The current "challenge" project for the Home Brew Group is to build a direct conversion receiver for the 80m WIA sunday broadcast on 3595KHz SSB.
While this is pretty trivial for many in the group it's appropriate for my level of construction and happily I have a working receiver which I'm listening to as I type.
The box is a CDROM drive box with the guts ripped out and a simple aluminium front panel added. This is an idea I first saw from Stephen VK2BLQ. At Wyong I picked up a few drives just for this purpose.
The circuit is the classic NE602 / LM386 design from early on in EMRFD. Construction is "ugly" but it seems quite stable.
Ergonomics leaves something to be desired, I think I'll move the antenna socket to the back, and the tuning needs to be less sensitive. (I have a lovely reduction drive but I'll save it for something more substantial).
Here it is achieving its objective, listening to the Sunday broadcast.
Stability is surprisingly good.
As requested by John, here is the circuit from Experimental Methods in RF Design. The only change for 80m was to use 40 turns of #33 wire on the two toroids.
Since the video I have made the tuning less sensitive by adding series capacitance but it probably still needs a fine tuning knob. Also, I'd love to have another go with smaller components and try to get this down to a more compact size suitable for travel.
Here's how it sounds listening to the latest broadcast on a speaker this time.
I've completed installing the radio in its case and fitted a fine tuning knob and power switch. Here's how it came out.
Old CD ROM drives make an excellent home brew box.
The perfect size for many smaller projects, that is ones too big to fit in an Altoids tin.
The battery clip is a little dodgy.
All boxed up, with a new fine tuning knob, listening to the broadcast.
I'm done with this project now.