[MLB-WIRELESS] Wireless connection -1200m apart

[Michael Borthwick]

On 18/02/2004, at 4:45 PM, Phil Mawson wrote:

>
>
>  I had seent he Vagi directional antennas by Hills. But it only has a 
> 15.6dBi rating. As I said before, I am new to wireless, but I gather 
> that a 25dBi rating is better, and the parabolic grid antenna is only 
> another $10. Or would the Vagi antenna be better because it is more 
> directional therefore a higher signal strength?

No. The Vagi has 10dBi *less* signal strength than the parabolic but 
what you're not appreciating (and you are in good company) is that once 
you have *enough* signal at each end (technically a high enough signal 
to noise ratio) for the two radios to connect at their highest data 
rate then any additional signal strength provides no increase in speed. 
Therefore it is not automatically "better" as you write above - unless 
you decide to swing one of them around and join us in the Melbourne 
Wireless network.

In fact over that distance you might get away with building any of a 
number of very cheap home made antennas such as helicals, cantennas, 
antcaps, corner reflectors which might offer you around 10dBi gain 
which could be plenty for your application.

You can work what you need by calculating what is called the "link 
budget" for your link. This is straightforward and will help you to 
understand what is going on.

Regards,

Mike
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