Kenwood TS-590S, Service Manual

Page: 10 / 162

TS-590S
10
■
From the preamplifi er (Q236) to the second IF
frequency (10.695MHz/11.374MHz)
The signal from the preamplifier (Q236) output to the
second IF amplifier 1 (Q451) is spread into 2 paths: RX-1
and RX-2, depending on the frequency band (refer to table
4). The RX-1 path is selected when the “L” signal is added
to Q273, and the RX-2 path is selected if the “H” signal is
added.
The RX-1 path signal passes through the LPF for IF trap,
is integrated with LO1 (12.495 to 32.195MHz) in the quad-
balance fi rst mixer (Q263 to Q266), and is then converted to
the fi rst IF (11.374MHz). The fi rst IF signal passes through
the 2-pole MCF (XF301) and enters the second IF amplifi er
1 (Q451).
The RX-2 path signal passes through the LPF for IF trap,
is integrated with LO1 (73.120 to 133.095MHz) in the quad-
balance fi rst mixer (Q321 to Q324), and is then converted to
the fi rst IF (73.095MHz). The fi rst IF signal passes through
the 2-pole MCF (XF371), and by the trans-feedback type
NFB (negative feedback) fi rst IF amplifi er (Q391), is ampli-
fi ed by approximately 12dB. The amplifi ed signal is mixed
with LO2 (62.4MHz) in the second mixer (D422, D423), con-
verted to the second IF (10.695MHz), and then enters the
second IF amplifi er 1 (Q451). The second mixer is a passive
type that uses a diode, and is a bilateral circuit that converts
both receive signal's frequency at the time of reception and
transmission signal's frequency at the time of transmission.
The second IF signal that passed through the RX-1 or
RX-2 path is amplifi ed by approximately 13dB in the second
Band BPF selection classifi cation IF switching frequency criteria
IF frequency
TX IF RX IF
135kHz f
<
522kHz f
<
522kHz
73M
73M RX-2
BC 0.522
≤
f
<
1.705MHz 0.522
≤
f
<
1.705MHz 73M RX-2
1.8MHz 1.705
≤
f
<
2.50MHz
1.705
≤
f
<
2.10MHz 11M RX-1
2.10
≤
f
<
3.40MHz 73M RX-2
3.5MHz 2.50
≤
f
<
4.10MHz
3.40
≤
f
<
4.10MHz 11M RX-1
5MHz 4.10
≤
f
<
6.90MHz 4.10
≤
f
<
6.90MHz 73M RX-2
7MHz 6.90
≤
f
<
7.50MHz 6.90
≤
f
<
7.50MHz 11M RX-1
10MHz
7.50
≤
f
<
10.5MHz 7.50
≤
f
<
10.5MHz 73M RX-2
10.5
≤
f
<
13.9MHz 10.5
≤
f
<
13.9MHz 73M RX-2
14MHz
13.9
≤
f
<
14.5MHz 13.9
≤
f
<
14.5MHz 11M RX-1
14.5
≤
f
<
21.5MHz
14.5
≤
f
<
20.9MHz 73M RX-2
18MHz
21MHz 20.9
≤
f
<
21.5MHz 11M RX-1
28MHz 21.5
≤
f
<
30.0MHz 21.5
≤
f
<
30.0MHz 73M RX-2
50MHz (TX) 49.0
≤
f
<
54.0MHz 49.0
≤
f
<
54.0MHz - -
50MHz (RX) 30.0
≤
f
<
60.0MHz 30.0
≤
f
<
60.0MHz - 73M RX-2
Table 4 Criteria for selecting the RX-1 or RX-2 path
IF amplifi er 1 (Q451), and is then divided into 2 paths: the
NB (noise blanker) circuit and the blanking circuit (D461 to
D464). Blanking is carried out by D461 to D464.
Then, the second IF signal passes through the IF fi lter.
One of 5 fi lters is selected, depending on the frequency and
the mode (refer to table 5).
The second IF signal that passed through the IF filter
enters the AGC circuit (diode ATT circuit: D522 to D524).
The AGC voltage output from the DSP is added to D522
to D524, the change of AGC voltage changes the current
on the pin diode and controls the attenuation of the signal
passing through. And, the second IF amplifi er 2 (Q541) and
the second IF amplifi er 3 (Q521, Q522) altogether amplify
by the total of approximately 32dB, and the signal passes
through the simplified diode ATT circuit (D525). The volt-
age determined in the adjustment mode is added to D525,
and adjusts the difference of the total gains of the RX-1 and
RX-2 paths.
IF
frequency
IF fi lter
Mode
FM AM SSB FSK CW
10.695MHz
15kHz
✔ ✔
6kHz
✔ ✔
2.7kHz ✔ ✔ ✔
11.374MHz
2.7kHz
✔ ✔ ✔
500Hz
✔ ✔ ✔
Table 5 Selecting an IF fi lter
CIRCUIT DESCRIPTION