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Post Time: 05/01/2009 09:25:12 |
jo2
Total Forum Posts: 19 |
Hi
We are still hoping to move house to somewhere that is safer than where we are now, (that we can afford, that someone else doesn't buy before we can sell our house, that doesn't have a terible survey etc, etc!) The person in our family who is ES reacts to levels of microwaves below the sensitivity of the electrosmog detector. I have been wondering for some time about buying the HFE35C, but I have a couple of queries about it.
Because the 'average' readings won't include peaks of pulsing frequncies, this obviously limits how useful they are. On the 'peak' setting, does the meter give a reading only for the highest peak it can detect - eg, if a house was affected by three types of microwaves, one with a measurement of 200, one at 250, one at 400, would the meter read '400'? The reason I ask is that if another house was affected by only one type of microwave, also at 400, then I think this would be safer than the one with three types at differing levels. But, is there a way to judge this, the cumulative total/potential cumulative effect using the HFE35C?
I was reading the thread about SPECTRAN spectrum analysers back in March 2008. I can see a SPECTRAN would be good in an ideal world, but I'm not sure about having a meter where I have to worry about misleading readings, or missing readings altogether.
Would you have any other suggestions about a meter that would give an idea of the total amount and strength of microwaves affecting a house, to quite a high sensitivity like the HFE35C. So long as it gave a reliable picture of houses, even just relative to each other, that would be great.
(I know that your new Accousticom might fit the bill, but I need to get hold of soemthing now - I would consider hiring something if it was too expensive to buy).
Thank you for any help you can give. |
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Post Time: 05/01/2009 16:38:34 |
marg5hatesmasts
Total Forum Posts: 15 |
To jo2
I will leave it to Alasdair or Sarah to give the technical replies.
I have had a Gigahertz HFE35C meter for over a year now. With the directional log per antenna [800 MHz - 2.50 GHz] and also the non-directional isotropic antenna that covers the wider frequency range. The meter range is from 0.1 to 1999 microwatts per square meter. I bought the 20 dB attenuator [x 100 factor]. The peak reading in my bedroom before shielding was about 4600 microwatts per square metre before shielding. Incidentally, the reading about a metre from a friend's DECT was 20,000 microwatts per square metre. That was measured using the meter with the 20dB attenuator attached. You do not get a reading for separate components. Just a peak or an average depending on switch position. You can hear the sounds of different sources. tap-tap-tap for wifi, buzzing for dect, various high pitched noises for phone masts - sounds vary. This is the page Gigahertz link to for the sounds:
http://www.milieuziektes.nl/Pagina109.html
Gigahertz Solutions in Germany <www.gigahertz-solutions.de>
produce a number of meters at different costs. It is possible to download the English language instruction manuals that come with the instruments http://www.gigahertz-solutions.de/en/Downloads.html
Alasdair/Sarah,
I notice that Gigahertz in their accessories have now added service specific filters.
Margaret |
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Post Time: 07/01/2009 15:53:59 |
marg5hatesmasts
Total Forum Posts: 15 |
To jo2
P.S. to my last message:
You wrote "if a house was affected by three types of microwaves, one with a measurement of 200, one at 250, one at 400, would the meter read '400'?
Just a peak or an average depending on switch position".
200 + 250 + 400 - the meter will read 850.
Margaret |
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Post Time: 10/01/2009 14:53:48 |
jo2
Total Forum Posts: 19 |
Hi Margaret
Thank you very much for both of your replies.
From what you say, I wonder if I am misunderstanding how the Gigaherz meter works!
When you add up the imaginary figures I gave for three types of microwave, and say that the meter will read 850, then this would reflect the sum total of different types. This would be great, and would be what I am looking for. Would this be in 'peak' mode? I was assuming it would only tell you the strength of the highest peak alone, no matter how many other, lower-value peaks there were on different frequencies?
Maybe this meter would be what I'm looking for after all!
Jo |
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Post Time: 11/01/2009 07:43:50 |
topazg
Total Forum Posts: 13 |
This is Alasdair on Graham's login (Topazg). Margaret is not quite right in her last reply. The HFE35C and the other Gigahertz instruments are all broadband instruments that make one overall instantaneous assessment of the signal level. Signals at different frequencies do not add linearly but as the "square root of the sum of squares". This strictly applies to signal strength in volts per metre, but the way the detector chips actually work mean that the calibrated power density in microwatts per square metre also add in this manner (they are effectively worked out internally in the meter from the total V/m value). Also, this will only happen if the three peaks occur at exactly the same time - not if they occur at different times, which is more likely with three signals from three different unconnected sources.
In Margaret's example the (200 + 250 + 400) - the meter will only read about 490, not the 850 that Margaret believes. Also, none of the broadband meters that I have seen anywhere will read low-level UTMS/3G signals adequately. That is because the signal is "spread spectrum" and relatively low level in signal strength (in V/m) but actually contains quite a lot of power. A bit like spreading a slice of toast with thick butter (GSM) and then spreading six slices of bread with the same amount of butter (3G). The amount of butter is the same but you would have to measure it in a different way. Some high-power RF meters (e.g. for ICNIRP compliance and above) actually measure true power by heating a resistor, but this is not possible for technical reasons below about 3 volts per metre. All low level (sensitive) meters measure power by working it out (in hardware or software) from what is effectively a V/m initial measurement. This is not a problem, but it is helpful when interpreting the measurements to understand their limitations.
A spectrum analyser (like the SPECTRAN) does have its place but needs to be used with caution and knowledge and we always rely on a good broadband meter reading in the first instance and then if more information is really needed and justified we also do a spectrum analysis. A good broadband meter basically shows you the totality of the signals in one simple reading. A spectrum analyser sweeps across a wide range of frequencies sequentially and then displays the levels against frequency. Some (including the SPECTRAN) do offer a mathematical summation of the signals, however these values can be very misleading. Because a spectrum analyser sequentially (at least those that cost less that about £100,000 - yes, you CAN get such things!) scans sequentially, they are very poor at finding short pulsing signals with large no signal gaps like WiFi, wLAN, DECT cordless phones, mobile phone handsets as they have to be on the precise frequency just when the short pulse is being transmitted. Otherwise they show no signal at all because they have measured that frequency at the time when the device is not transmitting. For example the SPECTRANs we have tested worked well with DECT cordless when you used the button to just show DECT, but completely failed to detect DECT if used to scan the microwave spectrum from, say, 300 MHz to 2500 MHz, so their "calculated total" was very wrong. This also applied to WiFi/wLAN signals. We have and use a £10,000 spectrum analyser (an Anritsu 2721), which is much better, but we only use it for detailed analysis of what signals are relatively occasionally and only use a Gigahertz HF59B (the HFE35C's big brother) for our residential microwave surveys.
At one small high-level HPA meeting their senior engineer gave a talk and demonstrated their measurement techniques using equipment cost about £35,000. He did not find the strong WiFi/wLAN signal that two of us were picking up in the room on an Electrosmog detector and a Gigahertz meter and he said that our "monitors" must be faulty. Over lunch we investigated further and found the signal to be coming from his laptop, that he had been using for over 6 months for his survey work; yet he had never picked up the, several volts per metre, short pulsing WiFi/wLAN beacon pulses that occurs at a rate of ten per second! That shows that relying on spectrum analysis, even when you are a knowledgeable engineer/scientist, is not an adequate or reliable method.
In my opinion, after almost 40 years of measuring microwaves with equipment ranging from the simplest to almost the very best, a sensitive broadband meter is the first, and most important, measurement tool. The Gigahertz meters are excellent as they also let you hear the signal and so, with relatively little practice, it is possible to easily identify whether the signal is GSM, WiFi, DECT, UMTS/3G, etc., or a combination of signals.
Finally, I am concerned that you write: "The person in our family who is ES reacts to levels of microwaves below the sensitivity of the electrosmog detector". There is a way of enhancing the sensitivity by sticking a patch of aluminium foil to the back (www.emfields.org/equipment/mw1foil.asp), however I suspect that you may be missing something else. I strongly believe that few people really are sensitive to levels below about 0.03/0.05 V/m of pulsing microwaves and, if they really are, then they need to move into the country, preferably woodland, in an area with virtually no mobile phone signal and mobile phone use.
If the person really is sensitive to such tiny levels of microwave signals, then it would be wise to try and help them become less sensitive. Some things that work well for some people are drinking plenty (aim for two litres per day) of water based drinks (not including tea, coffee or alcohol!); taking about 1g of MSM twice a day; using a hypo-allergenic skin moisturiser such as a good baby-lotion - especially if the person's skin is dry; taking a daily supplement of Omega 3, 6 and 9 oils (can be vegetable/crop based if animal/fish products are not tolerated); doing regular exercise.
Have you measured the power-frequency magnetic and, especially, electric fields? Many ES people also react to power-frequency electric fields and these can be high, especially in bedrooms. You need a completely different sort of meter to measure these (e.g. an EMFields Pro or a Gigahertz 3030B). Power-frequency electric fields for ES people should be below 10 V/m (and preferably below 1 V/m which is almost impossible in a modern home). That may well be another cause of the sensitivity problems you report.
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Post Time: 13/01/2009 08:30:13 |
jo2
Total Forum Posts: 19 |
Hi Alasdair
Thank you for your detailed and very interesting response - and thanks also for the tips on trying to reduce your own sensitivity in the first place. I've had a quick read of all your points, now I'll have to read it carefully and let all the info 'sink in'.
Thanks again.
Jo |
