simple microcontroller am radio transmitter.avi

http://www.swharden.com

Category:

Science & Technology

Tags:

• simple
• microcontroller
• am
• radio
• transmitter

[Vlakpage]

shouldn't you have resistor between the mcu pin and the fet gate?

[nibjb]

@Vlakpage Yes I certainly should! That would prevent the current drain on the microcontroller from getting too large. This was a quick proof-of-concept bread-boarded device (already disassembled) and there are quite a few other things that could have improved quality, but you're absolutely right - thanks for pointing it out! I'll make a note on the website regarding this.

[nibjb]

FM is around 100 mHz, too fast to clock this microcontroller with. However the chip could still generate the audio signal to modulate the FM carrier with!

[1979Iceman]

@nibjb lol, I guess I should have thought through my question a bit more. I was thinking about a beacon idea for my model rocket but my radio in my truck (Yaesu FT-8900R) is FM only and even then, 6 meter is higher than the chip can output.

[nibjb]

@1979Iceman you might consider a microcontroller keying a simple canned crystal oscillator. You can get them in various frequencies (50.000 MHz is common). It's described on swharden.com/blog/2010-07-14-h­igh-altitude-balloon-transmitt­er/ (28MHz) and I even used the same method for 3MHz with my previous project, swharden.com/blog/2011-08-05-i­-before-e-except-after-hellsch­reiber/

[Vlakpage]

@mkerna Yes or you fry the I/O drivers. FET is in fact charge controlled device. The gate makes capacitor to the other electrodes and as you know, capacitor conducts AC or simple fast change of voltages (=square wave edge) very well. You know, there are FET drivers with several ampere capability for a reason. In some cases you need as fast switching possible to minimze the linear region losses in the transistor. But anyway, you need to make sure the gate current isn't excessive for your driver.

[mkerna]

@Vlakpage No. FET gates draw essentially no current. They only need the presence of a voltage, which is what the "FE" part means: "field effect".

[Abdulla873]

This is not Am, this is ASK!!!

[meming4]

What is the antenna made of? Is it just a wire?

[1979Iceman]

@nibjb Thanks! I like the simplicity of the design and that is perfect for what I need.

[Vlakpage]

@nibjb Yeah, it's certainly nice minimalistic project. Now that I think about it, you could just leave out the transistor, and make simple DAC with two (or more) resistors to get the varying amplitude and put it through the cap into the antenna, right? Now that would be nice application for the 6 pin tiny AVRs :)