Hello,
I am new on analog design so I dont know well. I built this schematic on breadboard to feed an antenna. Only difference is I feed antenna with 12V instead of 5V. I put one of the probe after diode to check if card sends signal. When i bring card close enough to antenna, i can see signal but a little bit far, no signal can be seen. If i connect second probe or touch with my finger just before diode, I can see signal even if card is very far away. Also signal is getting clear.
It doesnt depend on whether ground of probe is connected or not but I power both from PC so they may be connected inside of computer.
I checked GND's and no connection issue. What could be the problem? How can I sol
Circuit that i built


Before connecting probe after diode


After connecting probe after diode

 

Hello,
I am new on analog design so I dont know well. I built this schematic on breadboard to feed an antenna. Only difference is I feed antenna with 12V instead of 5V. I put one of the probe after diode to check if card sends signal. When i bring card close enough to antenna, i can see signal but a little bit far, no signal can be seen. If i connect second probe or touch with my finger just before diode, I can see signal even if card is very far away. Also signal is getting clear.
It doesnt depend on whether ground of probe is connected or not but I power both from PC so they may be connected inside of computer.
I checked GND's and no connection issue. What could be the problem? How can I solView attachment 327156
Circuit that i built

View attachment 327158
Before connecting probe after diode

View attachment 327157
After connecting probe after diode

I am not sure but , since I also work with piezo transducer I guess connecting a resistor like 1M on where you placed that probe at may fixes your problem

 

Your circuit is not that of an oscillator.

Try one of these.

https://external-content.duckduckgo...6ebd8a4a7610185d040ce04b6882a6a96a&ipo=images

 

I am not sure but , since I also work with piezo transducer I guess connecting a resistor like 1M on where you placed that probe at may fixes your problem

Like your approach, i connect a 100pf capacitor and problem solved. When i measure probe, multimeter says that it is 77pf. Most probably connecting probe or 100pf capacitor makes circuit operate at resonance.
1M adds so much noise on signal.

Your circuit is not that of an oscillator.

Try one of these.

https://external-content.duckduckgo.com/iu/?u=https://www.electrical4u.com/wp-content/uploads/What-is-Crystal-Oscillator.png&f=1&nofb=1&ipt=484cb00f2f7949ab4d898d0757a6676ebd8a4a7610185d040ce04b6882a6a96a&ipo=images

I dont use any cristal oscillators, systems works with microcontroller and its inner oscillator. This accuracy is enogh for me.

 

DC is CORRECT!! That is not an oscillator circuit , and in addition, we have no information about what "Header 2 P4" is. But certainly it is an amplifier that could be made to oscillate with any feedback, such as could happen by touching the circuit near D2.
Where did you find this circuit??

 

DC is CORRECT!! That is not an oscillator circuit , and in addition, we have no information about what "Header 2 P4" is. But certainly it is an amplifier that could be made to oscillate with any feedback, such as could happen by touching the circuit near D2.
Where did you find this circuit??

Header 2 is antenna socket. I found this circuit while searching for RDM6300.

 

Unfortunately, not everything published on the WEB is accurate. In fact there is even a fair amount of intentionally faked stuff, presented just for the profit, which is based on the number of hits.
This includes some of the circuits that folks post in this forum, asking why they do not work as claimed.