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7.
8.6MHz trap
(1) Purpose:
To improve IF rejection by adjusting 8.6MHz trap.
(2) Measuring instruments:
1)
SSG
2)
AF vacuum tube voltmeter
3)
Oscilloscope
(3) Adjusting procedures:
1)
Connect
a dummy
Band SW
VFO
X44- | X44- | Adjust-
an
" |
Frequency
|0028-00/0027-00}
ment
Obtain the
1 | 35MHz|
3.750MHz]
Li | L1_ [beat about
1kHz with
the MARK
ER and
2 | 28.5 MHz | 28.800 MHz;
L5
LS
oro.
Adjust the
3 | 21.0 MHz | 21.225 MHz | L4
14
[eoreso
that maxi-
mum S
4 |14.0MHz
}14.175MHz}
L3 | L3_
[meter irr
dication
or beat
5 | 7.0MHz]
7.150MHz/
L2
L2
[note carr
be obtain-
ed.
Table 4
load
of 8 ohms,
AF
vacuum
tube
voltmeter
and oscilloscope
to
(3) Adjusting procedures:
1)
Connect the RF vacuum tube voltmeter to the
cathode
(pin 2) of RX
mixer 6CB6
(V3) in
the unit X48-0012-00 through a capacitor of
0.01uF and then adjust the VFO output to
0.8
volt by the trimmer
located
inside the
VFO
at approximately
''300'' of the VFO
calibration.
2)
Remove the capacitor of O.01yF.
3)
Obtain
a beat
at around
3.75MHz
and an
output
of 0.63
volt (S50mW/8 ohms)
at the
PHONES terminal.
4)
Adjust
T1
(orange)
on
the
IF
unit
X48-0012-00
to obtain a lower beat interfer-
ence output when compared with the output
Obtained
by
the
application
of the
signal
(3.75MHz}) of 3dB from SSG to the REC ANT
terminal.
9.
Carrier balance (Refer to Fig. 10)
(1) Purpose:
To
prevent
the signal
of carrier oscillator from
flowing
into
the
IF stage
through
a balanced
detector.
(2) Measuring instruments:
1)
SSG
2)
Oscilloscope
3) AF vacuum tube voltmeter
(3) Adjusting procedures:
1)
Tuning
must
be
taken
so
as
to assure
a
8.
the PHONES terminal.
2)
Set SSG
frequency
to 8.595MHz
and intro-
duce an input signal of 100dB
to the REC
ANT terminal.
3)
Set the band select switch to 14MHz and the
drive knob to the position of '12 o'clock"
4)
Locate
the VFO
calibration
around
''300"
and obtain a beat output and adjust 8.6MHz
trap so as to the make its output minimum.
Beat interference
(1) Purpose:
To minimize the beat interference by adjusting the
trap coil and VFO.
(2) Measuring instruments:
1)
SSG
2}
AF vacuum tube voltmeter
3)
RF vacuum tube voltmeter
4)
Oscilloscope
maximum
deflection of S meter while receiv-
ing the output (14.2MHz) of 30dB from SSG.
2)
Adjustment
must
be made to assure a mini-
mum
deflection
of S meter
by tuming alter-
natively
the
trimmer
TC2
(40pF)
on
the
generator unit and the semi-fixed resistor VR3
(7ke),
{Note]
If no measuring
instrument
is availajle, use the
built-in marker.
Carrier input
ft
§M input
VR3
YR2
TC2
"C1
Balanced Det
fa lanced Mod
(RX)
Q3
{1><)
1
Q2
YFR1
Carrier
Level Adj
Qi
Aa
!
iF output
MIC input
25
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