Tom:

You might also try aluminum conduit or galvanized water pipe.
Both can probably be had locally.  Get various sizes to nest, drill and bolt 
together.

Other options are towers.  I know here in indiana, I am always hearing of 
people giving towers away if some one will take it down.
Usually in the 30 to 40 foot range.

You might try a local realtor to check for folks either buying or selling 
houses who want towers removed.