[Amps] LDMOS Solid State Amplifiers

[Joe Subich, W4TV]

On 5/6/2012 12:42 PM, Tom Thompson wrote:
> I have two home brew solid state amplifiers, one at a kilowatt and
> one at 600 watts. You can see details at http://www.tomthompson.com
> Both of those amps are promoted by Communications Concepts and are
> Helge Granberg designs.

I am honestly surprised that nobody has updated the Grandberg 4 x
MFR150 design (EB 104) for the VRF-2933.  That would make a "single
board KW" for 90% Plus of all amateurs ... something within 0.5 dB
of the US "legal limit" and capable of handling SWR < 1.5:1 without
a tuner.

The only "real" work would be in optimizing the transformers for the
proper (lower) impedance.

73,

    ... Joe, W4TV


On 5/6/2012 12:42 PM, Tom Thompson wrote:
> Bob,
>
> I am using the Freescale 300 W part.  The part number is MRFE6VP6300H.
> I will probably not build this into an amplifier.  I have two home brew
> solid state amplifiers, one at a kilowatt and one at 600 watts.  You can
> see details at http://www.tomthompson.com   Both of those amps are
> promoted by Communications Concepts and are Helge Granberg designs.  The
> transistors were so expensive that I did not feel comfortable really
> playing around with them.  When the LDMOS transistors came out, the
> ruggedness and price were right for experimentation.  I built a test jig
> on a copper spreader and aluminum heat sink with a good fan.  The traces
> on the PC board are made with copper tape, so I can change the circuit
> easily.  I have thermistors mounted on the transistor flange, the copper
> spreader and the heat sink so I can see what the thermal resistance is
> between each interface.  The bias is easily adjusted so I can easily
> bias the transistors between Class B and Class A.  My Vdd supply is also
> adjustable so I can change the output impedance of the amp and look at
> various efficiencies.  You get the idea...it is just a learning platform.
>
> 73,   Tom   W0IVJ
>