OT: Radio station signals?

[SackAttack]

I thought I'd throw this out there in case somebody knows the answer to it, but basically, I've been noticing that one of the local sports stations doesn't come in nearly as clear at night as it does during the daylight hours. When the sun's up, it comes in strong, but after the sun is down, there's always a hint of Mexican trumpets in the background.

Does anybody know if it's common practice for radio stations to turn down the power behind their broadcast signal during the later hours, or is there just something I'm unaware of from an environmental perspective that could cause that change?

[kcchief19]

You'll love this. Unlike FM radio waves, which are line-of-sight broadcast (the reason why FM stations will disappear when you drive over a hill or through a tunnel), AM radio waves can travel by bouncing around. Ionospheric reflection, which is much higher at night, can help bounce and amplify AM radio waves.

To combat this, the FCC requires some AM stations to lower their broadcast frequency or sign-off completely at sundown. If every AM radio station broadcast at full power, there would be massive interference making AM radio impossible to listen to.

As a result, some stations with lower night power are hard to pick up, while more powerful AM stations can be picked up at night when they can't be picked up during the day. For example, when I lived in Columbia I could pick up WBAP sports talk from Dallas at night, but obviously not during the day.

[SackAttack]

That probably explains it, then, as the particular station I've been listening to is on the AM dial.

Thanks, chief. My curiosity is sated now. :)

[AgPete]

I used to pick up St. Louis sports radio in Texas. I always get a kick out of the distant AM stations I can listen to at night. :)

[Sporkimata]

I think a lot of times it is because the signals bounce at night. Thats also why you can pick up stations from all over the country. They tend to interfere with the signals. Same thing with heat outside. The hotter it is the weaker the signal.
Or so I think. I was in radio in college, would think I could remember some of it.

[Sporkimata]

Im up in Kennewick washington and listen to sports talk in San fran at night...

[SackAttack]

I wondered if heat had anything to do with it, but I would have guessed the opposite, since the signals always seemed to come in stronger when it was warmer, but kcchief's ionospheric reflection explanation seems to be the ticket.

[cuervo72]

This should be a good page for info:

http://www.fcc.gov/mb/audio/bickel/daytime.html

There is a search there as well, if you're curious about specific stations. Basically what kcchief said sums it up. I could have sworn that some stations also need to change the direction of their transmission antenna, but maybe I was just imagining things.

[SackAttack]

Thanks cuervo. I'll check it out.

[cuervo72]

No problem (you'd think in 4 years I'd have learned more about the FCC than I have....)

[sterlingice]

You'll love this. Unlike FM radio waves, which are line-of-sight broadcast (the reason why FM stations will disappear when you drive over a hill or through a tunnel), AM radio waves can travel by bouncing around. Ionospheric reflection, which is much higher at night, can help bounce and amplify AM radio waves.

To combat this, the FCC requires some AM stations to lower their broadcast frequency or sign-off completely at sundown. If every AM radio station broadcast at full power, there would be massive interference making AM radio impossible to listen to.

As a result, some stations with lower night power are hard to pick up, while more powerful AM stations can be picked up at night when they can't be picked up during the day. For example, when I lived in Columbia I could pick up WBAP sports talk from Dallas at night, but obviously not during the day.
When I used to drive back and forth to Columbia from Lawrence, I tried to find as many stations as I could. So in the middle of Kansas and Missouri, I could hear Topeka, KC, Jefferson City, etc but I also got St Louis, Denver, Dallas, San Antonio, Chicago, Paducah (KY), Cincy, Cleveland, and Atlanta. Sports paradise, I tell you. I could listen to any game I wanted.

SI

[Hurst2112]

I used to pick up St. Louis sports radio in Texas. I always get a kick out of the distant AM stations I can listen to at night. :)

I picked up a St. Louis station in the middle of Wisconsin driving one clear winder evening. I have also gotten a Toronto station here and there.

Cool stuff.

I have also gotten a milwaukee FM station in green bay before...during the summer evenings. At about 130 away, it is very strange.

[kcchief19]

I wondered if heat had anything to do with it, but I would have guessed the opposite, since the signals always seemed to come in stronger when it was warmer, but kcchief's ionospheric reflection explanation seems to be the ticket.This is probably where I get more confused because it's science, but my understanding is that ionospheric reflection depends on the density of the ionosphere, which is affected by solar radiation. The reason why the ionsphere bounces radio waves at not is because the field is stronger and is able to reflect waves more effectively. Somehow, I believe greater solar radiation causes higher ionospheric reflection, but the reflection is not as great during the day because of the solar radiation. Of course, I could be drunk.

I was a real radio nut back in the day. I'd wander out into the field to see what kind of stations I could pick up, and for a while we had a shortwave radio. It was in the early '80s and we could pick up a station in Japan that played Japanese versions of English songs, yet they seemed to be sung in an English accent. I remember "Centerfold" by the J. Geils Band was popular at the time. That was bizarre.

[Craptacular]

As a result, some stations with lower night power are hard to pick up, while more powerful AM stations can be picked up at night when they can't be picked up during the day. For example, when I lived in Columbia I could pick up WBAP sports talk from Dallas at night, but obviously not during the day.

Growing up north of Milwaukee, I could often pick up a Dallas AM station at night. It was weird the first time I heard "You're listening to the Dallas Mavericks show".

[DanGarion]

You'll love this. Unlike FM radio waves, which are line-of-sight broadcast (the reason why FM stations will disappear when you drive over a hill or through a tunnel), AM radio waves can travel by bouncing around. Ionospheric reflection, which is much higher at night, can help bounce and amplify AM radio waves.


Actually if you drive in a tunnel or underpass AM radio doens't go through concrete walls as good as FM. ;)

[sterlingice]

Actually if you drive in a tunnel or underpass AM radio doens't go through concrete walls as good as FM. ;)
Actually, with what I gleaned from my signals and system analysis class, I can answer that. FM are shorter wavelength so they can go "through" stuff better. This is also why AM waves travel further- they have a longer wavelength (but can be dispersed easier).

SI

[ice4277]

I have also gotten a milwaukee FM station in green bay before...during the summer evenings. At about 130 away, it is very strange.
I think I can top that one. A few months ago I was driving back to Detroit from Mt. Pleasant (home of THE Central Michigan University ;) ) flipping through the stations. I picked up a top 40 station on 95.5; I work for a top 40 station located at 95.5 in Detroit, but thought it was really strange picking us up from north of Lansing, almost 2 hours away. I then noticed that the display screen for my radio had the station tagged as Wild 955, definitely NOT my station. At first I thought we had done some wacky kind of flip over the weekend (don't put anything past Clear Channel ;)) but then I heard a bunch of promos for 'bash at the beach', definitely not something you would be advertising in Detroit in January. I got home and did a little search, and found out Wild 955 is based in Palm Beach, Florida :eek: How the hell did I pick them up?

[corbes]

At night in Philadelphia, we get WWBD (1110) out of Charlotte. That means we get ACC basketball sometimes!

[Tekneek]

How the hell did I pick them up?

Was there a band of storms reaching between there and Florida? FM signals can travel through a storm like a tunnel. About 10 years ago I was spending the weekend at my mom's then-brand-new house. They had no cable or satellite, and just had one little TV with "rabbit-ears" on it. They were so far out of Atlanta that you could not pick up ATL stations, and could only pick up the couple of low-power stations nearby. This bank of thunderstorms came through that stretched through the Carolinas. For the next 3 or 4 hours I was getting perfectly clear pictures from channels in Charlotte, NC which was easily a 4 to 5 hour drive from where I was. The distance is obviously not the same, but the basic situation could have been similar.

[JonInMiddleGA]

Ah yes, "clear channel radio stations" (not to be confused with "Clear Channel" radio stations ;) ).

A great part of childhood for me & a lot of other older sports fan I imagine. While my son only knows that there's pretty much a game(s) on TV and online pretty much all the time, he'll never know the thrill of sneaking a transistor radio (sometimes with the cheesy earplug things) into bed at night so you could listen to games that were played after your bedtime.

Marty & Joe on 700 WLW & Buck & the Cards on KMOX are a pretty good part of my baseball memories. Back in the "old days", when the only televised games were the NBC Game of the Week on Saturday & the Braves on WTCG/WTBS, my grandfather would stay up late to listen to certain games on those two stations. See, Pop was a diehard Dodger fan from way back, so he could listen to them whenever they played the Reds or the Cardinals. Garvey-Lopes-Russell-Cey-Yeager and whatever combo was in the outfield. Sigh. I miss him, and I miss the way he enjoyed those games. But I'm awfully glad I've got those memories.

[Ksyrup]

Remember the FSU/Louisville game a couple of years ago, the one where Louisville beat FSU in a downpour - in Louisville? We were driving that night from Tallahassee to Orlando, and I lost the Tallahassee station and couldn't yet pick up the Orlando feed, but somehow, I got the Louisville AM station. Which, of course, was a mixed blessing, since I had to listen to their announcers...and they won.

[spleen1015]

There was a new station that started up here in INdy about 18 months ago and this sort of thing was happening. I called and talkto the station manager and he explained it to me.

There is a mileage radius that applies and if there is a station within that radius that has been in existence longer than your station, then your station has to turn down the signal at night. There is a station out of STL using the same frequency so the one here has to do the turn down. Funny thing is, at my house, that frequency gets nothing after dark.

[Wolfpack]

A couple of years ago, I was back in North Carolina for Christmas. Having been fed up with FM music stations for a while now, I'm pretty much over on the AM band listening to news and sports. At any rate, as I'm driving home from Raleigh at night, I start scanning around the dial and land on I think 950 AM. WWJ 950 out of Detroit to be precise. I end up listening to a traffic report that I normally get any time up here in Michigan, but down in North Carolina instead. Kinda strange. Further experimentation revealed I could get St. Louis, Cincinnati, and I think Philadelphia or Baltimore (or was it NYC?) stations. Still it was weird getting a Detroit traffic report from over 700 miles away.

[BigJohn&TheLions]

Also AM stations are mostly directional. You ever notice how FM stations have one broadcast antenna, and most AM have 3 or more? The middle tower fires the signal, the others bend the signal. it is entirely possible to stand with a radio down the block from the transmitter and not hear the station, but have it come in clear 400 miles in the opposite direction. this is to avoid interference with other stations.

[sooner333]

My dad grew up all over the midwest and southwest, but he said when he was a kid, he'd always go to sleep listening to Harry Carey and the St. Louis Cardinals...I assume on KMOX. Another important thing clear channel radio did was popularize new music forms, such as country music on WSM from Nashville...they could reach a much bigger audience, including rural areas.

[ice4277]

Was there a band of storms reaching between there and Florida? FM signals can travel through a storm like a tunnel. About 10 years ago I was spending the weekend at my mom's then-brand-new house. They had no cable or satellite, and just had one little TV with "rabbit-ears" on it. They were so far out of Atlanta that you could not pick up ATL stations, and could only pick up the couple of low-power stations nearby. This bank of thunderstorms came through that stretched through the Carolinas. For the next 3 or 4 hours I was getting perfectly clear pictures from channels in Charlotte, NC which was easily a 4 to 5 hour drive from where I was. The distance is obviously not the same, but the basic situation could have been similar.
Truthfully I don't remember, if there were any storms they weren't very big because other than the radio thing it was a very uneventful drive. For what its worth I asked a couple people I work with who are much more technically-inclined when it comes to broadcast equipment, and they weren't really sure how it happened either.

[CamEdwards]

I can pick up a New Orleans station at night... or at least I could in my old car. I haven't gone dial surfing at night yet to find out what I can pick up.

[JeeberD]

I remember when the Space Shuttle blew up last year I was coming home from work and flipping through the AM dial trying to get any new info that was out there. What I got, however, was a Denver station that was carrying the Nuggets game.

Needless to say, I quickly switched stations as the Nuggets were making me depressed... ;)

[Poli]

I got a shiny quarter for the first person who can explain to me why a metal clothes hanger makes such a great antenna.

It's actually quite a fascinating reason, if you're into electronics such as me. :)

[Easy Mac]

I like driving around and listening to Cavalier broadcasts.

[sterlingice]

I like driving around and listening to Cavalier broadcasts.
That makes one of you ;)

Now go update the cartoon draft thread so we can finish.

SI