in reading the thread on bi-quad design, I was wondering what the overall radiation pattern would be for the standard dual antenna access point.
I mean - with the dual "donuts" around each antenna, the resulting pattern/coverage would have donut lobes around each vertical, with extended lopes at right angles to the bisected line between them ?
"P.Schuman" hath wroth:
There's only one pattern as only one antenna is active at a time. The pattern may change slightly as the diversity antenna switch, but with such low gain antennas, and such close spacing, there's not much change.
Nope. That would be true if both antennas were simultanously driven by a proper phasing harness or setup as a simple 2 element Yagi antenna. However, they're not. It's a switch.
See:
The WAP11 packages and antennas are identical to the typical WRT54G and is similar to all dual antenna access points.
The problem with modeling low gain (+2dBi) access point antennas is that the nearby environment has a HUGE effect on the pattern. The pattern sitting to top of a metal PC box is very different from that of one sitting on a wooden table. Nearby pieces of metal (i.e. monitor) can act as an unwanted reflector. For example, the WAP11 with a reflector on top of a ground plane.
With a low gain vertical colinear antenna (such as typical with the stock antennas), there's not much directionality. No matter how its positioned, it still looks like a very fat donut. For more extreme patterns (i.e. flattened donut) a higher gain antenna is required.
Also, A simple Biquad:
A badly built Biquad:
This is an all too common method of building a biquad, where the coaxial cable does NOT extend all the way to the beginning of the quad elements. I previous scribbled a rant about this at:
Amazingly, even built wrong, the badly built biquad antenna still has substantial gain.
If you're interested in antenna modeling, see 4NEC2 at:
It's free, and comes with quite a few examples.
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