Construction Cranes Radio Frequency Induction

[Studiot]

there is not enough science to set an standard for RF current induction

I take exception to this claim.
Indeed if you truly think this why did you come here?

I have told you some of my bckground, although I do not know any of yours. I had understood you had come to PF seeking scientific discussion and enlightenment but you seem to avoid any request for the necessary detail that would lead to such an aim.

When I was a young pup I was told

"Good Engineering is all about attention to detail."

 

[SafetyConsult]

I must clarified once again. SAR rates is measure based on power density which is good predictor for twa exposure levels over 6 minutes. At this point there is not a form of measurement as I understand (e field, h field, power density etc) that will predict the total current induced on a tower; for that reason the burden is put on new telecom tower installations within the prescribe radius (1km to 3km) to do the studies and take precaution to prevent reradiation. In the event of a crane induction (one example of many possible) there is not set standard as I mentioned before.

Berkeman look into AM Directional antenna arrays for the answer to your question.

This is my first posting on a forum of this kind, and have learned many valuable lessons from it. One is you are a very well knowledgeable group in your respective areas, but most of all TOUGH Crowd!

 

[John37309]

SafetyConsult,
There is enough scientific information posted in this message to help you analyse the problem, and solve the problem. Its up to yourself if you choose to use the information.

Lot of people trying to help you solve this, people with different knowledge and from different scientific backgrounds.

John.

 

[SafetyConsult]

I would definitely agreed with you John. I have enough to go on. I was hoping for a silver bullet.

 

[berkeman]

I must clarified once again. SAR rates is measure based on power density which is good predictor for twa exposure levels over 6 minutes. At this point there is not a form of measurement as I understand (e field, h field, power density etc) that will predict the total current induced on a tower; for that reason the burden is put on new telecom tower installations within the prescribe radius (1km to 3km) to do the studies and take precaution to prevent reradiation. In the event of a crane induction (one example of many possible) there is not set standard as I mentioned before.

Berkeman look into AM Directional antenna arrays for the answer to your question.

I am pretty familiar with antenna arrays. For AM radio transmitters, one of the most common is a 3-tower array, used for gain of a few dBi in the direction of the tower line. Using an array would not affect the definition of the near/far field by more than the added size of the antenna array, I don't think.

And I still think that with a simple field strength measurement at the frequency of interest around the crane area, you should be able to predict what the maximum currents will be in the crane's metal structure. You would just assume an efficient monopole element antenna as the model for the crane, and look to see how the metal structure sizes compared to resonant antenna lengths.

Glad that you are getting some useful info in the thread. The PF is a great place for discussing questions.