I read that the reception of a ferrite rod am antenna inside a radio depends on the surface area.?

Question

Surface area of what? Is it the area of the hollow circle created by the loop? The total surface area of the wound wire? Would a big loop, say, hula hoop size, with one winding, work just as good as a 4" rod inside the radio if the surface area of the windings were equal?

Rich:

Do you know if it's the SA of the exposed wire in the coil, or the total wire, or just the area exposed to the radio wave, since am is very directional?

Answer 1

It is the surface area of the coil. Old radios used to have big flat rectangular antennas that had their wire wound around like a spider web. The rod type antennas are more efficient because of their ferrite center to be compact enough to serve a small radio.

Answer 2

My opinion is that you should not argue with your boss until you get the offer for your next job. Change the subject and don't tell him he is an idiot until you are walking out the door. The fact that your boss is an idiot is not a matter of opinion, but scientific fact. Of course radio receivers do not absorb radio waves in a way that would cause them to "steal" radio waves from other receivers. A receiving antenna is "excited" or "energized" by all the waves that pass by, and the receiving circuit is designed to select waves in a certain frequency notch and amplify the waves. This does not reduce the strength of the wave in the air, which simply passes by and continues. Hard to say what causes your rush hour effect. Do you go through a cluster of tall buildings? Is there a mountain that passes between you and the transmitter? Lots of big trucks? Have you tried tuning to other stations to see if they are all attenuated? As for references, you are talking about pretty basic physics, under the heading "electricity and magnetism." Try searching on "electromagnetic wave propagation." The Wikipedia article is pretty good. Also try any textbook in general physics, or the Encyclopedia Britannica. The most readable source would be the Radio Amateur's Handbook, which explains all aspects of radio waves in simple terms. It is published by ARRL, the American Radio Relay League. Last time I checked, they still had a web site. You may still find the handbook in your public library.