Tuesday, November 30, 2010

SmallWonder Labs PSK-20 QRSS/WSPR mod

Some time ago I built a PSK-20. Even though PSK31 can be fun occasionally,I was thinking of added value to the radio.

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.
Please not, one needs to make sure that the BFO is set for USB!

Actually, I may start with option #1, to keep the original functionality.

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