3.
Set BAND SELECTOR
&
MAIN TUNING to desired band and frequency.
4.
Set MODE switch at TUNE and adjust transmitter as described in steps 1 and 2 of TRANS-
MITTER TUNE-UP FOR SSB OPERA TION. The CARRIE R BALANCE setting has no eff ect in CW
operation.
5.
For manual operation, set the MODE switch at CW and the FUNCTION switch at PTT. For
the duration of a transmission with manual operation, either the microphone PTT button must be held
depressed, or an external PTT switch wired to the microphone must be set at the transmit position.
When the microphone PTT button is released, the receive condition is obtained.
6.
For break-in operation, set the MODE switch at CW and the FUNCTION switch to VOX.
Depressing the key automatically switches the VOX relay from receive to transmit, and the relay will
hold at transmit until sending is stopped. The rear apron VOX-DELA Y control may be readjusted to
set the relay "hold-in" time as the operator desires.
NOTE
In CW operation, the usual practice is to transmit "zero beat" with
the station being worked, which would seem to require the RC VR
OFFSET tuning control be set at the center line (no offset). How-
ever, a small fixed off set, determined as follows, can be used to
obtain a comfortable, consistent listening note in receive, while
retaining exactly "zero beat" transmission. First, set the RCVR
OFFSET tuning control at the center line (zero offset) and tune in a
CW station to "zero beat" with the MAIN TUNING control. Since
there is zero receiver off set, you will transmit "zero beat" with
the station.
Now
tur
n
the
RC VR
OFFSET tuning control in the
direction of the strong side
of
"zero beat" to a point where a
comfortable listening note is heard. This is the small,
f
ixed off -
set refer red to above, which should be retained thoughout
CW
operation. Now,
if
you tune in any
CW
station subsequently with
the
MAIN TUNING
control only (RC
VR
OFFSET remains as set
previously), so as to produce the same comfortable listening note,
your transmitter will then be tuned exactly "zero beat" with the
received
CW
station.
AM OPERATION
1.
The following procedure is based on the assumption that the 753 has been set up for SSB opera-
tion, and that it is now intended to operate AM.
2.
Set the FUNCTION switch at either VOX or PTT, depending on the desired type of operation.
3.
Set BAND selector and MAIN TUNING at desired band and frequency.
4.
Set MODE switch at TUNE and adjust transmitter for a meter reading of 250-300ma under ''tune''
conditions.
5.
Set MODE switch at AM, and turn MIC GAIN fully ccw (but not past detent). Now trip the
relay to the transmit condition, either as described in step 1 (PTT operation) or step 2 (VOX operation)
of MICROPHONE GAIN ADJUSTME NT.
6.
If
the CARRIE R BALANCE has been adjusted previously as described for SSB operation, it
is not necessary to readjust this control for AM operation.
If
the meter reading is below 150ma in
transmit with the MIC GAIN fully ccw, a more critical adjustment of the EXCITE R TUNE may be
necessary. This adjustment may be made with the MODE switch at AM, and the EXCITER TUNE
control adjusted for a peak meter reading (around 150ma).
7
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