stacking antennas

Hi,

I'm trying to stack a couple antennas on a pole in order to connect
several neighboring buildings to a central one via several
point-to-point connections. My problem is that the anntennas interfere
with each other. I have a choice of using either yagi or parabolic
antennas. What can I do to reduce the interference between the
anntenas? Can I somehow isolate the waves of to the sides of the
antennas in order to project a tube, rather than having waves going of
to the sides onto other antennas?

thanks a lot

arthur

Arthur <(E-Mail Removed)> wrote:
> Hi,
>
> I'm trying to stack a couple antennas on a pole in order to connect
> several neighboring buildings to a central one via several
> point-to-point connections. My problem is that the anntennas interfere
> with each other. I have a choice of using either yagi or parabolic
> antennas. What can I do to reduce the interference between the
> anntenas? Can I somehow isolate the waves of to the sides of the
> antennas in order to project a tube, rather than having waves going of
> to the sides onto other antennas?

In general, spacing them apart by 2-3 times their diameter, or length
should be adequate.
Why do you think they are interfering?

If you are able to change the polarity of one of them it will help. but
remember to change the polarity of the antenna that its pointing too also.
"Ian Stirling" <(E-Mail Removed)> wrote in message
news:A5dZb.7009$(E-Mail Removed)...
> Arthur <(E-Mail Removed)> wrote:
> > Hi,
> >
> > I'm trying to stack a couple antennas on a pole in order to connect
> > several neighboring buildings to a central one via several
> > point-to-point connections. My problem is that the anntennas interfere
> > with each other. I have a choice of using either yagi or parabolic
> > antennas. What can I do to reduce the interference between the
> > anntenas? Can I somehow isolate the waves of to the sides of the
> > antennas in order to project a tube, rather than having waves going of
> > to the sides onto other antennas?
>
> In general, spacing them apart by 2-3 times their diameter, or length
> should be adequate.
> Why do you think they are interfering?

In article <(E-Mail Removed)>, Skeeter wrote:
> If you are able to change the polarity of one of them it will help. but
> remember to change the polarity of the antenna that its pointing too also.
>
I think you mean "polarisation", i.e the physical orientation of the antenna
elements, and not the polarity of the electrical connections.

Rod.

"skeeter" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...

> > In general, spacing them apart by 2-3 times their diameter, or length
> > should be adequate.
> > Why do you think they are interfering?

Well, it's an assumption of mine actually. I'm having difficulty with
connections when I have too many antennas close together. I also have
trouble with Planet WAP-4000 802.11g APs crashing for unexpected
reasons (or no evident reason, for that matter) at unexpected moments
(whenever, actually).

What should the effect of too many antennas too close together
theoretically be? Am I coming to a correct conclusion?

arthur

On 20 Feb 2004 06:13:39 -0800, (E-Mail Removed) (Arthur) wrote:

>"skeeter" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...
>
>> > In general, spacing them apart by 2-3 times their diameter, or length
>> > should be adequate.
>> > Why do you think they are interfering?
>
>Well, it's an assumption of mine actually. I'm having difficulty with
>connections when I have too many antennas close together. I also have
>trouble with Planet WAP-4000 802.11g APs crashing for unexpected
>reasons (or no evident reason, for that matter) at unexpected moments
>(whenever, actually).
>
>What should the effect of too many antennas too close together
>theoretically be? Am I coming to a correct conclusion?
>
>arthur


Visualize a bubble around the antenna which is actually the RF waves.
If one bubble overlaps another it will influence the reception or
radiation of that antenna. That's why the spacing suggestion.

One effect is that the overlap will cause the antenna to become
"untuned". Transmitters and antenna have to be matched in order to
get the optimum radiation of signal. When detuned the transmitter
does work as well and at the low power being used it doesn't take much
to screw things up. HAM radio transmitters, on the modern equipment,
will shut down if the SWR (Standing Wave Ratio) is off to far as it
can damage them.

If you've got an amateur radio club around ask them for help as they
will be well versed in antenna and their properties.



Kirk

"Moe, Larry, the cheese!", Curly

www.sandpoint.net/captkirk
www.stormyacres.com