The radio uses an intermediate frequency of 9MHz, which is mixed with a 5.0688MHz "computer" crystal oscillator.
I see two possibilities:
- Make the 5.0688MHz crystal replaceable with a 5.000MHz crystal. This mod will get you to the 20m QRSS band at 14.000800MHz and the radio will still be usable for PSK31.
- There is no WSPR in this mod? Yes, there is, it would be all about penning down a 5.120MHz crystal to 5.0956MHz, which is quite a stretch but doable.
- Some additional frequencies in the upper digi-mode band (14.101-14.112MHz) are reachable in a similar way.
- Finally, there is a 5.200MHz crystal, which would make up to a perfect single channel SSB DXpedition transceiver. I guess one needs to look at the IF-filter response in this one.
- Change the intermediate frequency to 10MHz and the local oscillator to 4.000MHz.
- PSK31 operation will be gone, since there is no (cheap) crystal for 4.070MHz. OK, the last statement is not entirely true, one could pen down a 4.096MHz crystal to 4.069MHz, although, 27kHz is a lot.
- But, WSPR is on the easy side by using a 4.096MHz xtal in the LO.
- Additionally, one SSB channel is available with the LO running at 4.194MHz; I guess one needs to look at the IF-filter response in this one. 14.194MHz would be ideal for SSB DXpeditions.
Actually, I may start with option #1, to keep the original functionality.