Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post

H. John Kohl · 10-07-2005, 03:56 PM

All,
A few comments about Cell phone operations. Some of this has already been stated but I want to go back to the basics to try and make a reference for my comments.

Cell phones work on the line of site principal. That means your cell phone antenna needs to see the Cell towers antenna. Distance does play a role in this discussion but site blockers like mountains, hills or being in a valley are more associated to this discussion. Normally trees are not a problem for cell phones but are a problem for satellite service. (They work on a much higher frequency.) Distance is an effect because the earth is round so as you get farther away the tower it disappears behind the curvature of the earth. That is why the 8 to 12 mile rule comes into play.

If your cell antenna cannot see the tower then you need to raise it. If you are using only the cell phone then you have to gain altitude by climbing the hill or going up stairs to a window on the cell tower side of the house or climbing a tree in an emergency.

An external antenna higher in the air will assist you with being able to see the cell tower. With that thought the higher you get it the better within reason. Now I will shift to signal strength.

The signal to and from your cell phone needs to be there. If the Cell tower is to weak on receive signal and you have all the altitude you can get then a gained antenna on the receive side will help. (Antenna theory will be discussed after power.) This is done with a gained antenna or a receiver preamplifier. These items do cost money. The preamplifier receives the weak signal and amplifies it. This is similar to a stereo amplifier it increase the output. This time the output is to the cell phone instead of to your ears. Because of different types of signaling the amplifiers have to be designed to increase that type of signaling. On the transmit side you can also increase the transmit signal by adding a post amplifier. There are regulations tied to this process. Increasing your transmit power can interfere with other cell phones receive capability. This interference concept is a completely different topic.

A comment was made on coax lose. This is an issue and does need to be considered in the concept of getting a stronger signal to and from the cell tower. The proper terminology is decibels when talking about signal gain but for this discussion I will use multiplication reference to try and make it simple.

Statement: the higher the frequency the higher lose in the coax. Since cell phone frequencies are up in the 900 MHZ range the signal lose on coax is much greater than the 27 MHZ range for citizens band radios. If you use an amplifier that send the signal out 5 times stronger than the cell phone and the coax has a 5 times lose then you are at zero gain. However if your antenna is 30 feet higher than you are and your line of site blocking item (hill) is only 20 feet tall you will be able to use your phone with the outside antenna set up. With that though, if your signal loses is 5 times in the coax with no amplifier and it is still strong enough to reach the cell tower then you have success. Therefore, I claim height is the most important concept of getting better coverage.

Antenna designs. Antennas need the transmitting or receiving part of the antenna and a “ground plane” or the other half of the antenna. If you look at your car AM/FM antenna the wire is the receive part and the body of the car is the “ground plan.” Cars with the windshield antenna are two wires one going left and the other going right. With that antenna one side is the same as the wire and the other side is the ground plan. If your car is non-metallic then there is no ground plan and a different antenna that has the ground plan built in is needed. Magnetic antennas use the ground plan concept because they use the car’s mental to act as a ground plan as well as the magnetism is the glue to hold it in place. Fiberglass boat antennas are designed to be self-sufficient or have a built in ground plan. When you buy your external antenna you should state that you need one that does not require a ground plan if you are going to mount it on a pole or hang it from a tree branch with a string. (Sorry, tricks I use for my Ham antennas.)

I know this has not solved the problem, but I hope it may help to answer some of the questions.

Good luck and tow safe.

10-07-2005, 03:56 PM	#19
H. John Kohl Montana Master Join Date: May 2003 Location: New Bern Posts: 4,294 M.O.C. #311	All, A few comments about Cell phone operations. Some of this has already been stated but I want to go back to the basics to try and make a reference for my comments. Cell phones work on the line of site principal. That means your cell phone antenna needs to see the Cell towers antenna. Distance does play a role in this discussion but site blockers like mountains, hills or being in a valley are more associated to this discussion. Normally trees are not a problem for cell phones but are a problem for satellite service. (They work on a much higher frequency.) Distance is an effect because the earth is round so as you get farther away the tower it disappears behind the curvature of the earth. That is why the 8 to 12 mile rule comes into play. If your cell antenna cannot see the tower then you need to raise it. If you are using only the cell phone then you have to gain altitude by climbing the hill or going up stairs to a window on the cell tower side of the house or climbing a tree in an emergency. An external antenna higher in the air will assist you with being able to see the cell tower. With that thought the higher you get it the better within reason. Now I will shift to signal strength. The signal to and from your cell phone needs to be there. If the Cell tower is to weak on receive signal and you have all the altitude you can get then a gained antenna on the receive side will help. (Antenna theory will be discussed after power.) This is done with a gained antenna or a receiver preamplifier. These items do cost money. The preamplifier receives the weak signal and amplifies it. This is similar to a stereo amplifier it increase the output. This time the output is to the cell phone instead of to your ears. Because of different types of signaling the amplifiers have to be designed to increase that type of signaling. On the transmit side you can also increase the transmit signal by adding a post amplifier. There are regulations tied to this process. Increasing your transmit power can interfere with other cell phones receive capability. This interference concept is a completely different topic. A comment was made on coax lose. This is an issue and does need to be considered in the concept of getting a stronger signal to and from the cell tower. The proper terminology is decibels when talking about signal gain but for this discussion I will use multiplication reference to try and make it simple. Statement: the higher the frequency the higher lose in the coax. Since cell phone frequencies are up in the 900 MHZ range the signal lose on coax is much greater than the 27 MHZ range for citizens band radios. If you use an amplifier that send the signal out 5 times stronger than the cell phone and the coax has a 5 times lose then you are at zero gain. However if your antenna is 30 feet higher than you are and your line of site blocking item (hill) is only 20 feet tall you will be able to use your phone with the outside antenna set up. With that though, if your signal loses is 5 times in the coax with no amplifier and it is still strong enough to reach the cell tower then you have success. Therefore, I claim height is the most important concept of getting better coverage. Antenna designs. Antennas need the transmitting or receiving part of the antenna and a “ground plane” or the other half of the antenna. If you look at your car AM/FM antenna the wire is the receive part and the body of the car is the “ground plan.” Cars with the windshield antenna are two wires one going left and the other going right. With that antenna one side is the same as the wire and the other side is the ground plan. If your car is non-metallic then there is no ground plan and a different antenna that has the ground plan built in is needed. Magnetic antennas use the ground plan concept because they use the car’s mental to act as a ground plan as well as the magnetism is the glue to hold it in place. Fiberglass boat antennas are designed to be self-sufficient or have a built in ground plan. When you buy your external antenna you should state that you need one that does not require a ground plan if you are going to mount it on a pole or hang it from a tree branch with a string. (Sorry, tricks I use for my Ham antennas.) I know this has not solved the problem, but I hope it may help to answer some of the questions. Good luck and tow safe.