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released and the spool is free to spin. The speed of
unwinding can be readily controlled by regulating
the braking effect with the crank. A spring return on
the crank automatically resets the brake to the normal
or locked position when it is released.
Tuning the antenna by adjusting its length should
be accomplished by allowing slightly more wire than
is necessary to run from the reel and then reeling
in slowly to obtain the proper length by observing
the resonant condition. During the reeling-out
operation, care should be taken that all of the wire
is not unreeled. The speed with which the reeling
takes place would be sufficient to snap the wire if it
reached its ultimate length, causing a loss of both the
weight and wire.
When unreeling wire, never allow the crank to
snap into the locking position when the spool is
rotating rapidly. The sudden stop which would
result may break the antenna wire and place undue
stress on the reel mechanism.
The following table gives the approximate antenna
length for various frequencies as well as the approxi-
mate counter reading when 250 feet of Wire W-106
or W-106-A is wound on the spool.
ICC
1/4 Wave
3/4 Wave
Length
(Ft)
Counter
Reading
Length
(Ft)
Counter
Reading
2000
123
108
3000
82
72
4000
62
54
5000
49
44
147
130
6000
41
36
123
108
7000
35
30
105
92
8000
31
28
93
82
9000
27
24
81
,72
10000
24
22
73
64
18. OPERATING ROUTINE
The operating routine and type of transmission to
be used will be governed by tactical requirements. The
following recommendations are given, however, to
assist in routine operation of the equipments :
a.
Complete equipment operation should be
checked before the start of any mission.
b. Make certain that spare fuseholders are filled
with good fuses, and that spare tubes (if carried) are in
good condition.
c. The transmission range of the equipment on CW
is considerably greater than on VOICE. If distance,
atmospheric noise, etc., make VOICE communication
difficult, changing to TONE or CW will probably
improve communication.
d.
In case of failure of one or two Tubes VT-4-C
with no spares on hand, CW communication can be
carried on by inserting the good tubes in the m-o and
p-a sockets. CW operation can also be maintained
when the Tube VT-25 is removed, although no side
tone will be supplied in this event. Note that the radio-
frequency and audio-frequency tubes are connected in
series parallel. If one tube is removed, another filament
will go out.
19. SUMMARY COVERING NORMAL
OPERATION
Although the normal operation of this equipment is
extremely simple after the correct installation has
been made, it is well to study the proper sequence of
various equipment procedures as summarized in the
following paragraphs. It is assumed that the installa-
tion has been tested and all circuits are normal.
Do not change any switches with the key or
,microphone button depressed.
a.
To Start the Equipment:
Place the OFF-ON
switch at ON. The dynamotor unit will start and the
filaments will light. Unless the TONE and VOICE
emissions have been adjusted, start up initially on
CW and adjust for the desired type of emission as
given below. To control carrier depress the key.
b.
To Stop the Equipment:
Open the key; then
place the OFF-ON switch at OFF.
c.
To Change Frequencies:
Select the required
transmitter tuning unit and place in the radio trans-
mitter. Place the M.O. TUNING control, BAND
CHANGE SWITCH (if any) and the P.A. TUNING
control on the desired calibrated frequency as given
on the calibration chart. Place the emission switch
on CW, start up the radio transmitter and immediately
check the P.A. TUNING dial for minimum plate cur-
rent as indicated on the TOTAL PLATE CURRENT
meter. Resonate the antenna circuit and load
to a total plate current of 210 to 220 milliamperes
with the p-a dial resonated, i.e., always tuned to a
minimum plate current. Proceed to key the carrier
on CW or select the other types of emission as given
below.
d.
To Select Any Available Type of Emission:
Start up the radio transmitter and tune for CW
transmission first as given in paragraph 19c., then,
open the key and place the TONE-CW-VOICE
switch on VOICE. Remove the tube shield and adjust
the MOD. BIAS control after key is depressed,
until the total plate current reads 20 to 35 milli-
amperes above the CW value. Proceed to control
carrier by microphone button and modulate by voice,
adjust the side-tone signal to the desired level by
means of the SIDE-TONE control located in the
tube compartment. Adjust the voice level by the
INPUT LEVEL control so the total plate current
reaches 300 to
no
milliamperes on peaks of sustained
voice.
For tone transmission the operator must always
adjust transmitter for VOICE, first. Then open the
9
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