zrob_12
03-25-2009, 07:36 PM
I am considering setting an a Bullet AP with an omni antenna. What are the advantages and disadvantages of using 2.4GHz or 5.8GHz?
View Full Version : 2.4GHz vs 5.8GHz
jp498
03-26-2009, 06:36 PM
5.8 omni antennas are pretty hit-or-miss. Their vertical pattern varies with frequency.
WHT
03-26-2009, 10:16 PM
2.4 Gig
Only three non-over lapping channels.
Lost of interference from other WISPs and consumer grade WiFi crap.
Less loss though a marginal LOS path like a few trees.
Wide Fresnel zone.
Highest typical gain of an omni antenna is 15 dBi.
5.8 Gig
Only three non-over lapping channels for similar power levels.
Very allergic to trees.
Small Fresnel zone.
Highest typical gain of an omni antenna is 12 dBi.
The wider range of the 5.4 to 5.8 Gig band makes it harder for an antenna to have a consistent pattern. Fortunately all the 5.8 Gig antenna are cut for the 5.8 Gig band as there is no market for 5.4 Gig antenna, thus the pattern is fairly consistent across the UNII-2 and UNII-3 bands.
The reason you don't see higher gain commercial omni antennas is the pattern would be very flat. People that build home made antennas up around 18 dBi gain don't have the technical resources to properly test and adjust the antenna, so the pattern will be funny due to phase pulling.
Only three non-over lapping channels.
Lost of interference from other WISPs and consumer grade WiFi crap.
Less loss though a marginal LOS path like a few trees.
Wide Fresnel zone.
Highest typical gain of an omni antenna is 15 dBi.
5.8 Gig
Only three non-over lapping channels for similar power levels.
Very allergic to trees.
Small Fresnel zone.
Highest typical gain of an omni antenna is 12 dBi.
The wider range of the 5.4 to 5.8 Gig band makes it harder for an antenna to have a consistent pattern. Fortunately all the 5.8 Gig antenna are cut for the 5.8 Gig band as there is no market for 5.4 Gig antenna, thus the pattern is fairly consistent across the UNII-2 and UNII-3 bands.
The reason you don't see higher gain commercial omni antennas is the pattern would be very flat. People that build home made antennas up around 18 dBi gain don't have the technical resources to properly test and adjust the antenna, so the pattern will be funny due to phase pulling.
zrob_12
03-27-2009, 08:50 AM
That's exactly what I wanted to know, thanks WHT!
rado3105
04-09-2009, 12:46 AM
Only three non-over lapping channels for similar power levels(5GHz), I dont understand this, I was thinking that there is much more channels for 5GHz(more than 20).
InoX
04-09-2009, 01:26 AM
he said 5.8Ghz not 5Ghz
rado3105
04-09-2009, 01:32 AM
ok sorry my mistake
WHT
04-09-2009, 09:41 AM
Only three non-over lapping channels for similar power levels(5GHz), I dont understand this, I was thinking that there is much more channels for 5GHz(more than 20).
Here is a clarification...
Yes, there are a banana boat load of channels, but...
The lower 4 each UNII-1 ch. 36-48 are for indoor use only and 17 dBm TPO.
The middle 4 each UNII-2 ch. 52-64 are limited to 24 dBm TPO.
The upper 4 each UNII-3 ch. 149-161 are allowed 30 dBm TPO.
Therefore, for each similar power rating there are only four channels. And with four channels, you can have three over lapping ones.
Here is a clarification...
Yes, there are a banana boat load of channels, but...
The lower 4 each UNII-1 ch. 36-48 are for indoor use only and 17 dBm TPO.
The middle 4 each UNII-2 ch. 52-64 are limited to 24 dBm TPO.
The upper 4 each UNII-3 ch. 149-161 are allowed 30 dBm TPO.
Therefore, for each similar power rating there are only four channels. And with four channels, you can have three over lapping ones.
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