mbarazeen
Member
Hi,
If any RF experts here please help me answering few things.
I found an old satellite phone, for 140MHz and i could drive its amplifier part with a crystal oscillated FM modulator by tuning its coils.
I have RF power meter and a kind of spectrum analyzer to see the frequency and outputs.
With about 500mW input the amplifier delivers 27W, using an output transistor C1946. Two of the coils always get very hot and i can feel the heat coming out from it. I think it was doing the same with original design for 140MHz too, but not to full level.
What is the exact reason for this heating? RF induced eddy current in the coil copper? what could be the best way to reduce it? i have not changed its orientation from original design. one of the coil is having a bobbin without ferite rod, other one is air core.
Any feedback would be helpful, i can post later if a diagram would help.
Thanks
If any RF experts here please help me answering few things.
I found an old satellite phone, for 140MHz and i could drive its amplifier part with a crystal oscillated FM modulator by tuning its coils.
I have RF power meter and a kind of spectrum analyzer to see the frequency and outputs.
With about 500mW input the amplifier delivers 27W, using an output transistor C1946. Two of the coils always get very hot and i can feel the heat coming out from it. I think it was doing the same with original design for 140MHz too, but not to full level.
What is the exact reason for this heating? RF induced eddy current in the coil copper? what could be the best way to reduce it? i have not changed its orientation from original design. one of the coil is having a bobbin without ferite rod, other one is air core.
Any feedback would be helpful, i can post later if a diagram would help.
Thanks