semi-open anechoic chamber

hello,

I'm studying the viability of constructing a semi-open anechoic chamber. I'd been asked to make a 0.5-18GHz semi-open chamber. We would have to build it in our company area, and we are located in the middle of a 100.000 people town. So I think it's to difficult to make it semi-open because of the noise and interference. That's why i've been told to study the spectrum in the area. I haven't done it yet.
The first idea is to install the transmiter in a tower and the semi-open chamber in one of our roof tops.

Can you give me ideas, disadvantages, indications or sources of information?

My boss wants something quick and cheap, since a bigger and better full anechoic chamber is being designed. So this would be something that I guess doesn't have to be very precise.

I think main problems are:
- rf interference radiations and noise from the outside.
- reflections from the transmitter, since we don't have anything close to an open field, it's all filled with 3 and 4 storie buildings around the area.

I think my boss wants a semi-open because he thinks it is much cheaper than a full anechoic. I must so its viability or on the contrary, so all the disadvantages.

thank you all
see ya