I found it quite challenging to make a user interface that does what I wanted while keeping the operation reasonably simple. It's probably the place that could do with the most improvement, perhaps with more buttons and visual clues on the display. I guess it's also an area where personal preferences vary widely. With that said, here's how it works now.
There are several modes. Button 1 cycles around the modes.
This is the default VFO mode. The display shows the frequency and step. Turn the knob to change frequency.
- Button 1 - Switch to QRSS mode.
- Button 2 - Toggle Quiet mode on and off. i.e, turn the RF output on and off. My main use of the DDS so far has been to drive a little QRP transmitter. I haven't built a receiver yet so I'm using a completely separate receiver. I switch to quiet mode on receive so I don't hear my own VFO.
- Button 3 - Cycle around the frequency steps. At power-on this defaults to 100 Hz. Button 3 will change it to 10 Hz, 1 Hz, 100 KHz, 10 KHz, 1 KHz and back to 100 Hz. It's a bit of a pain when you want to go "backwards", e.g. from 10 Hz back to 100 Hz because you need to press the button five times. A better idea might be to use some sort of two button rocker switch type device which can go forward and back.
This provides functionality for the simple CW transceiver with a direct conversion receiver as described here.
QRSS is very low power, slow CW where a dit or dot time is six seconds or more. It uses frequency shift keying with a shift of about 6 Hz. Receiving is usually done visually by feeding the audio from a receiver into a computer sound card and displaying with software such as Argo. This allows the reception of very weak signals.
Here's one of several web sites with information about QRSS. I have the DDS connected directly to an antenna running in this mode. If my oscilliscope is accurate then I'm getting about 2.6 volts peak to peak into 50 ohms at 10 MHz which is a power of about 17 mW. I've been running it near 10.140 MHz on 30m because that's where most of the grabbers are. As I write this, I've just seen my signal appear on VE1VDM's grabber in Nova Scotia.
Before trying it on this mode, you'll need to edit the software to set your own message. This is usually just your callsign and perhaps your grid square locator code.
- Button 1 - Switch to memory mode
- Button 2 - Reset sending to the begining of the message.
If you don't want this mode then edit the code in the NormalMode() function so that button 1 goes straight to memory mode.
This lets us save and retrieve frequencies. The display shows frequency and memory or "channel" number. The encoder knob selects the channel from 1 to 99.
- Button 1 - Switch to Calibrate mode.
- Button 2 - Retrieve the frequency saved in the selected channel.
- Momentarily push button 3 - Save the current VFO frequency in that channel location. It prompts with "Save ?" on the display. Pushing button 3 again saves and returns to normal mode. Pushing any other button returns to memory mode without saving.
- Hold button 3 - After five seconds the selected memory channel will be erased.
This is described on its own page.