ratings are not critical. Replacements may be
Caution: If there is danger of causing cross
made with approximate equivalent.
talk into another circuit, do not put more signal
onto the line than necessary. The LINE binding
post output, RADIO XMTR jack output, or the
transformers are of the hermetically sealed type.
1-volt output of the UC coupling coil will not give
These fit into the space provided for the original
an excessive signal. Never put more than a
units.
0-dbm signal into a line that feeds a carrier system
(1) Transformers T1 and T14 are not criti-
unless there is loss in the line between the fac-
cal and may be replaced by any one of
simile transceiver and the carrier equipment.
several types and makes of driver trans-
For example, if there is a 10-dbm loss in the line
formed stocked by depots. The first
between the transceiver and the carrier equipment,
choice is a transformer designed as a
a +10-dbm output at the transceiver will not
driver transformer for a pair of 6V6
overload the carrier equipment.
tubes or a single 6N7.
Note. In transmitting to a nearby receiving station over
(2) Transformer T5 may be replaced by a
a line having very little loss, the transmitting operator can
plate-to-line transformer of the ouncer
reduce the signal by readjusting tbe GAIN control to give
type.
a low meter reading (for example-10 db for maximum
signal) after the CONTRAST adjustments have been
(3) Transformers T12 and T13 may be
made.
replaced by similar chokes having a
current rating of about 250 ma. In an
emergency, T12 may be eliminated if the
Allowances
line voltage does not exceed 115 volts.
a. Normally, the transceiver must be capable
of producing a +2db meter reading with a line
signal input of .0035 volt. Under fixed conditions,
a. The specified requirements for contrast call
where it is known that the available signal is
for a 20-db difference between black and white.
considerably more than .0035 volt, the equipment
In an emergency, a range as low as 4 db will still
may be put into service if it does not meet this
permit the receiving station to record intelligible
sensitivity requirement.
photographic copy. For direct recording, a range
b. If the phasing system does not operate over
of 10 db is considered minimum. The transmitted
the normal GAIN control range, the receiving
copy must have extreme range between black and
operator can obtain satisfactory operation by
white so that the transmitted signal will have the
readjusting the GAIN control during the phasing
maximum possible range. If the recording is to be
operation. For recording, the GAIN control is
made on film, the receiving operator can assist
reset to its normal position. If it is essential that
by setting his equipment for reception of minimum
equipment be used when the phasing system is
signal 1 or 2 db above the normal setting. Film
inoperative, it is usually possible to obtain intel-
should be developed in a D-72 developer instead
ligible copy by recording on direct recording paper,
of a DK-60A. A high-contrast printing paper
cutting the paper at the proper point, and fitting
such as Azo No. 5 should be used.
the picture together. If the recording must be
b. Under most operating conditions, the fac-
made on film, fasten the film onto the drum with
simile transceiver will deliver a signal strong
transparent Scotch tape. Remove the tape before
enough to feed a wire line or radio set, even though
developing the film. With skill and practice the
the signal level at the transceiver output is con-
drum can be hand-phased. To do this, hold the
siderably lees than the rated minimum. For
drum by hand (with motor running) with the paper
example, if the line is connected to the LINE
overlap or film clamp directly in front of the lens
binding posts, and it is found that the output level
system. Watch or listen for the phasing pulse
is only one-half or one-fourth of the specified level,
and release the drum at the instant the pulse is
the receiving operator will, in most cases, be able
received.
to make up for the difference by adjusting the
c. If the recorder lamp becomes weak and a
GAIN control of the receiving transceiver. If he
replacement lamp is not available, satisfactory
is unable to do so, the UC coupling coil may be
results may be obtained by using a faster recording
plugged into the LINE JACK and the line
film or paper. Be careful to avoid fogging the
connected to the 6-volt output of the feed coil.
film. A paper which will give the effect of a signal
