GPS antenna comparison

bytebenderbytebender
in Installation, Antennas and Interference

Out of curiosity, I tried a different GPS antenna to see if there's a big difference. The one I tried is the ublox ANN-MB5 L1/L5, which costs around $35 and is also magnetic. It was positioned in the same indoor location as the one provided with the kiwi2. Screenshot differences attached. The one with improved signals is the ublox.


gps ublox.png
gps.png


Comments

  • jksjks
    edited May 10

    Coax loss is a big factor. I got talked into increasing the length of the RG174 on the antenna we ship from 3m to 5m. That was a terrible idea. The added loss at 1.6 GHz is huge. Even if it does make it easier to get the antenna out a window.

    http://kiwisdr.com/files/gps/gps_ant_issues_r1_5-07.pdf

  • bytebenderbytebender

    What kind of GPS reception should we aim for in the kiwi 2? For example, at least 4 green channels?

  • jksjks
    edited May 10

    You need at least 3 or 4 green (RSSI) channels (channels where the "subframe" blocks turn colors) in order to get a fix. Very important for the antenna to have a view of as much of the sky as possible. You will get some gain by putting the puck antenna on top of a metal ground plane of some sort. Doesn't have to be fancy -- a pie pan will do.

    Remember that you can also do a manual frequency calibration in lieu of GPS automatic calibration. See the admin page, config tab, bottom of the page for instructions.

  • TremolatTremolat
    edited May 10

    Good morning,

    when there is a long cable length, I would tend to choose a GPS antenna with 40 dB of gain, and especially a low loss cable.

    Here, the cable is 30 meters long, if I want the two GPS antennas to be exposed to a corner of the sky. The Kiwi receivers are on the ground floor of a 15 meter tower. It is temporarily low loss RG58. I need to find a better one. John is right to point out that the loss caused by the length of the cable is dramatic. And it goes very quickly. 10 meters from RG176... and there is no more signal. John's document (gps_ant_issues_r1_5-07) is very relevant, excellent.

    I chose two GPS antennas from agricultural tractors. My country is an agricultural region and we are used to these devices. They are placed inside a roof window. Even sheltered from bad weather, their exposure to satellites is correct.

    Best regards, Philippe

    IMG_0857.jpeg


  • bytebenderbytebender

    Here is an active GPS antenna rubber ducky that would need zero cables and screws right into the SMA port: https://www.2j-antennas.com/antennas/single-external-antennas/2j0801cf-c40g-a38g-gps-glonass-beidou-galileo-28-db-gain-right-angle-antenna/283

    It claims to have 28dB of active gain.

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