Antenna Question - mix of Yagi and Omni antennas?

Antenna Question --

I would like to know whether it would make sense to use a mix of an
omnidirectional antenna and a yagi directional antenna for a
particular application that I have in mind.

Two buildings are separated by about 600 feet line of site distance.

Internet access is available via DSL in Building-1 but not in
Building-2. Building-2 requires the use of wireless handheld
computers to access an internet application within a 200 to 300 foot
radius of the building.

I would like to be able to accomplish building a wireless bridge from
Building-1 to Building-2 so as to provide internet access to handheld
computers in close proximity to Building-2.

I would like to do it with only 2 access points if possible and
therefore I am wondering if I can use a directional Yagi antenna on
Building-1 and an OmniDirectional antenna on Building-2 so that the
antenna on Building-2 serves the dual purpose of providing the bridge
connecting to Building-1 and also providing coverage to hanheld
computers within a 200 to 300 foot proximity.

Building-1 has no requirement to provide wireless access to any
computing devices, only to bridge the signal to Building-2.

Any information would be greatly appreciated.

(E-Mail Removed)

Patrick Carnahan <(E-Mail Removed)> wrote:
> Antenna Question --
>
> I would like to know whether it would make sense to use a mix of an
> omnidirectional antenna and a yagi directional antenna for a
> particular application that I have in mind.
>
> Two buildings are separated by about 600 feet line of site distance.
>
> Internet access is available via DSL in Building-1 but not in
> Building-2. Building-2 requires the use of wireless handheld
> computers to access an internet application within a 200 to 300 foot
> radius of the building.
>
> I would like to be able to accomplish building a wireless bridge from
> Building-1 to Building-2 so as to provide internet access to handheld
> computers in close proximity to Building-2.
>
> I would like to do it with only 2 access points if possible and
> therefore I am wondering if I can use a directional Yagi antenna on
> Building-1 and an OmniDirectional antenna on Building-2 so that the
> antenna on Building-2 serves the dual purpose of providing the bridge
> connecting to Building-1 and also providing coverage to hanheld
> computers within a 200 to 300 foot proximity.
>
> Building-1 has no requirement to provide wireless access to any
> computing devices, only to bridge the signal to Building-2.

Sure.
As long as the gain is high enough.
There may be a third way.
If the buildings are line of sight, then one antenna in building one,
picked so that the radiation pattern just covers building two may work.

Directivity of an antenna is about 1.22*wavelength/diameter.

200m away, say a 20m building, 4m tall, that's a directivity of
1/10*1/50 radians.

So, that's 1/10radians = 1.22 * .125m /diameter
Rearranging gets
diameter = 1.22*.125 * 10 =1.5m (horizontally) by 7.5m (Vertically)

Hmm, a big antenna.
A 1.5m dish would probably work.

Maybe not.

Ian Stirling <(E-Mail Removed)> wrote:
> Patrick Carnahan <(E-Mail Removed)> wrote:
>> Antenna Question --
>>
>> I would like to know whether it would make sense to use a mix of an
>> omnidirectional antenna and a yagi directional antenna for a
>> particular application that I have in mind.
>>
>> Two buildings are separated by about 600 feet line of site distance.
<snip>
> There may be a third way.
> If the buildings are line of sight, then one antenna in building one,
> picked so that the radiation pattern just covers building two may work.
<snip>
> Hmm, a big antenna.
> A 1.5m dish would probably work.

While this is correct, it's the wrong way to go about it.
To get the same signal at 200m as at 30m, you need to generate some
fifty times the effective power, (power needed is proportional to
range squared).
An antenna with a beamwidth of around .4 radians (24 degrees) would be
around right, so that's a dish of over 40cm should do it.