Is it possible to determine the direction of a radio signal instantly,
i.e. without having to sweep some directional antenna? Perhaps by using
several orthogonal antennas, for example?

If it helps, here's the particular application I have in mind: I'm
wondering about something that could be embedded in a handheld device
which would determine the direction to the nearest WiFi (802.11) base
station(s). If it could simultaneously get a bearing to two or more
base stations, and the position of those base stations were known, then
it could could determine its own position and orientation.

Where would this fall on the scale from "trivial" to "requires magic"?

Thanks,
- Joe

Is it possible to determine the direction of a radio signal instantly,
i.e. without having to sweep some directional antenna? Perhaps by using
several orthogonal antennas, for example?

If it helps, here's the particular application I have in mind: I'm
wondering about something that could be embedded in a handheld device
which would determine the direction to the nearest WiFi (802.11) base
station(s). If it could simultaneously get a bearing to two or more
base stations, and the position of those base stations were known, then
it could could determine its own position and orientation.

Where would this fall on the scale from "trivial" to "requires magic"?

At that frequency, some where about you REALLY have to know what
you are doing.

I'd suggest a google search on radio direction finding to get a feel
for all the different techniques.

One problem is at that frequency it is a bitch to get most of them
to work.

The simplist is a small (and at that frequency it will be small)
directonal antenna you sweep by hand.

In article <dbeui4-m9h.ln1@mail.specsol.com>, jimp@specsol.spam.sux.com
wrote:

At that frequency, some where about you REALLY have to know what
you are doing.

I'd suggest a google search on radio direction finding to get a feel
for all the different techniques.

Thanks. I didn't even know what keywords to search on before, but now
I'm finding a lot of useful resources.

I see that what I had imagined is something like the Watson-Watt
technique, but there are many others.

If we have control over the fixed transmitters (which is a possibility
for my application, albeit a much more expensive one), then something
like the aircraft VOR technique might be even better -- it seems like
that puts the expense onto the transmitters, rather than onto the
receivers, which is where I'd rather have it. But VOR only worked with
a direct line of sight; if that's always true for this technique, then
it won't do, as I need something that can work in and among buildings,
trees, etc.

One problem is at that frequency it is a bitch to get most of them
to work.

I bet.

The simplist is a small (and at that frequency it will be small)
directonal antenna you sweep by hand.

True, but I need something automatic that can update at 30 Hz or more.
Maybe a pseudo-doppler technique, with a circular array of antennas?