[Amps] LDMOS Solid State Amplifiers

[Tom Thompson]

Joe,

I wonder if two of the VRF-2933 in parallel would have too much capacitance.

Tom

On 5/6/2012 11:44 AM, Joe Subich, W4TV wrote:
>
> 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
>>
>