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I am testing two consumer grade WiFi AP and if I believed specifications AP1 should be more powerful than AP2, but from the first tests I made that is not true.

Unfortunately both the AP manufacturer does not provide a serious complete datasheet (remember we are talking about consumer grade, low-budget devices).

I also tried to analyze the spectrum and switch channels but the result does not change.

Is there a way to really measure the antenna strength and plot an antenna radiation pattern?

Thanks

EDIT: Performed tests.

  • WiFi scan with Android App
  • WiFi scan with Windows laptop
  • WiFi scan with MacBook
  • WiFi scan with 2.4 CPE

EDIT2: AP1 does have two, big, detachable antennas weather AP2 does only have one, small, fixed one.

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  • How I wish you had described which tests you already performed, and what you mean by really test.
    – Run CMD
    Nov 13, 2015 at 10:02
  • There are ways to produce an antenna radiation diagram from measurements of signal strength, but at the frequencies used in WiFi and with commonly available equipment, making those measurements isn't necessarily trivial.
    – user
    Nov 13, 2015 at 10:20
  • @class-stacker I mean measure since I cannot trust the advertised specs.
    – kar.bon
    Nov 13, 2015 at 10:21
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    More points actually; some WiFi APs use dynamic WiFI power adaptation. I myself have here seen a better data rate with a more recent AP at lower signal strength as compared to an older AP with a "better" signal strength; using the same 802.11 mode, that is. Also, in the case of ac, beam forming may be used which may not be easy to measure. Are you sure you're interested in "the signal strength" or would it not be more helpful to measure net throughput. I support @MichaelKjörling if you will.
    – Run CMD
    Nov 13, 2015 at 10:26
  • @class-stacker Actually for now I am interested in strength because I have black spots. Also see the new edits to the question.
    – kar.bon
    Nov 13, 2015 at 10:41

1 Answer 1

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For measuring the radiation pattern you need a radio frequency anechoic chamber or a large open space, and proper measuring equipment.

In a consumer grade AP the radiation pattern will be nearly spherical anyway, on 2.4 GHz you'd need a rather bulky or tall antenna to make the radiation pattern anything but spherical. And near spherical pattern means 0 or 3 dBi of gain, depending on definition.

If you're using the AP indoors, the signal intensity will be mostly influenced by wall reflections and not so much by the radiation pattern of the device itself.

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  • Thanks @Vojtech for the clarification. I was interested in measurements because with AP2 (advertised as weaker) I have full coverage, whereas with AP1 (advertised as stronger) placed in the very same position I get some black spots. It would be great if there were something just like thermographic camera for waveforms :)
    – kar.bon
    Nov 13, 2015 at 11:24
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    Most of the times the coverage of an AP is dictated by its receive performance, not transmit. An AP can transmit a strong singal, but if it isn't able to hear a smartphone transmitting out of a tiny antenna at low power, it won't connect to the phone.
    – Vojtech
    Nov 13, 2015 at 15:19
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    Internal antennas of APs will have near pure spherical gain characteristic if they're not shielded by the PCB (usually not) or a metal mounting plate. If they are, then that changes to hemispherical, cut off by the metal. External stick antennas are similar, but the shape of the sphere may be somewhat squished, larger in perpendicular direction to the antenna axis, and smaller along the axis. This gets more pronounced the longer is the antenna. Always point the antenna up in a room and never towards the client device.
    – Vojtech
    Nov 13, 2015 at 15:21
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    But even then the gain difference isn't too huge due to reflections. What matter most is the receiver performance, namely the minimum SNR ratio of the receiver required to decode a signal at a certain bitrate. And that's something that is advertised only in semi-pro and pro accesspoints.
    – Vojtech
    Nov 13, 2015 at 15:24

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