| Author |
Message |
    
Kb9umt_don_123
Junior Member
Username: Kb9umt_don_123
Post Number: 37
Registered: 3-2004
| | Posted on Monday, September 05, 2005 - 11:17 am: | 
|
Wanted to bring up a subject that many are over looking or maybe just don't care of have concerns for...that is RF Safety and the amount of wattage vs the frequency used vs human distances away from the RF threat. I have noticed a few posts on big station amps (will not use Linear because I'm not so sure how Linear they are). I also read more and more that many that CB today are mobile and when close distances to your mobile antenna using more power than required you might not only be putting yourself in danger (and that is your choice) but others around you (that is NOT their choice and many don't even know this is going on...like those you pass on the street, your kids or neighbors that are next to your mobiles etc).
Here are some links to some information/reference on this and also an RF calculator:
http://www.arrl.org/tis/info/rfexpose.html
Below are some examples of this calculator:
Calculation Results Average Power at the Antenna 100.000 watts
Antenna Gain in dBi 2.20 dBi
Distance to the Area of Interest 3.00 feet
Frequency of Operation 27.185 MHz
Are Ground Reflections Calculated? Yes
Estimated RF Power Density 4.0436 mw/cm2
ControlledEnvironment UncontrolledEnvironment
Maximum Permissible Exposure (MPE) 1.22 mw/cm2 0.25 mw/cm2
Distance to Compliance From Center of Antenna 5.52 feet 12.27 feet
Does the Area of Interest Appear to be in Compliance? no no
** So a mag mount right above your head even using 100 watts on AM mode is not a good distance...should be 5 or 6 feet away.
Calculation Results Average Power at the Antenna 500.000 watts
Antenna Gain in dBi 2.20 dBi
Distance to the Area of Interest 9.00 feet
Frequency of Operation 27.185 MHz
Are Ground Reflections Calculated? Yes
Estimated RF Power Density 2.2464 mw/cm2
ControlledEnvironment UncontrolledEnvironment
Maximum Permissible Exposure (MPE) 1.22 mw/cm2 0.25 mw/cm2
Distance to Compliance From Center of Antenna 12.27 feet 27.38 feet
Does the Area of Interest Appear to be in Compliance? no no
Calculation Results Average Power at the Antenna 1000.000 watts
Antenna Gain in dBi 2.20 dBi
Distance to the Area of Interest 9.00 feet
Frequency of Operation 27.185 MHz
Are Ground Reflections Calculated? Yes
Estimated RF Power Density 4.4928 mw/cm2
ControlledEnvironment UncontrolledEnvironment
Maximum Permissible Exposure (MPE) 1.22 mw/cm2 0.25 mw/cm2
Distance to Compliance From Center of Antenna 17.34 feet 38.70 feet
Does the Area of Interest Appear to be in Compliance? no no
Calculation Results Average Power at the Antenna 5000.000 watts
Antenna Gain in dBi 2.20 dBi
Distance to the Area of Interest 9.00 feet
Frequency of Operation 27.185 MHz
Are Ground Reflections Calculated? Yes
Estimated RF Power Density 22.4640 mw/cm2
ControlledEnvironment UncontrolledEnvironment
Maximum Permissible Exposure (MPE) 1.22 mw/cm2 0.25 mw/cm2
Distance to Compliance From Center of Antenna 38.70 feet 86.48 feet
Does the Area of Interest Appear to be in Compliance? no no
Calculation Results Average Power at the Antenna 10000.000 watts
Antenna Gain in dBi 2.20 dBi
Distance to the Area of Interest 9.00 feet
Frequency of Operation 27.185 MHz
Are Ground Reflections Calculated? Yes
Estimated RF Power Density 44.9279 mw/cm2
ControlledEnvironment UncontrolledEnvironment
Maximum Permissible Exposure (MPE) 1.22 mw/cm2 0.25 mw/cm2
Distance to Compliance From Center of Antenna 54.71 feet 122.28 feet
Does the Area of Interest Appear to be in Compliance? no no
Just wanted to give you some examples if you did not know how to use the RF online calculator but as you can see you really should be at safe RF distances if you use very much wattage...and again it's very unfair for those that have or are around kids to have them in unsafe conditions.
de kb9umt Don123
|
Bigbob
Senior Member
Username: Bigbob
Post Number: 2175
Registered: 12-2001
| | Posted on Monday, September 05, 2005 - 12:39 pm: |
|
You have no idea how many times I've stressed this topic,if your cars computer is getting messed up by rf then maybe the one in your skull is too,or the scenario of turning your eyes to hardboiled eggs,skin cancer,2nd and 3rd degree burns ad infinitum.But the people here ARE concerned about safety,just don't beat them to death with it,I personally have p.o.'d some people on here in the past because I was raggin' them about it and it took awhile for them to post again.What you just posted is consise and to the point and we need reminders like this and I thank you .Bigbob |
Moonraker
Junior Member
Username: Moonraker
Post Number: 12
Registered: 3-2005
| | Posted on Monday, September 05, 2005 - 7:22 pm: |
|
My friends and i have often discussed this subject. What kind of damage to a person's body can be done? Would it take years of exposure to RF for long periods of time each day? just curious. |
Kb9umt_don_123
Junior Member
Username: Kb9umt_don_123
Post Number: 38
Registered: 3-2004
| | Posted on Monday, September 05, 2005 - 8:10 pm: |
|
Every station regulated by the FCC must comply with the RF safety issue...that is both Broadcast, Ham Radio Operators...etc, the only reason the CB Radio Service is not covered under this for a station requirement is that they are assuming most stations are at 4w am or 12w ssb (which as you know may or may not be the case). Here is a link that will answer many of the questions you might be wondering about:
http://www.fcc.gov/oet/rfsafety/rf-faqs.html
That is only one of the hundreds that you might find if you do a search on +RF EXPOSURE..+DAMAGE or+EFFECTS ..thanks for your questions Moonraker.
de kb9umt Don
http://www.HamRadioHelp.com |
Duck246
Member
Username: Duck246
Post Number: 59
Registered: 8-2004
| | Posted on Monday, September 05, 2005 - 8:10 pm: |
|
Where is this calculator link ?
|
Bruce
Senior Member
Username: Bruce
Post Number: 3102
Registered: 9-2003
| | Posted on Monday, September 05, 2005 - 8:27 pm: |
|
Don I have been in radio over 40 years and Rf has not EEEEEEEEEEEEEEEFECTED me. |
Truckerdon
Junior Member
Username: Truckerdon
Post Number: 25
Registered: 5-2004
| | Posted on Monday, September 05, 2005 - 9:07 pm: |
|
asked the radio tech who installed the radio towers on the CN tower in TOronto when I was a teenager. The Guys were fried from the Micro wave and RF coming from the commounication antennas..
Don |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2186
Registered: 12-2001
| | Posted on Tuesday, September 06, 2005 - 6:20 am: |
|
Well,I've seen the effects of static build-up on abandoned towers,a kid was killed 8 years ago by static discharge when he tried to climb an am broadcast tower,man litigation went on for years,the owner of the towers went out of business and the property owner assumed liability,he was ruined.Bigbob |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 494
Registered: 2-2003
| | Posted on Tuesday, September 06, 2005 - 8:09 am: |
|
You guys sound like your talking about commercial broadcast AM/FM towers. I usually run no than 400 watts in my mobile tops. Antenna mounted on the roof, not on the trunk. Let's see, aside from what bigbob cited above as dangers from rf, I've heard rf can damage sperm count, and DNA, make you lose your hair, etc. I consider 400 watts a paltry amount of RF. I've been in CB since 1976. Am I in danger??. If not, what is the wattage threshold that CBer's should worry about?? I already know that VHF amp operation is supposed to be really worse on humans and electronics. Tell me something.
Wolverine. |
Brewdirect
Intermediate Member
Username: Brewdirect
Post Number: 164
Registered: 7-2004
| | Posted on Tuesday, September 06, 2005 - 3:45 pm: |
|
RF energy is absorbed most easily by soft tissues. Your eyes are the most vunerable thing on your body. RF energy is radiated and when absorbed it will heat the tissue (very similar to the way a microwave oven works). Your testicles are also at risk.
I used a number of studies and calculations a while back and what I found was that in the 11 meter band with an antenna on top of your car the max amount that you could run while still falling within safety limits was around 250 watts. (This was hitting the max amount based on a 6 foot distance from the antenna with proper grounding.)
This doesn't mean that running 500 watts will kill you, but extended periods of exposure will cause damage.
Remember that 2 minute keydown you like to do?  Feel your eyes start to water? |
Kb9umt_don_123
Junior Member
Username: Kb9umt_don_123
Post Number: 40
Registered: 3-2004
| | Posted on Tuesday, September 06, 2005 - 11:30 pm: |
|
I can't get my links to post...sorry...if you want to access the calculator for this please do a google or search for "RF SAFETY CALCULATOR" and you will see it listed.
I have tried this several times and hope this one goes through...you must remember that if you are using 250 watts of AM a 100% duty mode with an antenna right overhead you are NOT within limits of RF safety....if you switch to SSB a 20% duty mode you will find that you might be in better shape. This really is an issue for those that are around your antenna/radio system using higher wattage...like kids or those passing by that don't know the danger.
de kb9umt Don/123 |
Wolverine
Advanced Member
Username: Wolverine
Post Number: 501
Registered: 2-2003
| | Posted on Wednesday, September 07, 2005 - 3:52 am: |
|
Only 250 watts??, 6 ft distance??. I'm cooking myself up everyday. Thanks for the link don.
Wolverine. |
Wolverine
Advanced Member
Username: Wolverine
Post Number: 502
Registered: 2-2003
| | Posted on Wednesday, September 07, 2005 - 4:17 am: |
|
According to the rf safety calculator, I need to be 9.46 feet from the antenna to be in compliance. This is using an average of 380 watts. I hope I haven't endangered my future generations (If you know what I mean), or shaved a few years off of my life.
Wolverine. |
Brewdirect
Intermediate Member
Username: Brewdirect
Post Number: 165
Registered: 7-2004
| | Posted on Wednesday, September 07, 2005 - 2:56 pm: |
|
The real effects would be felt if you ran lots of watts and keyed up for a long time.
500 watts at 10 seconds intervals probably won't cause any noticable effects, although it can cause changes in cell structure.
I used to work for a cell phone company and there was a study we were always supposed to quote when asked about RF effects and it said "We have found no long term effects for continued cell phone use" ....although the part they left out was - the section that said, " even with cell phones putting out the minimum amount of RF power we have found changes occurring in the cell structures of soft tissue during continued exposure at close ranges."
Go figure.
RF is bad for you - yes. Will you melt like in Indiana Jones? No. Long term effects - entirely possible. |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2188
Registered: 12-2001
| | Posted on Thursday, September 08, 2005 - 8:54 pm: |
|
MY STEP DAD worked near radar in ww2 on a sub tender,died of brain cancer at age of 70,dad operated caterpillar in ww2 near a radar station,he too died of brain cancer at 73,hmmm,could be!Bigbob |
Duck246
Member
Username: Duck246
Post Number: 64
Registered: 8-2004
| | Posted on Thursday, September 08, 2005 - 9:13 pm: |
|
I need to move my beam another 30ft away! |
Troublemaker
Intermediate Member
Username: Troublemaker
Post Number: 176
Registered: 2-2004
| | Posted on Thursday, September 08, 2005 - 11:17 pm: |
|
 Maybe thats why I aways have a headache every sunday morning from 10:00 to around 1:00? |
Sinker
Junior Member
Username: Sinker
Post Number: 47
Registered: 8-2005
| | Posted on Friday, September 09, 2005 - 7:52 am: |
|
Well I've already lost my hair, but that happened before I started with radios. Finished having kids
BUT
I would never want to hurt them either so maybe I will just keep the radio to a minimum while they are in the truck with me.
I had no idea about this. Can't believe all the stuff there is to learn. Even more amazed as I talk to some local guys who have NO CLUE. I mean they know tons more than I do about radios and linears and modifying them etc. but no idea about the grounding, polyphasers, dangers of RF exposure, rules & guidelines of the FCC etc., etc., they are more concerned with being super loud and being able to turn on the power and key up so you can't hear anyone else. They upset me as they pick on the truckers really bad, calling them names, using filthy language and keying up when the truckers are trying to get directions. Good to know they are getting paid back for it and the sweet part is they are doing it to themselves. Feel bad for their neighbors though and anyone driving next to them - YIKES -  |
Airplane1
Advanced Member
Username: Airplane1
Post Number: 564
Registered: 5-2004
| | Posted on Friday, September 09, 2005 - 7:55 am: |
|
Does RF come out of the radios and amps or just the antennas? I`m just wondering if i`m in harms way or is the coax containing the RF till it gets to the antenna? I an antenna 36ft high on a tower 10ft from house be safe running 500 watts?
This stuff scares me cause cancer runs in my family.
AP |
Wolverine
Advanced Member
Username: Wolverine
Post Number: 506
Registered: 2-2003
| | Posted on Friday, September 09, 2005 - 9:05 am: |
|
Now this outta be good!!! |
Rover
Intermediate Member
Username: Rover
Post Number: 274
Registered: 2-2004
| | Posted on Friday, September 09, 2005 - 11:29 am: |
|
This also points out something I have been saying all along. The rules WRT CB were enacted for good reason! The Feds are assuming the public are "appliance" operators. True, not all are, but they try to err on the side of safety. It is also why CB is limited to 4 and 12 watts respectively in regard to mode. The things that seem perfectly harmless to US *may* in fact do great harm to us and others. Thus, those "extra" channels you think don't "hurt" to use may do harm to others and your use of extra power may* do harm to you that you won't even know about until the doctor looks at you sadly and says, "Bill, you've got terminal cancer." So it is why ALL those rules we often chafe under are there. They aren't perfect, but they DO try to provide for the SAFE and effective use of radio spectrum of the majority of us--even when we don't know why. |
Tomcatinva
Member
Username: Tomcatinva
Post Number: 74
Registered: 11-2003
| | Posted on Friday, September 09, 2005 - 12:43 pm: |
|
Brewdirect,
I used to drive a little 2 seater and I had one of the "older" Cell phones installed in it. (you know the old analog 3 watt units) Well the install tech said are you sure you want the on glass antenna mounted on the back window (behind my head). I said yea why, he then told me about the effects of RF and I said well I only have a few brain cells left, I guess I had better protect them a little longer. I told him to put it on the front windshield (it was a little further away), but I had no Idea either. The scary thing is I don't think the general public will ever understand. As far as cell phones (the new type) it is too soon to even think about "long term" effects. As they are still fairly new, it won't be until more people have problems (tumors, cancer of the brain) before anything will be done. It's sad but true. Kind of like they won't install a stop light at a dangerous intersection until a certain amount of accidents happen or someone dies from an accident. 
I'm not saying that I am scared of everything but I am a little cautious about stuff I am not 199% sure of… I would like to be around to see my grand kids. And hopefully that will be a long time. That way I can embarrass my kids by telling their kids all of the stuff they used to do... 
TomCat in VA CEF217 
|
Brewdirect
Intermediate Member
Username: Brewdirect
Post Number: 166
Registered: 7-2004
| | Posted on Friday, September 09, 2005 - 3:08 pm: |
|
Yeah..don't everyone get all freaked out here..I was just giving some info.
I personally have run 100-200 watts + at time. But I always make sure my system is very well grounded, my antennas are always mounted at the back of the vehicle if possible and I don't keydown any longer than necessary to have my conversation.
Some of the tests I read while in the cell phone industry were very scary though - somehow they all were deemed inconclusive though ??
Cell phones nowadays put out only a fraction of the power of the ones from 10-15 years ago (I remember the bag-phones), BUT factor in that they are smaller, held closer to the ear and head now &&&&& people spend ALL day on them!!
And cell phones don't just transmit when you are talking either Most people don't know that your cellphone is connecting with the towers and talking to them on a regular basis even when you are not talking. They do this so that they can maintain their connection and location on the nearest tower (thi is what gives you the ability to dial and connect right away) otherwise the phone would take 10 seconds or so to connect to the tower.
I used to have a cell phone ONLY while I worked in the industry, but now I don't use cell phones except in an emergency. I don't leave them on while carrying them in my pants or anything AND don't keep it on the bedside table at night anymore while I sleep.
AS ALWAYS - EVERYTHING IN MODERATION. |
Kirk
Intermediate Member
Username: Kirk
Post Number: 300
Registered: 6-2002
| | Posted on Friday, September 09, 2005 - 10:01 pm: |
|
Personally....cause sometimes I like to do this...some of this is total hype. Yes...be careful, obey the rules. But if you guys are talking CB land or Ham under 30 Mhz....cmon. A couple hunder watts at 28 Mhz can't cook the body like 144/440/880 or even in the Microwave/Radar range (like Bigbob's Family members) had experienced. The higher the frequency, the closer resonant to your own body. Not saying you shouldnt be observant, but mercy....I've worked around RF for at least 15 years...lots of it TV at the MegaWatt range on site. Will it affect me? Who knows? But I'll tell ya, CB doesnt even come close to what I've stood around. Having said that, be careful and educate yourself!-- |
Moderator1516
Moderator
Username: Moderator1516
Post Number: 17
Registered: 8-2005
| | Posted on Saturday, September 10, 2005 - 9:31 am: |
|
since gettingmy ham ticket i think rf safety has been impressed on my mind more then any thing else ,and i would think twice before firing up a high power linear
moderator 1516
cef 139 ham 147
kirkxl
|
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 206
Registered: 4-2005
| | Posted on Sunday, September 11, 2005 - 12:26 pm: |
|
Here's a RED FLAG we were just modulating about this last night on the home channel. Myself running a small kicker with just enough to get over the hill...so I'm not innocent but Both friends have a couple hundred Watt kickers in their base. Each one has a problem with hearing themselves comming over other equipment in the shack like TVs or radios THAT ARE NOT EVEN PLUGGED INTO THE WALL! May be a simple anomoly but can't help thinking "DANGER WILL ROBINSON..DANGER"! Put on the Ray Bans and aluminum underware!
Am I wrong?...this IS stray RF current correct? Just doesn't seem right?
Hank...btw,,,GOOD THREAD! |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2193
Registered: 12-2001
| | Posted on Sunday, September 11, 2005 - 4:41 pm: |
|
RF is a.c.,AF is a.c. The voice coils on the radios,stereos and tvs are picking up txed rf and and transforming it into sound.Eventually the cell phones will be such high freq.and so low powered that the density of the skull bone will be enough to stop rf penetration.Bigbob |
Slowhand
Member
Username: Slowhand
Post Number: 75
Registered: 7-2005
| | Posted on Tuesday, September 13, 2005 - 4:36 pm: |
|
Worse than an amp!..Electric blankets create a magnetic field that penetrates about 6-7 inches into the body.
|
