Wednesday, April 22, 2009

Progress on NE602 based direct conversion receiver

So today I stayed home due to brain pain, it had been building up for the last few days. Also I had difficulty with my balance. To the point that walking involved bumping into everything. Lots of water and pain killers helped a little, breakfast and coffee later helped a little too. However the head ache didn't wear off until late into the afternoon with more sleep. So I spent some of the day sitting down, tidying the shed.

The cool thing about that was I found a couple of little paper bags with parts that I had bought months back and promptly filed for safe keeping in boxes! Anyhow, that list of parts contained an SA602, 3.579MHz crystals, a variable poly-cap, a large breadboard and some zeners.

This was all the missing parts for the NE602 based direct conversion receiver I've been wanting to build. So late this afternoon I sorted out all the other parts, put them in a box and setup on the kitchen table to assemble. My soldering iron and other tools are currently at a friends, so I pretty much had to assemble everything up on the breadboard.

Made dinner, a tasty curry with shallot pancakes. Then assembled it as per the circuit from W1AW. I am not sure where I first found it, google has a few references to it about. There are also a few variations on the NE602 direct conversion receiver, like the MRX-40_Mini_Receiver and another that I like using LC tank circuits for both the RF input filter and the oscillator side.

I fired it up but heard absolutely nothing. Much comparing with the diagram led to adding the vcc and ground rail for the LM386, after which I could hear familiar hash with the speaker held very close to my ear. I dug out the Pixie2 hoping to create some kind of signal. However the oscillator from the Pixie2 did not create the expected signal or inteference on the DC receiver. So this needs looking at another day when I can focus for more than ten minutes at a time. Hopefully this coming weekend wont involve any more headaches.



Terry said...

Hi Kim,
I have similar mess of components here sans breadboard but with a couple of eclipse mint tins that I've been meaning to build an 80m with myself. Now that I've finished moving house I'll hopefully find the time. My soldering iron is on the bench next to me, that's a good start.

There are a good many designs out there. I haven't settled on one yet. Maybe we can share?

Keen to hear how you go.


Kim said...

Hi Terry,

The circuit that I have built from is here; w1aw-receiver.jpg.

I am not sure of the origin of it, nor have much in the way of notes for it. Would be good to add more info on the receiver to the blog.

I have substitued a 5.6v zener instead of the 6v zener as per the diagram.


Terry said...

Cool, I think that one is from here:

I've had a google watch running for some time now searching for NE602 based receiver designs. They're all pretty much variations on a theme.

Have you had a chance to get it working yet?

Terry, VK2KTJ.