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Author Topic: EMR hazard..  (Read 208 times)
KB6MHK
Member

Posts: 44




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« on: July 24, 2004, 07:14:59 PM »

Plan to erect a 20m dipole 33ft above ground, The dipole will be directly over my shack. Max output will be 100watts. Any EMR hazard on me, the operator??

73!

KB6MHK
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KZ1X
Member

Posts: 3227




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« Reply #1 on: July 24, 2004, 07:31:49 PM »

No.
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AA4PB
Member

Posts: 12641




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« Reply #2 on: July 24, 2004, 07:55:28 PM »

Here's a link to a calculator.
http://n5xu.ae.utexas.edu/rfsafety/

As you will see, even if you subtract 10 feet (making the separation between you and the antenna 23 feet), run 100% duty cycle mode like RTTY, and use a maximum frequency of 30Mhz you are well within the limits for even an uncontrolled environment.
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AA4PB
Member

Posts: 12641




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« Reply #3 on: July 24, 2004, 07:57:41 PM »

I forgot to add - if you want to abide by the letter of the law then you need to run the calculations and keep the results on file with your station. Asking here is fine for your own piece of mind but it doesn't satisfy your legal requirements.
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X-WB1AUW
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Posts: 559




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« Reply #4 on: July 24, 2004, 08:36:42 PM »

The biggest hazard is that you will wonder "What if I make this into an inverted Vee?"

What if I want to make a dipole for another band and use the same feedline and center insulator?

Then you become hooked on experimenting with home made antennas.

73
Bob
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N6AJR
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Posts: 9879




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« Reply #5 on: July 24, 2004, 08:38:23 PM »

http://www.hamuniverse.com/multidipole.html

check this out
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K1CJS
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Posts: 5811




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« Reply #6 on: July 24, 2004, 09:41:05 PM »

Sounds like no problem, but make sure you mount it really well or gravity may give you another kind of surprize!  Just kidding! ;-)
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K0RFD
Member

Posts: 1368




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« Reply #7 on: July 24, 2004, 11:26:30 PM »

No hazard to YOU.  However, you might want to watch for signs of RF in the shack.  RF doesn't ALWAYS come in via the shield on the feedline, sometimes it just gets in as direct radiation from your antenna.

I have 40/15 and 20 meter antennas that are closer to the shack than ideal.  I can sometimes see RF as wavy lines on my computer monitor, and on a scope when I monitor the power supply.  No RF in my audio, but I do pay attention.  Just watch and listen and make sure it's not causing you problems.
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KC8VWM
Member

Posts: 3124




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« Reply #8 on: July 26, 2004, 10:18:48 AM »

Perhaps, I am stating the obvious - but for the benefit of the readers who may not be aware - here it goes.

First, EMR is mostly a "theory."

There is no scientific proof or documented evidence that proves EMR is actually a threat to humans.

The FCC has recently made it a requirement to "document" your antennas EMR fields in spite of this fact.

It was once thought that living near powerlines, using your cellphone, and many other related "myths" suggest that it caused human diseases such as cancer etc.

Again, there is no medical or scientific evidence - just speculation.


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