Replacement of the original GPS antenna

Hi,

My kiwi in Thailand has lost it's GPS antenna. It is placed in direct sunlight where it is VERY HOT during the day, so I expect it is the heat who have destroyed it.

These antennas are active, aren't they?

I am wondering if any of you have replaced the GPS antenna and eventually a link to what you bought.

Best regards

Geir, LA6LU

Cha-Am, Thailand

Home Page: www.la6lu.no

Public KiwiSDR in Norway: la6lukiwisdrno.ddns.net:8073

Public KiwiSDR in Thailand: la6lukiwisdrth.ddns.net:8073

Comments

  • jksjks
    edited February 7

    Yes, you want an active one that has at least +28 dB gain or so. And has the L1 center frequency (1575.42 MHz) with a bandwidth of +/- 1 MHz. And can accept 3.3V of course. Order one that has no more than 3 to 5m of that small diameter coax (typ RG174) to keep the losses down.

    We used these during development: https://www.mouser.com/datasheet/2/3/APAMP-111-245401.pdf But you'll find a million similar ones on AliExpress.

    You might also give your old antenna some time (hours) to see if it's really dead. If it doesn't have a full view of the sky then sometimes most of the sats can be out of view, too low on the horizon, etc. And you'll get no sats to track.

    You mentioned in the Debian 10 thread that your admin status tab showed GPS: acquire paused but that should only persist for maybe 30 seconds after restart. After that it should say acquire yes instead, even if there is no GPS antenna connected.

  • edited February 7

    Thanks John,

    After I did the debian 10 upgrade, I thought it's time to have closer look at the GPS problem. The GPS has been like this for weeks now so something is not right.

    What confuses me, is that there are signals, but only red bars which never changes to green. Perhaps someting else than the antenna is wrong?

    It seem to aquire, but no "good" or "fixes" and as mentioned, it has stayed that way for some weeks now.

    KiwiSDR 1, v1.661, 4 SDR channels, 12 GPS channels | Uptime: 1 day 1:37:15 | UTC: 06:11 | Local: 13:11 Asia/Bangkok (ICT)

    Debian 10.11

    GPS: acquire yes, track 1, good 0, fixes 0

    SNR: All 35 dB, HF 25 dB

    Geir, LA6LU


  • That is entirely normal (for a disconnected or broken antenna).

    What you're seeing is just the acquisition code trying to dig sats out of the noise. It tries the PRN of each sat as it scans the channels. And if the SNR is over 16 then it attempts to perform tracking. If the tracking is successful then the RSSI will increase and turn green and the subframe blocks start to turn colors if message decoding is successful.

  • Ok, great knowing this. So I guess ordering a new antenna is the best bet then? I will do that today as soon as you agrees on this.

    We are in Thailand in our own house for 3 months per year and we have 7 weeks left this time, so I need to get a new antenna before our flight back the 2'nd April. The internet is always paid upfront for a year so the kiwi will stay up for the next year as it did the previous year. But I like it to be 100% okay before we leave and there is plenty of time for that too if I order a new antenna today. 😊

  • Yes, I would do that. Those antennas are relatively inexpensive.

  • Yes indeed. I just ordered two new GPS antennas for just US $17.18 (8.59 each) from China. They have the same specs as you mentioned above. If it's the heat who destroys them, it's good having one spare.

    Many thanks for your quick support John. 😊

  • If you search for "GPS timing antenna" on ebay, you can often find used high quality antennas from cell towers, for example GPS-TMG-HR-40N. They last an eternity even in harsh environment, but are a bit more expensive.

  • I'm assuming the problem is due to direct sunlight on the black GPS puck, causing it to overheat.

    Can you shade the antenna in some way, with a material that will not block the GPS signals ?

    Regards,

    Martin

  • edited February 8

    G8JNJ,

    Thanks Martin. Too hot up there was my thoughts too. When I get up with a ladder and put my hands on my terrace roof, it's so hot that I can't hold my hand there. For now I have ordered two spares (flat brick antennas) like the one who is destroyed. A GPS antenna made for tube mounting will probably withstand the heat better. I will seek out as HB9TMc suggested and see what I can find. But if I end up with one of those brick antennas, I will use some garbage, stiff plastic and build some shading over it.

  • Or paint/spray it white...

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