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Offline jmschnur

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Antenna pattern
« on: January 30, 2015, 06:55:03 pm »
When in wifi extender mode, what is the antenna pattern both for transmitting and receiving.
The answer affect how best to orient my almond plus.

Offline Rahaman

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Re: Antenna pattern
« Reply #1 on: February 02, 2015, 05:34:14 am »
When in wifi extender mode, what is the antenna pattern both for transmitting and receiving.
The answer affect how best to orient my almond plus.

The antenna pattern is Omni-directional Pattern. As it is omni-directional pattern it doesn't matter how you place your A+ because it radiates radio wave power uniformly in all directions. For your information the antennas are placed in both side of A+.

Offline Automate

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Re: Antenna pattern
« Reply #2 on: February 02, 2015, 10:34:13 am »
Actually, if it is omni-directional then as stated by Wikipedia, "class of antenna which radiates radio wave power uniformly in all directions in one plane" its not equal in a all directions but equal in a single plane.  I would assume this would be the horizontal plane but it would be good to get confirmation from Securifi.  It also matters the pattern in the perpendicular plane as pointed out again by Wikipedia "Although the radiation of an omnidirectional antenna is symmetrical in azmuthal directions, it may vary in a complicated way with elevation angle, having lobes and nulls at different angles." It would also be good to know the antenna patterns of the other radios (Zwave and Zigbee)

Offline Zimmie

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Re: Antenna pattern
« Reply #3 on: February 02, 2015, 05:02:28 pm »
If that's Wikipedia's definition, then Wikipedia is wrong. Omnidirectional means in all directions. What they are describing would better be described as toroidal radiation, like a dipole. It is extremely difficult to get a real, honest-to-goodness omnidirectional radiation pattern. You can get a cardioid pattern using a dipole with a perpendicular coil, but you still end up with a null.

I suspect when Securifi says the radiation pattern of the device is omnidirectional that what they mean is that they are using three cross-polarized dipole antennas. That will result in any one antenna producing a toroidal pattern, but the combination of all three should give coverage from two antennas in every direction and coverage from three in most.

Offline jmschnur

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Re: Antenna pattern
« Reply #4 on: February 02, 2015, 07:07:37 pm »
It would be very interesting indeed if the plus was radiating a three dimensional homogenous pattern. I am skeptical that this is the case.

Offline Automate

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Re: Antenna pattern
« Reply #5 on: February 02, 2015, 10:19:56 pm »
If that's Wikipedia's definition, then Wikipedia is wrong.
I'll trust  Wikipedia http://en.wikipedia.org/wiki/Omnidirectional_antenna

They describe an antenna that truly radiates equal power on all directions as an isotropic antenna.

Offline Zimmie

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Re: Antenna pattern
« Reply #6 on: February 03, 2015, 11:56:21 am »
Meanwhile, I will trust my education and years of experience as a radio operator over a website that anybody can edit. ;) Dipole antennas are decidedly not omnidirectional, but you can get a largely-omnidirectional radiation pattern using the strategy I explained. That is a fairly common antenna arrangement for 802.11 access points with multiple internal antennas per band because the orthogonal radiation patterns help make the access points orientation-insensitive. It also typically makes the multiple spatial streams the radios support take separate physical paths through the environment, which can improve speed and reliability of the link.

The biggest downside is that it takes up a lot of space inside an access point. As a result, some use a Y arrangement, which gives a passable approximation of omnidirectional radiation. It gets the nulls out of coincidence, but you wind up with a bit more of an oblate spheroid (think an M&M) instead of a sphere. It's usually workable, but a little more orientation-sensitive than three dipoles all at 90 degrees from each other.

All of this discussion actually makes me really curious what antenna arrangement the Almond+ uses internally. I'm betting a Y oriented in the plane of the LCD, but it's deep enough there could be an antenna running the depth of the router on two corners.

Offline Automate

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Re: Antenna pattern
« Reply #7 on: February 03, 2015, 05:53:15 pm »
Meanwhile, I will trust my education and years of experience as a radio operator over a website that anybody can edit. ;)
I'm not saying that Wikipedia is always right but can you give may any links that collaborates your definition?  Everyone I find talks about equal in a single plane

 

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