Repeaters, Amplifiers, and External Antenae

Archived from groups: alt.cellular.sprintpcs (More info?)

<wmklein@nospam.netcom.com> wrote:

>Is there some place that talks about what these 3 things are - and what the
>differences (if any) are between them? I am looking for the least expensive
>(doesn't need to be portable) solution to my (see previous thread) "bad
>reception in old house" - with a Sanyo 200 - where reception OUTSIDE the house
>is OK.

The two websites I use are www.wilsoncellular.com and
www.digitalantenna.com. They both have FAQs and technical
information. I'm sure there are other good websites as well.

An amplifier increases the strength of the signals sent from and
received by your phone. One side of the amplifier is connected
directly to the phone via an antenna adapter. The other side is
connected to an antenna. Most newer amplifiers on the market are
bidirectional; that is, they amplify both the signals transmitted and
received by your phone. Amplifiers can only work with one phone, that
is the one connected to the amplifier.

Some amplifiers work only with 800 MHz, some with 1900 MHz, some with
both 800 and 1900 MHz, some with analog, some with CDMA, some with
IDEN, etc. The more popular amplifiers you find on the websites now
seem to cover a wide range of cellular technology. Mine works with
800 and 1900 MHz AMPS/TDMA/PCS/CDMA/GSM850/GSM1900/GPRS, but not IDEN
(Nextel).

A also repeater increases the strength of the signals sent and
received by your phone. One side is connected to an antenna inside
your house, car, boat, etc., the other side is connected to an outside
antenna. The repeater will amplify the signal of any phone that is
located within the "inside" space, as opposed to the amplifier, which
works with only the phone connected to it. Most repeaters you'll find
are bidirectional. As with amplifiers, the repeater must support your
phone technology and frequency.

Repeaters require a separation distance between the two antennas. For
example, car repeaters only require a metal surface or some kind of
roof/wall structure to be between the inside and outside antennas.
But the car repeater will only pick up phone signals from an inside
space area about the size of a car interior. If you use the car
repeater in a house, it will probably only cover one room. Whole
house repeaters service phone signals over your entire house, but may
require 20 or more feet of separation distance between the antennas; a
wall or roof is usually not enough.

Amps and repeaters are useful when in areas of low signal strength.
If you are in an area that has decent signal strength, but there is
something blocking that good signal from your phone (like a wall), a
simple antenna alone may be the solution. Antennas are generally
passive, that is, they don't use external power to amplify the signal.

A simple antenna pretty much radiates equally in all directions
(spherical pattern). For cellular phone use, it is sometimes a waste
of transmission energy to send your signal straight up (vertically)
towards space. It would be better if the antenna could concentrate the
transmission signal energy to follow more along the horizon, where the
cell towers are. The antenna can be constructed to do this, so that
the spherical transmission pattern is more of an ellipsoid. Kind of
like squeezing a round ballon...

This is a gross simplification, but the higher the gain, the less
spherical the pattern. You can check out the web for information on
determining what antenna gain is best for you. If you are out in the
country, somewhat distant from the tower with few obstructions, a high
gain antenna, where the signal follows the horizon would be a good
choice. If you are in the city with lots of tall obstructions, you
need an antenna with a lower gain, because your signal does need a
strong vertical component to get past the tall obstructions. Of
course there are other completely directional antennas, that only
transmit and receive in the direction that they are pointed.

When using only an antenna, beware of the cable length and the number
of connectors between the phone and the antenna. There is some signal
strength lost at each connector. Also, antenna cables cause a
decrease in the signal strength as well, some worse than others. If
you have a long, low quality cable patched together with a bunch of
connectors, it may decrease the signal strength such that the signal
your phone actually gets will be too weak to establish a connection
with the tower.

Lots of simplification here that probably has the resident RF
engineers in a tizzy, but so be it..

Joe Huber
huber.joseph@comcast.net

Archived from groups: alt.cellular.sprintpcs (More info?)

On Thu, 02 Jun 2005 20:02:18 GMT, "John R. Copeland"
>"Joseph Huber" wrote in message news:k6ps91l20shbct9ttlpo4b9i5rm2osvmku@4ax.com...
>A truly spherical pattern would violate Maxwell's Equations.
>You won't find a pure form of one in our little RF universe.
>Think "doughnut pattern" instead.

Point well taken...


Joe Huber
huber.joseph@comcast.net

Archived from groups: alt.cellular.sprintpcs (More info?)

"ll" <lkslittle@REMOVEcomcastTHIS.net> wrote in message news:42A07A2B.8447F634@REMOVEcomcastTHIS.net...
>
> I have a friend who says that raising the built-in
> antenna on a cell phone has no effect. Is this true?
> How about on reception? How about on the amount of
> power used?

Extending the telescoping antenna normally gives a small improvement.
My experience is that 1900-MHz improves less than 800-MHz,
but that would be very dependent upon trade-offs made by the designers.
My personal experience doesn't cover a vast number of handsets.

If you know how to put your phone into the "field debug" mode,
or whatever other mode displays your received signals numerically,
you should notice a few dB stronger signals with the antenna deployed.
To be more specific, my phone gives about 3- to 6-dB improvement.
Three dB is a multiplier of two in signal strength, so don't sneer at it.

It's not always easy to observe, because the numbers jump around a lot.
You'll need to average the readings mentally.

Yes, extending the antenna can save power, too.
In CDMA protocols, when the base station sees a stronger received signal,
it will command the handset to throttle its transmitted power downward,
which of course uses less total power and reduces battery drain by a little.
The system goal is to keep all signals received by a base station equal,
and also to keep them all so low that a very few packets get lost in noise.