[TowerTalk] FCC Requirements

[Tom Rauch]

Any time you deal with the government, the rules are secondary to 
what they want to see. What you learn to do, whether filing for type-
acceptance or doing a BC station, is do what they expect to hear. 
If you do what they expect, you never get put through the ringer.  

Part 73.189 (4) 

"At the present development of the art, it is considered that where 
a vertical radiator is employed with its base on the ground, the 
ground system should consist of buried radial wires at least **one 
fourth wavelength long**. There shall be as **many of** these 
radials as evenly spaced as practicable and in **no event less than 
90**." (120 radials of .35 to .4 wl and spaced 3 degrees is 
considered an excellent ground...blah blah on and on) 

This is the text that 120 radials 1/4 wl long came from. The FCC  
just loves seeing 120 1/4 wl radials, and a ground system like that 
will slide right through their reviews without raising any questions. If 
you add a screen, even though it is only required on a voltage fed 
antenna, it will slide through even better! 

So to properly slide through the FCC, engineers have been 
"trained" to use an (unnecessary) screen and 120 1/4 wl or longer 
radials. 

If you have less than 90 1/4 wl radials, a red flag pops up and they 
make you prove it still works. If they don't see a screen, they want 
to know if the antenna is really current fed (heaven help you if the 
radiator is .3 wl tall instead of .25 wl and there is no screen). They 
act like the applicant doesn't know what he is doing, and start 
looking at everything closely.  120 radials at least 1/4 wl long and a 
screen guarantees you pass that point without having to prove 
anything, because they see "headroom" over the minimum and 
think you are a conservative fellow who makes good solder 
connections.

Kinda like counting chads in Florida.   
73, Tom W8JI
w8ji@contesting.com

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com