An HF Amplifier for your QRP Rig

During our Sunday night Tech Net in Northern Virginia one of the participants described a 140 watt amplifier he just finished building for use on the HF bands.

My immediate thought was “Hmmm, he already has a 100 watt style typical HF radio. Why does he need something that does 140 watts?”

The I remembered he also has a QRP rig which generates the typical 5 watts or so and this linear amplifier allows this QRP rig to be just like the typical 100 watt radios when you need or want it.

The amplifier concept comes from a company called…

Communications Concepts

Their web site is

The company has a variety of HF and VHF amplifier web pages and will sell you the parts and sometimes a circuit board ready for you to build. They do not seem to sell built units, just the parts.

Depending on your power supply voltage they have amplifier reference designs in the several hundred watt class. Supply voltages range from 13 to 50 volts.

The model I think my friend built is the AN762 which uses the typical automobile voltage of 14V.

As the web site says “AN762 is also designed for an output of 100 watts using two MRF453 transistors or 180 watts using two MRF421 transistors.” This gives you some flexibility in power output choice just be selecting appropriate transistors.

The folks at Communication Concepts, Inc. indicate the amplifier designs come from engineers at Motorola, the makers of the power output transistors.

For you QRP folks out there who occasionally like to go to the full 100 watts, Communication Concepts may well have just what you need to build your very own linear amplifier.

If I were to purchase, oh I don’t know… an Elecraft K3, I might very well get the QRP version and build this amplifier to give my the full 100 watts when I feel the need.

Please note Communication Concepts does not sell kits. They sell parts and reference the applicable application notes from various manufacturers, such as Motorola. Don’t expect step by step instructions. You need to understand schematics and know what to put where.

If home brew is something you like to do, now you have another option to consider.

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