Hi Lawrence,
I have tried up to 420KHz with the present 12T coil and with the others 12T, 18T and 30T and this is by far the best. It runs when I can get it to start at 30KHz, and will give me 2 x 2.5W at about 2cm separation which is more than I need.
Raising the frequency to about 80KHz only gives me about 50% of the power.
Is it possible that the Fet is damaged in some way but still works? Looking at the curves shows no current under 4.5V Gs is this correct? I always thought that Fets behaved like valves. This IRF2807 appears to sink 9ma (1K Resistor +Ve to gate)
for there to be only 3V on the gate and the device appears to still be off....
Mike
PS,
Some of the stuff Nick directed me to had single turn coils and ran at around 1MHz but were not practical for this purpose, and RFI ??
Just disconnected the FET, It measures 1.2K Gate to Source And Drain to Source measures about 1K.
Obviously it is stuffed but why It should still work beats me. I will try a few power BJTs
I have tried up to 420KHz with the present 12T coil and with the others 12T, 18T and 30T and this is by far the best. It runs when I can get it to start at 30KHz, and will give me 2 x 2.5W at about 2cm separation which is more than I need.
Raising the frequency to about 80KHz only gives me about 50% of the power.
Is it possible that the Fet is damaged in some way but still works? Looking at the curves shows no current under 4.5V Gs is this correct? I always thought that Fets behaved like valves. This IRF2807 appears to sink 9ma (1K Resistor +Ve to gate)
for there to be only 3V on the gate and the device appears to still be off....
Mike
PS,
Some of the stuff Nick directed me to had single turn coils and ran at around 1MHz but were not practical for this purpose, and RFI ??
Just disconnected the FET, It measures 1.2K Gate to Source And Drain to Source measures about 1K.
Obviously it is stuffed but why It should still work beats me. I will try a few power BJTs
