Followup to my question. In order to get the benefit from antennas
like the Yagis, does a wire have to be connected from the antenna
to the phone? Or can the GSM phone's reception be improved simply
by being within a few meters of the antenna? I have two bars on
the GSM phone now and want to boost it to 3 or 4.
Thanks
Tim

Tim, you may want to think about keeping a land line at the office too,
since no cellular provider (in the U.S.) is under any statutory
obligation to provide emergency dial service to any particular location.
 It may prove handy when your secretary has trouble barfing up their
most recent donut acquistion.

Food for thought?

Consider fitting a "car kit" to your house.  This will have an
external antenna hard-wired to a cradle which holds the phone
(simultaneously disconnecting the phone's own antenna).  A whip
antenna with 5 dBm (or more) gain should be more than adequate.
Ensure it's an antenna which doesn't require a ground plane, and
you can mount it anywhere there's the best signal (to brickwork,
for example).

Any inductive coupling will result in attenuation of signal, so
avoid "through-the-glass" antennae - make sure the wire is
continuous from antenna to phone cradle.  If you can't pass a
wire through the building perimeter, a high-gain glue-on phased
array compact antenna stuck to the inside of a window is an
alternative.  Again, this will be hard-wired to the phone.

I use a phased array antenna with the car kit in my vehicle, and
a whip antenna with the car kit in my house.

As an aside, using a Bluetooth phone and headset gives me
considerable freedom of movement when the phone's in the antenna
cradle (more than the nominal 10 metres in my case, with a
Siemens S55).

As I live in Australia, any references to the antennae I use
would probably be useless to you.

John

You have four basic options.Two of the options will spark some heated
discussion.
First option, Get a High-gain antenna and a coupler for your cell:
http://www.cellantenna.com/Antennas/yagi.htm

If signal is really poor, then put a Signal booster in line:
http://www.cellantenna.com/Boosters/cellphone_signal_boosters.htm

The problem with those two options is you are married to your desk with the
coax (unless you get a Bluetooth Headset).

If you have good signal outside, and very poor signal inside, then try a
passive repeater. Basically a high-gain Yagi antenna outside, and a
high-gain antenna inside and connect the two with some low loss coax. This
will provide a "conduit" of sorts for the signal into the building.

the last and most debated option is a Bi-Directional Amplifier. aka, a Small
repeater. This is set up just like the passive repeater, but includes a
special signal booster for better coverage in the building.

http://www.cellantenna.com/Boosters/cellphone_signal_boosters.htm

with the second two options, you are not married to your desk or coax
connection, you will have improved signal in portion of the building.
However, many will argue the legality of the BDA, even though they are FCC
approved Amplifiers.
We have a Nextel BDA installed in our building for our phones since the
signal was very poor. Now there is good signal everywhere, including the
basement.