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RADIO BROADCAST
NOVEMBER, 1926
fig. 5
The well known Hartley circuit. The key may be inserted in the minus B lead. In Mr. Mann's set, the inductance consisted of ten turns of No. 14 gauge antenna wire. The condensers must be well insulated since they have to stand the full d. c. voltage applied to the plate
20
18
16
co 14 2
a. 12 10
8
*
IA IP
/ \ / \
-t 2
/
\
-6 —
/ / /
»
/
/
% \
\V
-5 —
f t t
r
/
\\
t *
-4 —
7"
1
1
1
1
1
3 —
1 t
2
— 1—
55 50 45
40 <A
35*?
30 25 20
2 3 4 5 6
TURNS IN GRID CIRCUIT
FIG. 8
The effect upon antenna and plate currents of varying the filament tap. The greatest ratio of antenna current to plate current is secured when there are five turns in the grid circuit
30 40 50 60 70 80 90 100 CLOSED CIRCUIT CONDENSER
FIG. 6
The closed circuit of the Hartley transmitter at 2 gy tunes from 1 5,000 to 5260 kc. (20 to 57 meters), as this chart shows
Radio Broadcast Photograph FIG. 4
A side view of the small 2 gy transmitter. It is operated entirely from dry batteries
15 20
30 35 40 45 50 ANTENNA CONDENSER
* ■ —
"i A
*
/
/
—J
1
i
f
r
/
-X
IP -10.5
/
10.0
V
-9.5
*
1/
55
50
45 !
FIG. 9
With the closed circuit adjusted for maximum efficiency, the antenna tunes according to this curve. This is a typical resonance curve. The wavelength is approximately 38.8 meters
FIG. 7 As the antenna series condenser is varied, the transmitter tunes as this chart shows. It also gives an idea of how the particular antenna tunes to different wavelengths. On the longer waves, the antenna is apparently of lower resistance since more current can be fed into it
35 30
3 25
£•20
15
10
I'''
V
300 250 200 150_
t—
100 <
< ^
50
150
PLATE V0LTS
250
50
30
10 20
ANTENNA CONDENSER
FIG. IO
The relation between power input and antenna current is shown here. The greater the plate voltage the greater the antenna current and naturally the plate current increases toe