[torbjorn]

There are some commercial cellular repeater systems but those are very bulky and expensive. They are used, for example, by network operators wanting to improve their coverage in subway tunnels or by military agencies wanting cell phone coverage in underground sites.

The main problem is that the repeater must allow simultaneous two-way communication without feedback problems etc.
On older "FDM" (frequency division multiplex) cell phone systems, like the now obsolete NMT system in Sweden, this was possible by using two duplex filters and two one-way amplifiers for each channel to be covered.
For newer "TDM" (time division multiplex) systems like GSM , the repeater will consist of a nearly complete cell phone and a base station interconnected at the baseband level.

A simpler approach that in fact has been useful in some cases is to just interconnect two antennas. One high-gain directional antenna which is placed outdoors and directed towards the desired base station, and one non-directional antenna placed indoors.
For a such arrangement to work well, it is extremely important to avoid all unnecessary cable losses. The cable between the antennas has to be as short as possible and it should be of good quality with low loss at the frequency involved. Thin RG-58 or similar cables should not be used no matter if the vendor has branded them as "low loss" or something similar.

[vtech]

..no mention of a "project" in your original post as it is NEVER a waste of time for an enthusiast to learn.

[ralfyd]

well, for me i never think that im wasted time if i want to build a project, especially if my project is successful. very nice to hear if im done a project that works. being enthusiast i fund to build it but if nothing shem that's ok. anyway thank you very much for replying my post.

[vtech]

While don't know of any such schematic , I can tell you that you are much better off trying to buy some sort of a repeater. (not cheap)
Even if you found a schematic, unless you know about high frequency RF and have equipment/parts, you are wasting your time.

[ralfyd]

I want a repeater antenna for the cellularphone
inside the house. I always looking for the signal because its weak signal coming inside the house. sometimes even in the window. So, if somebody has this schematic for the repeater antenna ranging 800mhz to above i think, pls share me. thanks!