Yes, I have one of these, but I find the Cornet ED85 EXS"Electro-Smog" meter to be easier to use. It is not directional, or a SA, but has more sensitivity.
So you have obviously been looking into them and done some tests. Which color works best?
Richard Clarke
"RobertMacy"
** Fuck OFF TROLL !!!!!
Actually, it's a spectrum analyzer of sorts with a tiny display. The price is certainly great for what it does: I got to play with the one with the SMA connector and soon found that the front end dynamic range was about 40dB. The data sheet claims
65dB. At the low end, anything worth seeing was buried below the noise. At the high end, any strong signal would limit in amplitude and produce impressive intermodulation lines. Sorta works ok when there is only a single source of RF and it's not too strong. Anywhere near a cell site was a big mess on the display. Useful for site surveys, but not measurements.Clear acrylic with full wave loops at 850 and/or 1900 MHz made from
18K gold wire. I like to make them in daisy shaped loops. Disk shaped mould for single band, and pyramid shaped for nultiband. As proof, these all disappeared overnight, as the cell site absorbed our towerbusting presents, while leaving the lesser scrap metal Orgonite, on the ground.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Sun, 27 Apr 2014 22:12:36 +0300, snipped-for-privacy@downunder.com Gave us:
Not dBm. Not for what he wants. dBm is a referenced value. Not something you would see when observing local "ambient" readings.
It would be straight dB.
On Sun, 27 Apr 2014 23:52:41 +0200, Cursitor Doom Gave us:
I was thinking more along the lines of Circus Cannon into space.
You know.. a nice rail gun to shoot them off toward the Sun with. Properly pre-acellerated so all the meat takes the trip when the gun fires.
It'd be a hell of a lot better for the planet than allowing them to remain and breath and waste Oxygen.
On Mon, 28 Apr 2014 22:15:35 +0300, snipped-for-privacy@downunder.com Gave us:
One old Navy demonstration was to affix a grapefruit to the end of a wooden pole, and put it in front of such a source to show that the exploding grapefruit represents a danger to the grapefruit between your ears too.
Not the best caution you ever ignored.
Maybe that is what made you less bright than you could be.
We'll never know without a reference.
I beg to differ. dB is a ratio. For ambient RF levels, what would you use for a reference in such a ratio? If it happens to be 1 milliwatt into 50 ohms, it's dBm. If it happens to be 1uV into 50 ohms, it's dBuV.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Mon, 28 Apr 2014 22:15:35 +0300, snipped-for-privacy@downunder.com Gave us:
That is at 1 meter distance.
A microwave oven typically radiates (leaks) at 30dBm. A value a hundred times more powerful.
I beg to differ. In the USA, microwave oven leakage is measured as a power density measurement at a given distance. FDA Title 21 limits leakage as "shall not exceed 1 milliwatt per square centimeter at any point 5 centimeters or more from the external surface of the oven, measured prior to acquisition by a purchaser, and, thereafter, 5 milliwatts per square centimeter at any such point." Note that the units of measure are in mW/cm^2
Incidentally, 30dBm compared to 0dBm is 1,000 times more power, not
100 times.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
30dBm is 1 watt. A typical oven has a external surface area of about 1m^2, which is 10,000 cm^2. At 1mW/cm^2, an oven could be (isotropically) leaking ten watts, or 40dBm, and still be legal for sale, or 50W after sale (47dBm), based on the numbers you have given.
If the microwave oven sheet metal was perforated like Swiss cheese, where the entire surface of the oven was radiating RF, that would certainly be true[1]. However, with a typical microwave oven sheet metal enclosure, most of the leakage will be along the door seal, and a much smaller amount around the vent slots and along the sheet metal joints. I'll just concentrate on the door.
The door seal on my oven is 45x28cm or 146 cm long. If I accidentally put a sheet of 0.01 cm thick paper along the length of the door seal, I would get an aperture area of 1.46 cm^2. For the 5mW/cm^2 FDA limit, that's a total leakage of 7.3 milliWatts or +8.6 dBm distributed along the entire length of the door seal. Want 10 times more leakage? Just use 10 times thicker paper.
Incidentally, to get a clue as to how bad most microwave oven seals really are, put a DECT or 2.4Ghz cordless phone handset inside the oven, close the door, DON'T push start, and use the "find phone" button on the cordless phone base to ring the phone. I have yet to find one that doesn't ring. Power output of the base and handset are around 5-10 milliwatts.
[1] There's no way to build a leaky microwave oven with 100% surface radiation. There has to be some blockage by the sheet metal surrounding the Swiss cheese holes. I'll assume 4:1 ratio of sheet metal to holes. Therefore, the leakage level will be 6dB below the above equivalent isotropic leaky oven model (12.5 watts instead of 50 watts).-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Every 1m in 3D evil grin
BTW how are you going to exclude all the mobile phone users whose phones are merrily transmitting from your region under test?
The funny thing about it is that most of the people protesting against cell phone masts walk around with a mobile phone permanently clamped to one ear all day. Or they are permanently looking down txting and crashing into street furniture as a result. Neanderthal foreheads will be making a comeback as they now have an evolutionary advantage!
A mobile phone going active transmits enough RF to disrupt the electronics of a classical tube based TV or computer monitor!
The signal from a mobile phone mast is cunningly designed to largely cancel on the ground nearby since it is optimised for maximum coverage. You might not want to stand too close and on axis with an emitter.
-- Regards, Martin Brown
"Martin Brown"
** Near where I live is an 8 story building with multiple radio comms installations covering the roof top - including a dozen or so cell phone antenna arrays facing in various directions.Recently, an 8 story apartment complex was built *right next door* so penthouse apartments face cell phone antennas at about 25 metres range and at the same level !!!!!!!!!!!!
The only concern the comms site owners expressed was that their cell phone antenna's radiation patterns would be disturbed.
The apartments were sold for very high prices and are now all occupied - by Chinese people.
Absolute fact.
.... Phil
But DECT phones don't operate at 2.4GHz - and microwave oven door seals use 1/4 wave transmission lines to convert an open circuit into a short at the operating frequency.
John
On a sunny day (Wed, 30 Apr 2014 06:59:26 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :
I dunno about that
Thats is ciorrect.
However, I have one of these detectors: eBay item number: 14102077324
And also a 'radioshack' type microwave leakage detector [1].
According to the radioshack one my microwave does not leak at all. But the ebay detector gives big alarm at up to 10 cm from the side of the microwave. That distance increases considerably if the door does not close 100%, say when there is some dirt inbetween the 1/4 wavelength stop-gap.
[1] seems just a wire with a diode and a 'heavy' moving coil meter, no amplification. So YMMV.The cheap 50$ or so microwaves are totally leaking crap. The metal is too thin and the things do not close properly after a while. So beware of those.
Good point. I should not have included a DECT phone. The choke joint in the microwave oven door is fairly narrow band and designed to operate with a slight air gap. Claim 6 offers a 250 MHz operating bandwidth at 2.4Ghz (Q=10), so you are correct that there isn't sufficient bandwidth for the door seal to operate at DECT 1.9 GHz frequencies. So, do the test with a 2.4Ghz cordless phone. I just found an old Panasonic 2.4 GHz cordless phone and tried it. It rings inside the oven (as does my DECT phone) with the base about 4 meters away.
I put my Google Nexus 7 tablet to the test. Just outside the microwave oven door, the indicated signal from my Wi-Fi access point was -48dBm. Inside, with the door closed, it was -88dBm. So, the seal has roughly 40dB attenuation. Extrapolating that to the full power of an oven that produces 1kW (+60dBm), it would leak 60 - 40 = +20 dBm or 100 mW of RF which is about the power of a common Wi-Fi access point.
Different types of choke joints, some of which include broadbanding needed to deal with construction tolerances: etc...
Hint: Unplug the microwave oven while testing.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
In the US, they operate from 1920-1930 MHz In EU, it's 1880-1900 MHz.
Yep. Diode detector. I have an MD-2000 leak detector: which of course I immediately disassembled on arrival: I spent quite a bit of time looking for a thermistor or bolometer. Nope. The SMD diode D1 is the detector. No RF isolation, no tuning, no microstrip, no calibration... junk. However, it mostly works and will detect a wi-fi access point if I put it next to the antenna.
I've done better with an SMD diode, wire choke, filter cap, and a scope probe.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
That looks plausible. Some time ago I compared the output of my
1kW microwave oven at 1m range with the output of a GSM1800 phone at the same distance using a dipole antenna tuned for each frequency and monitoring with a spectrum analyzer. The peak powers were similar, but the microwave oven had a much lower duty cycle so it would have been radiating a considerably lower average power than the mobile phone.John
On a sunny day (Wed, 30 Apr 2014 09:35:20 -0700) it happened Jeff Liebermann wrote in :
To correct your quoting, the ebay is very good, and has amplification. It will also beep if you flip a light switch, and more fun, when your GSM cellphone calls home.
That is the 'radioshack' one
Yes, I made this:
I dont really know what is a safe level, been among HF transmitters, and no low power either, all my life. Could be the same as with that very dangerous lead... But microwaves are a bit different, better check the levels.
Maybe they have read the independent science on this and you haven't. Biological abnormailites have been demonstrated down to several microvolts.
One might also wonder why hospitals are reporting an increase in cancers attributed to cell phone use, and government agencies worldwide are imposing bans and limitations on consumer wireless devices.
I don't believe in hysteria either but people should get up-to-date on the facts before trying to sound smart.
Or, you could just listen to industry who are particularly keen on selling us microwave emitters, mostly untested for health impacts.
Have a look at what happened with TETRA radios, and why the UK Police Federation wanted to get them axed.
Richard Clarke
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