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Post Time: 28/02/2008 23:39:27 |
donweir
Total Forum Posts: 8 |
Hi. I'm new to this forum. What would be considered as 'normal' or commonplace readings for microwave field strengths in a residential area? I live about 1km. from a Transco mast carrying a variety of microwave dishes. A spectrum analyzer shows pulsed signals from below 5 to above 6 GHz. |
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Post Time: 04/03/2008 10:37:38 |
alasdairP
Total Forum Posts: 173 |
Hi. The frequency (5 to 6 GHz) is not related to microwave field strength. Field strength is the power (in watts per square metre) or signal strength (in volts per metre) and is not directly related to the frequency in GHz.
Mobile phone networks run at 0.7 to 0.9 GHz, 1.7 to 1.9 GHz and 2.1 to 2.2 GHz.
The lower frequencies are more penetrating of building walls and windows (and people).
In my experience, taking measurements with a very high quality spectrum analyser (an Anritsu 2721A) around the UK, including central London, there is generally very little at present in the 5 to 6 GHz band other than close to a few internet cafes with high-band WiFi and a few companies running high-band wLANs, and the levels from those fall off very quickly away from the sites. Apart from the three WiFi bands, there is little else permitted in this band in the UK other than earth/space comms links which are usually highly focussed dishes pointing skywards.
I don't know what equipment you were using, but the cheap Aaronia SPECTRAN spectrum analysers are known to have some spurious (i.e. seen but not really there) signals in the 5 to 6 GHz band. Maybe that is the explanation?
What signals levels are typical?
In most residential areas now peak signal levels are rarely below 10 to 16 microwatts per sq.metre (0.06-0.08 V/m), rising to at least 1000 uW/m2 (0.6 V/m) if you or a close neighbour has a DECT cordless phone or a WiFi/wLAN system or if there is a mobile phone mast within a couple of hundred metres.
What levels matter? Well the best place to look is probably on our website at:
www.powerwatch.org.uk/news/20050722_bamberg.asp
I hope this helps. If you have a note of specific frequencies that you are concerned about, please report them here and I will take a look.
Alasdair
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Post Time: 04/03/2008 14:00:45 |
donweir
Total Forum Posts: 8 |
Thank you for your reply. Yes, it is an Aaronia HF-6060, purchased recently and in use for the first time. The signals are absurd - up to 20V/m - and from around 4.6 to 6+ GHz with a gap between 5.65 and 5.75 GHz. Is this similar to other poeple's experience with Aaronia?
Oddly, the analyzer appears to be picking up something, but severely mis-representing it. The 'signals' appear to be coming from Winter Hill (which has a large collection of microwave dishes), 10 miles to the Southeast and are semi-convincing in as much as they are directional and reduce considerably when behind walls or (k-glass) windows, compared to outside.
I don't see how I could get genuine readings like these unless a battleship parked on my front drive!
Thanks again for your reply, Don. |
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Post Time: 04/03/2008 17:41:27 |
marg5hatesmasts
Total Forum Posts: 15 |
Don - You are not alone!
A friend living outside Manchester bought an Aaronia HF-4040 Meter [version 1]some time ago. She was also getting crazy readings in the 5 GHz region.
The Buergerwelle website has published tests on Aaronia equipment in English. URL: http://www.buergerwelle.de/cms/content/view/57/70/
which you might wish to read.
If the link does not work then try this URL: www.buergerwelle.de
and then click the Union Jack flag. The relevant articles are at the top of the webpage.
I had intended buying a Aaronia HF-4040 meter [version 2] myself until I read the Buergerwelle reports.
I wonder whether the technical 'glitches' have now been fixed by Aaronia software updates??
Margaret
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Post Time: 04/03/2008 23:45:57 |
alasdairP
Total Forum Posts: 173 |
No, I gather they have made it worse by trying to hide the problem. They also now say that it needs CW signals to read correctly and pulsing signals are not always interpreted correctly.
See:
http://www.buergerwelle.de/pdf/new-test-aaronia-spectran.pdf
We tested an early-ish 6080 and found similar issues that made us return it and not purchase one - but we are lucky to have a £10k Anritsu set up (even if it meant no personal salary for ages!)
A great pity because if they worked well they would be brilliant. We always use a broadband meter as the main and first measuring device.
The directional nature of your measurements seem puzzling.
Try wrapping the antenna carefully in aluminium cooking foil, then a plastic bag, then another layer of aluminium foil. See what that does to the readings.
Alasdair
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Post Time: 05/03/2008 00:12:26 |
donweir
Total Forum Posts: 8 |
I guess I should have done more homework! It was actually more than a year ago when I looked at buying one of these so maybe missed some of the criticism. It's a version 3, so clearly the problems have not been fixed.
The good news is that I bought it second hand for less than half the new price. The bad news is that I can't send it back of course!
I will have to persevere and see what I can rescue from the wreckage.
Thank you both for your assistance. Don. |
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Post Time: 05/03/2008 10:14:48 |
alasdairP
Total Forum Posts: 173 |
Actually, it won't be as bad as all that - you just have to ignore those (few) spurious responses. In our tests, for most of the time, it wasn't bad and was sometimes very good. Our conclusion was that (a) use a broadband meter for overall signal levels and (b) use a SPECTRAN (or equiv) for (mostly) identifying the frequencies concerned, but use with thought and question unexpected results.
The pre-set buttons worked much better than setting it ouselves - especially with DECT cordless signals and WiFi/wLAN signals. I don't know why as we are used to setting up spectrum analysers (of various makes), so I suspect they have programmed in a few "fixes" to the pre-set button features.
You can also somewhat reduce the spurious responses by adjusting the resolution and video bandwidths and sanned frequency ranges. Alasdair.
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Post Time: 05/03/2008 13:48:00 |
donweir
Total Forum Posts: 8 |
One aspect of the Spectran I do like is the recordable display produced on a pc. The mobile phone frequency display labels the frequencies with their believed owners and the directional antenna helps to pinpoint the mast location. Used warily this could be useful.
The TV setting seems to work well, on both analogue and digital, but I'm not so sure about the DECT setting until I try a few 'phones out.
Overall, small alterations in settings can make a huge difference to the results and it's probably best to stick with the presets as you say.
With practice, I may even get to like this thing! Don. |
