This is very much in a comfortable range for of the new amateur radio MF band, i.e. 11.2kHz to the lower band edge and 18.2kHz to the higher band edge.
Now, how to generate the modulator signal? Phasing style, the easiest would be to build an oscillator for the 44.8 to 72.8kHz and use two Flip-Flops to generated the 90 degrees phase shift.
- Such an oscillator could be a rather simple function generator. Other solutions could be based on micro-controllers such as PICs, PICAXE, AT-Tiny, etc. With such a controller, it would also be possible to program features like memory channels, frequency display, beacon-keyer...
- Another approach would be to build a crystal oscillator, using cheap industrial xtals, and divide it down. Some ideas could be crystals from the XMHz range divided by N (by means of a binary counter) before feeding the Flip-Flops:
- 3.000MHz / 64 = 46.88kHz resulting in 472.5kHz
- 3.072MHz / 64 = 48.0kHz resulting in 472.8kHz
- 3.2768MHz / 64 = 51.2kHz finally resulting in 473.6kHz
- 3.579545MHz / 64 = 55.93kHz resulting in 474.78kHz
- 3.6864MHz / 64 = 57.6kHz resulting in 475.2kHz
- 3.93216MHz / 64 = 61.44kHz resulting in 476.16kHz
- 4.000MHz / 64 = 62.5kHz resulting in 476.4kHz
- 4.096MHz / 64 = 64.0kHz resulting in 4768kHz
- 4.194394MhZ / 64 = 65.54kHz resulting in 477.2kHz
- 4.433619MHz / 64 = 69.28kHz resulting in 478.1kHz
As to receiving, the 11.2kHz to 18.2kHz is in the comfort zone of any 48kbps sampling sound card.
There you have it, my presently preferred solution for the new 600m amateur radio band.