http://imgur.com/a/tMrIJ
http://imgur.com/a/tMrIJ
Climbing some radio towers
http://imgur.com/a/tMrIJ
Last edited by coothatower on 16 Sep 2013, 12:28 pm, edited 1 time in total.
you're not wrong about it being in the middle of nowhere! (only driven to it once, coudln't be bothered to return) Its elevation is the reason its such a popular site. A popular UHF CB repeater was here for a very long time, too (Ibelieve its recently moved)
The tallest one (that you climbed) is Telstras, there isnt much that bounces off it, although there are some 500W antennas that you **definitely** want to steer clear of.
The most northern tower on the site is Airservices and BOM
The other tower is the Powerlink site has Moreton Bay council, Brisbane amateur VHF and UHF channels, St John Ambulance, QLD water, DTMR, Emergex, and Optus
Yep we climbed the Telstra tower. Are you sure about the 500w? amca database said the max power of those Panel antennas are 70.8w. There in the R-GSM-900 band i couldn't see why they would be any more then that. I'm fascinated with radio tech but too scared to climb towers like that!
I met a guy at a recent cave clan explore who has climbed one of the translator sites at Mt Coot-tha (one of the big 150m bad boys)
If you're looking for the police site it's maybe 1.5km back down near the hook in the road, satellite view shows it poking out from some trees
BasicallyDynamite wrote:I'm curious as to what effects you would have from getting too close to a transmitter. Do they cause burns?
Stay away from commercial AM (ungrounded and risk of burns), commercial FM and TV (stupidly high levels of RF (think the top of the Mt Coot-tha towers)
Also don't stand or climb in front of anything directional and you'll generally be okay
In saying that, active sites that are used by a lot of different organisations mean it's somewhat likely you might get unexpected company..
+1Moose wrote:BasicallyDynamite wrote:I'm curious as to what effects you would have from getting too close to a transmitter. Do they cause burns?
Stay away from commercial AM (ungrounded and risk of burns), commercial FM and TV (stupidly high levels of RF (think the top of the Mt Coot-tha towers)
Also don't stand or climb in front of anything directional and you'll generally be okay
In saying that, active sites that are used by a lot of different organisations mean it's somewhat likely you might get unexpected company..
never even consider anything which broadcasts any kind of commercial radio or tv. Even the local fm radio stations broadcast at 12kw in Brisbane. Think food in your microwave, because thats pretty much your body at that amount of power.
It's important to note that directional antennas (yagis, dishes & panel antennas) almost always have powerful back lobes as well. Which means standing directly behind them is almost as bad as standing directly in front of them. Additionally there are usually complicated radiation patterns that can cause strong lobes at other weird angles. See here for an example: http://en.wikipedia.org/wiki/File:Sidelobes_en.svgcoothatower wrote:Are the overlays just on the amca database site? There all directional so you should be fine if you don't climb on the outside on them.
I have spoken to someone who developed cataracts after playing with microwave oven magnetrons from a considerable distance. 1000W omni at 10m is less than 0.1mW/cm^2. The quick sum would show that it is safe but when you add in directionality and reflections etc you can end up with dangerous numbers pretty quickly.
If that tower really does have 500W antennas you'd have to be an idiot to knowingly climb it.
I Have to call bs on this. Even if you had 1kw @10m and had a relatively high gain of 6db its stll going to be well under the MPE limit for a uncontrolled environment including ground reflections. No one is getting any cataracts from that power at that distance. If you make a call on a mobile phone its going to have a higher power density that that. There are powerful side lobes but any lobes on the back of the antenna are going to have a very low gain and even at high power its going to be fine for short amounts of time. The MPE limit for a controlled environment is 5mw/cm2 and since that when climbing these towers you are generally a few metres from any of the antennas its very unlikely that you will be exposed to anything near this limit when climbing behind the panel antennas found on these type of towers.Spoz wrote:I have spoken to someone who developed cataracts after playing with microwave oven magnetrons from a considerable distance. 1000W omni at 10m is less than 0.1mW/cm^2. The quick sum would show that it is safe but when you add in directionality and reflections etc you can end up with dangerous numbers pretty quickly.coothatower wrote:Are the overlays just on the amca database site? There all directional so you should be fine if you don't climb on the outside on them.
My advice to anyone thinking of climbing these towers is to be extremely cautious if you don't know what you're doing.
This is good advice.Spoz wrote:My advice to anyone thinking of climbing these towers is to be extremely cautious if you don't know what you're doing.
Im not a expert on climbing towers or rf/any of this so i could be completely wrong.
If you ever consider climbing any type of tower don't just go do. Do some research into what type of tower it is, what it transmits and at what power, what type of antennas are on it. Lean what the dangers of rf are and buy a rf meter capable of keeping you safe and letting you know if its unsafe to continue climbing, wear a harness when climbing it and bring a friend along incase something happens.
The best approach is to check the ACMA site and look at every single antenna that is on there. Anything more than 50W and I'd be seriously considering whether it's worth the risk. Anything more than 500W and I'd say it's never worth the risk.
Fields do overlap but can you show me a source that shows they subtract from each over.Spoz wrote:An RF meter won't necessarily save you. When you have HUNDREDS of antennas on a tower, there are going to be "hot spots" where fields overlap and add and subtract. Your eyes could theoretically be in one while your RF meter is in a null point.
Its going to be alot safer then not having one.
theoretically maybe but in practice its not going to happen.Spoz wrote:Your eyes could theoretically be in one while your RF meter is in a null point.
Correlation != causationSpoz wrote:I have spoken to someone who developed cataracts after playing with microwave oven magnetrons from a considerable distance.
- 
S= P x G
----------
4 x PI x R^2
s is the Power density
P is the Antenna power input
G is the Antenna power gain
R is the Distance to center of Antenna radiation
Take your microwave over magnetron at 10 metres @ 1000w
Lets say that it is not a isotropic (radiates equally in al directions) transmitter but focus most of teh energy in one direction and has a gain of 6db is reality this would be much less but for this example it would demonstrate worst case senario.
So after putting in the power,gain, and distance we get 0.3167mw/cm2 which is very low/ completely safe, lets say you make a phone call and your phone puts out 1w on average and has a gain of around 3db, your holding the phone within 3 cm of your eyes/ears if you put those figures in you get 17.6349mw/cm2 which is much hight but still not going to cause any damage. Many cb radio systems on trucks can be hundreds of watts and the antennas for them are right on the front or side of the cab of the truck these drivers suffer no ill effects.
S= P x G
----------
4 x PI x R^2
s is the Power density
P is the Antenna power input
G is the Antenna power gain
R is the Distance to center of Antenna radiation
Take your microwave over magnetron at 10 metres @ 1000w
Lets say that it is not a isotropic (radiates equally in al directions) transmitter but focus most of teh energy in one direction and has a gain of 6db is reality this would be much less but for this example it would demonstrate worst case senario.
So after putting in the power,gain, and distance we get 0.3167mw/cm2 which is very low/ completely safe, lets say you make a phone call and your phone puts out 1w on average and has a gain of around 3db, your holding the phone within 3 cm of your eyes/ears if you put those figures in you get 17.6349mw/cm2 which is much hight but still not going to cause any damage. Many cb radio systems on trucks can be hundreds of watts and the antennas for them are right on the front or side of the cab of the truck these drivers suffer no ill effects.
I don't know what the incidence of cataracts is in 30 year old males but I'm going to go out on a limb and say it's a little lower than the incidents of cataracts in 30 year old males who play with microwaves.aydun wrote:Correlation != causationSpoz wrote:I have spoken to someone who developed cataracts after playing with microwave oven magnetrons from a considerable distance.
The 1000W isotropic radiator at 10m was an assumption. He was a guy who knew the dangers and thought he was being safe and ended up harming himself as a result. If you want to do the same then at this point I will only encourage you.
No offence but given your first statement there you're not qualified to make the last one. I'm not going to do your research for you, I'm just telling other people that it's not safe to be climbing towers with such high powered transmitters on them on the off chance that someone mistakes you for some kind of authority.coothatower wrote:Fields do overlap but can you show me a source that shows they subtract from each over.Spoz wrote:An RF meter won't necessarily save you. When you have HUNDREDS of antennas on a tower, there are going to be "hot spots" where fields overlap and add and subtract. Your eyes could theoretically be in one while your RF meter is in a null point.
Its going to be alot safer then not having one.theoretically maybe but in practice its not going to happen.Spoz wrote:Your eyes could theoretically be in one while your RF meter is in a null point.
Well with a sample size of 1, that's a strong claim to make.. It's still just an observed correlation.Spoz wrote:I don't know what the incidence of cataracts is in 30 year old males but I'm going to go out on a limb and say it's a little lower than the incidents of cataracts in 30 year old males who play with microwaves.aydun wrote:Correlation != causationSpoz wrote:I have spoken to someone who developed cataracts after playing with microwave oven magnetrons from a considerable distance.
Cataracts can result many other factors, such as genetic disorders, drugs, medication etc..
Last edited by Aydun on 28 Aug 2013, 1:29 pm, edited 1 time in total.
I was asking you to prove some theory to back up your claims which are incorrect on many accounts. Im not say that your friend didn't get cataracts from messing with a microwave but form the situation you described its not going to happen. Im not telling people to climb anything but explaining the actual dangers. Im pretty sure I said never even think about climbing any kind of broadcast towers. I also said I'm no authority on this and said what I'm saying could be completely false, Judging by your last statement and failure to recognise or understand a very simple maths equation explaining how your fiend was exposed to very low power density of rf in the situation you described I think i have more authority giving people advice then you.Pussinboots wrote:No offence but given your first statement there you're not qualified to make the last one. I'm not going to do your research for you, I'm just telling other people that it's not safe to be climbing towers with such high powered transmitters on them on the off chance that someone mistakes you for some kind of authority.