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Cell phone amplifier repeater

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gary350

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We go camping in the RV and often are out of cell phone range. That is ok with me most of the time, no cell, no computer, no TV, no internet, relax and enjoy it. In case of emergency it would be nice to have cell phone service. I see cell phone antenna repeaters online. It appears the antenna amplifier pulls in a signal then transmits a signal to the phone. Do these 900 MHz yagi antenna amplifiers really work?

https://ak1.ostkcdn.com/images/prod...enna-c918da07-83d7-4c5c-b4bd-ed1069b07e52.jpg

https://ak1.ostkcdn.com/images/prod...enna-974eee86-3f50-4096-a218-78dd08c8ef45.jpg
 
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gophert

Well-Known Member
Most Helpful Member
We go camping in the RV and often are out of cell phone range. That is ok with me most of the time, no cell, no computer, no TV, no internet, relax and enjoy it. In case of emergency it would be nice to have cell phone service. I see cell phone antenna repeaters online. It appears the antenna amplifier pulls in a signal then transmits a signal to the phone. Do these 900 MHz yagi antenna amplifiers really work?

https://ak1.ostkcdn.com/images/prod...enna-c918da07-83d7-4c5c-b4bd-ed1069b07e52.jpg

https://ak1.ostkcdn.com/images/prod...enna-974eee86-3f50-4096-a218-78dd08c8ef45.jpg

They work if they are in a location that has cell phone service. They will not have better service than your phone.

They are mostly intended for buildings where some locations inside the building do not have good signal. They can bridge the connection of a signal that is picked up on the roof of the building and repeated into the zones of the building with poor signal.
 

gary350

Well-Known Member
We are often camped 1/4 mile too far form cell phone service. Some places we might be 3 to 7 miles from cell phone service. I know a good antenna can receive a better signal then a poor antenna. Wonder if Yagi antenna is better than cell phone built in antenna? We were camping last week no service standing on the ground but standing on the picnic table I had a weak signal. My phone keeps getting text message beeps, and phone rings but when I answer I can not talk to them. Signal is strong enough to reach my phone but my phone will not transmit to the cell tower. When I am far away phone no do anything. Maybe yagi antenna amp repeater is stronger signal TO the phone but not TO the cell tower may be transmitter only not transceiver? I have noticed if I am out of range for voice text message still works.
 

audioguru

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Don't cell phones use many frequencies, not just 900MHz?
Is the earth flat or is it curved and doesn't the UHF frequency go straight and not follow the curvature of earth?

Find a yagi antenna that works at all the cell phone frequencies and attach it to a kite or helium balloon. I don't know how you will rotate the directional antenna.
 

JonSea

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Line of sight depends on the height of both antennas.

d = 1.17 ×sqrt(h1) + 1.17 x sqrt(h2)

Where d is the distance in miles and
h is the height in feet.

Let's say your phone is at a height of 5' and the cell tower is at 50'. Line of sight distance is

d = 1.17×sqrt(5) + 1.17 × sqrt(50) = 10.9 miles = 17.9km

What happens if we use a yagi raised to 10'?

d increases to 12.0 miles = 19km

If we can get the antenna up to 15', the distance increases to 12.8 miles = 20.6km.

If the service is marginal, a few feet increase in elevation of the antenna may make the difference to get a reliable signal.

lightvisibility.gif
 
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gophert

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What happens if we use a yagi raised to 10'?

d increases to 12.0 miles = 19km
Note, the earth is not a smooth marble.
What happens if the original poster decides he wants to camp near a mountain stream instead of in the middle of the Great Plains?
Note: streams are usually in Valleys next to mountains, not on mountains.
 

JonSea

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Most Helpful Member
The stated problem is that at the place he usually camps, he has marginal reception. If that is the problem he's trying to solve, an amplifier with an antenna mounted higher will help.
 

Externet

Well-Known Member
The stated problem is that at the place he usually camps, he has marginal reception. If that is the problem he's trying to solve, an amplifier with an antenna mounted higher will help.
If you mean amplifying the transmission of the cell phone; its signal will travel farther and will reach a cell tower. But you will never know it did, as the cell phone receiver still will not receive the distant cell tower.
If the cell phone transmission is amplified, the amplifier and antenna would need to be away from the cell phone after a longish TX output only coaxial cable as the increased signal emitted would deafen the receiver duplexer which is not designed to reject higher levels of RF.
To use a true repeater, would need to be in the band(s) both the phone and the tower operate, and located half way between, with electrical power supply and substantial $
And would say two full duplex repeaters would be needed. The FCC will not like it:
Your cell phone transmits in frequency A ---> repeater 1 receives A and transmits in frequency B
Repeater 2 receives in frequency B and transmits frequency A ---> to the tower, as the cell phone intended.
Same process from the cell tower back to the cell phone via repeaters 2 and 1, with frequencies C and D.
And there is a huge microprocessed complexity for choosing vacant channels.

An external antenna with gain and directionality placed at a higher point would need a monster of low-loss coaxial cable to work and tapping the duplexer if there is no external connector on the cell phone.
 

JonSea

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T-mobile and other cell phone companies offer "mini repeaters" for use where service is marginal. The uplink antenna is mounted in a window or on the roof, while the other antenna is mounted in the house. Indeed, this is the type of device the OP asked about.

Using a device such as this will increase range in two ways:
  • The antenna will be more effective than the internal antenna in the phone.
  • The higher antenna position will increase the "line of sight" distance to the cell tower.
The improved antenna position is accomplished without any cable losses, as there is no cable involved.

20180611_193911.jpg
 

gophert

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I suggest the OP talks with his carrier. Verizon sent someone to our production site, they installed three repeaters, left an invoice for $12000 and were on their way out the door in about an hour. We never had a dead area at our site after that.
 

gary350

Well-Known Member
The stated problem is that at the place he usually camps, he has marginal reception. If that is the problem he's trying to solve, an amplifier with an antenna mounted higher will help.
That is true, one day I learned if I stand on the picnic table I can talk on the cell phone but standing 3 ft lower I can not use the cell phone.

Something I just realized, a yagi antenna repeater might help receive a signal but if it is not a transceiver then I can not make the cell phone transmit farther. A 1 sided conversation on a phone is worthless.
 

crutschow

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A bunch of cell phone repeaters come up with a Google search and I assume they are duplex, (transmitter and receiver) otherwise they would not be of much use.
 

Nigel Goodwin

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That is true, one day I learned if I stand on the picnic table I can talk on the cell phone but standing 3 ft lower I can not use the cell phone.

Something I just realized, a yagi antenna repeater might help receive a signal but if it is not a transceiver then I can not make the cell phone transmit farther. A 1 sided conversation on a phone is worthless.
As already mentioned, any cellphone repeater by definition does both.

If you're getting (poor) reception just holding the cellphone, then a decent yagi aerial at ten feet or so would probably give enough extra gain to cure the problem - the difference in gain from the crappy aerial inside the phone to a decent size yagi is huge. A ten element yagi has a gain of 10dB over a dipole (and the internal aerial is likely to be worse than a dipole!) - this means 3W to the aerial produces 30W out of the aerial, and the same the other way - if the cell tower is 10W, it effectively becomes 100W.

This assumes you can get a repeater with a yagi?, but I suspect you can get them with an aerial socket, and simply plug a yagi in.
 

audioguru

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Most Helpful Member
There are many cell phone radio frequency bands. Yagi antennas are made for only one or two bands and you must select the correct band for your carrier. Some carriers use up to 10 radio frequency bands. Then you need 10 antennas and a antenna mixer?
Are the bands divided over a country then only one band serves one location? My research shows that lower radio frequencies are used in areas that need more range and higher frequencies and their many more channels are used in areas with a lot of phones.
I guess the campsite uses a lower frequency so one Yagi antenna is needed and the carrier will tell you the frequency.
 

ChrisP58

Well-Known Member
Most Helpful Member
That is true, one day I learned if I stand on the picnic table I can talk on the cell phone but standing 3 ft lower I can not use the cell phone.

Something I just realized, a yagi antenna repeater might help receive a signal but if it is not a transceiver then I can not make the cell phone transmit farther. A 1 sided conversation on a phone is worthless.
A 1 sided cell phone conversation is effectively impossible, since any modern cell phone communication requires two-way handshaking just to establish the link, before the conversation can even start.
 
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