VK2EMU's Biscuit-Tin Direct Conversion Receiver

Bill and Pete:

First Sound

The enclosure came first, then the radio. The Homebrew challenge - build something in a Christmas Biscuit tin - only one rule, no mains power.

Step one - eat the contents.

VK2WI is an Australian version of W1AW and transmits weekly new bulletins on a number of bands from 160m to 23cm. On 80m the frequency is 3595kHz, so let's build a DC receiver for that.

I used a 7190kHz crystal, divided by 2 with a 74HC74 to get 3595kHz. The rest of the radio is pretty standard - double tuned front end, NE612 mixer, followed by a TL071 and a LM386. The reduction drive on the tuning cap gives a band spread of about +/- 300Hz.

The boards are all 2 inch x 2 inch and made on a PCB mill that I was given a few years ago. 

There should be enough room in the bottom of the tin a pack of 8 C cells to make the radio truly portable. Next step is to fit an audio low pass filter.

It is a pleasure to sit on the rear porch and listen to the Sunday night broadcast on a home brewed radio, while eating the contents of another identical tin - I wonder what I will do with that one?

73  Peter VK2EMU