A Radio Receiver

I have a long time interest in amateur radio. This got me noodling around the 'net and I found the most interesting circuit. A SSB receiver. And the most interesting thing about the circuit is the frequency control device. The CS2000. It generates a frequency from 6 to 75MHz with just a frequency input and a digital word. Mouser has them in stock for $8.93 each in lots of one. Not a bad price for such a wide ranging frequency source.

There are of course other ways of doing things. this guy likes the AD9854. It looks good. And costs over $50 for one. A little out of my price range this week.

Naturally there were some circuit modifications to be made. Like directly driving 5 volt logic from a 3.3 volt logic source. It works - usually - but is not guaranteed. In those places (where necessary - some 5V logic is designed to respond to TTL levels. A relic from another era. But very useful in this one.) I added a TTL level compliant buffer. S0 .8V for a logic low and 2.4V for a logic high are guaranteed.

Also the detector circuit requires matched capacitors. Four for the detectors and eight for the phase shift (all pass) filters. So I have designed a capacitor matcher. With it you can read out a .1 uF capacitor to parts per ten million - or better. The accuracy is much less. But for matching lots of resolution is good. It also gives an interesting view of the world. The changes that can be detected when bodies move.

Design of the all pass filter was simple using the (free) design software found here. You need to install it on your computer. I have installed it on mine.

I'm working on schematics, parts lists, and board layouts for all of this. I will post them here. When they are done. About a week or two.

Engineering is the art of making what you want from what you can get at a profit.