Amp Test 2012 11 25

Hello HF Projects Builder,

I have some positive news to report tonight. Work with the new HF SuperPacker Pro 100W Amp is first-stage functional. There is still lots of development and testing but I wanted to share my initial results.

HFSPPV3_2012_11_25

This is a description of the test setup.

We have the amp shown on the left side driven by my K2. The amp module is attached to a heat sink. The two MOSFETs are physically attached to the heat sink. The variable attenuator control test box can binary select from 1–15 dB using four toggle switches. 

The output of the amp feeds into the input of the LPF-140 Module. There is another row of toggle switches to select one of six filter positions from 160 to 10M.

The output of the LPF-140 Module is connected to a 50 ohm dummy load.

Solving a circuit problem

The first problem encountered was high input SWR using the traditional center-tapped transformer. I could not overcome the problem so I switched to the HF PackerAmp V4 balun input to couple the output of the binary resistive pi network to the amp. Works like a charm with acceptably low SWR even in the most sensitive setting.

Initial test results

Right now, I am powering the amp from 12V. My plan is to eventually have a 48V drain voltage. This will reduce the board currents substantially with higher output power. This is new uncharted territory with these MOSFETs so I don’t know how successful this will be. It certainly works in the HF PackerAmp V4 so I have high hopes it will work here also. The MOSFETs are rated to 50V.

I had about 3W drive on 75M to the input of the 4dB attenuator. That translates to about 1.2W drive to each gate. I was quick to get on the key and off again for this initial test. I saw 60W on my dummy load watt meter.

That brings a smile to my face. Now that I have some initial success, I will add the higher drain voltage and attempt to go further and hopefully characterize my results for the next report to you.

My plan after completion of tests on the amp is to revise the artwork and make a bare-bones kit available real soon that includes the amp, heat sink, LP Filter and Power Supply. There may not be too many interested in this but it would surely be a low-cost solution to the DIY builder. If you have an interest in this level of kit, please let me know.

73, K5OOR –  Virgil

HF Projects

 

 

 

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