Hook an antenna to your propeller, and here come the cops!

ElectricAye

Just curious about something...
I sometimes test my Propeller-based pulse counting system using the Propeller to generate a frequency and (on different pins) to measure those same frequencies, sometimes up to about 2 MHz, and I have wires going everywhere, some of which get kinda long - say, 12 inches or so. Is there a potential problem with the energy levels coming out of the Prop actually sending out radio signals that might interfere with things beyond, say, 50 feet? So far I haven't noticed any garage doors convulsing up and down in the neighborhood but... any reason for me to worry?

thanks,
Mark

Mike Green

It's hard to get an effective radiated signal accidentally, but it can happen. With a 12 inch piece of wire, it's pretty difficult since the resonant frequency is pretty high. On the other hand, a 1/4 wave antenna at 160MHz is around that length and the Propeller can produce a deliberate signal at that frequency.

Keep in mind that many forms of deliberate communication are regularly done with power levels on the order of 1mW to 10mW. Most of this is short range like Bluetooth and the 433 and 1215MHz unlicensed bands, but deliberate communication has been done over paths on the order of 1000s of miles with just milliWatts. This usually takes a large antenna, but a distance of a couple of miles is easy with a 1 ft. antenna at the right frequency under good conditions.

rjo_

I once added a small amplifier to get a cable signal from the back of my building into the basement... and the signal police were right on top of it.
No joke... I was absolutely flabbergasted. Since then we used one in our house, no complaints.