Alinco DX-70, Руководство по обслуживанию

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the capacitance of D706 is also changed, then 9.42MHz is changed. The center
frequency of the IF shift volume is determined by VR702.
While transmitting 0715 is turned ON by T8V to eliminate the influence by SHV
and VR 701, then the frequency is decided only by VR701.
In USB CN701 Pin26 (USB) and CN701 Pin 15 (TONS) are supplied the voltage of
8V. As in UT mode TONS becomes the sink, 0735 is turned OFF and USB is
supplied 0V , then Q730 is turned ON and a terminal of R767 is connected to the
ground to decrease the voltage of D706, beside the frequency of 9.42MHz is
decreased about 300Hz less while receiving and about 100Hz less while transmit­
ting than the vaiue in USB mode.
In the same manner, in LSB mode the voltages of CN701 Pin21 (LSB) and CN701
Pin 15 (TONS) are 8V. As in LT mode TONS becom es the sink, Q735 is turned
OFF and D729 is supplied the voltage by R767. Then voltage of D706 is in­
creased. Beside the frequency of 9.42Hz is increased about 300Hz more while
receiving and about 100Hz more while transmitting than the vaiue in LSB mode.
(7) The Emission of 455kHz Carrier Signal
The above-mentioned 9.875MHz signal is input to Mixer IC712 Pin6, and 9.42MHz
signal is input to IC712 PinB. The difference frequency of 455kHz is output from
IC712 Pin3 and sent to the MAIN unit from J701 after amplified in Q723. The
Output level is approximately -5dB
(Frequency Relations depending on the Mode)
USB{TX RX)
LSB(TX RX) FM(TX)
CWU CW L AM TUNE (TX)
CWU(RX)
CWL(RX)
UT(RX)
LT(RX)
UT(TX)
LTfTX)
AM FM (RX) does not output
{” *): While receiving IF Shift Operation (+/-1.5kHz)
(*): IF Shift Operation (+/-1.5kHz)
9.8765MHz-9.42MHz (**) =
9.8735MHz - 9.42MHz ( " ) =
9.8750MHz-9.42MHz
9.8758MHz - 9.42MHz (*) =
9.8742MHz-9.42MHz O =
9.8765MHz-9.4197M Hz ( >
9.8735MHz - 9.4203MHz (') =
9.8765MHz-9.4199MHz =
9.8735MHz-9.4201MHz ■
456.5kHz (•*)
453.5kHz D
455.0kHz O
453.5kHz (*)
453.5kHz (*)
456.8kHz (■)
: 453.2kHz (*)
456.6kHz
: 453.4kHz
(8) The Second Loca! Oscillating Signal
In V C 0 2 unit, after the frequency of 71.295MHz is oscillated in 0941 and amplified
in 0949, Q944 and Q945, the signal of approximately 3dB is supplied to MAIN unit
through J702 as the second local oscillating signal.
The signal for PLL loop is supplied from Q942 to PLL unit.
The signal of 71.295MHz is fed to Mixer IC711 Pin7 and the signal of 9.42MHz is
fed to Pin3, so that the deference frequency of 61.875MHi output from Pin6 only is
picked up by Q711, L712 and L711, and fed to PLL IC707, then locked at
61.675MHz.
Therefore, by rotating the IF shift volume, 9.42MHz, and also 71.295MHz are
changed.
The frequency of 30MHz is fed to IC707 through Pin1, and it is divided to get the
following frequency as the reference frequency, and also the frequency of