DS05- 7B (seven tube) superheterodyne radio debugging

Last Update Time: 2019-01-14 17:26:09



l  Principle

(1)The radio modulation is corrected by adjusting the transmission circuit of the radio, the frequency of the local oscillation and the medium frequency frequency of the medium circuit, so as to achieve a good frequency tracking characteristic in the frequency range received. The so-called tracking is in the frequency range received, when receiving the radio frequency radio, the oscillating frequency and the frequency to receive through the frequency mixing circuit to output the standard frequency frequency signal, in the extra heterodyne AM (amplitude modulation) band, the intermediate frequency frequency is 465kHz.

 

(2)The frequency range of the medium wave is 535~1605kHz, and the frequency range of the oscillation is 1000- 2070KHZ. The radio is a dual variable capacitance to change the frequency of the transmission and the frequency of the local oscillation. In an ideal state, the frequency and the frequency of the transmission loop are in the frequency range of the whole band. The difference in rate should be within 45kHz

 

l  DS05- 7B (seven tube) superheterodyne radio problems in the actual assembly adjustment.

1. Frequency conversion part

To judge whether the frequency conversion level is up to vibration, using the MF47 type multimeter DC 2.5V gear, the positive pen to connect the V1 emitter, the negative pen to ground, and then touch the dual oscillating connection (that is, the connection T2 end), the multimeter pointer should swing to the left, indicating that the circuit work is normal, otherwise the circuit has trouble. The working frequency of frequency conversion stage should not be too large, otherwise the noise will be large. The pins of the red oscillating coil housing and the two variable capacitance pins should be bent and welded to prevent the tuning chuck.

2. Intermediate frequency part

If the position of the middle frequency transformer is incorrect, the sensitivity and selectivity will be reduced, sometimes.

 


This article is from Allicdata Electronics.