Thus, here come the crystal combinations (what did you think???):
- 6.5536 + 7.000 = 13.5536
- 6.5536 + 7.005 = 13.5586
- 6.5536 + 7.015 = 13.5686
Spot on, I would say. For a DC-RX, I would consider to slightly pull one of the crystal and mix. This would possibly enable to observe the full 22m range.
The superhet solution would probably point towards a 6.5536MHz IF, since those crystal are certainly cheaper.
The nice thing on this combi is, there is a ceramic resonator available (7.02MHz), which can easily be pulled in an oscillator circuit.
Source for the crystals and the resonator: box73.de