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Dave Writes on the R.M Italy KL-203 linear amp

A new shipment of Amps and power supplies arrived today and I was keen to test the new KL203 with my Yaesu 817 miniature H.F rig. The Yaesu puts out 5W P.E.P in S.S.B, FM, AM, CW etc but I tested the KL203 with 5W FM using the V.S.W.R meter on the radio and a power meter in line with the Dummy Load.
RM say H.F and I was keen to see just what H.F means in this case.
From 14 to 28 mhz the Amp put out 110W to 70W with no V.S.W.R on the input to the amp.
10mhz the input V.S.W.R to the KL203 rose to about 3:1 but we still had 70W out.
7.0mhz we had no out output from the amp and no V.S.W.R either!
So we can say that the R.M KL203 is a 14-30mhz mini amp and does well. I did not notice much heat build up of the heatsink despite the FM tests. Amp draw to the amp was about 11 at 28mhz to 15 Amps on 14 mhz.

The specs on this amp say up to 20W in on S.S.B and 10W A.M/F.M. The 817 can not reach those figures so KL203 was hooked up to a Magnum 257 turned down to 15W S.S.B max and tested at 27.5mhz. 150W on S.S.B was the result! 10 W on F.M gave 125 out.
I am sure figures on 20 meters will be correspondingly higher. I will have to give this amp a hammering on air at 20W P.E.P input and see how hot it gets! It isn’t a big package and I am amazed at the output. The KL200 with the single 1446 seemed to get warmer in the tests.

Conclusion
This amp is a great addition to the FT817 being small and quite well powered.
Audio tests on 27mhz reported clear audio and a lift in signal from 1-3 to S9. Big difference for such a small footprint.
KL203 uses 4 MOSFET transistors in quite a complicated looking little package.

Specs say up to 10W A.M/F.M and 20 WATTS P.E.P S.S.B but that might be pushing it a bit.
70W seems a good level for such a small Amp. Ideal for strapping to the back of any 12 WATTS P.E.P radio or Q.R.P rig. Impressive.
91dd018 24-11-05