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April 9, 2024. An Unscientific Study.

Fools rush in and at times get the best seats -- but not always. So, I tried something fool hardy and now I need to prove the results with the math stuff and electronic theory.

I have seen some IRF510 designs (ON6MU) where a single IRF510 can produce 20 watts out at HF. 

Consistent with my lack of time and as Larry the cable guy would say Get er Done, I did a quick and dirty test to see if I could squeeze a bit more power out of an IRF510 at 7 MHz.


I have a bunch of stock boards in the CNC files, and one is the IRF510. About 10 minutes start to finish I had a board. The two changes I made were to use 24VDC on the Drain and to provide a 10:1 step down match to the input of the IRF510. The 24VDC I know the why, but not sure why I thought using a 10:1 would be a smart move. 

Prior to installing this on the 40M SDR I used the signal generator as the source and delivered 14V PTP to the input side and with a variable DC supply set to 24VDC was the source voltage. 

The IRF510 bias was set wide open at about 4.2 VDC. I got 64Volts PTP across 50 OHMs. I did note that at 13 Volts DC that the pattern was not a pure sine wave but at 24VDC it was pure as the driven snow. 

For the installation in the SDR I used a Mean Well DC to DC inverter (Black Square) good for 600ma at 24VDC. The supply to the inverter can be anywhere from 9 to 18VDC.


The 10 watts is >2 times what I got straight into the Gate and using 12VDC for source. 

So, now we need to know what the real input impedance to the IRF510 is and to match that input and to run some rigorous, repeatable tests. This was just a place to start.

I am able to drive the SB-200 directly with this amp using the IRF510 to hit 150 watts on voice peaks. So, a choice of either 10 watts or 150 watts would be a good outcome.

BTW 500 milliwatts to 10000 milliwatts is a 13dB gain.

73's
Pete N6QW

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