[TowerTalk] Site Elevation and TOA

[Paul Christensen]

I'm trying to locate land in south GA for a remote Internet station.  Two self-supporting towers are ready for installation.  Tower #1 is 140 ft and Tower #2 is 100 ft.  A full-size, 4L 40m monoband Yagi goes on the top of tower #1.  A 30m-10m LPDA goes on tower #2.  Siting has become a lot harder than I imagined.  Here are my siting constraints:

1) Low noise in the immediate area;
2) Easy utility power access;
3) High speed data access over FTTH or CATV.  No DSL unless I really get desperate.  Too many future applications will need the extra throughput;
4) High land that either remains flat for the TOA distance or slopes downward.  
5) Land that fits within the project budget.

Sounds easy. Way harder than you think -- unless a home goes up on the property and I move there where I have more options due to the higher price of properties.  Moreover, many counties won't allow a telecom shelter or other structure as a primary use without first establishing a residence through placement a house or manufactured home.  I don't want that.  I want a remote site only.  My main focus is Brantley County, GA.  There's no zoning in the county.  There's also super-high-speed fiber supplied to the entire rural county by the local telco.  The telco bet big and lost when they assumed a housing market explosion in 2005 that turned into an implosion.  Along the county highways are dozens of started subdivisions that are now ghost towns.  Cheap land, but the developers recorded much of it early on with deed restrictions.  Once just a few owners take possession, changing the covenants is a nightmare.  It's one thing to take up the cause when you already own the land.  It's insane to consider restricted land when you're looking to buy from the start.   

After looking at dozens of parcels, I've found a few that might work.  Here's my question: In terms of wavelength, at what distance is the TOA set for elevated, horizontal antennas?  I realize that the TOA is composed of near, intermediate and far fields above elevation, but there must be a distance where say...90% of the predicted TOA occurs.  What is that distance in wavelengths from the antenna?

Paul, W9AC