# decreasing wave frequency with sbl-1 mixer

#### jalil92

##### New Member
I used sbl-1 mixer for decreasing signal frequency from 3.174 MHz to 10 kHz. The generated signal has high noise level. The butterworth and sallen-key filter was used to eliminate noise, nevertheless there is the noise. There is also the possibility of sending images of the circuit. How can i eliminate the noise?
Thank you

#### ronsimpson

##### Well-Known Member
?? RF input 3174khz, Oscillator = 3164khz, IF = 10khz ??

#### unclejed613

##### Well-Known Member
your output will have sum AND difference frequencies in it, so, assuming you used 3184khz as the local oscillator, you will have equal amounts of 10khz (the difference) and 6358khz (the sum). so the next part of this answer is the fact that a SBL-1 uses diodes as a kind of commutating switch. this will also generate some sharp transitions in the waveform. the local oscillator signal level needs to be above a certain threshold to make sure the diodes in the mixer go into full conduction

#### jalil92

##### New Member
?? RF input 3174khz, Oscillator = 3164khz, IF = 10khz ??
the schematic is in the attachment file

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#### jalil92

##### New Member
your output will have sum AND difference frequencies in it, so, assuming you used 3184khz as the local oscillator, you will have equal amounts of 10khz (the difference) and 6358khz (the sum). so the next part of this answer is the fact that a SBL-1 uses diodes as a kind of commutating switch. this will also generate some sharp transitions in the waveform. the local oscillator signal level needs to be above a certain threshold to make sure the diodes in the mixer go into full conduction
The function generator was used as an local oscillator. Its voltage (peak to peak) is 5 V and Its current is probably 20 mA .