I was looking around for information regarding Arduinos and Rf transmitters. In the process I saw many articles asking about radio transmission and Arduino and I found a lot of answers where somewhat missing the mark.
I work professionally with automation and transmitters, I like to play with arduino and also I am an armature radio HAM. I was hoping I could make some simple points that may help any one interested in the topic.
An General, The LOWER the FREQUENCY you want to use the Longer the Antenna. We think of CB radios with their 5 footish antennas at 27 Mhz yet when your getting down to 7 mhz your having an antenna 40 to 100 feet long. An antenna resonated at a certain frequency depending on its length. the short story is the more your antenna is the WRONG length for your frequency the less power actually gets out to the airwaves. Antenna length is to radio what Good speakers are to a stereo, Great Tunes , Great AMP, Crummy speaker Bad sound.... With Radios wrong length antenna , distance goes to almost nothing.
There are two modes of radio waves.
Vertical - This is also know as line of sight.
SKIP or bounce -- think late night AM radio coming from the other side of the country
Vertical - This is Higher Frequencies, Day time or Night time- Short Straight distance with limited obstructions. Think Walkie-Takie. You radios waves go out in brute force in a straight line
SKIP. This is Lowe frequencies, Night time and the Signals can bounce of the upper atmosphere and come back down at an angle somehwere else. Kind of like sinking balls on a pool table by bouncing off the rims. in this case the rims are the upper atmosphere. This layer goes up and down ,on and off depending on how the sunlight hits it. you can get long distances but not predictable and not day time.
Hope this Helps. Good Luck
Kd3U
