So a co-worker tells me about a great new radio station, and at the end of the day, while negotiating my standard stop-and-go Austin commute, I tune in. Sure enough, the station is great, and really relieves the tension I normally feel while encased in the gridlock.
In the morning, when I re-start my jalopy, I note that the station seems to have disappeared from the airwaves overnight. While parked at a red light a few miles up the road, however, a bit of fiddling recaptures the signal, but there’s too much interference from another station for me to hear any more than a few scattered seconds at a time. Through the rest of the commute, I keep switching the radio on to see if the signal strength is getting any better. No luck.
The day thunders by at its standard glacial pace, and once again it is time for the afternoon lemming race. Lo and behold, the station signal is coming through loud and clear. Whiskey. Tango. Foxtrot.
So what’s going on here? Is there a reason why the signal strength would vary depending on the time of day? Some sort of distortion due to temperature variance? Sunspots? Aliens?
Radio wave propagation is affected by quite a few factors. It is not uncommon for the sun’s position in the sky to affect propagation due to electromagnetic interference and ionization of the atmosphere. (Solar radiation striking the upper atmosphere causes it to ionize, which more easily allows radio waves to pass through rather than be reflected.)
Also, a radio station’s transmission doesn’t eminate from the antenna in a perfect spherical shape, so if you could visualize the radio waves you’d see that the coverage area is unevenly shaped, and this doesn’t necessarily have to be at the fringe areas. Even in an area of generally strong signal, it is possible to have “holes” and “shadows” in the coverage… in radio industry parlance, they call it “gaps.” Pretty fancy huh?
Also, some automotive receivers just aren’t very sensitive, or the receiving antenna design had to be compromised for styling, cost, reliability or compatibility purposes. If it’s an AM station, the receiver probably uses an internal antenna, which means it’s surrounded by the radio wave-blocking steel of the car.
Creds: I’m an FCC licensed amateur radio operator and worked five years in the radio electronics industry… mostly military “counter communications” applications but we sold commercial TV, radio, and cell phone transmitters too.
I have the same problem with (what I assume is) the same radio station. My reception changes several times on my morning route as I go up and down hills and in different directions.
depends on AM or FM and the type of radio and antenna. all can do different things.
mostly you hear the strongest station. a station may be blocked by mountains or buildings, other stations may be stronger being reflected off the same. you also might go into a low spot and loose a station.
as mentioned a stations coverage may have lobes. you might have a very strong signal in a lobe yet loose the station between lobes.
day or night, season or sunspot activity will all effect radio signals. sometimes it can make it better or worse.
Thanks for the information. I think the reduced power scenario makes the most sense, but I’m certainly no expert. What makes the whole thing so strange is that I take the same route to and from work each day. In the afternoon, I can pick up the station. In the morning, I can’t. Same roads, just moving in opposite directions.
Then the most likely explanation is the station operates on reduced power for part of the day. Also, if the station is far away, night reception will be better than day (all other things being equal), so I guess it depends on what time of the day your travel is.
