Kenwood TS-890S, Подробное руководство

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02 RECEPTION CIRCUIT
3
Receiver Configuration
The TS-890S is the single-band transmitter-receiver of the down-conversion method, which is refined and diverted from
the circuit configuration of the main band receiver of the top-model TS-990S. During transmission, the receiver behavior
stops. Also, the bandscope circuit shows the status of IF signals during reception and transmission.
It is important for a receiver to eliminate interfering signals through narrow filters at an earlier stage and pass desired
signals to the later circuits. In addition to the RF bandpass filter placed in the front-end block of the receiver, eliminating
the adjacent interfering signals by using the IF bandpass filters with better selection characteristics prevents distortion
from occurring in the later circuits and improves practical anti-interference characteristics. The first mixer, through which
a number of interfering signals pass, needs to have high intercept point (hereinafter referred to as IP) characteristics.
The down-conversion method where the first IF signal is 8.248 MHz is adopted. The use of a low IF signal realizes the
bandpass filters with steep attenuation characteristics, and performance sufficiently tolerant to adjacent interfering
signals is secured.
Next is the bandpass filters placed in the front-end block. The use of a low first IF signal allows reception interference
and/or spurious reception by image frequencies to easily take place, thus it is necessary to place a number of bandpass
filters with steeper attenuation characteristics. As shown in the table “Bandpass Filter Division in the Receiver”, the
bandpass filters divided into multiple paths are designed to implement the high Q value and a coil with distortion
resistance characteristics.
Table 1 Bandpass Filter Division in the Main Band Receiver
Band Filter Bandwidth
135 k 30 k to 521.999 kHz
BC 522 k to 1.704 999 MHz
1.8 M 1.705 M to 2.499 999 MHz
3.5 M 2.5 M to 4.099 999 MHz
5 M 4.1 M to 5.999 999 MHz
7 M 6.0 M to 7.499 999 MHz
10 M 7.5 M to 10.499 999 MHz
14 M 10.5 M to 14.499 999 MHz
18 M 14.5 M to 18.499 999 MHz
21 M 18.5 M to 22.499 999 MHz
24 M 22.5 M to 27.499 999 MHz
28 M 27.5 M to 34.999 999 MHz
35 M 35.0 M to 41.499 999 MHz
45 M 41.5 M to 47.999 999 MHz
50 M 48.0 M to 54.999 999 MHz
60 M 55.0 M to 59.999 999 MHz
60 M* 60.0 M to 61.999 999 MHz
65 M* 62.0 M to 68.999 999 MHz
70 M* 69.0 M to 74.799 999 MHz
*European model only