Inspired by the VK3YE Beach 40, I have constructed the "Bush 40" which is a version tailored to The Australian outback. (Just kidding).
It is a direct conversion receiver and double sideband transmitter. I've replaced the VXO with a very simple, three component, VFO.
I'm joking a bit here too, it has an Arduino Nano, an Si5351 board, and a rotary encoder. On boot up it starts at 7.1MHz and you can tune up and down from there.
The mic amp, mixer, rf power stages and low pass filter are as per the Beach 40.
The receive audio stages are from the Soldersmoke High School DC receiver.
Overall, this is a minimal design and the door is open to many improvements.
As you can see, it's a gadget of great beauty. At this stage the receiver is working but is quite deaf - I'll keep working on this.
Notes for future builds:
- Use a larger baseboard so there's plenty of space for access to the boards
- Always put a reverse diode on the relay coil - I killed an Arduino Nano presumably from inductive spikes on the power line.
- Don't try to drive a mixer directly from an Si5351. (I was puzzled about why the balanced mixer was so far off balance when I switched from the VXO to Si5351, the reason is that the output RF is 0-3.3V not AC) A 0.1uF capacitor fixed this.
- Building modules on their own boards for easy debugging is the way to go. Also, this means the successful stages can be re-used easily.