Few days later I changed the coils in the lowpass filter.
Almost doubled the inductance from the RFsimm calculated values.
Also thicker wire used 1.2mm . And the Spraque C's replaced by an Arco 80pF compression type trimmer.
Now the heat developed is much lower and the efficiency increased to about 50%.
Great tool RFsimm99 but still I need to do the old solder work to change real components and test again.
Now the only wish is having a bit more gain it needs >10W drive for full output. I can not let out the 1Ohm parasite stopper at the gate. If so i see oscillations.
I tried a wire trough 1 ferrite pearl with 3 ferrite rings no drive power came through! 1 ring i had power but the ring got hot!
Messured 1 wire gives about 70nH (at 500kHz) Those tiny rings do a lot more then thought!
The BLF177 takes a lot RF gate current at low impedance.
A few days I let it rest it was useless to continue the trial and error method. I went ice-scathing.
Then I did check the low-pass filter using RFsim99 this is a great tool. RFsim99 does not work under W7 btw.
It had to be redesigned for a higher cut off frequency. Then the matching improved a lot.
A good thing to suppress unwanted oscillations was to use a stopper resistor at the gate of the BLF177 10 Ohm was good but I had only a small R that got brown by the drive power. Now I use 2x 0.5W 1 Ohm carbon types.
The capacitors stay cool in the filter. I believe the pass through is okay now.
Possible it was never optimal for 50MHz too and the BLX15 could have been better performing.
But I did not want to give up on this modern MOS power BLF177.
I have to learn more how to use this great tool.
The L/C calculated L's compared to the measured values with the L/C meter gave quite some differences but roughly the L's in use should be about 70nH now, much smaller values then they where before.
Almost doubled the inductance from the RFsimm calculated values.
Also thicker wire used 1.2mm . And the Spraque C's replaced by an Arco 80pF compression type trimmer.
Now the heat developed is much lower and the efficiency increased to about 50%.
Great tool RFsimm99 but still I need to do the old solder work to change real components and test again.
Now the only wish is having a bit more gain it needs >10W drive for full output. I can not let out the 1Ohm parasite stopper at the gate. If so i see oscillations.
I tried a wire trough 1 ferrite pearl with 3 ferrite rings no drive power came through! 1 ring i had power but the ring got hot!
Messured 1 wire gives about 70nH (at 500kHz) Those tiny rings do a lot more then thought!
The BLF177 takes a lot RF gate current at low impedance.
A few days I let it rest it was useless to continue the trial and error method. I went ice-scathing.
Then I did check the low-pass filter using RFsim99 this is a great tool. RFsim99 does not work under W7 btw.
It had to be redesigned for a higher cut off frequency. Then the matching improved a lot.
A good thing to suppress unwanted oscillations was to use a stopper resistor at the gate of the BLF177 10 Ohm was good but I had only a small R that got brown by the drive power. Now I use 2x 0.5W 1 Ohm carbon types.
The capacitors stay cool in the filter. I believe the pass through is okay now.
Possible it was never optimal for 50MHz too and the BLX15 could have been better performing.
But I did not want to give up on this modern MOS power BLF177.
I have to learn more how to use this great tool.
The L/C calculated L's compared to the measured values with the L/C meter gave quite some differences but roughly the L's in use should be about 70nH now, much smaller values then they where before.
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