Re: QMX+ back up clock accuracy
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Hello Mark
Fixing the accuracy of the RTC is again something on my to-do list. The RTC runs from the 32.768 kHz crystal and like any uncompensated uncalibrated crystal they can be off. I will include some kind of software calibration to use the 25 MHz TCXO or GPS (if available) to fix this.?
Right now my priority is on SSB... I've got the SSB modulation working very well (see attached 700/1900 two tone test with excellent IMD3 performance) and now moving on to tackle the microphone audio processing, filtering and compression.?
But I will get to this RTC accuracy issue in due course. It's nothing wrong with your radio. So just wait a little please...
73 Hans G0UPL
I'm using a QMX+ with the CR2032 installed and "QMX+ RTC" selected.
The problem is with the accuracy of the clock when the unit isn't switched on.
AFAICT, it's pretty accurate when the radio is operating in WSPR mode: it can run happily for several days at a time without any GPS input. However, if the unit's not powered up, the clock goes fast very quickly - I put the radio away for a few days and find the clock is several minutes fast, roughly 30 seconds a day. :-(
The 25MHz reference oscillator is virtually spot on: I've checked it using Hans's 20m WSPR tools (checked with both tx and rx), tweaked it a tiny bit (7Hz) and now everything's almost perfect.
Similarly, I've checked the CR2032's connections, cleaned the contacts and that seems well: the cell gives 3.15 volts measured at the PCB (healthy enough, surely?).
I find the on-screen time display helpful for logging purposes - I don't want to have to connect up the GPS or manually set it every time I leave the rig unused for a few days. What's up? How can I improve the accuracy?
73 Mark G?OIW
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