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Question on antennas
- Thread starter Yohhan
- Start date
dBi is the number of decibels of gain in comparison to the zero dB gain of a freespace isotropic radiator.
Get that? lol
In laymens terms it's the gain on an antenna. All radiating antennas are not created equal regardless of the gain but it is a good measurement of what you might expect. If you want to really know what the gain will give you it's a much more detailed mathematical equation that I can explain in a BBS post. You have to factor receive senstivity of the radio, amperage to the antenna and also calculate any loss from transmission cable run, connectors, not to mention the ambient factors of the link itself. Humidity, fresnel zone clearance etc....
In simple terms, higher gain will give you longer distances, all things being equal. What kind of distances are you trying to get? I, or anybody for that matter, can only give you ballpark numbers when your talking line of sight from radio to radio.
Get that? lol
In laymens terms it's the gain on an antenna. All radiating antennas are not created equal regardless of the gain but it is a good measurement of what you might expect. If you want to really know what the gain will give you it's a much more detailed mathematical equation that I can explain in a BBS post. You have to factor receive senstivity of the radio, amperage to the antenna and also calculate any loss from transmission cable run, connectors, not to mention the ambient factors of the link itself. Humidity, fresnel zone clearance etc....
In simple terms, higher gain will give you longer distances, all things being equal. What kind of distances are you trying to get? I, or anybody for that matter, can only give you ballpark numbers when your talking line of sight from radio to radio.
Keep in mind that get gain by concentraiting RF energy in a tighter spot, this is exactly what directional antennas do. A yagi with more directors will just concentrate the RF energy into a smaller beamwidth. For onmi-directional antennas, gain is dirived by stacking multiple dipole on top of each other.
Also watch out for dBi and dBd. As ktwebb said dBi is gain over a reference Isotropic radiator, while dBd is gain over a reference Dipole.
'73
Also watch out for dBi and dBd. As ktwebb said dBi is gain over a reference Isotropic radiator, while dBd is gain over a reference Dipole.
'73
directon antenna will give more range at same power/dbi of out put, as CentronMe pointed out, then a omni anti will do.
point in case the omni stock antenna on my dlink di614+ will only go about 300-500 feet (max range for connection with clear LOS) to my laptop with its weak internal antenna.
put on my can-tenna and i get over 750 feet with ease to the same laptop with the same weak internal antenna. put on can-tenna to can-tenna i will get over 1 mile with out any problems (winxp shows 3 of 4 bars power). i have shot from one can-tena to a yagi (over water) almost 4 miles!!! nice big cabin cruser with yagi on the boat on 25' antenna
point in case the omni stock antenna on my dlink di614+ will only go about 300-500 feet (max range for connection with clear LOS) to my laptop with its weak internal antenna.
put on my can-tenna and i get over 750 feet with ease to the same laptop with the same weak internal antenna. put on can-tenna to can-tenna i will get over 1 mile with out any problems (winxp shows 3 of 4 bars power). i have shot from one can-tena to a yagi (over water) almost 4 miles!!! nice big cabin cruser with yagi on the boat on 25' antenna