NOTE ON ANTENNAE RESISTANCE. 
R. R. RAMSEY. 
Attention is called to the fact that in the modern oscillating receiving 
circuits using telephones as current indicators the “half deflection method” 
of resistance measurements will not give correct results. 
A LONG WAVE RECEIVER. 
R. R. RAMSEY. 
In wireless work all wave lengths are used from 200 meters or less, 
amatures, to 20,000 meters in transcontinental transmission. It is cus- 
tomary to limit the wave length range of reception of any receiver to a com- 
parative small band of this range. This is due to the fact that in order to 
keep the natural frequency of the coil high, which involves the necessity of 
the distributed capacity of the coil being low, it is usual to wind the coils 
with one layer of wire. Single layer coils in order to have a high induc- 
tance must be made of large dimentions of very fine wire which necessi- 
tates a very large resistance. 
In the coil which I have made I have endeavored to avoid this difficulty 
by winding the coils of relatively large wire in banks or coils one inch in 
width and five layers deep. The distributed capacity is kept to a low 
value by separating each layer by means of heavy card board. The coils 
are wound on card board tubes whose length is seven inches and whose 
diameters are, primary coil 14 em. and secondary coil 10 cm. Each coil con- 
sists of six banks one inch wide, five layers deep. Each layer containing 
twenty turns of No. 20 wire. The total number of turns per coil is 600. 
The original design of the coil called for No. 24 wire 30 turns per inch or 
about 1,000 turns in all. This would give an inductance of about .07 
henrys or a wave length of about 20,000 meters using an ordinary .001 
microfarad condensed. The smaller wire was not available so the larger 
wire was used and the lack of inductance was made up by using a variable 
condenser whose maximum capacity is .01 microfarads. 
On the secondary coil ten taps are brought out. The taps are arranged 
as follows. Tap No. 1 contains 1 turn; 2, 3 turns; 3, 7 turns; 4, 15 turns; 
5, 1 layer; 6, 2 layers; 7, 1 bank; 8, 2 banks; 9, 4 banks; 10, the entire 
secondary coil. Cut out or dead end switches are inserted between taps 
No. 6 and 7, and taps 8 and 9. The windings of the primary are arranged 
after the same plan as that in the secondary except that there are 8 taps 
instead of 10. The coils are mounted so that the secondary will slide into 
the primary coil according to the well known plan of the slide tuner. A 
feed back or regenerative coil of 425 turns of No. 30 wire is mounted so as 
to slide into the primary coil from the opposite end from the secondary coil. 
This coil is seldom used as it is found that an ‘auto feed back” connection 
on the secondary gives better results. This consists of a switch by means 
of which the filament of the tube can be connected to a point near the middle 
of the secondary coil. The diagramatic connections are shown in figure 1. 
