RF exposure safety from indoor antenna

[GKLdiy88]

I found an online version of "The ARRL Ham Radio License Manual" (dated 2010) at - The ARRL Ham Radio License Manual

on page 182 it says that radios of 25 watts or less offer no real danger from RF radiation, here is an excerpt from that page:



So does everyone agree with that ? (when you search online you can find different opinions on safe distances if needed)

The reason I ask is that I need to have my Comet GP-1 antenna in the same room near the radio and when sitting in front of the radio the base of the antenna will only be about 2 feet away from my head.

Another question:

Should I use the 25 foot run of DX Engineering 400MAX PL-259 Low-Loss 50-ohm Coax or a shorter (12 foot run) of cheaper coax "KMR 400 UHF Coax" ?

So is the premium quality 25 foot run better to use than the lesser quality 12 foot run ?

I have not yet tried using the Comet GP-1 antenna, but have it sitting where I hope to use it, it is on the top shelf (it is a wire shelf so the bottom of the antenna comes thru to hook the coax up to) it simply sits there freely without any need to be fastened to anything to sit there. (the radio sits just over 2 feet below the base)

After I am sure it will be safe I will see about connecting the coax and powering up the radio.

(let me add I would prefer my Comet GP-1 antenna be outside, but in the interest of maintaining peace I need to abide by my local "WOA" ....my "wife's official answer" in not wanting any holes drilled in the house for coax. )

(Note: on another thread others already offered other ideas for getting the coax outside but none fit my specific situation so far.)

 

[k6cpo]

I found an online version of "The ARRL Ham Radio License Manual" (dated 2010) at - The ARRL Ham Radio License Manual

on page 182 it says that radios of 25 watts or less offer no real danger from RF radiation, here is an excerpt from that page:

View attachment 137595

So does everyone agree with that ? (when you search online you can find different opinions on safe distances if needed)

The reason I ask is that I need to have my Comet GP-1 antenna in the same room near the radio and when sitting in front of the radio the base of the antenna will only be about 2 feet away from my head.

Another question:

Should I use the 25 foot run of DX Engineering 400MAX PL-259 Low-Loss 50-ohm Coax or a shorter (12 foot run) of cheaper coax "KMR 400 UHF Coax" ?

So is the premium quality 25 foot run better to use than the lesser quality 12 foot run ?

I have not yet tried using the Comet GP-1 antenna, but have it sitting where I hope to use it, it is on the top shelf (it is a wire shelf so the bottom of the antenna comes thru to hook the coax up to) it simply sits there freely without any need to be fastened to anything to sit there. (the radio sits just over 2 feet below the base)
View attachment 137596
After I am sure it will be safe I will see about connecting the coax and powering up the radio.

(let me add I would prefer my Comet GP-1 antenna be outside, but in the interest of maintaining peace I need to abide by my local "WOA" ....my "wife's official answer" in not wanting any holes drilled in the house for coax. )

(Note: on another thread others already offered other ideas for getting the coax outside but none fit my specific situation so far.)

Is the Commander In Chief opposed to removing screens from the windows? If not, you could use the solution I used. It's nothing than a piece of 1x4 with some sheet metal added on either side then drilled for SO-239 barrel connectors and placed in the window. I got the idea from the MFJ-4601.

My Radio Gear (and miscellaneous pictures.) - John Wright

Home-brew window feed-thru panel (Copied from MFJ...)

thewrightstuff.smugmug.com

 

[GKLdiy88]

Is the Commander In Chief opposed to removing screens from the windows? If not, you could use the solution I used. It's nothing than a piece of 1x4 with some sheet metal added on either side then drilled for SO-239 barrel connectors and placed in the window. I got the idea from the MFJ-4601.

My Radio Gear (and miscellaneous pictures.) - John Wright

Home-brew window feed-thru panel (Copied from MFJ...)

thewrightstuff.smugmug.com

Thanks, but a version of that idea (a 2x4 with a hole drilled thru it and the window closed down on it) was already considered but the only "window" really close enough is a sliding glass door. (the small window further away gets pretty much filled in with an air conditioner)

 

[DS506]

Check out RF Exposure Calculator

 

[GKLdiy88]

Check out RF Exposure Calculator

Thanks !

looks like depending on the settings you can be as close as about one foot to two feet, but I am not totally sure what settings I would need to set it at so I tried 2 different settings as far as the mode duty cycle.

 

[MTS2000des]

Aside from RF exposure concerns, which are valid indeed, you also have to consider that "INtennas" (a trademark of Cobra actually) SUCK. Antennas like the Comet are designed to radiate in free space, and their tuning is thrown way off when smack up against building materials. Your receive suffers with all the hash and trash generating RFI inside your house. RF output from the radio will also get into everything electronic including power supplies (switching power supplies don't like RF) and cause issues.

That thing really needs to be outside. Worst case, is an attic not an option? It could be mounted to a rafter with at least a few feet of free space around it, and you'd be safely away from it.

 

[GKLdiy88]

Aside from RF exposure concerns, which are valid indeed, you also have to consider that "INtennas" (a trademark of Cobra actually) SUCK. Antennas like the Comet are designed to radiate in free space, and their tuning is thrown way off when smack up against building materials. Your receive suffers with all the hash and trash generating RFI inside your house. RF output from the radio will also get into everything electronic including power supplies (switching power supplies don't like RF) and cause issues.

That thing really needs to be outside. Worst case, is an attic not an option? It could be mounted to a rafter with at least a few feet of free space around it, and you'd be safely away from it.

Thanks for the idea, but no attic (manufactured home)

I understand outside is best, (when possible) but I have read some positive stories on the internet where people still had pretty good results with an indoor antenna.

 

[suprpump]

I don't quite know what to say. People will think I'm nuts. During a hurricane in Key West the radio club I was a member of worked with law enforcement a nd helped patrol areas of the island because flooding made parts of the city an island. Well the storm got too bad and we had to shut down and get out. I wound up in a navy shelter with my CB but no antenna. A coat hanger from the radio up on to a window screen allowed me to talk all over the island and I was lucky it didn't hurt the radio. This was about 1964. I sold that old tube type radio in 1972 and it still worked just as good as the day I got it.

 

[FKimble]

I am afraid an antenna that close to the radio would cause it to reboot or worse every time the radio was keyed!

Frank

 

[MTS2000des]

Thanks for the idea, but no attic (manufactured home)

I understand outside is best, (when possible) but I have read some positive stories on the internet where people still had pretty good results with an indoor antenna.

Stories on the Internet. Urban legends. Than there is proper RF practice.

I've deployed thousands of public safety subscribers from portables to control stations and desktop stations. Quite often, we are faced with similar situations where someone wants a desktop radio, grabs a mag mount antenna, and slaps it to the side of the desk. Then they wonder why the 35 watt radio causes their computer to shut down, people's desk lamps around them to flicker, and laser printers 5 feet away to power cycle. Nevermind the radio affiliates to the system multiple times because it has a weak inbound signal so it's constantly pounding on the control channel.

Solution? Install a proper outside antenna, properly grounded to R-56 standards, and run appropriate cable to radio. Problems disappear, radio was then reprogrammed to low power (3 watts) and has a solid -85dbm inbound.

There is the right way and the "get her done way". They are usually not interchangeable.

 

[GKLdiy88]

I don't quite know what to say. People will think I'm nuts. During a hurricane in Key West the radio club I was a member of worked with law enforcement a nd helped patrol areas of the island because flooding made parts of the city an island. Well the storm got too bad and we had to shut down and get out. I wound up in a navy shelter with my CB but no antenna. A coat hanger from the radio up on to a window screen allowed me to talk all over the island and I was lucky it didn't hurt the radio. This was about 1964. I sold that old tube type radio in 1972 and it still worked just as good as the day I got it.

I am afraid an antenna that close to the radio would cause it to reboot or worse every time the radio was keyed!

Frank

Stories on the Internet. Urban legends. Than there is proper RF practice.

I've deployed thousands of public safety subscribers from portables to control stations and desktop stations. Quite often, we are faced with similar situations where someone wants a desktop radio, grabs a mag mount antenna, and slaps it to the side of the desk. Then they wonder why the 35 watt radio causes their computer to shut down, people's desk lamps around them to flicker, and laser printers 5 feet away to power cycle. Nevermind the radio affiliates to the system multiple times because it has a weak inbound signal so it's constantly pounding on the control channel.

Solution? Install a proper outside antenna, properly grounded to R-56 standards, and run appropriate cable to radio. Problems disappear, radio was then reprogrammed to low power (3 watts) and has a solid -85dbm inbound.

There is the right way and the "get her done way". They are usually not interchangeable.

Thanks for all the input, it is appreciated, but since an outside antenna seems to be out of the question then I have to ponder on if it is worth the risk of possibly damaging my radio by using an indoor antenna, if not then I might need to just pack away my base station radio and Comet GP-1 antenna and just be content with using my Yaesu FT-60R HT, only thing with my 5 watt HT is so far I have not been able make contact with anyone but just receive an occasional transmission.

Not meaning to doubt anyone, I am sure they are real concerns, but I am somewhat puzzled by the reports I have read on the internet of those who said they had fairly good success with an indoor antenna and didn't mention having any real problems, maybe they are the rare exceptions.

 

[mmckenna]

only thing with my 5 watt HT is so far I have not been able make contact with anyone but just receive an occasional transmission.

Take it portable. Take the antenna and your radio outside, to a park, etc and set it up where you can operate. 5 watts with a good antenna should get you something.

Not meaning to doubt anyone, I am sure they are real concerns, but I am somewhat puzzled by the reports I have read on the internet of those who said they had fairly good success with an indoor antenna and didn't mention having any real problems, maybe they are the rare exceptions.

Depends on their exact situation. If they are close to repeaters, it may work just fine. If they are in a building with building materials that block RF, then it may not work.

Only way to know is try. It might work just fine.

 

[GKLdiy88]

Take it portable. Take the antenna and your radio outside, to a park, etc and set it up where you can operate. 5 watts with a good antenna should get you something.


Depends on their exact situation. If they are close to repeaters, it may work just fine. If they are in a building with building materials that block RF, then it may not work.

Only way to know is try. It might work just fine.

The semi-rural area I live in does not have any repeaters in the same county so my 5 watt HT might not be able to transmit that far, if that is the case the only chance of making a contact is if I would just happen to catch someone going thru the local area transmitting at the same time I am listening.

As far as using an inside antenna with the base station with some comments I read I was concerned about damaging the radio with it being only 2 feet from the base of the antenna.

 

[mmckenna]

The semi-rural area I live in does not have any repeaters in the same county so my 5 watt HT might not be able to transmit that far, if that is the case the only chance of making a contact is if I would just happen to catch someone going thru the local area transmitting at the same time I am listening.

It's not so much about the power output of the radio. It is all about the antenna. 5 watts into a good antenna will get you a long ways. If you can get some altitude, it would benefit you.

As far as using an inside antenna with the base station with some comments I read I was concerned about damaging the radio with it being only 2 feet from the base of the antenna.

Unlikely to damage the radio unless you get your SWR really high and it stays there while you transmit for a very long time. High SWR does not present itself as a mushroom cloud coming out of the back of the radio. It's heat that builds up and can eventually do damage. Ideally you want to keep it low, as it prevents that issue, and it also means that most of the power is getting radiated by the antenna.

Your bigger concern is what that amount of RF will do to nearby electronics. Most will do fine, some might freak out, but be OK once you stop transmitting. The rare consumer item can be damaged by high RF fields.

I would take what you read on the internet with a grain of salt, and try it anyway.
But I think you'll have some level of disappointment. The antenna will do better if you can get it outside, but I know that's a challenge based on your home.

 

[GKLdiy88]

It's not so much about the power output of the radio. It is all about the antenna. 5 watts into a good antenna will get you a long ways. If you can get some altitude, it would benefit you.



Unlikely to damage the radio unless you get your SWR really high and it stays there while you transmit for a very long time. High SWR does not present itself as a mushroom cloud coming out of the back of the radio. It's heat that builds up and can eventually do damage. Ideally you want to keep it low, as it prevents that issue, and it also means that most of the power is getting radiated by the antenna.

Your bigger concern is what that amount of RF will do to nearby electronics. Most will do fine, some might freak out, but be OK once you stop transmitting. The rare consumer item can be damaged by high RF fields.

I would take what you read on the internet with a grain of salt, and try it anyway.
But I think you'll have some level of disappointment. The antenna will do better if you can get it outside, but I know that's a challenge based on your home.

Thanks for the info and reassurance, I likely will give it a try this week, still finishing getting over a stomach virus and haven't been up to doing much the past 2 days.

My base radio is only 25 watts so that should be safe for indoor transmitting as opposed to a 50 watt or more.

 

[popnokick]

Thanks for the idea, but no attic (manufactured home)

By chance is your manufactured home wrapped in metal siding? E.g. aluminum or similar? How about the roof? Any metal in that? If the answer is yes to either, then your home is not a good candidate for an indoor antenna that will help much. The performance of your handheld HT which you wrote is not receiving much is another indication that your home may be a Faraday cage. I have a three story wood frame house but there are tin ceilings on every floor… and they block cellular, wifi, and much other RF. Fortunately the top floor is the attic, and that is where some of my antennas are.

 

[prcguy]

By chance is your manufactured home wrapped in metal siding? E.g. aluminum or similar? How about the roof? Any metal in that? If the answer is yes to either, then your home is not a good candidate for an indoor antenna that will help much. The performance of your handheld HT which you wrote is not receiving much is another indication that your home may be a Faraday cage. I have a three story wood frame house but there are tin ceilings on every floor… and they block cellular, wifi, and much other RF. Fortunately the top floor is the attic, and that is where some of my antennas are.

My house is mostly stucco covered. That has metal lath or an RF shield over the entire house for the stucco to stick to.

 

[prcguy]

Aside from RF exposure concerns, which are valid indeed, you also have to consider that "INtennas" (a trademark of Cobra actually) SUCK.

"Intenna" was trademarked by the Microwave Filter Company. It actually worked pretty well for what it was, I installed many of them in the 70s.

 

[GKLdiy88]

By chance is your manufactured home wrapped in metal siding? E.g. aluminum or similar? How about the roof? Any metal in that? If the answer is yes to either, then your home is not a good candidate for an indoor antenna that will help much. The performance of your handheld HT which you wrote is not receiving much is another indication that your home may be a Faraday cage. I have a three story wood frame house but there are tin ceilings on every floor… and they block cellular, wifi, and much other RF. Fortunately the top floor is the attic, and that is where some of my antennas are.

vinyl siding, asphalt single roof

My house is mostly stucco covered. That has metal lath or an RF shield over the entire house for the stucco to stick to.

"Intenna" was trademarked by the Microwave Filter Company. It actually worked pretty well for what it was, I installed many of them in the 70s.

interesting, antennas made specifically for indoors

 

[prcguy]

vinyl siding, asphalt single roof


interesting, antennas made specifically for indoors

Its made for vehicle use and its a tuning box that mounts and grounds on one side of a window with a wire that stretches across the window and grounds at the other side. It makes the vehicle into a "slot antenna" where the skin of the vehicle is the antenna. The tuning box has a series and shunt variable capacitor to tune the resonant frequency and tune out reactance in the wire.