What Radio Readers Want to Know 



Announcement 



Beginning with this issue, tlie Editors are extending the scope of the Questions and Answers 

 Department so as to include a Radio Headers' Service Bureau. Answers to any questions you wish 

 to ash us will be sent by mail directly to you. Queries of general interest, with their answers, will be 

 published monthly in these pages. 



This new service it furnished free to our readers. The questions will be answered by authorities 

 in the branches concerned. Your inquiries may be on any topic related to wireless telegraphy or 

 telephony. 



The Editors suggest, however, that queries as to the wave-lengths of aerials and the working 

 distance ranges of various senders and receivers be uriihhcld. These subjects have been explained 

 so often that almost any desired informal'ion as to them may be found by reading over the earlier issues 

 of the magazine. 



What books to read, hoir to build apparatus, hou' to adjust it, and where to buy it, arc only a few of 

 the things we can tell you. If we can help you, write to ws/ 



A Simple Wireless Telephone 



L. N. P., WaynesviUe, O., writes: 



Q. I. Please state where I can obtain direc- 

 tions to make a simple wireless telephone set 

 that will transmit to a distance of one or two 

 miles. I desire an apparatus that does not in- 

 clude an arc gap or other expensive apparatus. 

 Please give instructions for the construction of 

 a simple set. 



A. I. You are advised to purchase a copy 

 of "Simple Wireless Telephones and How to 

 Make Them," on sale by the Book Department 

 of this magazine. The price is 25c per copy. 



A very simple wireless telephone set for 

 amateur purposes may be constructed in the 

 following manner: If you are already in pos- 

 session of a wireless telegraph transmitting set, 

 you can take the high potential transformer and 

 connect it directly to the terminals or the spark 

 gap, the latter in turn being connected in scries 

 with the antenna system. A microphone trans- 

 mitter is connected in series with the earth lead 

 for variation of the antenna current in accordance 

 with the vibrations of the human voice. Due to 

 the small capacity of the antenna the spark as- 

 sumes the nature of an arc, and oscillations of an 

 exceedingly high spark frequency flow in the 

 antenna circuit. In fact they are of sufficient fre- 

 quency to permit the transmission of the human 

 voice. You should have no difficulty in covering 

 a distance of one or two miles with this apparatus. 



Receiving Long Waves 

 M. M., Danville, Pa., inquires: 



Q. I. What is the wave length of my aerial 

 which is 140 feet in length, 35 feet in height, con- 

 sisting of two copper wires on four foot spreaders. 

 The lead-in wires are 25 feet in length. 



A. I. The fundamental wave length is ap- 

 pro.\imately 3IQ meters. 



Q. 2. Please give the size and dimensions of a 

 long wave length loose coupler to be used with 

 this aerial. 



A. 2. The longest wave length used by any 

 spark station is that of the Marconi Company 

 at Glace Bay, which employs a frequency wave 

 length of 8,125 meters. In the November, 1915, 

 issue and the April, 1916, issue of this magazine, 

 there are described the complete circuits for an 

 oscillating audion detector which will permit 

 loud response from stations using damped and 

 undamped oscillations, and you would secure 

 better results by constructing apparatus of this 

 type rather than a simple inductively coupled 

 receiving tuner. However for crystalline detectors 

 the tuner may have the following dimensions: 

 The secondary winding 6" in diameter, 12" in 

 length, wound with No. 30 S. S. C. wire. It is 

 intended to be shunted by a condenser of .0005 

 microfarads. The corresponding primary wind- 

 ing is 7" in diameter, 12" in length, wound 

 closely with No. 24 S. S. C. wire. The loading 

 coil for the antenna circuit is 14" in length, 7" 

 in diameter, wound with No. 22 S. S. C. wire. 



Sending on Short Wave 



W. D. H., Olathe, Kansas, writes: 



Q. I. I have an aerial 50 feet in height, 200 

 feet in length, composed of a single wire. The 

 lead-in is 35 feet in length and the ground lead 

 20 feet. Please advise how to construct a short 

 wave condenser that will reduce the sending 

 wave length to 200 meters. I use a 5 K. W. 

 high potential transformer. 



A. I. The fundamental wave length of your 

 aerial is approximately 360 meters which is 

 rather long to be operated at wave lengths of 200 

 meters. In fact a series condenser will just 

 barely reduce the natural wave length to 200 

 meters and will not allow turns to be placed in the 

 secondary winding of the oscillation transformer. 

 You are advised to reduce the length of the aerial 

 to 130 feet and then if possible attach the lead-in 

 wire to the center of the flat top portion. With 

 this connection you can send at the wave length 

 of 200 meters without a series condenser. 



453 



