[Elecraft] Raspberry Pi4 & K4

[Dave]

The K4 has a built in USB sound/RS232 connection. No external hardware
needed.

In addition, unlike the K3, the audio response on DATA transmit from the K4
is flat, so no matter what audio frequency (within reason) you select, the
TX output will be the same. The K3 had a fairly "lumpy" response across the
passband, I guess which was due to using crystal filters.

73 Dave G4AON
K4D #286