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FAQ: Antennas, Masts, Aerials etc | General Exploring Chat Forum | 28DaysLater.co.uk

FAQ: Antennas, Masts, Aerials etc



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big in japan
28DL Full Member
#1
Many people write here asking something like:

'Yo! can I climb this mast?, here is a picture.'

Normally the answers are a garbled mix of 'lol, so you've had all your babies then..' to 'it'll be totally fine', and in most cases the people giving the answers have as much of a clue as the people asking the questions.
I've done quite a bit of reading on this (in addition to having a degree in electronic engineering) and often end up writing the responses to these questions to make sure keenos eager to score internet points don't end up cooking themselves in our name.

Seen as I usually end up writing the same things, I've decided to summarise the guidelines I go by when I'm looking at antennas I might be interested in climbing.

***THIS SHOULD NOT BE TAKEN AS A BIBLE.***

This document is not exhaustive, nor can I guarantee that its 100% correct. I'm not a telecomms engineer. I hope you find this helpful.


Forward:

CLIMBING ANY MAST IS DANGEROUS. I mean this in the sense of the immediate physical harm that will come to you if you fall, the internal burning you can receive from close proximity to transmission equipment and the long-term effects resulting from the electromagnetic radiation you will be exposed to on a live antenna. These risks can be minimised but not completely eliminated and you should understand this before embarking on any climb of a radio mast. I would also recommend a bit of googling around the mast you intend to climb as well as a good look at it. Is it live? What services does it transmit? What is the transmission power of the gear attached to it? etc. Knowing this information could mean the difference between a good night out and a proper cooking. The long term effects of exposure to non-ionising radiation are still widely unknown, and as such, the recommended daily dosage limits issued by the WHO are very small. You will almost certainly exceed these climbing any live mast, and you should be well aware of this fact before you do.



AM radio antennas
Example: Moorside edge transmitting station
wp249589a6_01_1a.jpg

High power LW/MW AM antennas are generally NOT SAFE to climb unless de-activated or de-powered. The whole mast *is* the transmission antenna, so as you climb it, there is the potential for your body to become part of the antenna. This means that large amounts on energy can be directed through your body and will become especially concentrated at your ankles and wrists (where you are making contact with the mast). Serious internal burning can result from this, and will manifest itself by nausea and headache in the first instance and prolonged pain later on as the tissues repair themselves. You can also end up receiving electric shocks from the mast, which could be enough to dislodge you from the structure and cause you to fall. I would never climb a mast like this unless I was 100% sure it was deactivated.

FM Radio dipoles / whips
Example:

You will find these attached at height to most combined masts. They usually deal with the transmission of FM radio services. Don't hang around near them and pass as quickly as possible. They can emit relatively high amounts of energy.

Analogue Terrestrial TV
thorncliffe-farmshop.jpg


Post DVB switch over - there are non of these remaining in the UK although you may encounter them in other countries. They will be most often be positioned at the highest point on a mast and you should avoid climbing up to them as they emit extremely large amounts of energy. They look like long thick cylinders and are similar in appearance to the newer style DVB-T transmitters.

DVB-T main antennas
Example: Crystal Palace

The large thick white antenna at the top of the image (and the smaller clusters below it) is the main DVB-T transmission set for London. The level of radiation emitted by a transmitter of this type is extremely high and should be avoided. The patten of dispersion is planar, and as such, you can stand at a much closer vertical distance than you can horizontal. Personally, I would keep *at least* one or two levels between me and a set of gear like this. Not very scientific but neither is climbing masts.
You can also see many FM dipoles attached below.

DVB-T repeaters
Example: Alexandra Palace
ap2.jpg


These are smaller antennas used to boost signal to local areas that might not have line of sight to the main transmitter because of hills etc. You can see the gear on top in this image. They are MUCH lower power than the main transmitters, but are still dangerous and you should seek to stay off the horizontal plane.

Microwave / telecoms drums
Screen Shot 2017-08-16 at 17.17.51.png


Found on many masts, they are used for communication between masts for shifting data (mostly cell-phone) up and down the UK. They are safe to stand behind for brief moments, but don't hang around as they can have strong rear lobes. (see diagram below)
AA1.jpg


Local cell / mobile phone
cellphone.JPG


The long white sticks often found at low levels. Not too much of a worry and very directional. Don't stand in front of them.


If anyone with additional / more accurate knowledge would like to comment then please please do.

If you're still unsure, the best thing to do is just not to climb. I've known two people who have gotten extreamly sick after climbing masts they weren't sure about, and the possible long term effects on their health are unknown.

Use your head and stay safe.


Footnote/Update:

I recently saw an interesting post from someone in response to a youtube post put up by two guys who climbed Moel-y-Parc mast in wales. Rather than stopping underneath the active TV transmitter, they continued through it to the top of the mast, a decision that may have serious medical consequences in their later life.
It's worth a read.

You need to seek medical attention ASAP because you could have exposed yourselves to a dose of RF radiation hundreds of times more than the safe limit. Could even be thousands because you were right in front of the aerial array. As a Radio Engineer it just doesn't bear thinking about. It is forbidden for anyone like PROFESSIONAL Aerial riggers to climb on the tower whilst it is radiating power. There are strict guide lines set in law about this and there are safety interlocks on transmitters to prevent power being applied to the aerials whilst a technician is working near them. If a transmitter engineer were to defeat the interlocks and cause power to be applied whilst a technician was on the tower he would face a prison sentence, that is how dangerous and serious it is. This tower has an ERP of about 100,000w, I will say that again, ONE HUNDRED THOUSAND WATTS at a frequency of 600 - 800MHz the wavelength of that is 37cm. For serious internal heating to occur (which you wouldn't necessarily be aware of) an organ in your body would only need to be one quarter of that figure i.e. 9cm, that would include the spleen, liver, kidneys, heart and Brain although some RF heating would occur to anything anyway at that power level and frequency. Although the eyes are smaller than that they would be particularly vulnerable because they are filled with an egg white type jell. By way of comparison a domestic microwave oven is only 600w but at a higher frequency. So what might happen to you as a result of this stunt? Well it is not unreasonable to expect early development of cataracts, reduced liver, kidney, spleen function at an early age if you are not already at that point now. There is also a serious cancer risk. As I say it doesn't bear thinking about and I'm glad its not me.

However you may be lucky because all transmitters have what is called High VSWR protection. Put simply what this means is; all the power from the transmitter should go from the transmitter to the aerials and then be radiated out into space. However if something gets in front of the aerials some of that power will be reflected back to the transmitter, this would cause a high VSWR condition and could cause the transmitter to shut down to protect itself. I hope to god this happened in this case. If you know the date you did this, a check could be made with the transmitter recorded data and if a shutdown occurred you are two lucky dudes.
 
Last edited:

Ojay

Admin
Staff member
Admin
#3
This

If anyone with additional / more accurate knowledge would like to comment then please please do.
I'd normally lock threads like this, but as it seems to be a 'hot potatoe' ATM (excuse the pun)

Then I'm inclined to leave it open for sensible discussion ONLY

I will if course be heavily pruning any post replies that fail to serve as any useful purpose!

Thanks FB for taking the time to do this :)
 

LonDan

28DL Full Member
28DL Full Member
#4
Nice contribution fb, I has a learn!

All, it's probably worth reading up and discussing any laws related to climbing them too.
They're owned by multiple companies that and the transmission equipment attached can be owned by a number of different ones too.
Not that I know any laws about anything but just a thought.
 

OliverT

28DL Full Member
28DL Full Member
#5
I've only climbed one mast, which was transmitting DVB-T, so we only climbed half way. All three of us came down with headaches and nausea.
 

p1ynth

Hasnt Ex'd many Urbs!!
28DL Full Member
#8
Easiest way for non-techies to think about RF transmitters is to imagine the antenna is a high powered light or heating element.
e.g. Would you stand in front of a 5KW (5000watt) lamp??!! Well dont stand in front of an 900MHz RF transmitter then!!!


On a similar note, a friend of mine has served in Afghanistan.
Certain vehicles were eqipped with a device which was intended to block certain RF frequencies within a known distance.
On a small number of occasions, lads who were not entirely in the know mounted the vehicle by grasping the antenna for just a few seconds. They later they found they had severe burns to their hands, not only on the surface (as you would expect with a burn), but all the way through their hand.

Bear also in mind, that there is direct correlation between the frequency the transmitter outputs and the energy it outputs. (Unfortunately I cant remember the formula right now)
i.e. 1500MHz at 10KW carries a shite load more energy than 1500KHz at 10KW.

Its also the same reason why to get a really decent quality sound output from your domestic sound system, you need a high power sub-woofer, reasonable mid-range speakers, and only low power tweaters...... because the high frequencies carry more energy than the lower ones.
i.e. yes, this shit burns! Some are like a massive microwave, but without the rotating plate or latching door!
 

tweek

meek
Regular User
#9
I remember when we did Moel-y-Parc and the process of research basically involved Bigjobs looking at it on the horizon and saying, "let's go climb that big red stick". We knew not what we were doing. Some in the group were more cautious and put off climbing too high for these concerns. As it turned out, the two of us got about as far as we could quickly and safely on a transmitter that wasn't as dangerous as it could so easily have been. We stopped 2/3rds of the way up. More research was done by the time some of the group (plus I think you fishy?) went back... And by chance alone, we'd dodged a bullet. Don't do what we did. If you did this at Holme Moss transmitter, for example, you'd definitely fuck yourself up!
 

Landy101fc

28DL Full Member
28DL Full Member
#10
i asked a friend who was a broadcast mast expert,can i climb a 50Kw AM mast his reply...


Yes, if its shunt fed. Getting on the thing is the only real danger of a shock. With shunt fed you would have the base grounded, so get on and climb, safer still inside it. You only get a shock when your body bridges across areas of different voltage. A few volts won't harm as if the antenna is tuned reasonably well, there might be just a few volts. you wouldn't feel that. If its sat on an insulator, don't venture near it even. I am ignoring any perception of RF cooking of course. You would get the same stood a few yards away, so no difference. Many of us have worked in the 'near field' ,(less than a wavelength) from antennas for many years. I still have two great kids and plenty of hair, so think the 'danger' at low frequencies certainly is over-dramatised. I would not buy a house next to a microwave frequency digital radiator though. RF itself isn't dangerous; they use it in hospitals to heal; look up diathermy which basically sends MW up to SW signals into your arms / legs etc to sooth muscles, and some microwave stuff is used to cauterise veins in surgery, etc. RF is lovely, lets have more!


and a warning from another friend:

= CLIMBING ANY MAST IS DANGEROUS. I mean this in the sense of the immediate physical harm that will come to you if you fall, the internal burning you can receive from close proximity to transmission equipment and the long-term effects resulting from the electromagnetic radiation you will be exposed to on a live antenna. These risks can be minimised but not completely eliminated and you should understand this before embarking on any climb of a radio mast. I would also recommend a bit of googling around the mast you intend to climb as well as a good look at it. Is it live? What services does it transmit? What is the transmission power of the gear attached to it? etc. Knowing this information could mean the difference between a good night out and a proper cooking. The long term effects of exposure to non-ionising radiation are still widely unknown, and as such, the recommended daily dosage limits issued by the WHO are very small. You will almost certainly exceed these climbing any live mast, and you should be well aware of this fact before you do. =
 

tumbles

Trip Hopping
Regular User
#11
Some very good info here, while I have a degree in radar & comms it's pretty sketchy from not being in the industry for 10 years now. I have always said I'm happy to try and give my advice depending on the antenna/array design I think the only thing I would add to the stuff above is after reading the advice is that it should be your decision and your decision only to attempt a climb - don't take anything as gospel as it'll never be clear what power and frequency some of these could be kicking out.
 

p1ynth

Hasnt Ex'd many Urbs!!
28DL Full Member
#12
Landy.... no disrespect, but..... The MW (Micro Wave) and SW (Short Wave) RF employed in the medical situations you write of is VERY controlled (power output, modulation and duration). Climbing a mast, whether you're below the actual antenna (coz its at the top) or along side a dipole (threaded through the tower you intend to climb) is in a different domain. Vast amounts more ERP (effective radiated power) than any medical device can produce, uncontrolled, and continuous.

As I said above, a 1KW transmitter @ 1GHz contains a shite load more RF energy than a 1KW transmitter at 198KHz. (IIRC Fourier Series formula, if anyone really wants to fuck their head up, allows you to calculate the energy carried in an RF wave.) The mode of modulation can also have a small bearing on the energy carried too.

This is all, of course, IF the antenna concerned is a transmitter.
If its attached to a receiver then its absolutely harmless. (But how do you tell?!)

As Tumbles says though, the knowledge is here.
There are hazzards, you could fry bits of yourself or your reproductive organs, or just get a bad head for an hour.
The decision, is yours.
 

Landy101fc

28DL Full Member
28DL Full Member
#13
P1ynth, what i put down is what others thought me, two replies of two diffirent people.
Yes i do know that frequency is key to why some stations got further on 539meters then they did on 192meters
Near Huddersfield i saw two antenna's that where nice to climb, i gave them a id on being MW, with lines running up them both sides. Top fed, seemed isolated at the bottom. I dread to think about the KW's running through that lot ... But it was tempting if my body could do it.
 

Landy101fc

28DL Full Member
28DL Full Member
#15
Moor side transmitting station.
When i picked up the dog i had a nice view on it, with a few men
Telling me it is offlimits :) i try to understand the logic and science about transmitting equipment.