Re: PLL FM transmitter 300mW RDVV problem

Unfortunately I'm not familiar with PIC at all : ( It must be confusing if there are three hex files; it might be worth contacting the person who designed it, to ask them which hex file is correct.
Really the PIC is just manipulating the SDA and SCL lines, to instruct the TSA chip. You could see if there really is data on those lines but it needs a scope : (
Without that, I think it may be worth to consult the supplier of the hex file just to double-check that it is ok.

It works!
The pll locks now! The problem was the burned TSA5511! I ordered a new one, I put it on the board an now the pll locks and I can hear the signal on a radio!

However there is a problem: If it gets locked, it never unlocks! When it locks, if I remove the coil from the board, the display and the green led show that the transmitter is still locked, although I can't hear the signal on the radio! That's because I've removed the coil! Is this normal? I have tried 3 different hex files.............

Furthermore I hear an awful sound on the radio when it is locked, something like a helicopter... By adjusting the coil, the sound changes frequency and sometimes is just a constant sound signal...... What is this?

Thank you for your help till now!

The TSA5511 has no "lock detect" pin so the pic processor has to 'ask' the tsa5511 if it's in lock or not. If this is done only once and not on a regulair basis than the the message "locked " will never change.
The helicopter sound is prob. a indication that the loop is instable. This could be a loop filter problem or that the vco is on the edge of oscillating. Try to change the inductance of the vco coil.

Thank you very much! This means that the "LOCK" stays forever, and it's normal :)

The helicopter sound cannot be due to the vco being on the edge of oscillating, because I've tried many different coils and the problem continues....

Can I change the 100pF capacitor in series with the varicap? (I use the BB209)

What can I do to discover if the problem comes from the loop filter? Is there a way I can solve it?

Thank you everyone for your answers!

I hadn't soldered well a capacitor at the loop filter, so it didn't work well!

Now the transmitter locks from 87 to 100.2 MHz which is enough for me! The sound is really clear, I had a grounding problem but I fixed it..
Thank you! :)

If I reduce the current in the transistor output using the 1K variable resistor, the transmission distance does not change at all, although the BFR96 gets cold....The transmission distance should decrease, but it does not. I use rg58 coax and homemade dipole ...

So the only output of the transmitter now is from BFR91, and the power is not enough to driver the linear with the 2SC1971 I recently made ..

We may blame the coils out (because they are in the form of resistance rather than air coils)?
The filter output values ​​for inductors and capacitors in the schematics are okay?

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DIY fm transmitter