[BC] RF fields around base of shunt fed monopole

[Cowboy]

On Sunday 22 February 2009 07:20 pm, John Lyles wrote:
>  I have some questions for the collective:
>   Has anyone actually verified these calculations around their tower base?

>   I could quote the 1-3 meter distance from OET-65 in my report but is this 
>   conservative or will the actual be grossly higher?  

 Of the stations I've personally measured ( which takes some specialized
 knowledge. Not just anyone can grab a Holaday or Narda and get it right )
 in EVERY case, I've found the OET-65 numbers to be EXTREMELY conservative.

 Some, I've found you can "legally" get the ANSI limit at a point where the
 contact shock hazard far exceeds any RFR hazard.

 I'd suspect you'll find the actual is grossly lower, but as Tom points
 out, you don't really know until you have it measured.

 There are other factors as well, that you can't always predict.
 I measured one where the H-plane field far exceeded the
 ANSI limits 30 meters from the 5 kW stick, from other conductors
 in the area, and extremely poor grounding, resulting from hack
 engineering due to extreme cheapness, but in proximity to the
 intentional radiators, the fields ( both E and H plane ) were well
 below OET-65.
 Another where the 110 AC line had H-plane fields at a wall socket
 that exceeded the field at the tower feed lightning loop !

 Don't know why. That's not what I was hired to do.

 If you can quote OET-65, pending revision by actual measurement,
 and get a workable agreement, I'd do it that way, and revise as
 necessary after it's built.

-- 
Cowboy