In the material section I explained that I wanted to start with a good cooling block. Building of it was quite some work. But it paid of. It is a solid piece of hardware. The inner sides of the amplifier area were ' paved' with PCB's, and everything soldered nicely together at the inner side. Before I fixed the PCB finally to the cooling block, I made the holes for the FETs and the 5V power regulator (7805). 

Then I drilled two holes for the power entry and fixed the plugs for it. The minus is soldered to the PCB board thoroughly and the plus is soldered to an 'island' on the bottom of the PCB board. Also a thick copper wire from the minus to the output of the output transformer.On the right side of this page you can look at it in the picture.

Next job was to fix the both FETs on the copper cooling block. Make sure you use insulators (mica), because the IRF530's have there drains to the cooling pad of the FET !!!!!!! I also used a tiny bit of cooling pasta (CPU pasta) between the copper block and the mica insulator, and the insulator and the FET. Then you screw it together. Also here you will find it not trivial to drill a nice hole in the copper block ! Use specific copper drills, and also use a bit of oil while drilling. Otherwise you can end up with the top part of your drill in the copper end the rest in your drilling device,...!!

The I glued the ferrites together with 2 comp glue, and made the coil. primary is 2 windings with in the middle the entry for the power. Make sure the Capacitor is a high voltage one. I used one of 1KV, stay on the safe site. Voltages in normal state go up to a 100V, and if you forget your antenna of dummy load,......it can go much higher,........

Around the FETs it looks a bit messy, but I made several connections with thick copper wire to the ground and the FETs sources. I want to make sure no losses are caused by to much resistance. Double check that there are no unwanted connections and you have the FETs connected correctly.

After that I build the rest of the amplifier pretty straight forward.

I added some more photo's to give an idea how it looks after the complete build.

The output filter works very well. I build it on a separate board and tested it. The output curve is in the passband flat within 1 dB, and at 14.500 MHz it starts to filter. At 20MHz the attenuation was -50 dB. I think that is good enough to filter out all harmonics. After this test I build the filter in the amplifier box.

The next important thing is to check whether the electronic switches are working correctly. To check that I connected the QRX CW transceiver output to the input of the amplifier. The QRX was powered with 13.8 Volt. The output is 1.5 to 2 watt.

The output for driving the PTT of the transceiver (see the doc of the kit, it is a bit tricky to solder a wire to pin 3 of the IC10)  was connected to the PTT input of the amplifier. To do that properly I made a standard entry plug at the right front of the amplifier box.

Now make sure that the QRX is in practice mode. It will switch the amplifier PTT, but will not give any output. Check then all the voltage levels in both the TX and RX mode.

In the RX mode you should hear noise in the headphone. During TX mode the noise is gone and the CW beep is there. Switching from RX tot TX, I did with my keyer.

If that is working all well, than measure the bias voltages on the Bias1 and Bias2 points in the scheme.

Turn slowly and look for any current flowing from your power supply. I put it on 30-40 mA for one FET. So together you will have about 70 mA flowing through the drains.

Than it is time to set the QRX back to normal (not in practice mode anymore). So at a push on the keyer, rf energy is going into the amplifier. MAKE SURE that you have a Dummy Load connected to your amplifier.

Good, the time of the truth has come.

I put my power supply on 12Volt to start with. Than I pushed my key,..........

mmmmm,....I only got 10 Watt, and the current was pretty low, about a 2 ampere. I increased the power supply to 15V and the current increased to about 2.5 amps. The power also increased to about 15 Watt. Ok, everything looked ok, and nothing got terribly hot, so I increased the power supply to 20 Volt. The current increased to a little over 2.8 amps. The power increased to about 25 Watt.

I was confused. In the documentation I found that the amplifier should give about a 35-40 Watt at 15 Volts and about 45-50 Watt at 20 Volt. So, I dared to increase the voltage to 24 Volt, just to see what would happen.

Well, the current went to about 3.5 amps, and the output increased to a little under 40 Watt. With a little tuning of the bias voltage, I got it on 42 Watt.

2.4 Volt times 3.5 amps gives an dc input power of 84 Watt, so I got something like 50% efficiency. I was not very impressed. But the most strange thing I found is that I need 24 Volts to get to 42 Watt. Why was the current so low. According to the docs, I was expecting 10 amps at 13.8V, and an output power of at least 50-55 Watt.

So, I have some work to do,............

Look for the new chapter.