A mobile antenna needs a metal ground plane beneath it.

I have used the top of a file cabinet, close drier, or the top of the air
conditioning compressor unit for a ground plane with pretty good success.
Once, I even appropriated a speed limit sign which the city left lying in my
mother's front yard a little too long.

If possible, try to get the antenna into the attic where it will be as high
as practical, and out of the way.

MFJ Enterprises makes a 1/4 wave and a 5/8 wave ground plane which are
easily installed in an attic. They also make a small 3 element 2 meter beam.
I used this antenna quite successfully mounted onto a balcony railing.

You will experience sharp signal nulls with any indoor antenna. These nulls
are caused by house wiring, air conditioning ducts, and other metal
throughout the house. They're unavoidable. You may have to try the antenna
in several locations around the house  to find the one which gives you the
overall best coverage.
Unless you have a very tall attic with lots of room, you won't get much more
gain than the above antennas from anything that your physical environment
will allow you to install.

Mike Duke, K5XU
American Council of Blind Radio Amateurs