Page:Popular Science Monthly Volume 89.djvu/812

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��Popular Science Montldy

��Receiving Wavelength

C. H., Farniington, Conn., inquires: Q. 1. A|)proxiinately to what wavelength can I adjust with a tuning coil 20 in. in length, 2} in. in diameter, wound with No. 30 bare wire? The re- mainder of the apparatus comprises a condenser, a galena detector and i5(K)-ohm telephones.

A. 1. With the average amateur aerial this tuning coil will permit adjustment to wavelengths inclusive of 6,000 meters, and by the addition of a condenser in shunt to the terminals of the detector circuit, the wavelength can Ix' furl her increased.

Damped Wave Reception on Oscillating Audion

J. B. E., Newark, N. J., writes:

Q. 1. Referring to the article by W. Ross McKnight in the April, 1916, issue of the Popular Science Monthly (page 613) 1 would like to know if this equipment will respond to both dampeil and undamped waves, that is, will the equipment respond to ordinary spark stations without change of circuit.

A. 1. The receiving apparatus described by Mr. McKnight is applicable to the reception of both damped and undamped oscillations, but is more sensitive with the latter. When the audion is in a state of oscillation, an impure beat-nole is produced in the reception of damped oscillations. The result is that the s|)ark note of the distant transmitting stations is distorted, the signal sound being of different character and usually lower than the normal note. The receiver described by Mr. McKnight was built expressly for the reception of long wavelengths and will not give good results on the shorter wavelengths in the vicinity of 600 to 1,000 meters.

Long Distance Stations

S. W. D., Hamilton, Ohio, inquires: Q. Please give the wavelength, type of trans- mitting apparatus, and the call letters of as many as you can of the following Transatlantic stations:

��Strength of Received Signals Where Connecting Leads Are Long

1). r. I)., I.imon, Colo., inquires:

Q. 1. Will there be any loss in the loudness or in the strength of signals when the receiving apparatus is located 20 to 25 ft. from the light- ning switch, the latter being erected on the out- side of the building, and the receiving instru- ments placed on the opposite side of the room to that at which the lead is brought in from the lightning switch?

A. 1. No; it is of course desirable to make the connecting lead as short as possible, but the loss in efficiency will not be appreciable.

Q. 2. What cfTect will it have on the strength of wireless telegraph signals if the antenna and ground wires are run parallel; that is to .say, are twisted together for a distance of from 20 to 25 feet from the lightning switch to the receiving apparatus?

A. 2. The twisted cable will have distributed capacity and will act as a condenser connected in shunt to the primary winding and consequently will occasion a loss in the strength of the signals. It would be better to separate these wires by a distance from 6 to 8 feet.

Q. 3. My receiving aerial is 60 ft. in length composed of five wires spaced three feet apart. It points east and west. The lead-in is taken oft the east end and extends to the lightning switch which is mounted on the outside of the window of the second floor. The distance from the (loint where the lead-in is taken off cast to the lightning switch is go ft. Could 1 get better results if the lead-in was taken from the center of the aerial instead of from the end?

A. 3. For general receiving purposes it had better remain as it is.

Q. 4. Will the above aerial be satisfactory to receive from the amateur stations, providing a variable condenser is used to adjust the shorter wavelengths?

A. 4. Yes, if the condenser is in scries with the antenna.

Q. 5. What is the wavelength of this aerial?

A. 5. The wavelength is close to 150 meters.

�� �Cdl

�Name Station

�L:tl rs

�Hanover, Germany

�OUI

�Nauen, Germany

�POZ

�Eiffel Tower, Paris

� �Honolulu, T. II.

�KHL

�Darien, C. Z.

�NBA

�Colon, Panama

�NAX

�Glace Bay, N. S.

�wss

�Poldhu, Knghinil

�zz

�Tui kerton, N. J.

�wc.c.

�Siosconsetl, N. J.

�wsc

�Sayville, 1.. I.

�WSI.

�New nriinswick, N. J.

�Wll

�Lake BlufT, 111.

�NAJ

��Type of Appanilus Goldschmill High Frequency Alternator Joly lligli l're(|uency Allern;ilor I)ain|)ed and Undamped Transmitters, Type

L'nknown Poulsen Arc Generator Poulsen Arc Generator Quenched Spark Transmitter Marconi Rol:iry Disk Pischargcr Marconi Rotary Pisk Discharger Goldschmill High l-"re(|uency Alternator 500 Cycle Transmitter j K.W. Joly High I'requeiicy Alternator M;irconi RoMry Disk Discharger Poulsen Arc Generator

��Wavelength (MclfTs) 7400 9400

2500 (for time signals) 1 0000

(XXX)- 1 (KXK) 300, (XX), I (XX)

7<)25 2800

7400

3(X), (lOo

c)4<«)

8(xx), I ,sooo

(XXKl

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