k. Regulated Pow er Supply Circuit
IC t1 is the BV Regulated Power Supply Circuit. T8V that is necessary tor trans
mitting is made in 033, and R8V that is necessary (or receiving is made in Q35.
IC10, 032 and 034 control the transmission/reception. When PTT line is con
nected to the ground through the microphone terminal or CW keying output (Q46),
H level is supplied from IC10: A and it is led to CPU of front unit to detect the
transmission/reception switching.
IC10: C delays the rise of receiving in R227, C224 and D62 and controls in Q32
and Q33.
While receiving, the current is flowing from 13.8V through R230 and D75, then the
base voltage Q33 is approximately 8.7V, and the emitter output is just 8V.
While transmitting, the base voltage of Q33 is OV because Q32 is turned ON, and
R8V is not provided.
While transmitting R8V is short by D77, and it makes the charge voltage such as
electrolytic capacitor discharge momentarily not to remain R8V.
As for 035, as same as R8V the current is flowing from 13.8V through R230 and
D75, then the base voltage of Q35 is approximately 8.7V and the emitter output is
just 8V while receiving. While transmitting, the base voltage is OV because 034 is
turned ON, and T8V is not provided.
While transmitting T8V is short by D77, and it makes the charge voltage such as
electrolytic capacitor discharge momentarily not to remain T8V.
After delayed the transmitting rise time in IC10:B, the.signal is inverted in 1C18:D,
then T8V is controlled in 034.
When Pin8 IC10:A is supplied the voltage, the unit enters PTT lock mode without
changing the output of PinlO even if the PTT line is connected to the ground.
I. M ode Voltage, Function Control
(BPF/ LPF Selector)
The enable terminals of IC15 and IC16 select the signal ENX or ENY by using
IC24 and Q62.
The data from CPU (DAT2) consists of 16-bit serial data, two 8-bit shift resistors
are connected in series.
IC22 and IC23 control the band selection, ON/OFF of preamplifier, ATT, power, TX
mute function,, etc. They are operated in Low level.
IC15 controls the Mode voltage, and IC16 controls filter, AGC, Break-in, PTT lock,
and Noise blanker. The voltage o1 every mode (USB, LSB, AM, CW, CWU, CWL,
FM, TUNE) turns ON 041, Q42, 043 and Q44 to supply 8V .
m- LPF
HF supplied from PA final stage eliminates harmonics through LPF of filter unit.
Input/Output of this filter is switched by the relay, and Input/Output of unused filter
is short at the relay contact.
LPF control is used the BPF control voltage of the main unit.
Every LPF consists of Chebyshev filter, and double or more harmonics are
attenuated about 40dB or more.
LO
~ 2.5MHz
BBO, BB1
1.8MHz band
L1
2.5MHz~4.0MHz
BB2
3.5MHz band
L2
4.0MHz~7.5MHz
BB3
7MHz band
L3
7.5MHz~14.5MHz
BB4, BB5
10, 14MHz band
Содержание DX-70
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