Re: how can I build an arial TV antenna.

I'm not sure if you're asking how to build an antenna or how to 
build an elevated installation for a TV antenna.

Relative to installing TV antennas, there are a number of 
handyman-oriented books on the topic.  A book catalog search on "television 
antennas", "television", or "video installation" should be able to identify 
suitable books.  Did you try asking a librarian for assistance at the 
library?  Other places you might try are the local bookstore, one of the 
online book retailers, or the book section of the local electronics store. 
"The Radio Amateur's Handbook", a work oriented at radio hobbyists 
published by the American Radio Relay League (see their Web page), also has 
some good information on installing antennas on towers, although the info 
is not specific to TV antennas.

You might also try doing a Web search to find home pages for TV antenna 
manufacturers.

Building a TV antenna from scratch is possible for a dedicated hobbyist.  
Places to look for information include "The Radio Amateur's Handook", and 
various technical texts on the subject of antenna engineering.  The public 
library and many electronic stores have the Radio Amateur's Handbook; 
you'll need to visit the library of an engineering college for the antenna 
engineering handbooks, or do a search of one of the big online book 
retailers.  

None of the books I mentioned, unfortunately, will give you step by step 
instructions on building a TV antenna, but the former will have antenna 
designs that can be adapted for television (it's really just a matter of 
scaling the antenna size appropriately to match television broadcast 
frequencies; in particular, look at their description of VHF and UHF 
antennas), and the latter will have the detailed design equations for many 
different types of antennas.

If you're interested in experimenting, I'd recommend starting with simple  
half-wave dipole antennas, and then trying a simple broadband antenna, then 
working your way upwards to simple reflector arrays of broadband elements, 
and then Yagi and log periodic antennas.

Good luck!

Steve Czarnecki