Hi A342,
I used to have a home built 16 element CoCo made from a generic coax. I eventually worked out that the Velocity Factor was 0.66 so cut my elements accordingly. I then placed it in some 22mm plastic waste pipe and mounted it at the apex of the roof. It worked very well until we had a winter storm and the pipe snapped just above the mounting point. It used to swing about a lot in light winds so I wasn’t surprised it eventually broke.
Make yourself a 12 and a 16 element CoCo and test them outdoors but not up the pole on the roof. You may have read on this forum that a lot of people have trouble making a CoCo that works, so congratulations on your build 
As others have said, you need a filter to remove the unwanted signals in the 900 Mhz band. You seem to be a DIYer so take a look at a thread I started about Interdigital filters.
[Note] I have NO experience of radio/physics etc. apart from what I’ve learned on this forum and a lot of reading 