The Project

I've got a nice old RF Signal Generator in my workshop - its a Logimetrics 921A which is a lovely bit of kit but it's huge, heavy and becoming increasingly unreliable. So I decided to have a go at building my own. 


In this blog I'll try and document what I've done. Firstly, in the hope that it is of use to others, secondly in the hope that I won't forget what I've done.


I looked at all manner of different options for making a signal generator, oscillator configurations, temperature controlled ovens and it all seemed very complicated! I've built a few variable oscillators for radio sets and other things but never made anything super stable. Then I stumbled across the idea of direct digital synthesis. Here a sine wave is synthesised by a chip dividing down a stable crystal clock and looking up values and sending them out to a digital to analogue converter. The results are a very stable oscillator, with nice low harmonics and a very wide tuning range.


So now all I had to do was pick a DDS platform and away I'd go! I had a look round and found the AmQRP DDS-60. This little board belts out a nice fat 4V p-p signal into a 50 ohm load and is tuneable from DC to 60MHz (though the buffers don't output much below 10kHz). Also it is tuneable in minute 0.042Hz steps! 


So I sent off for the DDS-60 kit and waited!