Scale of dbi for broadband antenna

Zxalfan

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Hello

I was trying to find a scale for the dbi of 5, 7,8 dbi omni directional antenna. I seem to get different figures with different searches I do on the net. Can some tell me where to get a good scale of dbi. I do not mean an exact measurement. But a good rough measurement.
 
I don't quite understand the question, dBi is the scale. Are you asking how it translates to RSSI/dBm?
 
@EndlessWaves
Hello. What I ment was what is the range of a 7 dbi omni directional broadband antenna or any broadband antenna 5 dbi 8 dbi e.t.c. How far does it reach e.g. 1 mile, 2000 metere's e.t.c.
 
@EndlessWaves
Hello. What I ment was what is the range of a 7 dbi omni directional broadband antenna or any broadband antenna 5 dbi 8 dbi e.t.c. How far does it reach e.g. 1 mile, 2000 metere's e.t.c.
The range is more to do with power of the transmitting aerial. dBi is about gain compared to an isotropic source - not the same thing.


So two candles (twice the "power") are brighter as the isotropic source (if we consider the source as one candle that is twice as bright). The light will light up a greater area (reach further). The mirror will reflect that and the light is four times as bright as one candle. But still twice as bright as the two. Gain is still the same at times two - or 3dBi.

Then of course low power and very directional microwave frequencies travel further (if not impeded). Gain though would still be double or whatever.

When receiving, higher gain "might" mean you capture "more signal". It might not. Boosted aerials will boost all the signal, including noise. If on the fringe of the reception area (power of the transmitter), you need a bigger receiving aerial matched to the RF signal being transmitted - usually directional. An omni-directional transmitter sends nothing (usable) directly to your position outside of the direct line from you to the transmitter. The signal that reaches you at the set power of the transmitter is all you have to work with. Omni-directional receiving aerials might work better if you have multiple sources (transmitters) transmitting the same thing, or to pick up the single signal that has been reflected so you don't know which direction the signal is you want.

All the above is very layman's terms - about my level of understanding :rotfl:
 
@EndlessWaves
Hello. What I ment was what is the range of a 7 dbi omni directional broadband antenna or any broadband antenna 5 dbi 8 dbi e.t.c. How far does it reach e.g. 1 mile, 2000 metere's e.t.c.

That also depends on the frequency and transmission power, not just the gain. That'll vary depending on the broadband infrastructure you're interested in.

You also get decreasing speed as the signal gets weaker, so you have to pick a speed to declare to be the maximum range and that can be subjective. 500Kbps is probably too low these days but is 2Mbps? 10Mbps?

So the broad ranges of answers you've seen are probably all accurate in different circumstances.
 

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