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Transmitting UHF/VHF Station RF Safety Question

Joined
Jan 23, 2019
Messages
3
#1
Hi all,

Just wanted to ask a question about a local radio tower I came across last week here in Scotland. It was actually a LORAN A station operating from Dec 1943 as part of a military installation during WWII - but now it's been transformed into a CAA NATS transmitting station for local air traffic control (Site Number NB03SW 49) with a receiving station nearby.

It's about 35 - 40 meters high (picture attached) and I think it's a UHF and VHF transmitter. I was walking around the site because we're looking for locations to shoot a couple of scenes for a short film and this looked good as it's next to some awesome clifftop coastline.

The site and access road is totally open to the public, although the buildings are of course secured and the bottom of the tower is fenced off to stop anyone from scaling it. We only intend to do a shot of someone walking past the tower about ten meters away at ground level and of course wouldn't try to touch anything, mess with signals or anything silly like that.

As I'm pretty much an idiot with this type of thing, I was wondering about the radiation safety of spending half an hour or so at ground level near the base of a tower like this? I understand that the radio waves are probably being transmitted horizontally from the aerials at the top and not much RF radiation leaks out vertically. However, I thought it would be best to check with people who know a lot more than me. There is a yellow 'RF Warning' triangle at the base of the ladder, but I assume that indicates the point where you shouldn't pass.

Any advice at all would be much appreciated. This forum seems to be a cool place to find out about stuff like this!
 

Attachments

Joined
Jun 30, 2006
Messages
7,619
Location
So Cal - Richardson, TX - Tewksbury, MA
#3
You are correct that the signals off those antennas go mostly horizontal above your head. At 1m or less there is probably a hazard but RF acts like light when adding distance. Every time you double the distance from the antenna the RF level will drop by 75%, so if its a danger at 1m then 2m should be fine. 4m away its down another 75% and so on.
 
Joined
Jan 18, 2010
Messages
163
Location
People's Republik of Massachusetts
#6
Another agreement that it will be perfectly safe and no issue at all. I work in the RF industry and RF safety is very important. TT
Just curious, what's a good rule of thumb for distance on a cellular macro site? Maybe not walking in front of it, but at least to the side of behind it? I find myself on roof tops often, and I try to keep my distance from them.
 
Joined
Jan 23, 2019
Messages
3
#7
Hi everyone, thanks very much for your opinions and info - you've set my mind at ease. I'll have to pop in a nod to the RadioReference forums in the film credits!
 
Joined
Jul 27, 2005
Messages
10,274
Location
Point Nemo.
#8
Just curious, what's a good rule of thumb for distance on a cellular macro site? Maybe not walking in front of it, but at least to the side of behind it? I find myself on roof tops often, and I try to keep my distance from them.
Usually not much risk behind them. They are directional/sectorized (usually) so as long as you are not on the business end of them you are OK.

I work around a bunch of that sort of stuff. I carry a NARDA S3 when I'm in a new or questionable area. Never had an issue. I've got it set for 50% and 100% level alarms. I can get it to trigger when near a 21KW erp FM broadcast transmitter, but I don't think I've ever had it trigger off a cell site, unless I was right against the front of the panel antennas.
 
Joined
Jan 18, 2010
Messages
163
Location
People's Republik of Massachusetts
#10
Usually not much risk behind them. They are directional/sectorized (usually) so as long as you are not on the business end of them you are OK.

I work around a bunch of that sort of stuff. I carry a NARDA S3 when I'm in a new or questionable area. Never had an issue. I've got it set for 50% and 100% level alarms. I can get it to trigger when near a 21KW erp FM broadcast transmitter, but I don't think I've ever had it trigger off a cell site, unless I was right against the front of the panel antennas.
Ooo fancy, maybe if there's leftover budget, I can convince my work to buy me a NARDA S3.
 
Joined
Feb 1, 2010
Messages
586
Location
Tampa, FL
#11
Distance depends on time. Our guidance is max distance from antenna for minimum amount of time as practical. Dont eat lunch next to a transmitting antenna unless you have to. Personally, I look away from the panel antennas as I walk by them. TT
 
Joined
Feb 28, 2019
Messages
176
#13
Quick-n-dirty...
If you're close enough to lick that antenna then you're in trouble. If you aren't that close then you aren't in trouble.

It's not a good idea to go around licking antennas...
 
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