JPS6350893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving device that changes the oscillation frequency of a BFO and the center frequency of a peak filter in the same direction and by the same amount.

[Conventional technology]

In conventional CW receivers, IF signals and
Beat detection was performed using the oscillation output from the BFO, and the output was passed through a peak filter to improve selectivity, and after amplification, it was adjusted for listening through speakers, etc.

[Problem that the invention seeks to solve]

However, in the conventional technology described above, the peak filter has extremely sharp attenuation characteristics, so when the BFO is changed, the received beat sound becomes
There was a possibility that it would not be able to pass through the peak filter. The present invention has been made for the purpose of improving these drawbacks of conventionally known receiving devices.

[Means for solving problems]

The present invention is a receiving device in which the center frequency of a peak filter can be externally varied, and is controlled by a voltage correction circuit so that the center of the frequency band generated by variable BFO oscillation is always the center of the peak filter. This solution solves the conventional problems of .

〔Example〕

The receiving device of the present invention will be explained based on the drawings. An IF signal and the output of a BFO oscillation circuit 2 are input to a mixer circuit 1 to generate a bead detection signal. This BFO oscillation circuit 2 is a circuit that varies the frequency using a voltage variable capacitance element. The bead detection signal passes through the peak filter 3, but since the attenuation characteristic of the peak filter 3 is very sharp as mentioned above, when the capacitance of the voltage variable capacitance element of the oscillation frequency element of BFO2 is changed by voltage change, the mixer 1 The beat detection signal from the peak filter 3 cannot pass through the peak filter 3.

Therefore, it is necessary to set the center frequency of the peak filter 3 in synchronization with the frequency change of the BFO 2, and the center frequency is varied by changing the internal resistance using a DC voltage using a voltage variable capacitance element. However, even in this case, strictly speaking, it is difficult to synchronize the frequency change of the BFO 2 and the center frequency of the peak filter 3, and the beat detection signal may not pass through.
Therefore, the voltage applied to the voltage variable capacitance element is BFO
It is necessary to apply a voltage that has been corrected for processing without applying a common voltage to BFO 2 and peak filter 3. Potentiometer 6 is connected between the DC voltage on the (+) side and the ground, and the output voltage is Apply it to the voltage variable capacitance element of BFO2 through the correction circuit 4 of No.1,
The output voltage of the potentiometer 6 is
The voltage is applied to the voltage variable capacitance element of the peak filter 3 through the correction circuit 5 .

BFO2 is an oscillation circuit using a voltage variable capacitance element such as EFT, and peak filter 3
Alternatively, the same EFT voltage variable capacitance element may be used to vary the center frequency by varying the internal resistance with a DC voltage.

Note that the first and second correction circuits that correct the DC voltage varied by the potentiometer 6 may be controlled using values stored in advance in a computer or the like, or when the correction value is a simple change. may be corrected by only one of the first and second correction circuits. Therefore, the detection output by the variable frequency of the BFO 2 and the center frequency of the peak filter 3 are synchronized by the change in the potentiometer 6 and the correction value of an appropriate correction circuit.

〔Effect of the invention〕

As detailed above, in the CW receiver of the present invention, even if a peak filter with extremely sharp attenuation characteristics is used in the AF circuit, the center frequency of the peak filter will not be detuned when the BFO is varied. Since it can be used, it has great practical effects.

[Brief explanation of the drawing]

The figure shows a receiving device according to an embodiment of the present invention in which the oscillation frequency of the BFO and the center frequency of the peak filter are synchronized by changing the DC voltage applied to the BFO and the peak filter, thereby making the isodirectional equivalence variable. It is a figure showing an aspect. 1... Mixer, 2... BFO, 3... Peak filter, 4, 5... Correction circuit, 6... Potentiometer.

Claims (1)

[Claims] 1 AF with a detector and peak filter that detects the beat of the IF signal using the oscillation output from the BFO
In the circuit, BFO with voltage variable capacitance element
means for applying an output voltage controlled by a potentiometer to the voltage variable capacitance element of the BFO through a first correction circuit;
A part of the control output of the potentiometer is
2. A CW receiving device characterized by comprising: means for applying a voltage to a voltage variable capacitance element for varying the center frequency of a peak filter through a correction circuit to change the center frequency in a synchronized manner by an equal amount in an equal direction.