Safe wattage for indoor slimjim

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adacats

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I just got my first non HT rafio, the Yaesu ftm-400xdr. I got a 6 foot slimjim antenna, and I have to mount this in my apartment about 5 feet from where I will be sitting. What safe operating wattage can I operate this antenna at. I know 5 watts is fine, but is there risk in operating this at 20 watts at that distance?

Thanks!

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AK9R

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There's an article about RF Radiation and Electromagnetic Field Safety on the ARRL web site that would be worth reading. The issue really isn't the type antenna you are using, but your exposure to RF radiation from using high power with an indoor antenna. And, don't forget about the exposure to other people in your apartment and your neighbors.
 

wyShack

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Another item to keep in mind is the safety of your neighbors- if your antenna is mounted on a common wall you need to operate in such a manner that someone on the other side of the wall is not exposed to hazardous RF levels. As a licensed Amateur YOU are responsible for the operation (or misoperation) of your station. A RF Exposure evaluation of your station is required to be part of your station records.

I didn't know is not an excuse any more than it is when you are driving a vehicle That is why Amateurs are called operators and not users.

73 and never stop learning
 

adacats

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If I understand correctly, if you are operating below 50 watts a station evaluation is not required.

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majoco

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From personal experience, even 5 watts may cause feedback problems with the RF getting back into the microphone and/or lead,power supply etc.
 

TheSpaceMann

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Is there any way you can get your antenna outside of the building structure (camouflaged,etc.)? That would definitely help to reduce your RF exposure.
 

wyShack

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There is a table in part 97 on when a evaluation is not needed-it specifies 50 watts PEP for VHF. So that would mean you have satisfied the rules if you are not using a gain antenna and power into the antenna is 50/2/sqrt(2)=17.68 watts. That puts most of us 'on the hook' especially if we are using an antenna with any gain (not just Beams).
 

Kb2Jpd

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From personal experience, even 5 watts may cause feedback problems with the RF getting back into the microphone and/or lead,power supply etc.



Put the antenna in an position as far away from people and your operating position as possible. Use the minimum possible amount of wattage to make your QSO.

Operate and enjoy. Live long and prosper.


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adacats

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I am only transmitting using 5 watts and occasionally to reach further, 20 watts, hooked up to a slim jim antenna.
 

prcguy

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Ive measured a 5W VHF handheld with 6" rubber antenna to be at the 5mw/cm2 level at about 2" to 3" from your body. That's within the near field of the antenna, which is difficult to predict and relate to other distances, but in general the level will diminish 4X when you double the distance from the antenna.

That means if you double the distance and raise the power 4X from 5W to 20W you should be at or near the 6 minute occupational RF exposure limit of 5mw/cm2 at maybe 6" but add a little more due to the uncertainty of the near field measurement.

If your running 20W and the antenna is say 10ft from you its well below any occupational or un-informed public safety level. However, you must determine if you want to bath in that level of RF even though it may be considered safe.
prcguy

I am only transmitting using 5 watts and occasionally to reach further, 20 watts, hooked up to a slim jim antenna.
 

ipfd320

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You Also have to Take Into Account with the Indoor Antenna Locking Up Cable Boxes in Neighboring Apts. Around You and also Other Sensitive Equipment they have--I Used an Indoor Antenna for GMRS UHF and the Results were Horrible even @ 5 Watts with Interference to all the Cable Boxes in my House--as for the Stereo--well That was an Issue all of its Own...lol---Best Bet try to Locate the Antenna Somewhere Outside a Window or Maybe Some sort of Mag-Mount on an Air-Conditioner

Good Luck with Your Ventures
 
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