The Rx is from W1FB's QRP notebook and using the ubiquitous NE602 mixer/oscillator. The oscillator is very stable and I now have a good RIT type tuning capability. Measurements to follow.
The control board has a sidetone multivibrator oscillator. The sidetone is routed through the very sharp active audio filter which improves the sidetone quality. Still room for improvement.
There is an active audio filter installed (specs to follow). This filter is tunable and works well in conjunction with the RIT type tuning control to optimize signal reception.
There is still much room for improvement. However the scope must be kept limited to the original objective which is a very simple rig that can be used for NVIS operations during daylight hours on short walks to the park over the weekend.
Room for improvement:
- Still a loud pop in my ear on T/R. Need to improve the changeover.
- Build a mini-boots to take it up to 5 watts
- Install a keyer chip
- Try a passive audio filter. Have a design from ZS4SF which has a nice 900Hz bandwidth. The one I am using is a bit sharp for this application under some band conditions.
- Install all in a rugged field box.
|L-R. Audio Filter, DC Rx, Control/Sidetone, Tx-1.5W|