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2.4 to 2.4835 Ghz services occupy large part of the 12cm amateur radio band 2400-2450 Mhz aTV1 assigned to: 2406-2424 Mhz (2415 -/+9Mhz bw for AM or FM) & aTV2 assigned to: 2430-2448 Mhz (2439 +/-9Mhz bw for AM or FM) 2.4 Ghz services Video - Audio - Data and Telephone devices as well as domestic and commercial ovens (for cooking / heating water) at 2450Mhz +/-50Mhz Typical TX power levels 1mW to 10mW (max) for domestic equipment, licensed amateurs allowed much more. Typical distance of most domestic communication gear is ~10 meters to 100 meters (300feet) more if using narrowcast antenna (dish like objects on poles). |
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| Wireless Audio Services |
Security TV |
Wireless Video Services |
"Bluetooth" Headsets Cordless Phones |
IEEE 802.11b =DSSS 802.11g =OFDM |
Wireless Data Services |
Amateur Radio and TV |
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| Audio Services |
Video Services |
18 Mhz Bandwidth |
2.402 - 2.480Ghz |
2.4Ghz Data.Ch. |
5 Mhz Bandwidth |
2400 Mhz to |
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| Phones Cordless |
. | . | Audio Channels |
-- | 2402 Mhz | 2403 Mhz satellites |
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| Intercoms | . | . | Audio Channels |
-- | 2407 | 2406 CW & SSB |
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| wireless headsets |
. | . | Audio Channels |
01 | 2412 | 2406 Mhz aTV1 |
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| wireless speakers |
2.4Ghz TV Ch.1 |
2413 Mhz | Audio Channels |
-- | ---- | aTV1 | ||
| "Bluetooth" | . | . | Audio Channels |
02 | 2417 Mhz | aTV1 | ||
| InfraRed extenders |
. | . | Audio Channels |
03 | 2422 | aTV1 2424 Mhz |
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| . | . | . | Audio Channels |
04 | 2427 | 2425 Mhz fm sstv rtty |
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| . | 2.4Ghz TV Ch.2 |
2432 Mhz | Audio Channels |
05 | 2432 | 2430 Mhz aTV2 |
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| . | . | . | Audio Channels |
06 | 2437 | aTV2 | ||
| . | . | . | Audio Channels |
07 | 2442 | aTV2 | ||
| . | . | . | Audio Channels |
08 | 2447 | aTV2 2448 Mhz |
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microwave oven 2450 Mhz +/- 50Mhz bandwidth |
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| . | 2.4Ghz TV Ch.3 |
2452 Mhz | Audio Channels |
09 | 2452 Mhz | fm links to 2450 Mhz |
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| . | . | . | Audio Channels |
10 | 2457 | public park |
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| Data Services |
. | . | Audio Channels |
11 | 2462 | public park |
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| Data Loggers |
. | . | Audio Channels |
12 | 2467 | public park |
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| WiFi Networks |
2.4Ghz TV Ch.4 |
2472 Mhz | Audio Channels |
13 | 2472 | public park |
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| . | . | . | Audio Channels |
-- | 2477 | public park |
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| . | . | . | Audio Channels |
-- | 2482 | public park |
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| . | . | . | Data Channel |
14 | 2484 | public park |
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| . | . | . | Out of band / guard band |
-- | 2487 - 2497 Mhz |
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Terms: DSSS = Direct Sequence Spread Spectrum OFDM = Orthogonal Frequency Division Multiplexing "Bluetooth" also uses this frequency, hoping many 1000's times a second. "Frequency Hoping" Allows more people to use this narrow part of the radio frequency spectrum by changing channels rapidly in predefined sequences. Thus allowing the "electronic smarts" to easily recover the audio / video / data information from what sounds like a hash of noise. Older video / audio systems show this noise as pulsating line interference or strong varying audio hiss. 2.4Ghz is considered a poor long distance (10's of km) terrestrial communication frequency due to the physics of water (vapour) absorption. Also as microwave ovens exploit this feature and operate at 1000's of Watts inside a metal box to heat food the noise in the band can be quite high. As more short range devices (1 to 250 meters) use this band, the interference level will become very high, to counter act this interference different modulation techniques and frequency hopping algorithms are used. Transmitter output power levels for each set of devices may add to the reception problems of other non-linking devices but with encoded signals turned on, polarised antenna (oriented horizontal or vertical) or physical separation of devices, operation and security from other users can be achieved. The other "public license" bands / frequencies that have similar uses for voice (phone) video (security) data (internet) are 900Mhz, 1.8Ghz, 5.8Ghz. Some of these bands are also used for mobile / cell phones, hence the ease of "Bluetooth" or wireless functionality with your other communication / multi-media devices. |
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