Hi Peter

A passive repeater?

Yes they work but it may not solve your problem. It's the kind of thing
that may need some modelling etc first.

I use to have one setup where the outside signal was "very strong" but
the inside was "very weak". That worked well. I also (commercially)
modelled for a tender a railway cutting/tunnel (improvment) that was
about 3km from the base station. That bought the signal level in the
cutting from about -107 to -85dBm.

You may find a signal improvement only occurs with a few metres of the
inside antenna. Like I said it needs some modelling.

You will probably need a gain antenna (eg yagi) outside the house and
not in the attic.

There are also active repeaters azvailable for cellphone bands. They may
or may not be legal for use in your country though.

Cheers Bob VK2YQA

peter wrote:
Is it possible to connect two external cellphone antenna together and put
one in the attic, the other inside my house to improve the situation?