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 Subject :questions and concerns regarding exposure.. 2013-11-24- 11:29:07 
Joined: 2013-10-16- 10:21:44
Posts: 6

SO, with my mesh node running with a 24dbi parabolic dish, lets say i were to get an 8 watt amp, as another poster in this forum did, 8 watts into 24dbi, wouldnt that work out to OVER 6kw EIRP??? wouldnt that cook you like a microwave, or a bird or animal in front of the dish? Im not sure what would happen if there was a neighbor behind me that a bad heart and my dish would be 35-40 feet high, but its still in their general direction. Thanks

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 Subject :Re:questions and concerns regarding exposure.. 2014-03-23- 16:53:28 
Joined: 2013-11-15- 21:10:09
Posts: 2
We are hams, who are suppose to know these issues. Yes, high gain and microwave energy is an issue to make you stop and calculate over. There are IEEE exposure limit guidelines that are universal, and country specific exposure regs.
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 Subject :Re:questions and concerns regarding exposure.. 2014-03-26- 00:14:39 
Joined: 2013-01-02- 00:30:45
Posts: 188
Location: Austin, TX

You should not be putting an 8 watt amp on a mesh node.  Maybe in a very few specialized situations, it might be appropriate, but in general, no.  You'll be unnecessarily interfering with other legitimate users of the frequency without really gaining that much increased usage yourself.

You need to use the minimum amount of power necessary and minimize interference to other users of the frequency.

With any amateur radio, you need to understand and evaluate the radiation exposure considerations.  It's part of the FCC licensing requirements.

One important point is that even if you have "6 kW" ERP, you still only have 8 watts.  You can't dump more than 8 watts into anything.  However you can dump 8 watts into something a further distance away.   No matter where you are, even with a high gain antenna, you won't be receiving any more radiation than you would standing right next to an omnidirectional antenna with 8 watts.   

Also, with a high gain antenna, the signal strength is only higher when you're in the beam of the antenna.  Off axis, the signal strength will be lower than with an omni antenna.   If you're not pointing the beam near the neighbor's house, the signal strength there will be lower, not higher. 

As to whether 8 watts is enough to cause harm, that's questionable, but it's your responsibility.  Personally, I would take some care to not get my eyes right next to the antenna.  The cornea has poor cooling and is near the right length to receive energy at microwave frequencies.  I also would probably limit close exposure to a pacemaker, too.

As for worries about cancer and such, in theory, microwaves can harm by generating heat or electric shock, but don't cause cancer or other biological effects.  We should be overly cautious on this, and the FCC lists exposure limits to give us guidelines.

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I'm not part of the development team, so take what I say with a grain of salt. I'm also easily confused.

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 Subject :Re:questions and concerns regarding exposure.. 2014-06-22- 19:50:59 
Joined: 2011-10-28- 14:57:45
Posts: 13
Location: Keizer, Oregon CN84lx
Broadband-Hamnet max power setting is 19dbm or about 79mW. Putting 79mW into an antenna of 24dbi would give on center of your beam about 20W ERP. if communication with an alike set up in line of site you should be able to achieve 25 to 30 miles with no problem.
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 Subject :Re:questions and concerns regarding exposure.. 2014-06-23- 14:28:36 
Joined: 2010-10-06- 23:04:25
Posts: 54
I am guessing if you are considering 8 watts, you have a path issue. Possibly trees? Microwave propagation works much differently than lower frequencies. More power 99% of the time will accomplish nothing, or next to it. Time to consider; 1.) more height on either end or both, and/or something in between to repeat you 2.) Gear on non microwave frequencies. I just looked at your QTH on street view, you have less tree's than where I live in Wisconsin. Try and talk to whoever owns that 200 foot tower not to far away. Looks like there is other microwave gear on there. Looks like line of site to that would be easy. Exposure has to do with field strengths. I'd be more concerned about if you have a bluetooth dongle in your ear most of the day, than something just 50 feet off the ground at even a few hundred watts ERP.
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