RF exposure????

K8SWR · Post by **K8SWR** » Thu Dec 05, 2002 6:39 am

I 'm going to mount a 2 meter antenna on my chevy truck on the front fender... like I have seen many others... My question is what kind of Rf exposure is there? and should it be a concern I will only be using 5 watts most of the time ...

Monty · Post by **Monty** » Thu Dec 05, 2002 7:37 am

HI:

Well, in the majority of the cases, you will not
have a problem ( other than a unique radiation pattern )
and perhaps some vswr.

Antennas like flat surfaces.

With a 5 Watt HT, Motorola has a Instruction sheet that
shows one should keep the Radio ( HT ) in this case held
Vertical and 3" away from the Eyes, Face, ears, etc when
in a transmitt condition to minimize RF exposure

So, your Mobile Antenna I am sure will be mounted
more than [ 3" ] away, and the power level is pretty
low.

Persons running 100+ Watts on UHF & VHF should have
the Antennas Mounted Properly for the radio class being
used.

Monty

Jonathan KC8RYW · Post by **Jonathan KC8RYW** » Thu Dec 05, 2002 11:23 am

For anything under 10 watts, you are pretty safe. Keep in mind duty cycle plays a large role in RF exposure. The less you talk, the better.

The worst band for RF exposure is VHF (including low band.) This is because of the Specific Absorbtion Rate of the human body. There is a chapter in regards to this in "Now You're Talking" by ARRL.

RF exposure is sort of a fuzzy area. Studies that have been released are very inconclusive. Still, I believe that RF safety is important, and people should be at least aware of it. It's better to be safe, then sorry later. For example, a 110 watt VHF Micor mobile shouldn't be run to a mag-mount mobile antenna attached to a file cabinet inside of your house.

Anything over 50 Watts PEP on 10m, 6m, 2m or 1.25m, requires an RF safety review, according to FCC.

http://www.arrl.org/news/rfsafety/eval/

If you ever want to plug in numbers, there is a calculator at:

http://n5xu.ae.utexas.edu/rfsafety/

About mounting on the fender... why?

That will result in a loss of gain, simply because of where it is located. I would put the number at least 2 db loss.

<img src="http://www.radialllarsen.com/products/m ... ileant.gif">

If it's a 2m antenna with gain, that you are considering for the fender, then you might be better off in the end, just putting a 1/4 wave 2m antenna mag-mount on the roof of the cab.

Best of luck!

Tom in D.C. · Post by **Tom in D.C.** » Thu Dec 05, 2002 1:55 pm

Jonathan hit the nail on the head by giving you the ARRL website for this information. I had to use it to set up my VHF station down in the country where the third-floor condo owner, just above me, is located not far from my antenna.

The formulas are easy to use, and I'll bet that you end up surprised by the results.

Tom, W2NJS
...in D.C.

jcobb · Post by **jcobb** » Thu Dec 05, 2002 9:24 pm

If RF exposure wasn't a problem - why do you think so many of us here are so freakin' goofy?

(And yeah, that IS why Mickey divorced Minnie!)

Jack

Zero dbm · Post by **Zero dbm** » Sat Dec 07, 2002 6:35 am

Apparently the human body resonates at about 105 MHz. We must also remember that, in regards to RF exposure, the effects are not accumulative. So, if one happens to be bombarded one day, he/she could just stay out of strong RF fields the next, and so on.

jim · Post by **jim** » Sat Dec 07, 2002 8:11 am

Nothing like a motorcycle with a 110 watt Spectra!

Tron · Post by **Tron** » Sat Dec 07, 2002 8:01 pm

If the human body resonates at 105 mc/s, how come we can't hear FM station in our heads....and where is the "tuner" control?

Tron

jcobb · Post by **jcobb** » Sat Dec 07, 2002 9:15 pm

Uhhhh, you really don't want to know about the tuner control.........

and how do you know we DON'T hear voices in our heads already?

Jack

Jonathan KC8RYW · Post by **Jonathan KC8RYW** » Sat Dec 07, 2002 10:50 pm

Tron wrote:If the human body resonates at 105 mc/s, how come we can't hear FM station in our heads....and where is the "tuner" control?

Tron

Wow. This would be one way to make a human detector. LOL. Remember about those CheckPoint EAS Retail systems that operate at ~10 MHz... think about using 105 MHz...

It must be nice to the local station on 105 MHz, I could see a large jump in their market ratings, if this "tuner" theory holds true.

mancow · Post by **mancow** » Sat Dec 07, 2002 11:36 pm

A friend of mine swears he develped headaches when living in an aparment on a high level in downtown KC Missouri. He blamed all the RF from all the nearby TV and radio stations etc... I still think it was from living in a S***** neighborhood. But anyway, it was bad. The RF messed with the TV something horrible and using an HT was out of the question on many frequencies. It stll amazes me that stations get by with transmitting 100,000 watts continuously. Add them up with everything else and it's frightening to think about.

The thing that troubles me most of the time is RF interference from modern computer equipment. I know it's off the topic but does anyone have any ideas on how to suppress this. What about grounding computer cases etc... However, most of this stuff is plastic. My Linksys router renders scanning 154.755 useless in the entire house without PL squelch enabled. I think the CAT5 is acting like an antenna. I made a coil out of the excess and zip tied it. That helped quite a bit but it's still ridiculous.

mancow

RF exposure????

RF exposure????

RF Exposure...