TheMartian
Junior Member level 3
Hey, I have replaced the VFO (6MHz to 6.5MHz range) with DDS (AD 9834 chip) in the superhet 3.5MHz-4MHz receiver.
It works and I am able to tune into strong signals, receive the SSB, etc, but there is always high pitch noise, which pitch tone changes only when I tune. I mean, every frequency output from DDS has slightly different high pitch noise, sometimes louder, sometimes quieter...
My DDS output has low pass filter connected (rejects everything above 10MHz)
DDS is connected to first mixer, which outputs 10MHz IF, then goes trough the crystal ladder filter, and then to second mixer which outputs audio signal.
What might be the cause of this high pitch noise? Is it caused by high or low frequency interference?
It works and I am able to tune into strong signals, receive the SSB, etc, but there is always high pitch noise, which pitch tone changes only when I tune. I mean, every frequency output from DDS has slightly different high pitch noise, sometimes louder, sometimes quieter...
My DDS output has low pass filter connected (rejects everything above 10MHz)
DDS is connected to first mixer, which outputs 10MHz IF, then goes trough the crystal ladder filter, and then to second mixer which outputs audio signal.
What might be the cause of this high pitch noise? Is it caused by high or low frequency interference?