Radio Broadcast (Nov. 1925-Apr 1926)

680 RADIO BROADCAST APRIL, 1926 there is no reason why any one cannot be in communication with any one else without a lot of expensive apparatus. Witness the fact that with 9 ccq, a power input of .04 watts was successful in maintaining communication over a distance which represents a record of 26,500 miles per watt. It required less power to transmit the messages than it did to receive them. The photographs of the transmitter should give all the constructional details that are necessary !„_„_ and the simplicity of the antenna throwover switch is shown in Fig. 3. The plate batteries are contained in the lower compartment as shown in Fig. 4 and the whole outfit can be set up for operation in less than five minutes. All that is necessary is to remove the front board which has on it the key, plug in the A and B battery cables, throw a wire over a tree and spread on the ground the counterpoise — or use the automobile as a counterpoise — tune the antenna and closed circuits by means of the proper condensers until maximum current is obtained on the wavelength desired. The current on inputs up to 20 watts should not be high, at least not over one half ampere. DATE TIME STATION DISTANCE WATT INPUT MILES PER WATT 11/13 9:35 P.M. 4 DO /45 14.4 51 .6 11/13 1 1 :55 P.M. 9 DZN 970 6.7 145.0 11/14 12 :35 A.M. 9 AJI 750 6.7 112.0 11/23 9:45 P.M. 9 DSL 850 10.8 80 0 1 1 /23 10:00 P.M. 9 TJ 1080 108 100.0 11/23 ID. 10 P.M. 9 DXX 860 10 8 80.0 11/24 1 :10 A.M. 9 ECL 1080 10.8 100.0 12 /ll 8:15 P.M. 9 ECC 1030 .342 juuu.o 12/15 9:32 P.M. 8 BZK 600 1.04 580.0 12/16 8:20 P.M. 9 DCG 740 1.80 410.0 12/17 8:40 P.M. 9 CBZ 700 .21 3500.0 12/17 10:00 P.M. 9 CCQ 1060 .04 26500.0 12/24 9:00 P.M. 9 CCQ 1060 .11 9650.0 12/29 8:40 P.M. 9 DIB 860 17.0 50.5 12/29 9:40 P.M. 9 BAL 860 17.0 50.5 If the current is higher than .5 amperes, more wire should be added to the antenna to increase the radiation resistance. Quite often it is impossible to raise any one on .5 amperes, but adding ten feet to the antenna will decrease the current to .2 with the result that good distance can be worked. Sangamo condensers will stand voltages up to 1000 volts, provided of course that the currents are not high. Ordinary receiving condensers will serve as tuning capacities. Practically any tube will do. At 2 cy excellent results have been obtained with the standard 201 -a tube of various manufacturers. A Ureco 112 tube is practically the equal of the uv210 tube which requires more filament current. The center tap to the closed circuit inductance which completes the Hartley circuit is variable and should be near the grid end of the coil for maximum efficiency. Moving it toward the plate end will increase the power taken by the tube without much increase in the power taken by the tube and with little increase in antenna current. Only „,„_™,J two meters are essential and one of these can be avoided if a small flashlight bulb is used to indicate antenna resonance. This was explained in the January article in Radio Broadcast by Nicklaus Hageman. If a 201-A or 1 12 tube is used, the filament voltage should be only high enough to insure that the maximum efficiency is being obtained. This can be obtained by watching plate or antenna current meters and varying the filament rheostat. If a 210 tube is used, it may be run on 6 volts without a rheostat — and naturally no filament voltmeter is necessary. Regardless of the fact that no especial insulation has been used at 2 gy, the antenna-counterpoise system should be as FIG. 4 A photograph of 9 ccq at Braymer, Missouri. The three 201-A tubes with their elements in parallel, the calibrated short wave receiver, and the compendium of amateur information — QST — are worthy of notice. We suspect the big box at the left is a broadcast receiver