Tower Site Dangers
Posted by Roadwolf on January 23, 2014
Some of us like to explore rooftops and areas which include a lot of communications towers. And I know that some of the people on this site know a bit about RF Radiation and can add some useful information to this thread. However I think that a thread about this, to advise new explorers of the dangers of RF Radiation is a good idea.
High level RF (or Radio Frequency) Radiation is more dangerous than you may think.
Lets start with AM Broadcast sites: AM Radio was very popular at one time, and there are many abandoned AM Tower sites... However there are many active AM Broadcast sites as well. This is a picture of an Abandoned AM Site...
Not much to see... Transmitters are expensive and are usually sold off...
However Active sites may look abandoned... it is hard to tell sometimes because lower budget radio stations may not spend the money to upkeep their transmitter.
AM Towers have to be fenced in as per Safety Code 6 requirements. No matter where they are or how accessable they are, because the whole tower is energized with RF.
This is a picture of a couple AM Transmitter towers:
AM Towers are usually always multi-tower arrays. And you will generally not see any other antennas on AM Towers... the towers are usually just straight towers with nothing but warning lights attached to them. However sometimes there will be an "STL" Antenna (Studio - Transmitter Link) Attached to the tower which might look like this:
Typical STL Antenna Install on an AM Tower. The guy standing there is a professional tower climber. In order to get onto a AM Tower without being zapped, you basically have to jump onto it without touching the ground. And when you are on the tower, there is a potential for you to hit a "hot spot" where the RF is so strong that you can not hold on to the tower.
Typical UHF STL Antenna up close.
AM Towers, as mentioned before are also completely energized. This picture shows how an AM Tower is insulated from the ground by an insulator...
As you can see, the tower is completely being supported by this brown insulator. The rods with the metal balls are actually spark gaps for lightning protection.
The voltage on an AM Tower is usually a couple thousand volts. It really depends on the transmitter and the actual transmission. But the amperage of the towers can be pretty high - the towers I work on are usually around 20 amps at 3000 volts.
I was talking to someone I work with, and he actually got zapped by some RF a long time ago while working on a Transmitter hut... which is basically a room at the base of the tower filled with coils and such, which are all wide open and unprotected. I couldn't find a good picture of these coils inside a room.. but here is a picture of them inside a small cabinet.
Anyhow, basically he was sweeping the floor and his shoulder brushed against a live coil. his skin started to melt instantly... he said his skin actually liquified and he had to stand still while it re-solidified... so basically RF Can Melt You !!!
FM Broadcast Sites:
FM Sites are generally safer for those walking around on the ground. As the antennas are usually higher up at the top of a tower... Here is a picture of your average FM Broadcast tower install...
Some may be slightly more complex... such as:
or others may be much cleaner...
Either way... An FM Site generally only consists of ONE Tower, which has several antennas on it. They range in power from as low as 500 Watts... (or lower) to upwards of 100,000 Watts or higher in some cases. But are generally around 20,000 Watts which is enough to cover a city the size of the Greater Toronto Area.
Often 2 or more FM Stations will use one set of antennas... and in this case there will be a Combiner room where each stations transmitter feeds into tuneing chambers and filters and gets combined into one single RF Transmission line.
It is possiable for FM Broadcast band RF Radiation to harm people who are close to the antennas. Usually a sign of a high RF Feild is a headache or migrane, called a RF Headache, which will go away when you exit the RF Feild. However usually once you are in that feild you have already done damage and the RF can cause you to be impotent quite quickly depending on the level of RF. I know people who have been working in RF for a long time, and they were impotent within a year of working with RF... so it can happen quite fast, all you need is that one blast of high power RF to do it!
Low Frequency Stuff:
Large arrays and sites are fairly common in the VLF LF MF and HF bands... However, they are few and far between. they are generally used for long range communications (Amature Radio), Marine Radio, and Aeronautical (Navigation Radio), Broadcast (AM Radio), and Military stuff... Some pics...
Here is a pic of a HAM's (Amature Radio Operator) home setup of MF and HF antennas... on his roof !
I would probably say your generally safe walking around in low frequency feilds. however dont go near any antennas as they might be energized.
VHF and UHF Communication sites:
Commercial Communications sites are quite common... Here are some pictures...
This is your average VHF Base Tower... VHF is commonly used for communication in more rural areas and is being generally phased out in urban centers. Things like the Fire Dept, Police, Works Dept, Trains, Marine, Public Transportation, and Taxis commonly use VHF Communications. VHF is the prefired method for long range coverage for communications over a wide area... as it tends to pass thru trees and small hills easier then UHF Communications.
VHF Towers for communications usually only operate up to 500 Watts...
VHF Towers generally don't need to be very powerful because of the ability to pass thru small hills and terrain easier then other forms of communication. However don't be fooled, VHF Communications, if powerful enough can still give you headaches and cause you harm if your close enough.
UHF Sites are far more common in urban centers... here is a picture of a UHF Antenna
Usually they look like this... these are common antennas called folded di-poles. Used for both VHF and UHF... they are very common, the difference between this one and the VHF one is that UHF folded Dipoles are smaller, about half the size of the VHF folded Dipoles.
There are also directional antennas... such as this one...
Yagi Antenna
which is a home made UHF Yagi antenna... I tried to find a pic of one on a tower but was too lazy too look very hard.
UHF-Lo is usually used for federal communication (FBI, RCMP), Transit, and Commercial stuff.
Same rules apply for UHF-Lo as they do for VHF, in terms of safety... dont touch the antennas - and don't stand infront of antennas... they usually aren't too powerful. and if they are, they will usually warn you.
UHF-Hi sites are pretty common now... This is the band that alot of cell towers operate at. Other users include police, fire, municipal, and commercial.
This is a Cell phone tower, as well as a LTR Trunking tower for 800 MHz trunking and cell systems. they are fairly safe on the ground, however I would not advise going up and climbing up near the antennas... not a good idea if you want to have children one day.
TV Stations:
This is a VHF D-TV Antenna.
This is a VHF TV Antenna
And this is a UHF D-TV Antenna
TV sites are usually quite powerful and they also usually have Microwave STL equipment which can be dangerous. Try and stay well away from TV sites.
Microwave ground to ground link sites:
Microwave links are actually quite common. Here are a few pics...
Those drums are microwave antennas... standing directly infront of it would not be advisable as they will probably harm you. however because they are so high up usually, you are normally fine around towers that have them. However if your on a roof and you are near one, I wouldn't stay there long.
Here is a picture of a newer type of Microwave Link...
Anyhow, stay away from the front of these antennas...
Microwave ground to space links:
You have seen these. regular dishes... I would tend not to hang around them, as you dont know the power of the dish. some may be quite powerful, however usually they don't require alot of power to shoot into space. no more then 50 watts atleast. but at a microwave frequency that can do damage.
Radars:
Wheather it be for weather, airplanes, or boats... radars are generally pretty dangerous to stand beside if they are operating. they are quite powerful, so much so that you can sometimes hear them pulsing on radio bands far away from the band at which the radar is tuned for.
I would generally advise you to stay well away from a radar site.
Safety Code 6:
Safety Code 6 in Canada is what protects us (the general public) from harmful RF Radiation. It requires companies to warn the general public where a dangerous RF feild is present and usually requires fencing around dangerous areas. In most cases you will not be able to enter a dangerous RF Zone without first atleast passing a sign stating its dangerous... This code even requires the company to fence off areas in which the RF level is above a certian point. for AM Broadcast stuff that is at 60 volts per meter... They even have to do this if there is already a fence around the property.
Anyhow, I hope that this has been useful.. and I hope others can add to it. I spent a fair bit of time on it 
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Next Radio Codes
Yagi Antenna
which is a home made UHF Yagi antenna... I tried to find a pic of one on a tower but was too lazy too look very hard.
UHF-Lo is usually used for federal communication (FBI, RCMP), Transit, and Commercial stuff.
Same rules apply for UHF-Lo as they do for VHF, in terms of safety... dont touch the antennas - and don't stand infront of antennas... they usually aren't too powerful. and if they are, they will usually warn you.
UHF-Hi sites are pretty common now... This is the band that alot of cell towers operate at. Other users include police, fire, municipal, and commercial.
