TS-590SG
10
nFrom the preamplifier (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 first mixer (Q263 to Q266), and is then converted
to the first IF (11.374MHz). The first IF signal is split further
into two paths when NB1 is selected and other than NB1 is
selected. If NB1 is not selected, the first IF signal passes
through the 2-pole MCF (XF301) through path. Signals from
both paths then enters the second IF amplifier 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 first mixer (Q321 to Q324), and is then converted to
the first IF (73.095MHz). The first IF signal passes through
the 2-pole MCF (XF371), and by the trans-feedback type
NFB (negative feedback) first IF amplifier (Q391), is ampli-
fied by approximately 12dB. The amplified signal is mixed
with LO2 (62.4MHz) in the second mixer (D422, D423),
converted to the second IF (10.695MHz), and then enters
the second IF amplifier 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 re-
ception and transmission signal's frequency at the time of
transmission.
Band BPF selection classification IF switching frequency criteria IF frequency
TX IF RX IF
135kHz/475kHz 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
18MHz 14.5≤f <21.5MHz 14.5≤f <20.9MHz 73M RX-2
21MHz 20.9≤f <21.5MHz 11M RX-1
24MHz/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
The second IF signal that passed through the RX-1 or
RX-2 path is amplified by approximately 13dB in the second
IF amplifier 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 filter.
One of 5 filters is selected, depending on the frequency
and the mode (refer to table 5).
The second IF signal that passes through the IF filter en-
ters the AGC circuit which consists of the MOSFET (Q541).
The control voltage output from the DSP changes the at-
tenuation of the signal passing through. The signal is ampli-
fied by approximately 20dB at the second IF amplifier (Q521,
Q522) and passed through the ATT diode (D525). The gain
difference between the RX-1 and RX-2 paths is then com-
pensated.
IF
frequency IF filter Mode
FM AM SSB FSK CW
10.695MHz
15kHz 44
6kHz 44
2.7kHz 444
11.374MHz 2.7kHz 444
500Hz 444
Table 5 Selecting an IF filter
CIRCUIT DESCRIPTION
