BS: Dangers from radio waves

Subject: BS: Dangers from radio waves
From: Nigel Paterson
Date: 09 Apr 10 - 05:06 AM

My neighbour is a licensed radio 'ham'. In his garden, which is right next to mine, he has assembled, over the last few years, an increasingly complex aerial array. I can stand as close as one metre away if I visit my shed. The distance from the array to my house is roughly thirty meters. Are there any known health risks with this sort of set-up? Information I've found on the web is rather vague & not terribly helpful. My wi-fi connection drops out more frequently than it used to too...could there be a problem here as well? Talking to my neighbour about it is not an option...we are not best friends!
                                                                                                          Nigel P.

Subject: RE: BS: Dangers from radio waves
From: The Fooles Troupe
Date: 09 Apr 10 - 05:35 AM

If he is a 'ham' he is only allowed to broadcast on certain bands - or ranges of frequencies at restricted levels of transmitted power. Very few have such a low level of life as to be on all the time... :-)

Most hams are more interested in picking up low level signals from as far away as possible with minimal equipment.

"an increasingly complex aerial array"
Because of the range of frequencies, different aerials are needed for each band - and it is usual that only one band is being 'worked' (transmitted on) at a time. He may monitor many frequencies at once, but that involves no transmission of power.

"My wi-fi connection drops out more frequently than it used to"

It is not necessarily his fault. Many others things, such as OTHER wi-fiers may be moer likely interfering. While unlikely, 'false signals' MAY appear in that 'wi-fi' band - but I say unlikely, as such by-products reduce the power of the wanted transmitted signal on the desired frequency, something any ham would be eager to fix ASAP.

It is many years since I was up on the technical details - I never get around to sitting for my licence - I got busy with other things, so I cannot remember the full technical details now. From memory, the power would be less than the total of surrounding mobile towers.

Subject: RE: BS: Dangers from radio waves
From: The Fooles Troupe
Date: 09 Apr 10 - 05:37 AM

Oh - and any power transmitted would only be for the short periods he is actually talking.

Subject: RE: BS: Dangers from radio waves
From: Nigel Paterson
Date: 09 Apr 10 - 06:00 AM

Thank you very much for the detailed reply, Foolestroupe...interesting stuff.
                                                                               Nigel P.

Subject: RE: BS: Dangers from radio waves
From: John J
Date: 09 Apr 10 - 08:33 AM

A very major part of UK regs is taken up by interference to other services - including neighbours.

You may or may not like what I have to say, but I hope it helps:

Assuming your neighbour is using commercial equipment, it's very likely to have a 'clean' output. ie a transmission on 14.100mhz is just that - and spurious and harmonic emmissions are minimal, certainly within the parameters specified by the licencing authority.

Sadly much domestic equipment is not very tolerant of RF. That is not the fault of the RF but of the equipment inadvertantly 'receiving' the transmission.

It's all down to money - manufacturers of radios,TVs,WiFi stuff etc want to keep their costs down so they can sell at competitive prices. The cost-cutting is often noticeable in 'wide-open' front ends with minimal or even non-existant filtering.

In UK you can get a form from the Post Office (if you can find one still open!) and send it, along with a fee, to what used to be called the Radio Interference Department. They will investigate.

If their findings clear the radio amateur, you recourse would then be to the manufacturer of the equipment that is being effected. It is THEIR responsibility to supply equipment fit for purpose - and that includes having the equipment operate correctly in the presence of an RF field.

Most radio amateurs are eager to help in such situations, they SHOULD have the knowledge to deal with interference problems....if it is interference and not inadvertant reception of their transmission by poorly designed equipment. After all they don't want to be shut down.

Good luck, and please feel free to contact me if I can help.

John

Subject: RE: BS: Dangers from radio waves
From: beeliner
Date: 09 Apr 10 - 08:49 AM

The original inquiry concerned health risks. There are none (unless you trip over the antenna).

There is another recent thread on this subject, specifically regarding cell phone towers.

Interference is a completely different matter.

Subject: RE: BS: Dangers from radio waves
From: Rapparee
Date: 09 Apr 10 - 10:16 AM

I was going to say....

Subject: RE: BS: Dangers from radio waves
From: Greg F.
Date: 09 Apr 10 - 11:39 AM

Info here:

www.rsgb.org.uk

Subject: RE: BS: Dangers from radio waves
From: Nigel Paterson
Date: 09 Apr 10 - 11:43 AM

Thanks very much to everyone for the informative contributions...plenty to ponder on.
                                                                     Nigel P.

Subject: RE: BS: Dangers from radio waves
From: gnu
Date: 09 Apr 10 - 02:06 PM

The most dangerous are the ones used to ransmit rap.

Subject: RE: BS: Dangers from radio waves
From: beeliner
Date: 09 Apr 10 - 02:51 PM

The most dangerous are the ones used to ransmit rap.

..or cransmit crap.

Subject: RE: BS: Dangers from radio waves
From: gnu
Date: 09 Apr 10 - 03:06 PM

Six hip, half a dozen hop. Ya know?

Subject: RE: BS: Dangers from radio waves
From: John J
Date: 09 Apr 10 - 04:59 PM

Whoops- should have read the O.P. properly!

Firstly, I'm not a doctor - but I've played with RF for 35+ years and I'm aware of some of the problems that RF can cause.

There certainly are health effects but they are frequency and power related. I wouldn't have thought an amateur station would radiate sufficient power for the RF field to cause you a problem.

Most amateurs don't run high power at the extremely high frequencies that can cause problems. High frequencies (HF) and VHF & UHF are more popular and unless you're running VERY high power you're not going to have a problem - even then you would have to be extremely close to the radiating element.

If you grabbed hold of the business bit of the antenna it MAY give you a nasty burn or even a lethal shock - depending whereabouts you grabbed hold. Some parts of the antenna can be at very high voltage.

I would think it unlikely that any high voltage bits would be easily accessible from ground level - any radio operator would want the antenna as high up as possible. I would guess that the bits of the antenna you can get close to are the mountings rather than the antenna itself.

JJ

Subject: RE: BS: Dangers from radio waves
From: GUEST,HughM
Date: 09 Apr 10 - 06:25 PM

The maximum legal power for amateurs in the U.K. is 400 watts peak and less than 150 watts average. In practice the average power will probably be less than 100 watts. Assuming that the aerial radiates equally in all directions (it doesn't, but more about that later), the 100 watts will be spread out over the surface of a sphere of radius 30 meters as far as the occupants of the house are concerned. That gives a power density of 100/4 x pi x 30 x 30 or about 0.009 watts per square meter. On the wall where I work there is a chart on which it is stated that the limit for public exposure is 0.2 milliwatts per square centimetre. 0.009 W/ sq. metre = 9mW/ sq. metre = 0.0009 mW/ sq. cm, so there is a safety factor of over 200. This will be more than enough to allow for the any directional properties the aerial might have.
    The situation in the shed is less clear, but 100W at one meter would be like 1W at 10cm (inverse square law and all that), so less worry than using a mobile 'phone, which wouldn't be 10cm from your head. As long as you use the shed only for storage and you don't stay in it for long periods there is probably nothing to worry about.
   It may be worth logging the times when the wi-fi misbehaves. The amateur also has to keep a log of the times when he starts and finishes transmitting. If you need to call in help, the post office will probaby refer you to Ofcom. Their inspector could compare the two logs to find out whether the problem is associated with the amateur's transmissions.
Domestic equipment has to withstand a field strength of 3 volts per metre to meet the relevant European standards. To convert watts per square meter to volts per metre, multiply by 377 and take the square root. 0.009W/sq. m is equivalent to about 1.8V/m, so if the aerial is directional (concentrates the power in a particular direction) there could be problems. As stated above, if the amateur is obeying the power limit, the onus is on the manufacturer of any affected equipment to solve the problem. If you are told "it must be okay because it meets the standard", point out that compliance with the standard gives a presumption of conformity with the requirements (allowing free movement of the goods within the European Union), not a guarantee of conformity.

Subject: RE: BS: Dangers from radio waves
From: The Fooles Troupe
Date: 09 Apr 10 - 06:38 PM

Thanks HughM

"100W at one meter"

to the foot of the tower - the aerial would be higher, so the squaws on the hippopotamus hide argue that the rough real distance would be nearer to the height of the tower.

"It may be worth logging the times when the wi-fi misbehaves"

This is a very good idea - and if you think it is worth it trying to approach the neighbour first at all - politely suggest you have researched with other hams and would like him to see if it matches up with his broadcast log times. If he can see a problem, then he can look at it without needing the authorities to get involved - a faster and better approach for you both.

Subject: RE: BS: Dangers from radio waves
From: Sandy Mc Lean
Date: 09 Apr 10 - 09:05 PM

I spent about 30 years of my life as a technician maintaining microwave transmission sites. No doubt I sopped up quite a bit of radiation but I am still healthy except for an overpowering urge to howl at the full moon.

Subject: RE: BS: Dangers from radio waves
From: The Fooles Troupe
Date: 09 Apr 10 - 09:52 PM

I'll send you some microwaves then...


~~~~~~~~~~~~~~~~


:-)

Subject: RE: BS: Dangers from radio waves
From: GUEST,HughM
Date: 10 Apr 10 - 04:48 AM

Just realised I goofed!
When I was thinking about the garden shed, I assumed the worst case would be if all the power was coming from the part of the aerial one metre away. (As Foulestroupe points out, it won't be this bad.) What I forgot to allow for was that the power might be concentrated in a paticular direction. Therefore if there is anything looking like a TV aerial or a satellite dish concentrating the power into a narrow beam and pointing at the shed, it would probably not be a good idea to linger one metre in front of it.
However, from the description given it doesn't sound as if this is the case, and normally nobody would mount this type of aerial so close to the ground because they would want the beam to be clear of obstructions.
Second goof: I missed out some brackets and probably confused some people. The expression for the power density near the house should have been 100/(4 x pi x 30 x 30) watts per square metre.

Subject: RE: BS: Dangers from radio waves
From: Nigel Paterson
Date: 10 Apr 10 - 04:50 AM

I did contact my ISP recently about the wi-fi drop outs. An engineer called & scanned the area with what looked like an iPhone (is there an app. that does that?) He suggested changing the setting on my wi-fi hub from 'auto' to a specific channel number on which he had detected no activity. Surely though, that 'inactive' channel could have become busy again at any point in time? So, is 'auto' not a better option in the long run? Selecting a specific wi-fi channel did not solve the problem. The drop outs are intermittent, I can go for weeks with no breaks of service, & then, on a particular day, it might happen as many as three or four times in fairly quick succession. Resetting the hub solves the problem, no big deal if I'm just casually surfing, but some drop outs have occurred right in the middle of a software update which is a tad more irritating! Sincere thanks once again for all the detailed & knowledgeable posts. Such a wealth of experience out there in MudcatLand!
                                                                                                          Nigel P.

Subject: RE: BS: Dangers from radio waves
From: Nigel Paterson
Date: 10 Apr 10 - 04:59 AM

To put HughM's mind at rest, there are no dishlike aerials concentrating power in the direction of my shed...as far as I can tell! A photo for you all to see might be interesting, but as my relationship with my neighbour is 'fragile', taking the picture could be more trouble than it's worth!
                         Nigel P.

Subject: RE: BS: Dangers from radio waves
From: The Fooles Troupe
Date: 10 Apr 10 - 07:26 AM

Nigel

You don't NEED dishes - Hams would probably use 'Yagi' antennas for many of the frequency bands used - dishes up to 30 metres wide can be a bit unwieldy! :-) Google it....
http://en.wikipedia.org/wiki/Yagi_antenna

There are many other weirdly shaped directional antenna - but all that is of little real interest in this thread... :-)

You are correct in your guesses about traffic on certain wi-fi channels and it being intermittent. The guy was right AT THE TIME HE DID THE MEASUREMENTS, but life goes on... :-)

Glad you found your old book!

Subject: RE: BS: Dangers from radio waves
From: The Fooles Troupe
Date: 10 Apr 10 - 07:27 AM

Another link if you want to read some more basic info ... :-)

http://en.wikipedia.org/wiki/Antenna_(radio)#Antennas_and_antenna_arrays

Subject: RE: BS: Dangers from radio waves
From: Nigel Paterson
Date: 11 Apr 10 - 04:31 AM

I've read & re-read all the fascinating contributions to this thread & it certainly looks as if I have very little to worry about. The wi-fi drop outs are an irritation I could do without, but in the grand scheme of things, a pretty minor irritation when all's said & done! As Foolestroupe says: "Life goes on..." I'm very grateful to all of you who took the time & trouble to post, thank you,
                  Nigel P.

Subject: RE: BS: Dangers from radio waves
From: Nigel Paterson
Date: 04 Feb 11 - 03:54 AM

A much overdue update re. the wifi drop out problems I was experiencing. Being a dedicated Mac user, I have 'Time Capsule' which handles all my backups. Hadn't appreciated that it also functions as a dual band base station. Those nice people at Apple showed me how to connect wirelessly to 'Time Capsule', rather than the BT hub. The 'Time Capsule' is connected to the BT hub with a cat.6 ethernet cable, relegating the hub to the role of a modem (it's wireless functionality has been disabled). Using this new configuration, I have had no more wifi drop outs, not a single one.
                                       Nigel.