Living close to cellphone tower

[cdev]

I am assuming that the top of that tower contains huge TV and radio broadcasting antennas for the entire area, if so, be aware that sometimes they do cause all sorts of strange effects especially when its foggy.

Example- fluorescent lights blinking - when they are not on.

[Richard Crowley]

There are certainly some cell antennas shown in the photo (the vertical rectangular boxes).
But most of those are round microwave dishes. This is clearly a major communication hub of some kind.
Both cell antennas and microwave dishes have very little RF radiation immediately below the antenna.
(Or above the antenna, for that matter.)  Directing power above or below the antenna is quite wasteful.
The antennas have been designed for horizontal radiation for efficiency and coverage reasons.

The tower is much bigger than would be warranted by a bunch of smallish round microwave dishes.
There must be something higher up that would require a tower of that size.
There also appears to be rather a large bundle of cables and waveguides feeding antennas above the photo.
Is this also a broadcast TV and/or FM transmitting site?

[vk6zgo]

There are certainly some cell antennas shown in the photo (the vertical rectangular boxes).
But most of those are round microwave dishes. This is clearly a major communication hub of some kind.
Both cell antennas and microwave dishes have very little RF radiation immediately below the antenna.
(Or above the antenna, for that matter.)  Directing power above or below the antenna is quite wasteful.
The antennas have been designed for horizontal radiation for efficiency and coverage reasons.

The tower is much bigger than would be warranted by a bunch of smallish round microwave dishes.
There must be something higher up that would require a tower of that size.
There also appears to be rather a large bundle of cables and waveguides feeding antennas above the photo.
Is this also a broadcast TV and/or FM transmitting site?

It is a reasonable sized tower,but I've seen plenty of that size in Oz with only microwave antennas on them.
There is a somewhat larger dish further up.

[dogbox]

Now that make sense thats tower must be use as end link to FO connection thats why its carry many microwave link. I have no expertise about health issue for this kind of situation.
I just talk from my no science experience I worked with high power transmitter with 1 to 250kw transmitter but nothing so far health issue connected to my work.

btw nice city with a fine beach but no surfing

No surfing..wanna bet shhh its our little secret...

[Syntax_Error]

The only thing I would look out for is if you see one or more of those microwave dishes damaged or dipping down so they point directly at you. Other than that, I wouldn't worry about it.

[Alexei.Polkhanov]

I just noticed one thing looking at the info which says 34.7 dbW in a screenshot I posted. So 37.4 dbW is converted to Watts:

Pw = 1 * 10 ^(PdbW / 10) = 1 * 10^(34.7/10) = 2951.2 W

That is 3 kilowatts!!! Per sector!

or 64.7 dBm

Is that real? No wonder some people concerned.

[Richard Crowley]

3 KW per sector seems reasonable to me.  Remember that it is not blasting 3 KW continuously.
And remember that it is carefully directed horizontally away from the antenna and has very little power around the immediate area of the tower.
How do we think cell phone coverage at GHz frequencies can reliably work with receiving antennas measured in mm, and buried in a ladies handbag inside a car?
Or in the back pocket under a 300 pound = 130kg = 21.5 stone steelworker sitting in a bus.
The only people who are "concerned" are those who don't understand the physics (and the biology).

3 KW is orders of magnitude less than most AM/LW, FM, TV broadcast transmitters which DO operate continuously.
For ~50 years now, and with no documented harm that would cause actual "concern".

[Gyro]

One thing's for sure, the house isn't going to be at risk from direct lightning strikes! 

On the other hand, I'm not sure about the possible effects of INDIRECT ones... just a thought. I'm guessing here that thunderstorms are fairly common in Sumatra.

[KJDS]

I just noticed one thing looking at the info which says 34.7 dbW in a screenshot I posted. So 37.4 dbW is converted to Watts:

Pw = 1 * 10 ^(PdbW / 10) = 1 * 10^(34.7/10) = 2951.2 W

That is 3 kilowatts!!! Per sector!

or 64.7 dBm

Is that real? No wonder some people concerned.

That's not real for any cell system I've ever encountered.

[uncle_bob]

One thing's for sure, the house isn't going to be at risk from direct lightning strikes! 

On the other hand, I'm not sure about the possible effects of INDIRECT ones... just a thought. I'm guessing here that thunderstorms are fairly common in Sumatra.

Hi

If you have ever spent time working on a tower based system .... Lightning strikes (often) ... current flows (lots of it) .... current spike is induced in anything nearby .... magnetic pulse does odd things to stuff nearby. Now hat CRT's are a lot less common, the magnetic part of that may not be quite as big a deal.

-----

In terms of testing things, the problem is often intermodulation. Signal A and Signal B and Signal C all come on at the same time and you get some weird combination of them and their harmonics. That drops into your gizmo and you get a chirp. Of course once you figure out what frequency causes the chirp you could do something about it. There are better ways to spend your time ...

In all likelihood, you are in an RF dead zone right at the base of the tower. None of the stuff in the picture is putting out much power. Cell phones run on batteries. They need the same power to talk back to tower that the tower needs to talk to them (actually not quite true, the tower has a much better antenna).  Net result is that, even handling a lot of calls, a tower does not put out massive amounts of power.. 

Looks like a nice house. If I rented it, I'd make sure I could put one of *my* antennas up on the tower ....

Bob

[Alexei.Polkhanov]

That's not real for any cell system I've ever encountered.

Quote from UK-based site (http://www.powerwatch.org.uk/science/faq.asp):

"The area a macrocell is intended to cover is very variable, from at least 500 metres up to a maximum of about 35 km dependent upon capacity and clutter. The powers above need multiplying by the maximum number of active carriers and by the forward gain of the antennas, resulting in EIRPs between about 50 watts (17 dBW) and 1000 watts (30 dBW) per carrier frequency. Base stations typically have 4 carriers, but may have up to 16."

So, I am not sure if Cell Map has listed power at the output of PA or EIRP. But given max 1000 Watts per carrier frequency and given that 3 frequencies used (Usual here in North America 850MHz, 1900MHZ and 2600 MHz) it does in fact match 34.7dbW or ~2.9kW


Here is the map with all towers you can explore yourself:
http://www.ertyu.org/steven_nikkel/cancellsites.html

[vk6zgo]

That's not real for any cell system I've ever encountered.

Quote from UK-based site (http://www.powerwatch.org.uk/science/faq.asp):

"The area a macrocell is intended to cover is very variable, from at least 500 metres up to a maximum of about 35 km dependent upon capacity and clutter. The powers above need multiplying by the maximum number of active carriers and by the forward gain of the antennas, resulting in EIRPs between about 50 watts (17 dBW) and 1000 watts (30 dBW) per carrier frequency. Base stations typically have 4 carriers, but may have up to 16."

So, I am not sure if Cell Map has listed power at the output of PA or EIRP. But given max 1000 Watts per carrier frequency and given that 3 frequencies used (Usual here in North America 850MHz, 1900MHZ and 2600 MHz) it does in fact match 34.7dbW or ~2.9kW


Here is the map with all towers you can explore yourself:
http://www.ertyu.org/steven_nikkel/cancellsites.html

It is very unlikely that your Cell Map refers to power at the output of the PA--"real watts".

Using very large power outputs in one spot is contrary to the whole concept of Cellphones.
If you are having trouble getting sufficient coverage with your existing setup,just stick up another phone tower in the difficult area.

[CatalinaWOW]

While the argument about the electrical danger of this tower will go on for decades, there is no question that you have a higher risk of the tower falling on you than someone who is further away.  The tower might fall due to high winds, earthquake, corrosion, fatigue or collision by either ground traffic or a low flying aerial vehicle.  In my personal opinion that risk is very small, but still larger than the electrical risk.

[vk6zgo]

One thing's for sure, the house isn't going to be at risk from direct lightning strikes! 

On the other hand, I'm not sure about the possible effects of INDIRECT ones... just a thought. I'm guessing here that thunderstorms are fairly common in Sumatra.

Hi

If you have ever spent time working on a tower based system .... Lightning strikes (often) ... current flows (lots of it) .... current spike is induced in anything nearby .... magnetic pulse does odd things to stuff nearby. Now hat CRT's are a lot less common, the magnetic part of that may not be quite as big a deal.

Only most of my working life.

I can remember only a few such problem,

One was at a Transmitter site,when,due to a rack's earthing not being properly linked to that of the Tower,the the burglar alarm & the input transistors on some Video Amplifiers got cooked.

On another occasion,a video switcher on the Studio  outside CCTV failed following a storm.

Maybe a strike on the Telstra microwave tower which was reasonably close to the car park camera,or maybe not!

Years before that,in Kalgoorlie,we had reed relays on an alarm interface to the phone lines.
These kept welding themselves together,apparently due to thunderstorm activity.
They were replaced with normal relays---no more trouble.

[cdev]

In San Francisco, in the Clarendon area right underneath Sutro Tower, (the huge TV tower that looms over SF) when it gets foggy, like it does quite frequently in the summer, florescent lights around there will sometimes flicker and glow without needing to be turned on.

Yes, it does sometimes make electrical equipment go nuts.

[Alexei.Polkhanov]

I know nothing about biology. My degree is in physics so I don't know anything about effects of RF on health. If I worried I probably had a stash of equipment to measure it, fact that I don't have good measurement equipment speaks for itself 

Still I am very curious to calculate how much exactly of RF power from that specific tower reaches my apartment for example. In nW/cm2?

In my case distance from tower to the antenna that I used in this test is 119 meters. No direct path unfortunately. Azimuth shown on Google Earth matches the azimuth of last 2600 MHz segment from that tower as shown on cell tower map. I think this is the one because frequency and bandwidth (20 mb) match.

If I calculate the ideal free space loss of power for 119 m and 2600 MHz:

FreeSpaceLoss = 36.56 + 20 log10(f) + 20 log10(d) = -82.23 dB.

This Vivaldi antenna has gain of about 6 dBi at 2.6 GHz (9 dBi at 3.5up).

So how do I accurately estimate the power of that transmitting antenna? I assume that it is 60 or 120 deg segment, most likely 60.

Now in terms of power density if it was really 1 kW out

Pd = (Pt * Gt) / (4 * Pi * R^2) or in meters
Pd = (1000 * 10) / (4 * Pi * 119^2) = 0.056W/m2 or 0.0056 mW /cm2 or 5uW/cm2.

European Parliament recommendation is 10 nW/cm2 so if it was true 1kW it would be waaaaay out of norm according to EU but in US 579,000 nW/cm2 is a norm.

Also I have to say that two things that someone mentioned here - base station only transmits periodically. True, but only for channels that used to voice. This 20Mb channel - is continuous, always on data stream.  All GSM stations have broadcast channel (strongest) and control channel(s) and these are always on.

Not all buildings allow base stations so cell companies ended up installing base stations on lower building - see elevation of that base station is 14 meters. My apartment is 68 meters above ground level. It means that apartments on floors 5-7 exposed directly to the signal if transmitting antenna is pointed horizontally.

[1xrtt]

I'm just guessing, but with the tower this close, is there a container at the base of it, with a very loud air conditioner blowing hot air in the direction of the house?

[dannyf]

It probably represents a bigger risk to your bank accounts than hour health, assuming that you own it.

[KJDS]

That's not real for any cell system I've ever encountered.

Quote from UK-based site (http://www.powerwatch.org.uk/science/faq.asp):

"The area a macrocell is intended to cover is very variable, from at least 500 metres up to a maximum of about 35 km dependent upon capacity and clutter. The powers above need multiplying by the maximum number of active carriers and by the forward gain of the antennas, resulting in EIRPs between about 50 watts (17 dBW) and 1000 watts (30 dBW) per carrier frequency. Base stations typically have 4 carriers, but may have up to 16."

So, I am not sure if Cell Map has listed power at the output of PA or EIRP. But given max 1000 Watts per carrier frequency and given that 3 frequencies used (Usual here in North America 850MHz, 1900MHZ and 2600 MHz) it does in fact match 34.7dbW or ~2.9kW


Here is the map with all towers you can explore yourself:
http://www.ertyu.org/steven_nikkel/cancellsites.html

If I put 10W from a transmitter into a 40dBi antenna, that doesn't mean if you stand in front of it you'd absorb 50dBW. You might, if standing very close in the worst possible place absorb 10W, but you can't absorb any more than that because that's all that is going in. Cell basestation transmitters typically run at no more than 40W average, and there are 4 combined, but the combining means that only 10W from each carrier gets to the antenna.

[CatalinaWOW]

I just noticed one thing looking at the info which says 34.7 dbW in a screenshot I posted. So 37.4 dbW is converted to Watts:

Pw = 1 * 10 ^(PdbW / 10) = 1 * 10^(34.7/10) = 2951.2 W

That is 3 kilowatts!!! Per sector!

or 64.7 dBm

Is that real? No wonder some people concerned.

I know that the backup batteries they put in these things for power outages wouldn't support 3Kw for more than a few seconds, so there is something fishy in the numbers.

[uncle_bob]

I just noticed one thing looking at the info which says 34.7 dbW in a screenshot I posted. So 37.4 dbW is converted to Watts:

Pw = 1 * 10 ^(PdbW / 10) = 1 * 10^(34.7/10) = 2951.2 W

That is 3 kilowatts!!! Per sector!

or 64.7 dBm

Is that real? No wonder some people concerned.

I know that the backup batteries they put in these things for power outages wouldn't support 3Kw for more than a few seconds, so there is something fishy in the numbers.

Hi

The same battery issue applies to the cell phone they are talking to. If the power on both ends is the same (path loss is the same, pretty good bet), they both have the same ERP in each other's direction. The cell phone is omnidirectional, so it gets no benefit from antenna gain. It's only putting out a few hundred mW. If you call that 0 dbW, it's a stretch. A more realistic number is -10 dbW.

In order to need 1KW (ERP) out of a base station, it's going to have to service a thousand calls off of a single antenna at 0 dbW. At -10 dbW it's 10,000 calls. Numbers like 30 to 100 calls are a lot more common on a per antenna basis. You also have the issue that not everybody will be at max range. That keeps you well below 1KW even with 10,000 callers.

Bob

[KJDS]

I just noticed one thing looking at the info which says 34.7 dbW in a screenshot I posted. So 37.4 dbW is converted to Watts:

Pw = 1 * 10 ^(PdbW / 10) = 1 * 10^(34.7/10) = 2951.2 W

That is 3 kilowatts!!! Per sector!

or 64.7 dBm

Is that real? No wonder some people concerned.

I know that the backup batteries they put in these things for power outages wouldn't support 3Kw for more than a few seconds, so there is something fishy in the numbers.

If I have a 1W transmitter running an isotropic antenna and the transmitter is 20% efficient then I need 5W power supply and get 1dBW radiated power

If I use the same transmitter running a 40dBi antenna then I still need a 5W power supply but get a radiated power of 10kW EIRP

[Alexei.Polkhanov]

Yes, EIRP, I think it started to make sense now. Cell Map is correct.
They have 46 dBm transmitter (40W) and 18 dBi antenna. I checked some data sheets for base stations - many come with 18 dBi sector antennas. So that translates to ...
46 + 18 = 64 dBm or 34 dbW. Table on Cell map shows 34.7 dbW.

Huh, universe is correct again! 

So it will in fact result in 5uW/cm2 if you are 120m away and in direct path of antenna beam.