[Amps] Mobile Amps ?

[Manfred Mornhinweg]

Mike,

> In my limited research I've found:
> (RM Italy seems like lower power and some are illegal in NA)
> (SGC no longer making the power cube I don't think)
> (THP out of business)
> 
> What else is out there? 

Homebrew, of course! Whenever you need or want something that no company 
makes, or something they do make but at an unreasonable price or with 
unconvincing quality, then the logical choice is homebrewing it.

You could go the simple route and built several unit amplifiers around 
RD100HHF1 MOSFETs, which are easily available at a reasonable cost, and 
then join them with a splitter and combiner. Those MOSFETs run directly 
from 13.8V. Or you can build a DC-DC converter that raises the car's 
voltage to 48V, and use a single high power LDMOSFET. At 600W or so the 
cooling would be manageable, while the same LDMOSFET used at a kilowatt 
or so becomes hard or even impossible to cool adequately.

Considering that the power available in a typical car is a bit limited 
for a big amplifier, this is an ideal case for building a high 
efficiency amplifier. Maybe using the same LDMOSFET, but modulating the 
DC-DC converter to improve efficiency. This would allow you to get much 
more RF output power without exceeding the alternator's capability. You 
could run the amplifier in full saturation, which is easy given the high 
gain of LDMOSFETs, and use envelope feedback to the DC-DC modulator to 
keep things linear.

And if you don't have enough knowledge and experience in homebrewing to 
tackle such a project, maybe you can find some other ham locally who 
could elmer you?

An intermediate approach is buying kits and ready-built modules from the 
web (amplifier blocks, splitters, combiners, low pass filter banks), and 
integrating them into a complete unit.

Building you own is certainly more involved than just ordering a 
factory-built amplifier, but I can assure you that it's much more 
satisfying to operate a station in which as much as possible of the 
equipment is homebrew!

Manfred

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