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check polarity of the diodes on 4024 and their availability.
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What instrument are you using to measure frequency? If you have oscilloscope, you should see square waves on each of the 4024 output pins. Anyway, my calculations say you should be looking for 1250Hz on pin 6.
Also, of the JFETs you listed, I think 2N4393 is your best choice, 2N4392 should also work.
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Thanks hot rock for your answers tomorrow I'll take a picture of the waveform on pin 6.Originally posted by rolling rock View Post
I am using a LEADER LBO524 analog oscilloscope, I also have a Chinese 20 dollar digital oscilloscope.
I am using the 2N3819 I will change them to the 2N4392. The 2N4393 I only have 2.Comment
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Here I publish the measurements with the two oscilloscopes, one is the TX signal and the other is the signal from Pin 6 of the 4024.
Are those measurements correct?Comment
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Your transmit signal is not a very clean sine wave, but indicates that the parallel capacitor is not exactly the correct value to resonate at the frequency you have chosen. A very near miss, but could be improved. You should adjust VR2 until the waveform is not obviously distorted. That would be easier than replacing the capacitor, but it's your choice. You will also need to be adjusting VR1 to adjust signal amplitude, back and forth, until optimized signal purity and amplitude are attained.
However, your lack of discrimination is a separate problem.Comment
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Thank you very much for your rolling rock tips !!
I don't know much about what the wave should look like but I'm going to give it a try.Comment
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In post #65, "Analog 5V transmit 20us", that wave is not symmetrical. Just like KT315 told you (in different words), it has to be a LOW DISTORTION sine wave.
Provided you have enough travel on VR2, you should adjust VR2 as you watch the oscilloscope: the wave will increase and decrease as you turn the trimmer. Adjust VR2 for maximum amplitude, then use VR1 to get about 16Vp-p (no more, assuming your transmit supply is +8V). Then, use VR2 again, to make sure of best low distortion possible. Go back and forth, as many times as necessary.
The correct position for VR2 depends on the LC values, they go hand-in-hand.
Fo = 0.159/(square root (LC))
Multi-turn trimpots are really good to have here.
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rolling, yup,,, in later circuit same constructor did put a trigger between 555 and tx driver. it gives clear symmetry.
simplest decision. we know this schematic like TROY SHADOW.Comment
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Here i have a picture.Comment
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Originally posted by Ruben2000 View Post
Referring to the picture in post 34, the answer to your question is NO.
What do you have, off the page, connected to point B?? That is supposed to be a square-wave, with slightly rounded edges. What you are showing at B is (was) very bad. I believe you were going to replace your 2N3819 with 2N4393, so, what does point B look like now?
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Also, in post 28. Again, test point B (a different B).
As KT315 pointed out, that "square" wave is looking lopsided, agree?
Supposedly, we have gotten past that ugly waveform, because otherwise, you would probably not have a nicely symmetrical, low distortion sine wave at point A.
SO, what is the story? Please do not overlook important details or you waste everybody's time.
Check again, using the high dollar scope. That should be a 50-50 square wave, or at least have almost immeasurable deviation from being square.Comment
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in our language MEANDER is the clear symmetrical square signal. in your one i see, i googled, MEANDER has more widely concept, sometimes not 50/50.
ok. if we take a full period the signal is sure half of it. SURE 50% of full period.Comment
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Moving right along... I must have been seeing thing.
Where I come from they call it... OPTICAL ILLUSIONS!!
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