surface between 

 the mainland and the station. This location allowed 

 measurements over a range of wind directions of ap- 

 proximately 180°, but no relevant soundings could be 

 made when the wind had an easterly component, since 

 the air would have had a land trajectory for at least 

 a short period. It was necessary to take all soundings 

 very close to the water's edge to prevent solar heating 

 of the beach from influencing the bottom of the meas- 

 ured M curve. At both Duxbury and Provincetown 

 soundings were taken on a prearranged schedule 

 which, when possible, involved both day and night 

 operation. Soundings, surface wind velocities and 

 hourly observations of sky conditions, etc., were made 

 at both Duxbury and Eace Point. The water tempera- 

 ture was also measured at the Provincetown station. 



A 60-ft pole was erected at Eace Point carrying 

 four anemometers, four psyclirographs, and a wind 

 direction indicator. The original scheme involved con- 

 tinuous recording of temperature, humidity, and wind 

 speed at four levels by means of the instruments on 

 the pole, but unfortunately a large sand bar formed 



