Cell phone amplifiers / external antennas

pskhaat

2005 Expedition Trophy Champion
#16
I still have a mobile contract with the `old' AMPS network. It's the 850Mhz analog and was the old stand-by when the digital mode would not connect. I utilize a 3w Motorola bag phone and Wilson external AMPS antenna. I can get reception in places one would never expect.

AMPS is unfortunately to be phased out in 2008 :( but if you can manage to get AMPS service from someone, do it, it's crystal clear (no one is on it anymore), phones are cheap, and coverage is almost everywhere (at least where there's ever been a mobile tower).
 

DaveInDenver

Expedition Leader
#17
pskhaat said:
I still have a mobile contract with the `old' AMPS network. It's the 850Mhz analog and was the old stand-by when the digital mode would not connect. I utilize a 3w Motorola bag phone and Wilson external AMPS antenna. I can get reception in places one would never expect.
I think I've read that this is pretty much what Mark Whatley does it up in AK, although he uses a Yagi instead of a whip.
 

Grim Reaper

Expedition Leader
#18
I'm SHocked. I have been in the phone Business for 18 years and this is one of the very few discussions I have ever seen that actually had any merit on a forum that wasn't related to directly to phones.

I carry a FCC GROL and I am a level 2 or level 3 certified bench tech for consumer product for Analog, TDMA and GSM for Nokia, Motorola and Ericsson.

Analog ran on 3watts because it was a new system with minimal towers. As more towers were built the output power needed to handle the call decreased.

Hand helds were regulated down to .6 watts because of concerns of excessive radiation. It also is a much more practical output with regards to size of the product and the battery capacity needed to power it. Fact of the matter is most phones don't exceed .4 watts max output to keep battery size down. They don't need to produce more in most urban areas anymore. Most phones are running at.2 watts or less (the system steps them down) including traditional 3watt analog.

Most of this discussion has been about CDMA (Verizon) and Analog. Let me point out that Analog is very close to being shut down and TDMA is not far behind. Analog products have not been available from the carriers in several years nor has TDMA. Don't waste money on a product designed for these technologies. They will be gone in a little over a year.

By far your biggest gain is an external antenna with a ground plane. The car is interference. Tinted windows are interference. If the tint blocks UV it blocks signal. The difference between visible light and radio signal is the broadcast frequency. Thats it. The hand held phone has such a small antenna that it is near impossible to make it efficient. Most phones are directional on the antenna as well. The flip blocks the antenna o if the antenna is built int the housing the circuit card blocks half the area it can transmit. All these conditions need to be taken into consideration. A external antenna helps tremendously for all of these reasons.

The boosters on CDMA, TDMA and GSM I really can't endorse.

These technologies were designed for minimal transmit power to increase channel reuse to increase capacity. The system depends on minimal transmit distances in population areas. There is only so many available channels in the spectrum width. Tower spacing has more to do with system call capacity and physical line of sight impediments then anything else.

A 200 ft tower on level ground can easily handle calls 50 miles out if the antenna is good on both ends. A tower on level ground in a hard woood forest in winter has less range as the trees become interference. Its even worse when the trees have leaves.

Its ground clutter and population density that dictate where the coverage area will be for a tower. In a dense population area a tower will be adjusted by power output and antenna angle to have a lower physical service area to all for more towers to be installed. There area also other issues including geographic coverage licenses. A carrier will down tilt the antennas to stay within that licensed area and that is forced by the FCC. So if you are on the edge of your carriers coverage area and a different carrier licensed on a different technology or there is no roaming agreement in place the system will drop you when you are beyond its licensed coverage area.

The phones have output power settings as well that the system will kick the phone to the minimum power it can still receive a good signal at the tower. While it would help to have a booster on the fringe of the system you may get into an issue where the tower would see you overdriving and tell the phone to lower out put. If it cant lower that output to the expected range for the level it may dump the call to prevent co channel interference. So these sort of liner boosters may actually increase dropped calls in urban areas.

Towers are programed to know what to expect the phone within its service area to be powered at when they hand off. This aids in tower hand-offs so that the system can make space for the next call once it hits a signal level that the system will feel it at the end of where it can provide a clear signal. Again the boosted output would throw a monkey wrench into the programmed parameters.
 

mountainpete

Spamicus Eliminatus
#19
jeff@work said:
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?
While I have used both, I currently use the 301103 and have been very impressed with it. I would not hesitate to purchase it again.
 

mountainpete

Spamicus Eliminatus
#20
DaveInDenver said:
Removed the bow down thingie. I actually trained as an RF engineer in EE school, just never got the chance to work in the field. So I became a ham and dusted off the fields and communications books... I'm clueless on way too many other things, that I might as well try to puke a little in hopes that some of it is actually right.

Well I'm giving it right back :bowdown:

Too cool that you are trained as an RF Engineer...
 

mountainpete

Spamicus Eliminatus
#21
pskhaat said:
I still have a mobile contract with the `old' AMPS network. It's the 850Mhz analog and was the old stand-by when the digital mode would not connect. I utilize a 3w Motorola bag phone and Wilson external AMPS antenna. I can get reception in places one would never expect.

AMPS is unfortunately to be phased out in 2008 but if you can manage to get AMPS service from someone, do it, it's crystal clear (no one is on it anymore), phones are cheap, and coverage is almost everywhere (at least where there's ever been a mobile tower).
The bonus about these boosters is that most will work on AMPS too. So if you have a tri-mode handset (which many still are) you can force it to analogue (or analog for you Americans!) and get basically the same setup as that old bag phone is.

DaveInDenver said:
I think I've read that this is pretty much what Mark Whatley does it up in AK, although he uses a Yagi instead of a whip.
I have a 3 watt analogue bagphone that I have attached to a Yagi in the past. You have to get it up high and your directions right, but man can you get calls out in places you never expect. But you have to be pretty serious and know exactly which direction the site is to use it.

Pete
 

mountainpete

Spamicus Eliminatus
#22
Grim Reaper said:
I carry a FCC GROL and I am a level 2 or level 3 certified bench tech for consumer product for Analog, TDMA and GSM for Nokia, Motorola and Ericsson.
Very cool!

Analog ran on 3watts because it was a new system with minimal towers. As more towers were built the output power needed to handle the call decreased.

Hand helds were regulated down to .6 watts because of concerns of excessive radiation. It also is a much more practical output with regards to size of the product and the battery capacity needed to power it. Fact of the matter is most phones don't exceed .4 watts max output to keep battery size down. They don't need to produce more in most urban areas anymore. Most phones are running at.2 watts or less (the system steps them down) including traditional 3watt analog.

Most of this discussion has been about CDMA (Verizon) and Analog. Let me point out that Analog is very close to being shut down and TDMA is not far behind. Analog products have not been available from the carriers in several years nor has TDMA. Don't waste money on a product designed for these technologies. They will be gone in a little over a year.

By far your biggest gain is an external antenna with a ground plane. The car is interference. Tinted windows are interference. If the tint blocks UV it blocks signal. The difference between visible light and radio signal is the broadcast frequency. Thats it. The hand held phone has such a small antenna that it is near impossible to make it efficient. Most phones are directional on the antenna as well. The flip blocks the antenna o if the antenna is built int the housing the circuit card blocks half the area it can transmit. All these conditions need to be taken into consideration. A external antenna helps tremendously for all of these reasons.
Great information and advice!


The boosters on CDMA, TDMA and GSM I really can't endorse.

These technologies were designed for minimal transmit power to increase channel reuse to increase capacity. The system depends on minimal transmit distances in population areas. There is only so many available channels in the spectrum width. Tower spacing has more to do with system call capacity and physical line of sight impediments then anything else.

A 200 ft tower on level ground can easily handle calls 50 miles out if the antenna is good on both ends. A tower on level ground in a hard woood forest in winter has less range as the trees become interference. Its even worse when the trees have leaves.
This is really great information and you make some excellent points. I really like how you mentioned things like leaves on trees - makes a huge difference. Especially the needle length of Douglas Fir trees... very similar in length to a 800 MHZ wave.

Its ground clutter and population density that dictate where the coverage area will be for a tower. In a dense population area a tower will be adjusted by power output and antenna angle to have a lower physical service area to all for more towers to be installed. There area also other issues including geographic coverage licenses. A carrier will down tilt the antennas to stay within that licensed area and that is forced by the FCC. So if you are on the edge of your carriers coverage area and a different carrier licensed on a different technology or there is no roaming agreement in place the system will drop you when you are beyond its licensed coverage area.
The carrier I work for does set limits on certain sites but it is more of an optimization strategy than licence related. Certain large, high capacity sites may have a 50 km distance limit imposed in order to ensure there is no conflicts with surrounding sites that use a similar portion of the spectrum. However in mountainous rural sites, these limits are set far less often. But then again, this is to the best of my knowledge and experience and I am obviously not a tech.

The phones have output power settings as well that the system will kick the phone to the minimum power it can still receive a good signal at the tower. While it would help to have a booster on the fringe of the system you may get into an issue where the tower would see you overdriving and tell the phone to lower out put. If it cant lower that output to the expected range for the level it may dump the call to prevent co channel interference. So these sort of liner boosters may actually increase dropped calls in urban areas.

Towers are programed to know what to expect the phone within its service area to be powered at when they hand off. This aids in tower hand-offs so that the system can make space for the next call once it hits a signal level that the system will feel it at the end of where it can provide a clear signal. Again the boosted output would throw a monkey wrench into the programmed parameters.
First, I totally agree that boosters do not belong in urban areas. I think they are an absolute waste of money there. Second, the Wilson in-line boosters still allow the network to adjust the power of the phone and booster to avoid the "dump". So eventhough your booster may be 3 watts, it's output is to a maximum of 3 watts and could be as low as 0.1 if that's what the network dictates. The inline boosters is treated as an extension of the handset by the network. However, I think the wireless versions of the boosters may have this problem and that is why most carriers don't sell them directly.

Really glad you chimed in Grim Reaper - great post!
 
#23
At one time a guy at AT&T told me Nokia was going to going to bring into production digital bag phones with 3 watts. If I could wait about 3 months it would be on the market. I waited 3 months, called and nobody had any idea of what I was talking about. Of course it could also be because it went from someone with a distinct Carolinas accent, to a lady who answered the phone with, "good mornin, whats'a matta wit you phone, and what can I do to heppa you" (I started laughing, I thought she was puttin me own, she wasnt) I had been having connection problems after getting switched from amps to whatever other band they had chosen. My old bag phone was great, had an external anttenna hooked up and most people would ask if I was in the office when I called.

Technology may be responible for improvement on many things, but when it comes to cell phones its gone down the crapper.
 
Last edited:

Grim Reaper

Expedition Leader
#24
mountainpete said:
First, I totally agree that boosters do not belong in urban areas. I think they are an absolute waste of money there. Second, the Wilson in-line boosters still allow the network to adjust the power of the phone and booster to avoid the "dump". So eventhough your booster may be 3 watts, it's output is to a maximum of 3 watts and could be as low as 0.1 if that's what the network dictates. The inline boosters is treated as an extension of the handset by the network. However, I think the wireless versions of the boosters may have this problem and that is why most carriers don't sell them directly.

Really glad you chimed in Grim Reaper - great post!
Most of these "Boosters" are just a linear broad frequency amplifier. What ever gets pumped into them at 800 or 1900 it roughly triples the output power.

Understanding that the booster is indiscriminate and just multiplies output x3 then the lowest output the booster is capable is still three times the output of the phone. I would have to dig out my Manuals. It's been almost three years since I worked as a bench tech but the lowers out put is something ridiculously low like .012 watts. Not only does it boost its out put power it boosts its output trash. So if you have a cheesy transmitter that is dumping noise that noise gets boosted as well.

Now a gain antenna doesn't boost power at all, it boost range. It is like an omni directional Yagi. A non gain antenna makes a donut of signal if you were to look at a cross section of its signal area.

With a gain antenna antenna is divided into two or possible three sections with a tuning coil between those sections. What happens is when you stack those sections and take the tuning coil to get them phased together it pushes down against the "ground plane" and that pushes the signal out farther. Its like taking that donut and squashing it flat on a table. You didn't change the quantity (output power) you just change its shape.

The problem is it makes it more directional. If the tower was in front of you and you drove uphill then the signal would be pointed up hill and over shoot the top of the tower. So you get a 20db gain antenna that signal output hight is very short and very directional. Works great when you are scooting across the plains but you get in the foot hills and its shooting into the sky or the ground. Tilting the antenna doesn't fix this because the antennas relation to the ground plane is what dictates its direction.

So knowing that in a hilly area the lower gain antenna will actually work better because it can do a better job at hitting towers on hills and valleys in relation to where the antenna is.

Now most dB ratings on antenna's is "theoretical" and not proven. The reason being is gain in that design depends on the ground plane (flat sheet of conductive material. Now the Wilson's do attempt to make a ground plane with the horizontal masts at the bottom but if you mount that antenna on a mirror like they do on a semi then its much less effective then if it was mounted in the center of the roof.

When I was running a install shop I always made a point that on Roof mounts that you had the antenna mounted so the the hight of the mast you also had that distance around the antenna on the roof. This simple rule helps ensure an effective ground plane. you stick a antenna on the edge of a roof then half the signal falls off the roof and it loose a lot of the gain on that side. It also tends to pull up the signal direction on the opposite side. Thats why I run a cheap 1/4 wave mag mount stuck to the center of my hood. It has a much better ground plane then a full wave 102 inch whip hanging on a spare tire rack and in most instance it will out perform that 102
 

Grim Reaper

Expedition Leader
#25
perterra said:
At one time a guy at AT&T told me Nokia was going to going to bring into production digital bag phones with 3 watts. If I could wait about 3 months it would be on the market. I waited 3 months, called and nobody had any idea of what I was talking about. Of course it could also be because it went from someone with a distinct Carolinas accent, to a lady who answered the phone with, "good mornin, whats'a matta wit you phone, and what can I do to heppa you" (I started laughing, I thought she was puttin me own, she wasnt) I had been having connection problems after getting switched from amps to whatever other band they had chosen. My old bag phone was great, had an external anttenna hooked up and most people would ask if I was in the office when I called.

Technology may be responible for improvement on many things, but when it comes to cell phones its gone down the crapper.

There were some 3watt digitals out. All of them that I saw were made by Motorola or Harris (and the Harris was a Motorola knock off that most of the parts were sourced from Motorola). That was around 86 when the Olympics were in Atlanta.

There were a few reasons why they never really took off. Bag phones suck to carry. The trend was going to hand held so that you could use the phone all the time and stick it in your pocket instead of carrying a 5lb bag.

The other reason is capacity. In 86 the US was nearly 10 years behind in technology to Europe. You can thank the FCC and government regulations for that. This was the requirement that the carriers keep Analog viable. Most of the world never used TDMA or CDMA. the problem is GSM is very complicated and at the time nobody could figure out how to make Analog jive with GSM in a small hand held device. So they trimmed down GSM into a more simple technology's of TDMA and CDMA. That was key because the trend in the rest of the world was hand held and we were following it.

Like I pointed out TDMA is actually trimmed down GSM that the rest of the world went to. CDMA is a variant of that. This one step allowed the carriers to triple capacity with out tripling the quantity of towers. The users were exceeding capacity and with government regulations as they were towers could not be built at a fast enough rate to keep up with capacity needs.


TDMA= Time Division Multiple Access. What happens is three (in theory up to 6) uses share a channel by rotating who gets to broadcast. They do that by taking what you say turning it into a digital signal, cutting it into small pieces, compressing it and transmitting it in bursts. It can be related to how Ethernet works. Packets of data.

CDMA= Code Division Multiple Access. Again it allows three (and up to 6 in theory) different users to share a single channel but it does it by assigning a "Code" to each user. On he other end only the conversation with the same code is listened to and the rest is ignored.

Now why neither of these technologies when to a 6 user per channel design is on TDMA they could not build fast enough devices for a practical price to do it. On CDMA Noise floor is critical and the noise floor with 6 users per channel exceed the sensitivity that a reasonably priced receiver could handle.

So here we are just now catching up with GSM and UMTS.

So back to the original topic...Not enough people would buy a 3watt bag phone to make it worth building. So the decision was made to regulate the hole "digital system" down to .6 watts. That allowed for battery battery times and lighter weight products that the consumer trend was for.

Another reason why Analog had a more "warm" sound is it was analog. You talk in analog and analog replicates that very well. Digital loose a percentage of what you say and guesses what was lost so its just a bit off. The sound quality never had anything to do with the output power. In most urban areas a 3watt capable phone would be brodcasting at the same power ratings as a .6 watt and held. :confused:

There were some "booster install kits for hand held that allowed an Analog and a TDMA product to have 3 watt capability but most people don't realize that if you were on a Digital call the booster was shut off. All the gain in reception was the external antenna. :eek: ;)
 
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