This HF2K belongs to a serie of amps by http://www.om-power.com/ You can see other higher powers, too, if interested in Hi Power RTTY. Clever thing here is a sum of two power supplies fed from two 220VAC phases. After ACOM1000 (very good) and SPE 1KFA (otherwise good, but terrible QSK), I am still looking for KPA500. Benny OH9NB