I have built a transmitter/receiver with an antenna and crystal. I am wondering if it is stable.

Here is my transmitter:


simulate this circuit – Schematic created using CircuitLab

Here is my receiver:


simulate this circuit

I read in the data with my Arduino (using analogRead(pin)) and print it out to the console. I get: 670, 671 & 673 when it is idle. When I apply about 3.53V to the the antenna, my crystal reads: 690 & 691. I added a button so when I press the button the Arduino gives 3.53V to the antenna. I added two LEDs (one yellow one red) to the program, the yellow one would light up if the reading from the crystal was < or = to 670 but less than 675. The red LED lights up if the reading from the crystal is greater than 675. I see very buggy behavior sometimes, the red LED lights up even when I don't apply a signal to the antenna. Though I have never seen the reading go more than 673 when not applying any voltage to the antenna. Any suggestions? Thanks!


I am new to E.E. so i'm sorry if my schematic is a little off.

  • 4
    \$\begingroup\$ What makes you think this would ever work in the first place? For that matter, how did you come up with the part values you have. Your circuit makes no sense. You have no RF oscillator, the transistor is backwards, the crystal won't do anything because you have a static bias across it (with a cap for good measure!). \$\endgroup\$ – Connor Wolf Apr 3 '13 at 22:10
  • \$\begingroup\$ You really, really need to go read about how RF circuits work. Get a text-book, or read a bunch of ham-radio sites. \$\endgroup\$ – Connor Wolf Apr 3 '13 at 22:14
  • \$\begingroup\$ Sorry, me schematic could be a little off, though my circuit does work... \$\endgroup\$ – 0101011 Apr 3 '13 at 22:44
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    \$\begingroup\$ Actually, your circuit cannot possibly work (ever. even a little bit), at least using RF, as there is nothing in your circuit that could generate radio-waves. Assuming you're using the same arduino for the input and output, it's possible there is come capacitive or high-impedance resistive coupling between the two sections. \$\endgroup\$ – Connor Wolf Apr 4 '13 at 3:37
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    \$\begingroup\$ It is highly unlikely that your circuits work as you expect them to, but it may teach you a valuable lesson or two. One important lesson is that you really want to fully separate transmitter and receiver when testing things like this. You want to be sure that the receiver can only be influenced through radio waves. This means: two Arduino's, two power supplies. The other lesson was already mentioned before, find a couple good books on this topic. Third lesson may be to pick a simpler goal to start with in electronics engineering. Last lesson is not getting demotivated by our comments. \$\endgroup\$ – jippie Apr 4 '13 at 6:52

Neither of your circuits make any sense. That is simply not how transistors, capacitors, and crystals work. Unfortunately, they are so far off that trying to explain why they won't work is too large a task for a reasonable answer here. Also, you'd need to understand more electronics to understand the answer, and trying to teach all that electronics first would again be too much here.

To put this in perspective you can relate to, your question is kindof like "I am trying to build car. So far I have a tomato sitting on a rock. Do you think it will have good handling around corners?".

Keep trying to learn, but do it one step at a time. Perhaps you can come back asking more specific questions about capacitors, transistors, and the like.

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