Cell phone amplifiers / external antennas

[jeff@work]

I was just wondering if anyone has had any experience with cell phone amplifiers and external antenna's. Do they work or are they a waste of money?
It'd really be nice to be able to boost the coverage of my cell phone when i'm out in the boonies! I'm thinking about something like the wilson direct connect amplifier.

http://www.wilsonelectronics.com/Products.php?Type=A

 

[bigreen505]

Jeff, do a search on www.4wdtrips.net. The question was recently ask over there and answered by some people who know what they are talking about. Perhaps DaveinDenver might be willing to rehash some of the knowledge.

 

[Scenic WonderRunner]

Good idea Jeff..........

I need the same thing!

So I just looked at the Wilson wireless amp. at your link and I think that's a great idea!

Seems to me the wireless one would be great....easy to use.

....and best of all.

Your buddies around you who need to make a call could just go stand by your truck and make and receive calls! No screwing in to your antenna slot on your cell phones.

So how much $$$ does it cost............next thing I have to look up.


So...........is the wireless unit any less effective than a wired up system?

 

[bigreen505]

Mark, same advice I gave Jeff, go read the thread on the other board. The advice was priceless and one thing that came up is different antennas are needed in mountainous terrain versus a flat area. http://www.4wdtrips.net/forum/showthread.php?t=3305

 

[DaveInDenver]

Yo, Dave here. No comments specifically on particular cell phone amps. Heck, I just /got/ a cell phone this year!

I would think that an external antenna would be an excellent addition for the somewhat non-intrepid traveler, though. This alone will probably do wonders for the range of your phone. What little I know about the cell system would barely pass for complete ignorance. I believe that the max a cell phone can radiate is 3W, which is around 10X what most handheld phone internal transmitters can do. This is a 10dB increase in power and would work out to around double the range in the city and probably about 4X range in open terrain line-of-sight. It ideally takes about 6dB increase in power to increase range by two. An easy to remember rule of thumb is roughly 10 times, or 10dB, power increase to effectively double the range with some assurance, 6dB is technically 4 times increase in power and assuming ideal conditions you'll double the range. Mostly though to get double the range you need more than 4 times the power, which allows for marginal conditions.

An external antenna is going to do about the same, heck even a unity gain antenna mounted outside the car is going to make a HUGE difference in efficiency, since your truck acts like a very good Farraday cage for 800MHz frequencies. I'd say that the combo of an external antenna and a 3W amp would do around 20dB increase in effective radiated power (basically 100x times the external ERP of just the phone inside your car), which is going to give you around 8x to 10X the range when working line of sight. Which, is BTW, an important point. Cell phones (and really anything at and above 2M wavelength) is line of sight. All the power in the world isn't going to help if the receiver/transmitter (i.e. cell tower) is beyond your line of sight. On level ground, that means about 10 miles max, so keep in mind that going to higher ground is key.

Anyway, to answer your questions, yes on both probably. I would definitely add an external antenna if you need cell coverage. That will help a ton. Add the amp if you find you're still marginal. But it all depends on a cell tower being reasonably close, by which I mean like 20 or so miles. An antenna and amp aren't going to give you cell coverage in the middle of the Yukon or something, though.

 

[mountainpete]

I started that post over at 4wdtrips and have since had a lot of experience with the booster and other versions of it. I can honestly say that the in-line direct booster does significantly increase performance and "range" of a cell phone when paired with the correct antenna.In my experience, I have extended coverage by over 30 km in mountainous terrain (in British Columbia no less!). However, like any wireless device, range cannot be guaranteed and is very topography dependant.

I have actually done tests with some Wireless Engineer co-workers of mine directly over the cellular network. Even simply a good external antenna with no booster connected to the antenna port of a phone can see RSSI changes of over 15 db. Good boosters still allow the network to control the power output of the phone, but I have had personal experience where I would go from a no-service condition to a mid 80's RSSI. A massive difference!

As for the wireless boosters, I am not sold on them. They really easy to use and work well in theory... but.... First, no wireless booster can match a direct connect and even Wilson techs will readily admit that. The bottom line is that wired connections are more efficient and reliable - you can also get pretty nice and long cables if you want.

Second, your cell phone must be very close to the booster antenna. (The one you would put inside your truck, not the one outside on the roof) Ideally 12 - 16 inches. Anything over 3 feet severely degrades performance. Unfortuantely US and Canadian law states that wireless boosters must serve only a very small personal area around the antenna and therefore power is extremely low. That is why in-building coverage boosters usually require an engineer for anything more than a single room. If you are thinking you can sit on a chair outside of your truck and still see the benefits of the booster... well it's not going to happen. You basically have to get into the truck and sit close the that antenna - the closer you are the better you will recieve.

Third, and this is only a PERSONAL OPINION, but I am still concerned with potential health effects of this type of booster. I know that the power is low and the frequencies are not proven to cause issues, but since the number of people using this product is still extremely low I am not totally comfortable with what is essentially a low power repeater inside my truck. I would rather buy a new $8.00 adapter with every one I change (and yes, I change phones alot!) and only use a wired booster when I need it.

The wired and wireless boosters run differently as well. The wired version essentially becomes an extension of your phone and allows the network to control it. The wireless version is more of a repeater and that is why many networks do not sell it themselves. I am sure the Wilson site can explain it better than I can.

If anyone wants I can snap a few pics of my install, but it's pretty darn simple as the unit is really small.

Pete

 

[Scenic WonderRunner]

Great info guys!

I've seen the thread over at 4WDTrips........but never dug into it.

Now that I'm planning a longer range trip with many out of the way campsites.....I'm more interested.

Here is a site I found with a system and price.

I agree that the "wired" system is prolly best.

This info could be so important to the right person..........it could even save someones life one day if you Really got into trouble and needed Help right away!

I'm sure there are tons of places selling this. But here is what popped up on a search for me today


http://mycellularsolutions.com/dbdirectm_signal_booster.html




.

 

[mountainpete]

I'm sure there are tons of places selling this. But here is what popped up on a search for me today


http://mycellularsolutions.com/dbdirectm_signal_booster.html

That's a decent package as long as it's mated with this antenna: http://mycellularsolutions.com/MAGNET_MOUNT_ANTENNA.html I actually tested this antenna on mag mount versus an NMO mount. They were both on company vehicles designed for drive testing the cellular network so the installs were both perfect. There was so little performance difference that it makes the removable mag mount more appealing - especially if you want to carry a canoe like me!

Just a thought... dual band (800 & 1.9) boosters are great, but the 1.9 portion is sometimes redundant. You may want to find out if your cell phone carrier even deploys 1.9 frequency towers in non-urban areas. Most reserve 1.9 for major cities and highly populated areas. 800 mhz also has some excellent coverage properties which make it more appealing for carriers in rural areas - especially on CDMA.

Personally, I use a 800 mhz only booster as I never need to use the booster close to an urban area and there is no 1.9 in the mountains. But if there is little or no cost difference, you might as well go with the dual band version.

Pete

 

[mountainpete]

Cell phones (and really anything at and above 2M wavelength) is line of sight. All the power in the world isn't going to help if the receiver/transmitter (i.e. cell tower) is beyond your line of sight.

Generally it should be line of sight but Optimization Techs will tell you that it's not a rule. First, I am no tech or engineer, but I have seen some absolutely unbelievable things with ducting and signals following topography.

Years ago, I was involved with an issue where one customer was always hitting a tower that was over 70 kms away when there was two towers closer - as a result all they were being charged long distance for many of their local calls. It turns out that the signal snaked it's way along a small river valley all the way to his house. It actually went under the signal from other sites to make it there. A tech had to do a drive by to believe it. The site had to be re-tuned and the antenna angle adjusted to prevent this from happening again.

So I would say that in ideal conditions it is line of sight, but in reality cellular can be sneaky

 

[DaveInDenver]

FWIW, I read Pete's explaination and it occurred to me that some people might not understand it all. He works in the industry and his explainations are detailed and excellent!

I started that post over at 4wdtrips and have since had a lot of experience with the booster and other versions of it.

Even simply a good external antenna with no booster connected to the antenna port of a phone can see RSSI changes of over 15 db. Good boosters still allow the network to control the power output of the phone, but I have had personal experience where I would go from a no-service condition to a mid 80's RSSI. A massive difference!

RSSI is the measure of received field strength (it stands for received signal strength indicator). It's basically a measure of radio frequency energy at the handset. It's calculated using a series of summing stages, so it's technically an analog measure between or right after the RF/IF stages. There are 2 important values of RSSI, the dynamic range (in dB) and gain (usually uV/dB, but sometimes uA/dB). Both are important, but mostly in this case dynamic range is key, since that's the measure of signal to noise. The better the SNR, the lower the BER (bit error rate) and the more likely you are to get service.

 

[mountainpete]

RSSI is the measure of received field strength (it stands for received signal strength indicator). It's basically a measure of radio frequency energy at the handset. It's calculated using a series of summing stages, so it's technically an analog measure between or right after the RF/IF stages. There are 2 important values of RSSI, the dynamic range (in dB) and gain (usually uV/dB, but sometimes uA/dB). Both are important, but mostly in this case dynamic range is key, since that's the measure of signal to noise. The better the SNR, the lower the BER (bit error rate) and the more likely you are to get service.

Dave, you rock :bowdown:

Many cell phones allow you to jump into a test mode. Just search Google for you phone model the words "test mode". The majority of test modes will give you the phone's RSSI perspective. The lower the number the better.

I've at arms lenght from the technical side way too long... might have to visit might have to arrange for a few ride alongs again :sombrero:

 

[mountainpete]

Totally agree with you Dave :sombrero:

 

[jeff@work]

Wow thanks guys! Even better info than i was expecting. It sounds like the amplifier and antenna would definitely be worth it for what i want. I have to admit i did get a bit lost on trying to decide which antenna would be best for me. I'm mostly concerned with improving reception in mountain areas and i'm looking at either the wilson

Mini Magnet Mount Cellular Antenna (301113)
Part Number 301113
Frequency Range 806-894 MHz / 1850-1990 MHz
Impedance 50 ohms
Antenna Gain 2.12 dBi 806-894MHz / 3.12 dBi 1850-1990 MHz
Radiation Omni
Polarization Vertical
Wavelength 1/4 Wavelength 806-894 MHz / 9/16 Wavelength 1850-1990 MHz
Ground Plane Metal ground plane required
Connector FME Female
Material Whip - Plastic-Coated Steel Wire
Coax Cable RG174 - 10 feet / 3.05 meters
Height 4.175 inches / 10.60 cm
Mount Rare earth magnet

or the

Magnet Mount Cellular Antenna (301103)
Part Number 301103
Frequency Range 806-894 MHz / 1850-1990 MHz
Impedance 50 ohms
Antenna Gain 5.12 dBi 806-894MHz / 6.12 dBi 1850-1990 MHz
Radiation Omni
Polarization Vertical
Wavelength 0.9 Wavelength 806-894 MHz / 2.0 Wavelength 1850-1990 MHz
Ground Plane Metal ground plane required
Connector FME Female
Material Whip - Stainless Steel
Coax Cable RG174 - 10 feet / 3.05 meters
Height 12.25 inches / 31.12 cm
Mount Rare earth magnet

Thoughts?

 

[bigreen505]

I'm mostly concerned with improving reception in mountain areas

Start by switching to Verizon. They have the best coverage in Colorado by miles.

 

[DaveInDenver]

Yeah, Jeff, it sort of drifted, eh?

You should go back and read the 4WD Trips link that William posted. There is some info regarding the gain numbers associated with antennas. The quick answer is that I'd probably spend my money on the 1/4 wavelength (301113) for all around use in the mountains. Pete, whatcha think?