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2.4 GHz Services
Channel to Frequency

Jump to ( WiFi 2G Table )

2.4 to 2.4835 Ghz services
Occupy large part of the 12cm Amateur Radio Band 2400 - 2450Mhz

2.4 Ghz services: Video, Audio, Data and Telephone devices of domestic and commercial use. Even microwave ovens use this frequency for cooking by heating water at 2450Mhz, the frequency which water molecules (H2O) will vibrate at and heat up.

For most domestic communication gear (AV senders or data routers) typical distance is ~10 meters to100 meters (300feet) or more if using narrow-cast antenna, 2 dish like objects each with their own mast and pointed at each other. Typical domestic devices transmit at power levels of about 1mW to 10mW (max) and commercial devices like alarm sensors from ~1mW through to microwave ovens of 1000+ Watts and licensedradio amateurs are allowed 10's to 100's of watts.

The 2.4Ghz (2400Mhz) band can be very noisy and a hostile communication place, it is considered a 'public park' whereeveryone can use it and everyone has to put up with the interference from each other, users that try to abuseor dominate the frequency are eventually dealt with by the Media Authority. The 5.8 Ghz band is quieter, less crowded, also considered a 'public park' and has it own set of characteristics for communication activities.

2.4 Ghz Amateur TV is assigned these frequencies:
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)
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
Audio
Services
Video
Services
18 Mhz
bw
2.402 -
2.480Ghz
2.4Ghz
Data.Ch.
5 Mhz
bw
2400 Mhz
to
Cordless
Phones
..Audio
Channels
--2402
Mhz
2403 Mhz
satellites
Intercoms..Audio
Channels
--24072406
CW & SSB
Wireless
Headsets
..Audio
Channels
0124122406 Mhz
aTV1
Wireless
Speakers
2.4Ghz
TV Ch.1
2413
Mhz
Audio
Channels
------aTV1
Bluetooth..Audio
Channels
022417
Mhz
aTV1
InfraRed
Extenders
..Audio
Channels
032422aTV1
2424 Mhz
...Audio
Channels
0424272425 Mhz
fm sstv rtty
.2.4Ghz
TV Ch.2
2432
Mhz
Audio
Channels
0524322430 Mhz
aTV2
...Audio
Channels
062437aTV2
...Audio
Channels
072442aTV2
...Audio
Channels
082447aTV2
2448 Mhz
. .microwave
oven
2450 Mhz
+/- 50Mhz
bandwidth
.. ..
.2.4Ghz
TV Ch.3
2452
Mhz
Audio
Channels
092452
Mhz
fm links to
2450 Mhz
...Audio
Channels
102457public
park
Data
Services
..Audio
Channels
112462public
park
Data
Loggers
..Audio
Channels
122467public
park
WiFi
Networks
2.4Ghz
TV Ch.4
2472
Mhz
Audio
Channels
132472public
park
...Audio
Channels
--2477public
park
...Audio
Channels
--2482public
park
...Data
Channel
142484Reserved
...
...Out of band
or guard band
--2487 - 2497
Mhz
.
WiFi typeProtocol.Freq StrtFreq End Data Rate5.8GHZ
chart
A802.11a-5150587554Mbps.
.......
B802.11b-2400250011Mbps.
G802.11g-2400250054Mbps.
G+802.11g+-24002500125Mbps.
N802.11n-24002500300Mbps.
.......



Terms:
DSSS = Direct Sequence Spread Spectrum
OFDM = Orthogonal Frequency Division Multiplexing
Bluetooth = a communications protocol used on 2.4Ghz
802.11x = a communications protocol used on 2.4 & 5.8Ghz

"Frequency Hopping" 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.

Note: 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 700Mhz, 850Mhz, 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.

*


WiFi 2 GHz Channels
to Frequencies
Red out of bounds Ch.
2G
WiFi
CH#
GHz
Freq.
in MHz
20
MHz
OFDM
40
MHz
OFDM
Other
use
---
--2402..ARB sat.
--2407..ARB ----
012412\\ARB aTV1
022417||ARB aTV1
032422||ARB aTV1
042427/|ARB ----
052432\|ARB aTV2
062437||ARB aTV2
072442||ARB aTV2
082447/|ARB aTV2
092452\/ARB ----
102457|.Park Pub
112462|.Park Pub
122467/.Park Pub
132472..Park Pub
142484..Reserved

If you can not get a clear channel: To limit interference & decoding delays, pick the same channel as the strongest signal. The wifi receivers can detect & reject signals not for them as they each slot-in their own carrier wave signals. As adjacent overlapping channels can not detect all carrier waves, they assume interference and need to resend data... The OFDM scheme of 20Mhz bandwidth occupies 4 x 5MHz channels, i.e. 1 below & 2 above the selected channel; ch.02, 06 & 10 or 2 below & 1 above: ch.03, 07 & 11. Effectively 13 channels (60MHz) allow 3 non-overlaping groups. The OFDM scheme of 40Mhz bandwidth occupies 8 x 5Mhz channels effectively accommodating one large group placed with-in 13 Channels. There is no set channel usage for either scheme, just a rule of thumb to apply and minimise interference. Everybody has their own idea of what is best for them and manufacturer defaults are not designed for minimum interference. Advanced WiFi users should scan the band and workout best channel to occupy and review when throughput becomes slower. Several smartphone apps can advise a less noiser channel to occupy, but this will change over time...

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