How is it possible??

[lakota]

I put a CB in my jeep. The other day I was scrolling through the channels and on 17 there was all knids of activity. There were people claiming they were in South Carolina and one guy that said he was in Mobile Alabama. I am in Northern Ohio and they were coming in loud and clear. I didnt try talking to them.

I though a CB was a low power transmiter only capable of reaching out 30 miles or so depending on conditions. What were these guys talking on?

[kctibs]

Probably talking on skip. Usually can talk skip on a regular basis. Here is a defination. In radio propagation, skip refers to a radio signal being reflected or refracted by the atmosphere or ionosphere, and returning to Earth in far away locations. This phenomenon happens often with AM radio, enabling listeners to hear broadcasts across long distances.

Skip becomes stronger and weaker in accordance with an 11-year solar cycle; 2006 marked a bottom point of that cycle.

Occasionally (sometimes when meteor showers make ionized trails in the atmosphere), VHF signals skip. Some radio enthusiasts look for such signals and consider them TV and FM DX. Thermal inversions may also produce skipping

[charles p]

Can FM also skip?  Isn't it suppose to be line of sight?

When I was in the Coast Guard at a station in NC, I listened to a call from a cruise ship that had an engine room fire.  The call was on Channel 16 of our FM band.  The ship was near Cuba and talking to Miami.

On another occasion I listened to traffic from a ship off the west coast of Africa.

Both transmissions were late at night when the frequency was clear.

[lakota]

Can FM also skip?  Isn't it suppose to be line of sight?

When I was in the Coast Guard at a station in NC, I listened to a call from a cruise ship that had an engine room fire.  The call was on Channel 16 of our FM band.  The ship was near Cuba and talking to Miami.

On another occasion I listened to traffic from a ship off the west coast of Africa.

Both transmissions were late at night when the frequency was clear.

When I was on a fire department I remember sitting in the radio room and hearing Los Angeles Fire doing their morning radio checks occasionaly.

[trotterlg]

The form of modulation (AM or FM) has nothing to do with skip.  The frequency it is on is the factor.  Some frequencies are more apt to reflect than others, mostly higher frequiencies don't and lower ones do, just in general.  CB has always been prone to it, and it is very interesting to listen to.  Larry

[mrussel]

Can FM also skip?  Isn't it suppose to be line of sight?

When I was in the Coast Guard at a station in NC, I listened to a call from a cruise ship that had an engine room fire.  The call was on Channel 16 of our FM band.  The ship was near Cuba and talking to Miami.

On another occasion I listened to traffic from a ship off the west coast of Africa.

Both transmissions were late at night when the frequency was clear.

 Its not a matter of the modulation scheme but of the frequency. What people refer to as FM is around 80-110mhz. Those frequencies are pretty much line of sight. (and higher frequencies are as well.) Much of the CB band used to be called (long ago) by Ham Radio operators the "11 meter" band. It was their best DX or long distance band. They were not happy when it was taken away. Any of the bands around and below 30mhz can be used for very long distance communications,often with very low power. While more is often better,you can actually communicate with the other side of the planet using "skip" with as little as 1 watt. (A CB is usually around 5w) In fact many ham radio operators do this for fun,making very simple and inexpensive low power transmitters and trying to communicate long distances.

 One thing to keep in mind is that AM and FM are modulation schemes. AM encodes voice on the signal by varying the amplitude of the signal. FM varies the frequency instead,and is more immune to static and noise. This can be done on any frequency,but the FCC for several reasons only allows commercial radio stations to broadcast AM in the range of .540-1.6Mhz. In the range of 88-108Mhz,they are allowed to use FM modulation. As you can see,FM stations will tend to act in a more "line of sight" manner while AM stations can under the right circumstances travel quite a distance and in fact,stations are required to take steps not to interfere with other stations on the same frequencies in other areas.

[Rickk]

I used to be chief engineer for WTCC-FM (90.7 Mhz) in Massachusetts. One summer we started getting strange audio from our of the air monitor. The monitor reciever's antenna was only 50 feet below the 4KW transmitting antenna.

What we were hearing, and it was completely capturing and overpowering our own transmitter, was an FM station in Florida on the same frequency.

The situation lasted for an entire week. About the second day of it we found that they Florida station was hearing us as well.

Of course, many of the Massachusetts listeners were hearing the florida station, and many florida stations were hearing us. We called the florida station and had many phone conversations on the air between the air personalities of both stations.

While it would have been a problem if it kept up, it was kind of funny for the few days that it lasted.

During the same period, the local 2 meter repeater was getting lots of hits from down south mobiles as well.

[SHOOTALL]

When in college I had a friend with a CB . His dad was a radio man in the Navy and had that boys CB tuned up real sharp. He had an amp on the ant. and something else called a driver i think. he could switch them around to make the radio do different things. Depending on weather or our location in the mts. we could pick up far off stations alot of nights. We had to be far enough from school or his broadcast would be heard on radios and even a TV if we were in the dorm parking lot. He talked to people all up and down the EAST Coast. In 1990 years later i had a CB and was in Arkansas comming home . Some guy was spouting off with bad stuff and another guy keyed his mike and covered him up for a few mins. Later the bad guy started up and got shut out again. He was bleeding 5 channels either way. Anyway the truck I was following and had been talking to all day ask the good guy where he was - reply Wyoming . Later when we got to tenn. the bad guy came back on and no sound from the guy in wy. Some guy in New York ask bad man where he was - reply Kingston Jamaica . Said there was no limit down there.
It is fun to listen to folks way off even if not so legal for them to do so.