Weather Station Aids Fire Fighters
During the fire-weather season in the forested areas of California there are a great many instances when weather forecasts are extremely necessary. On a large going fire covering several thousand acres, an accurate weather forecasting service can save many thousands of dollars. The United States Weather Bureau, in co-operation with the forest services, has mounted a mobile forecast unit on a motor truck. This unit is in charge of Mr. Gray of the United States Weather Bureau and who has had considerable experience as a forecaster. The only manner in which the official can get the information on which to base weather forecasts, is from the weather broadcast sent out each morning and evening, by the United States Weather Bureau, through NPG the naval radio station at Mare Island. This broadcast contains all the information necessary for constructing a weather chart from which the forecaster can determine what the coming weather will be . These broadcasts must be received under various conditions. The receiving set had to serve under most trying conditions. This made it necessary to construct a receiver that would cover sveral wave bands. To do this it was decided to build a receiver which would cover the frequencies from 16,000 to 108 kilocycles. This was done by making three separate receivers on one panel and completely shielding them from each other. All are mounted on an aluminum panel. These are seperated into the short wave, broadcast band and long wave receivers. The short wave unit and the long wave unit both use a common amplifier. The broadcast band receiver has a separate amplifier for quality reproductions.
The short wave unit uses a screen grid tube as a radio frequency amplifier. This is untuned. A regenerative detector using condenser control of regeneration and a two stage amplifier complete this unit. The broadcast band unit has one stage of tuned radio frequency using a screen grid tube, regenerative detector having a midget condenser for regeneration control. Two stages of high quality audio amplification completes this unit. In this case the condensers are Cardwell taper plate and the coils Silver Marshall.
The long wave unit has a regenerative detector and two stages of transformer coupled audio. The primary coil is in the center with the secondary tickler coils on each side. Regeneration is controlled with a filament rheostat.
The common amplifier uses transformer coupling and is a two stage. The amplifier is connected to a switch which connects it to whichever unit is desired.
The entire receiver is housed in an aluminum cabinet. While enroute the entire receiver is packed in a case and the case suspended on four springs. This was ncessarv because of the extreme roughness of the roads encountered in the remote regions. In many cases there were no roads at all. The “A” battery is connected to a switch so that the car generator may be used to charge it.
On test runs no difficulty was encountered in copying the 8590 or 108 kcs on a speaker, and broadcast stations within a radius of a thousand miles are easily tuned in on a loud speaker. Short wave stations over practically the entire world were received. No difficulty with broken apparatus was encountered because of the method of carrying them while in transportation.
In addition to this radio equipment, the mobile fire weather unit has been equipped with meteorological instruments for use on the fire area. The unit will maintain telegraphic communication with San Francisco and keep the dispatching agency notified of the whereabouts of the unit, actual and prospective.
Upon receipt of orders, the unit will proceed immediately to a large going fire, set up radio apparatus, establish temporary check or key weather stations in the fire vicinity, and issue detailed forecasts of weather, wind, temperature, relative humidity and other factors influencing the choice of fire tactics and the ultimate control of the fire. Forecasts will be of the short period type, issued twice daily, together with such special advices as may be required in connection with backfiring and similar operations.