Vojtech's Omnia Basic CW Firmware 0.4

This is Vojtech's experimental firmware for the Omnia Basic SDR transceiver. This firmware integrates a standalone CW keyer with a smooth side tone and a standalone CW carrier generator, so there is virtually no latency between the keyer and the first dit sent, and the PC host application does not need to be aware that the SDR transmits. For the details, please read the release notes for the version 0.2 and version 0.3

This release adds amplifier sequencing control to avoid relay hot switching, wear and audio noise: The signal may be delayed from the side tone by 0 to 15ms, and a AMP hold off time may be set. Additionally it is now possible to enable / disable amplifier from the HDSDR UI.

Vojtech's Omnia Basic CW Firmware 0.3 Expermental Release

This is Vojtech's experimental firmware for the Omnia Basic SDR transceiver. This firmware integrates a standalone CW keyer with a smooth side tone and a standalone CW carrier generator, so there is virtually no latency between the keyer and the first dit sent, and the PC host application does not need to be aware that the SDR transmits. For the details, please read the release notes for the version 0.2

This release adds an application interface for the https://github.com/bubnikv/ExtIO_Omnia to control the output power and IQ phase / balance of the transmitted signal.

Vojtech's Omnia Basic CW Firmware 0.2 Expermental Release

This is Vojtech's experimental firmware for the Omnia Basic SDR transceiver. This firmware integrates a standalone CW keyer with a smooth side tone and a standalone CW carrier generator, so there is virtually no latency between the keyer and the first dit sent, and the PC host application does not need to be aware that the SDR transmits.

When transmitting, the firmware produces a 1kHz quadrature tone with smooth click-free 4ms rise and fall envelope. A low frequency IQ audio tone is beneficial, as the possible mirror image falls close to the main signal, and the D/A converter produces a cleaner output signal for low audio frequencies. To make the tuning around easy, the firmware has been accompanied with a HDSDR plugin, which sends the center CW frequency to the Omnia every time the user clicks on the waterfall, and the firmware retunes the Si570 VFO on key down accordingly.

To install the HDSDR plugin, please follow
https://github.com/bubnikv/ExtIO_Omnia/releases/tag/v0.2

The side tone is generated on pin P1[4]. The pin cannot drive a speaker directly, you will need to use some kind of amplifier. Amplified PC speakers will work as well as an ubiquitous LM386 integrated amplifier. A circuit diagram follows. Please note that the keyer buttons are currently not used by the firmware. As of now, the sidetone frequency is fixed to 1200Hz. It has been chosen to be a 2nd harmonic of a 600Hz side tone, and the freuquency is is high enough to drive a tiny electromagnetic transducer loud enough.

https://github.com/bubnikv/omniasdrbasicfirmware/blob/master/kicad/omnia-addon-schematic.png

What's missing?

There is currently no way of adjusting the IQ transmit balance. As of now, the not fully suppressed unwanted image is to be found at -2kHz from the main signal. Some kind of IQ balance adjustment is planned.