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what are my values are correct coils, 5.9 mH and 7 mH ?
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The 5.9mH is OK for transmit but for your 7mH to work in the receive side you should change the value of C6
In private communication you questioned the effect of changing the tuning capacitor so I took time to run this simulation.
The green trace represents the ground balance ZCD output (U102-7) at some arbitrarily selected rotation. The red traces represent your rx
signal at U101-7, for differing values of parallel tuning capacitance with a 7mH coil.
You can see here the effect that different values of capacitor have on the phase of your received signal.
(Try to ignore the amplitude differences.)
I believe that close to 14.2nF should be about right for your 7mH coil but you will have to decide for yourself, with some experimentation.
The effect with 15nF and 13.5nF are also shown for comparison.
You have to understand that your discrimination channel will be affected as your rx signal phase changes. -
ok, thank you for the explanations, so if I change to a C6 14.2 nF my discrimination will not work properly?Comment
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That's not what I was trying to say. Ummh, why would I say to use 14.2nF if I thought it would screw up your discrimination?Originally posted by ashefr10 View Post
I was trying to imply that you may be able to ground balance with different values of capacitors but that does not mean that your discrimination will work correctly. But I suppose maybe that's a useless point to make, so just disregard that statement.
Things are much easier to make work if you don't deviate too far from the norm and then you find the need to make adjustments. (I'm wondering whose set of instructions you followed when you wound the coils.)
Like Don has told you, you should measure your transmit frequency and then using the value of your rx coil and the formulas I posted here, find the value of capacitor that makes your rx tank tune to 1.11 x the transmit frequency.
I have a feeling it will be something close to 14.2nF. Am I right?Comment
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ok , thanks , I then have to measure the frequency of the Tx and then multiply by 1.11 and then do the math to get the value of the capacitor over the frequency obtainedComment
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