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PLL around Resonant LC Circuit

I think you should add any capacitance on the Primary side, not on the secondary. I think this will give you lower losses. You can model this in some kind of SPICE program.

I think there is no particular disadvantage in adding the capacitor. It will reduce the resonant frequency, so you might need fewer turns. Is there a particular reason why you wanted the frequency around 10MHz? You could use the ISM band at 13.56MHz, or someone else might know about a lower frequency which can also be used for ISM proposes. I think under

150kHz the rules are also less strict, though I don't know the details.

Ok, a LC oscillator will do that.

It is pretty easy to make it oscillate, and only 4 components are really needed.

Ok, but it is an ugly way of passing. Sort of like making the percentage of pollution in your drain pipe below the legal maximum by leaving the tap running all the time.

Reply to
Chris Jones
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etc

The Baxandall circuits suggested a Q of 5-10. I suspect your pcb track resistance is going to be the killer, even of such low Q's.

--
Tony Williams.
Reply to
Tony Williams

Chris Jones skrev:

The frequency of 10MHz is selected to let me use cheap 4000 CMOS logic around the LC circuit. Regarding 13.56MHz ISM band, the resonant frequency will change when the circuit coils are moved apart - so I'll have problems getting the exact frequency. Offcourse, I couldn then trim the frequency back to the ISM band with a varicap diode and a capacitor.

I have no experience in making HF oscillators, but then this project might be a time to start. Good point

It isn't nice, but sometimes the agenties enforcing the standards aren't nice either. We have had tons of problems with UL/VDE suddenly disregarding previous aggreements and coming up with all sorts of strange tests. The latest "joke" is that a varistor now suddenly can short in a semiconducting way, so we are forced to add a fuse at the mains side

Thanks

Klaus

Reply to
Klaus Kragelund

Joerg skrev:

Yep - can't avoid it any longer ;-)

Actually an idea is to start the pulse and shut if off at some current limit. With a bad Q the oscillation will die out fast, so I could just wait some periods before applying another pulse. Then I have no need to syncronize ..... ahemm - making a oscillator (powerlevel is lower however)

Thanks

Klaus

Reply to
Klaus Kragelund

Hello Klaus,

Then you would have re-invented :

"The oscillator" :-)

Regards, Joerg

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Reply to
Joerg

Hello Klaus,

You could make a power oscillator that takes care of it automatically, quits when the Q gets too low.

Make sure you don't run into trouble with the regulatory folks. They don't like it if someone is blasting off power on non-ISM frequencies. If your levels are marginal you might want to think about a little dithering to keep it legal.

Regards, Joerg

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Reply to
Joerg

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