Why Everything Wireless Is 2.4 GHz
wired.com
Why Everything Wireless Is 2.4 GHz
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Re: Why Everything Wireless Is 2.4 GHz
#2If the article is tl;dr here's the gist.
ITU states that the ISM (industrial, scientific, medical) bands are nearly-anything-goes free for all in the frequency blocks. 5.8GHz was too expensive at the time wireless caught on, but 2.4GHz was cheap enough.
ITU chose 2.4GHz and 5.8GHz because the microwave emits broad spectrum radiation and harmonics at those frequencies, so they ignored them and made them free to use and abuse.
KC9JEF
Re: Why Everything Wireless Is 2.4 GHz
#3Per the garage door reference. Any garage door opener manufactured between 1984 and the preset operates on frequencies between 300-400 Mhz, Which is smack dab right in the middle of US military allocations. There are well documented cases of military communications systems interfering with garage door openers resulting in many problems for the owners.
Edit: Preset == Present
Re: Why Everything Wireless Is 2.4 GHz
#4Per the garage door reference. Any garage door opener manufactured between 1984 and the preset operates on frequencies between 300-400 Mhz, Which is smack dab right in the middle of US military allocations. There are well documented cases of military communications systems interfering with garage door openers resulting in many problems for the owners. Edit: Preset == Present
They use a bunch of other unlicensed bands around 416Mhz
Re: Why Everything Wireless Is 2.4 GHz
#5If the article is tl;dr here's the gist. ITU states that the ISM (industrial, scientific, medical) bands are nearly-anything-goes free for all in the frequency blocks. 5.8GHz was too expensive at the time wireless caught on, but 2.4GHz was cheap enough. ITU chose 2.4GHz and 5.8GHz because the microwave emits broad spectrum radiation and harmonics at those frequencies, so they ignored them and made them free to use an…
I'm surprised the article didn't mention that a ham band partly overlaps the 2.4 GHz WiFi frequencies. In theory at least, anyone operating WiFi gear isn't allowed to interfere with licensed services, including hams. Also, our unlicensed WiFi gear must accept any interference including that which "may cause undesired operation"... from anything, including the neighbors WiFi. (see FCC notice in U.S. WiFi product manuals)
Another related tidbit: Microwave ovens getting water molecules so excited at 2.4 GHz ties in with WiFi performance. It's a tidbit the head tech at a local wireless ISP didn't even know... 2.4 GHz WiFi is particularly prone to fading in fog/rain because water absorbs energy so efficiently at that frequency.
If they really want to get into strange frequency trivia, they should explain why Channel 37 has never been used by any over-the-air television station in Canada or the United States. Hint: little green men
Re: Why Everything Wireless Is 2.4 GHz
#6Per the garage door reference. Any garage door opener manufactured between 1984 and the preset operates on frequencies between 300-400 Mhz, Which is smack dab right in the middle of US military allocations. There are well documented cases of military communications systems interfering with garage door openers resulting in many problems for the owners. Edit: Preset == Present
Prior to that, there was equipment using channels that were between some of the channels on the old 23 channel Citizens' Band. That was far worse. C.B. operators running splatter-prone illegal amplifiers were bad enough, but people discovered these apparently "empty" channels (sometimes called 3A 7A 11A 15A 19A 22A and 22B) and modified their radios to use them. Eventually the F.C.C. gave up on those channels being viable for things like garage doors and R.C. model airplanes, and they became part of 40 channel C.B.
I think some of that remote control equipment shared 72 to 76 Mhz for a while. That's a gap, 2/3 the size of a t.v. channel between channels 4 and 5.
I'm wondering if the F.C.C. will take away t.v. channels 2 through 6. Almost everywhere, the stations formerly on those went to U.H.F. with the digital transition. I guess they figure that few people want to buy really big antennas for the lowest frequencies. (UHF and 7-13 use much shorter antenna elements). Anyway, those channels have the best coverage potential of all of them, but they're hardly used now. (see tvfool.com or the FCC database)
Re: Why Everything Wireless Is 2.4 GHz
#7[deleted]
Re: Why Everything Wireless Is 2.4 GHz
#8Am I the only one amused that wired.com is writing about wireless?
Re: Why Everything Wireless Is 2.4 GHz
#9If the article is tl;dr here's the gist. ITU states that the ISM (industrial, scientific, medical) bands are nearly-anything-goes free for all in the frequency blocks. 5.8GHz was too expensive at the time wireless caught on, but 2.4GHz was cheap enough. ITU chose 2.4GHz and 5.8GHz because the microwave emits broad spectrum radiation and harmonics at those frequencies, so they ignored them and made them free to use an…
I'm surprised the article didn't mention that a ham band partly overlaps the 2.4 GHz WiFi frequencies. In theory at least, anyone operating WiFi gear isn't allowed to interfere with licensed services, including hams. Also, our unlicensed WiFi gear must accept any interference including that which "may cause undesired operation"... from anything, including the neighbors WiFi. (see FCC notice in U.S. WiFi product manua…
Microwave ovens getting water molecules so excited at 2.4 GHz ties in with WiFi performance. It's a tidbit the head tech at a local wireless ISP didn't even know... 2.4 GHz WiFi is particularly prone to fading in fog/rain because water absorbs energy so efficiently at that frequency.
No, no, no, no, no.
http://earth.esa.int/applications/data_util/SARDOCS/_icons/c...
Re: Why Everything Wireless Is 2.4 GHz
#10If the article is tl;dr here's the gist. ITU states that the ISM (industrial, scientific, medical) bands are nearly-anything-goes free for all in the frequency blocks. 5.8GHz was too expensive at the time wireless caught on, but 2.4GHz was cheap enough. ITU chose 2.4GHz and 5.8GHz because the microwave emits broad spectrum radiation and harmonics at those frequencies, so they ignored them and made them free to use an…
I'm surprised the article didn't mention that a ham band partly overlaps the 2.4 GHz WiFi frequencies. In theory at least, anyone operating WiFi gear isn't allowed to interfere with licensed services, including hams. Also, our unlicensed WiFi gear must accept any interference including that which "may cause undesired operation"... from anything, including the neighbors WiFi. (see FCC notice in U.S. WiFi product manua…
NASA publications indicate a microwave absorption peak due to water vapor occurs at 22.234 GHz and peaks due to oxygen occur lear 60 GHz and 118 GHz (..). Below 10 GHz absorption caused by atmospheric gases is small.
The associated absorption graphs do indicate there is a small peak of 2 dB per kilometer around the 2.4 GHz band due to water. (I'd expect to have a larger drop through a wall.)
From: NASA Reference Publication 1108(02) 1987; "Propagation Effects on Satellite Systems at Frequencies Below 10 GHz; A Handbook for Satellite Systems Design; Second Edition" by Warren L Flock.