Thursday, March 25, 2010

JOBT (3) Power up!

Watch out the pile up....I'm coming in..... with an fantastic 4w of output power.... I broke pile up's with less power (2 people count has pileup?)... the important is the antenna and my old aluminum tube outside the shack window, does wonders!!!
I had some coils (3 out of 4) with the wrong number of turns so I had to rebuild them because I normally count one pass in the hole is one turn but looks like that in binocular cores is one pass in both holes 1 turn. Live and learn! The diode in the ouput stage is an 1N4148 but I still have to confirm if it's not any other type.
The first coil I changed to a normal toroid since I was out of thin wire to fit in a binocular coil.
I could not get more than 4.47W but for me is enough, the lowest measure value was of 2.71W at 10Mhz. The measuring device is the uncalibrated rf probe somewhere on this blog. Calculation of power is the square of the voltage at the ouput load divided by the load. So it's the measure value plus the drop in the probe diode (assumed 0.25). If you have 10v then is (10.25*10.25)/50 = 2.10W.
The signal generator was the MFJ antenna analyser and I still tryed the amplifier at 50Mhz but only got 0.3W.... fair!
I still have to improve the temperature control since it's powering on to soon, I have to change the schematic two posts bellow in the blog. By the way in the tests the only thing I notice warm was the homebrew dummy load that was rated to only 1w.

The photo:

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