Barebones AM Transmitter Test

Okay, so I put the bare bones transmitter in the previous entry to the test. Before I go any farther, let’s hit the legal. DO NOT ATTEMPT THIS. I DID NOT DO THIS. THIS IS HYPOTHETICAL ONLY. ATTEMPTING ANYTHING SIMILAR TO WHAT IS ABOUT TO BE DESCRIBED MAY BE ILLEGAL IN YOUR COUNTRY. DO NOT ATTEMPT! THE DESCRIBED CIRCUITRY HAS NO OUTPUT FILTERING AND MAY SERVE AS AN EFFECTIVE RADIO JAMMER. EAT FRUITS AND VEGGIES DAILY. Anyway, I changed the circuitry a bit though. I kept the oscillator (50.0000MHz) continuously powered and programmed the ATTiny 2313 microcontroller (using PWM output) to oscillate (high/low) to the base of a transistor (NPN). In this way the microcontroller PWM output didn’t supply power to the oscillator, but rather grounded it, effectively removing power from it. In retrospect, I should have added a resistor between the oscillator and the transistor so that it didn’t completely ground it, because I think the oscillator would have functioned better if it were not fully grounded. Anyway, I got a big boost in range this way. Yesterday I couldn’t even hear the signal in the parking lot of my apartment, whereas today I heard it loud and clear. I decided to take a drive with my scanner, laptop, and argo to see how far away I could get. With this bare bones transmitter setup (using my ungrounded 2m jpole antenna NOT TUNED for the transmitter frequency) I was able to detect it over 4000 ft away. The receiving antenna was a 2m ~1ft high antenna magmounted on top of my car. In retrospect, I should have built a decent antenna and kept ARGO running at my apartment and drove the transmitter farther and farther away. I presume that my transmitter is functioning decently, and that if I attached it to a proper antenna (and had a better receiving antenna) I might be able to get some cross-town distance? I’m still n00b. I’m learning. That’s the point though right?

Here’s the signal (on my laptop) as I drove away…

This is where I was when the signal died. The red dot is my apartment (transmitter location), and the signal began to die right as I traveled south on Chickasaw past Lake Underhill (~4000 ft away). This immediate loss may be due to the fact that I passed under power lines which parallel Lake Underhill which interrupted the line-of-sight path between my 3rd story apartment balcony and me. If this were the case, supposedly if I kept driving south the signal may have improved.