JPH0693634B2 - CW receiver - Google Patents

Description

The present invention relates to a receiver for receiving CW (unmodulated wave),
In particular, BFO (beat frequency oscillator) and AF
The present invention relates to a CW receiver that works in conjunction with a peak filter that passes an (audio frequency) signal.

[Prior Art] A conventional CW receiver has an intermediate frequency (I
F) The frequency of BFO2 applied to the detector (DET) 1 for detecting the signal and the center frequency of the peak filter 4 were adjusted by the variable resistors 3 and 5 separately.

In such a receiver, if the generation frequency of BFO2 is changed by the variable resistor 3 so that the frequency of the sound generated by the speaker 6 is changed, the audible frequency passing through the peak filter 4 is also changed. The center frequency had to be readjusted with the variable resistor 5.

In order to save such trouble, a switched capacitor filter is used for the peak filter 4 as shown in FIG.
Even if the central frequency is changed by the oscillation frequency of the clock oscillator 11 and the oscillation frequency of the clock oscillator 11 and the oscillation frequency of the BFO 10 are changed by the common variable resistor 12, different oscillators are used for the clock oscillator and the BFO. It was difficult to match the center frequency of the peak filter to the audible frequency passing through the peak filter for use.

[Problems to be Solved by the Invention] The present invention has been made in order to solve the problems in the above-described conventional technology, and it is necessary to readjust the center frequency of the peak filter by linking the frequency adjustment of the BFO and the peak filter. The purpose is to provide a CW receiver without.

[Means for Solving the Problem] The CW receiver according to the present invention is configured to detect an intermediate frequency signal of a detector and a BFO.
In a CW receiver that obtains an AF signal that is the difference frequency by adding a signal, an oscillator and a divider that divides the output of the oscillator by a predetermined dividing ratio constitute a BFO circuit and the output of the divider. Is added to the detector as a BFO signal, and a switched capacitor filter whose center frequency changes in conjunction with the clock frequency is used as a peak filter for passing the detected AF signal, and the center frequency of the switched capacitor filter and the clock frequency The signal obtained by mixing the ratio with the predetermined frequency division ratio and mixing the output signal of the oscillator with a signal having a frequency whose ratio with the intermediate frequency matches the predetermined frequency division ratio is switched. As the clock signal of the capacitor filter, the frequency of the BFO signal and the center frequency of the peak filter are interlocked.

[Operation] When the CW that is the received signal and the local oscillation output are mixed, it becomes an intermediate frequency signal of a constant frequency, and when the BFO signal is mixed with this intermediate frequency signal, it becomes an AF (audible frequency) signal that is the difference between the two frequencies. Become. The AF signal is passed through the peak filter to improve the S / N ratio, but if the BFO signal frequency is changed to change the frequency of the sound generated by the speaker, A
The frequency of the F signal also changes, and it is necessary to change the center frequency of the peak filter to match the AF signal frequency.

When a switched capacitor filter is used for the peak filter, its center frequency can be changed in proportion to the clock frequency.

Therefore, a BFO circuit is configured with an oscillator and a frequency divider that divides the output of the oscillator at a predetermined frequency division ratio, and the output of the frequency divider is added as a BFO signal to a detector to pass the detected AF signal. As the peak filter to be used, a switched capacitor filter whose center frequency changes in conjunction with the clock frequency is used, and the ratio of the center frequency of the switched capacitor filter to the clock frequency is matched with the predetermined frequency division ratio, and the oscillator The signal obtained by mixing the output signal with a signal having a frequency whose ratio to the intermediate frequency matches the predetermined frequency division ratio is used as the clock signal of the switched capacitor filter, and the frequency of the BFO signal and the center of the peak filter. If the frequencies are linked, the AF signal frequency and the center frequency of the switched capacitor filter will be automatic even if the BFO signal frequency is changed. Match each other.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention.

In the figure, 1 is a wave detector, which mixes a BFO signal with an intermediate frequency signal of 100 KHz to obtain an AF signal.

The AF signal passes through the peak filter 4 and sounds the speaker 6.

Reference numeral 20 is an oscillator that constitutes a BFO, and the oscillation frequency is adjusted by the variable resistor 21.

The oscillation frequency of the oscillator 20 is divided by the frequency divider 22 to 1/100 and the BFO
Frequency.

The output of the oscillator 20 is mixed with the signal of 10 MHz oscillated by the crystal oscillator by the mixer 23 to generate the clock signal frequency of the peak filter 4 which is a switched capacitor filter.

The center frequency of the peak filter 4 is 1/10 of the clock frequency.
It is set to be 0.

As shown in the figure, when the oscillation frequency of the oscillator 20 is 9.92 MHz, AF becomes 800 Hz, the peak filter clock frequency becomes 80 KHz, and the center frequency of the peak filter coincides with AF. (The center frequency of the peak filter is 1/100 of the clock frequency.) Adjust the variable resistor 21 to set the oscillation frequency of the oscillator 20 to 9.9MHz.
Then, AF becomes 1KHz, and the clock frequency of the peak filter 4 becomes 100KHz, so the center frequency of the peak filter automatically matches the AF. Even if the AF is changed so that the tone of the speaker is changed. , The peak filter center frequency always matches AF.

As described above, according to the CW receiver of the present invention, the BF
Since the center frequency of O and the peak filter move in conjunction with each other, only one adjustment volume is required and adjustment becomes easy.

Further, it is sufficient to provide only one frequency-variable oscillator circuit, so that the circuit can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional technique, and FIG. 3 is a block diagram showing another conventional technique. 1 ... Detector, 2 ... BFO, 3 ... Variable resistor, 4 ...
Peak filter, 5 ... Variable resistor, 6 ... Speaker,
10 …… BFO, 11 …… Clock oscillator, 12 …… Variable resistor, 20 …… Oscillation circuit, 21 …… Variable resistor, 22 …… Divider, 23 …… Mixer.

Claims (1)

[Claims] 1. A CW receiver for adding an intermediate frequency signal and a BFO signal to a detector to obtain an AF signal which is a difference frequency between the oscillator and an oscillator and a frequency divider for dividing an output of the oscillator by a predetermined dividing ratio. The BFO circuit is configured with
In addition to the detector as a signal, a switched capacitor filter whose center frequency changes in conjunction with the clock frequency is used as a peak filter for passing the detected AF signal, and the ratio of the center frequency of the switched capacitor filter to the clock frequency is A signal obtained by mixing the output signal of the oscillator with a signal having a frequency whose ratio to the intermediate frequency matches the predetermined frequency division ratio while matching the predetermined frequency division ratio is used as the switched capacitor filter. A CW receiver characterized by linking the frequency of a BFO signal and the center frequency of a peak filter as the clock signal of.