Radio Broadcast (May 1928-Apr 1929)

AUGUST, 1928 WHAT ABOUT THE 5-METER BAND? 213 FIG. I. A RECEIVER THAT GETS 5 METERS An ancient ymeter receiver — still good. This set was used to make 1200 field observations on transmissions from 2EB at Jamaica and ioa at Hartford and Glastonbury. The circuit is perfectly normal, being of the general type of the circuit shown in Fig. 2 plus a second audio stage. With so simple equipment the signals from a ux-852 have been copied in a moving car through ignition noises at 5 miles, and at 60 miles with the car stationary and a 20-foot antenna hung on a tree. The pencil points toward the tuning inductance down at all on this earth, except, mayhap, in the antipodes. However, the wanderlust drives on the same group that originally departed from the 200meter reservation. With the group consisting of Ducati of Italian, 'acd,' Douglas out in Kansas, Phelps and Kruse on the east coast, it became necessary to make some more detailed study in place of mere "blind" transmissions. EXPLORING 5 METERS AT THIS point there entered the radio flivver, financed by Phelps and known as Conny because of its Connecticut and New York licenses. The flivver wandered restlessly about Jamaica and Hartford, gradually determining what one may expect 5-meter waves to do. The results were surprisingly normal and unalarming. The signals do not die off in the rapid manner that we had been warned against, nor do they do anything especially freakish. Some 14 months prior to the days of Conny a few signals from an ancient 5-watt uv-202 transmitter of Phelps, at Staten Island, had managed to put signals at 5.2 meters into Glastonbury, Connecticut, where an amazing "haywire" receiver of mine received them. We hoped to repeat this and make it more consistent. We did repeat it, but not before many trials were made, more power used, the apparatus repeatedly improved, and an appalling number of tests run. Our difficulty was with a tremendous "noise level," far worse than at longer waves. This having finally been greatly reduced by means of a double detection receiver, we again hoped for communication, but failed. Phelps then built a huge automatic key that ground out his call and a test signal by the week, and after some listening this was heard in Kansas by Douglas and in Seattle by another listener. My own signals struggled as far as Kansas, and I heard Ducati's signals. Ducati's transmitter was located at Bologna, Italy, and used about 400 watts. This began to look more hopeful but the contacts were always brief. Phelps then organized a two-way contact with E. S. Strout, 2NZ, of Newark, N. J., and several conversations were held at 25 mile distance. However, the "lure of distance" was again at work. . MORE DISTANT RECEPTION TN THE fall of 1927 a trip to the West Coast 1 seemed to offer a good opportunity. A 5meter double-detection receiver was rather hastily discarded in favor of a new detector-audio receiver which I took to Lawrence, Kansas. However, it proved to be not sensitive enough and was replaced by another and better double FIG. 2. A SIMPLE 5-METER RECEIVER CIRCUIT This receiver is of the detector-audio type. Regeneration control is by the resistor, R, only the Frost type having proved satisfactory at 5 meters. The ux-112 and 112A detector tubes are best. Ci, C2, and Cj all have the same capacity, about 10 mmfds., obtained by trimming down a "vernier" condenser. Li may range from 1 to 4 turns of about 1" diameter. Ci must be driven by a quiet vernier dial, such as National type F, while Cj needs only a knob for "set and forget" use — otherwise the tuning will be all mixed up since the use of this condenser disturbs calibration. C4 should have a capacity of not over 0.0001 mfd. The grid condenser is about 100 mmfds. with a high leak (8 megs). The detector tube must be cushioned on sponge rubber and all leads to it made flexible.