Standalone SI570 controlled SDR

[9h1fq]

Hi all.

I have built various AVR and PIC controlled  SI570 kits  for a standalone Softrock RXTX, but they all have a tuning noise, as you tune. Apparently its in the software, but so far, no one has came up with a solution. When controlled by a PC, the SI570 is as smooth as any old fashioned LC VFO. Anyone has any news please

Paul

[KI6J]

I have a Weber Dual Band radio which had an annoying, very low level hum in the audio, and the hum was pulse-modulated by the turning of the tuning encoder.  I have been playing with re-writing the firmware to modify the radio for 5 band operation; it uses an ATMega48 and a AD9834. 

As I was testing the DDS driver part of my new firmware, without any of the display multiplexing signals being generated, I noticed that there was no more hum in the receive audio.

If you have the ability to "comment out" the display signal generation and any other serial communication signals from the controller firmware,  I would give it a try.