Meshtastic

The importance of GPS antennas (and request to 3d case & documentation people)

Hi,

So I’m currently locked in a building and noticed that my stock TTGO GPS antennas would just barely get signal. However, I did have this cheap amplified antenna. OMG SO MUCH BETTER. If you need optimal GPS data for your usage, I recommend you buy one of these $4 wonders.

Also - I noticed that even the few layers (6?) of PETG in my cases made a huge difference in GPS signal quality. Removing the antenna from the case helped a lot. Therefore if anyone wants to work on either of the following two things that would be awesome:

  • Add a note to docs/FAQ.md mentioning this issue and the possibility of switching to a better antenna.

  • If you are making 3D printable case designs - make sure to use only a very thin layer over the GPS antenna.

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The 3d case cover I use is thinner around the GPS antenna. https://www.thingiverse.com/thing:4168101
Pointing the case cover towards the sky (45ish degree) helps a lot indoors.
Have the bigger GPS antenna too, it works so much better…Unfortunately does not fit inside my case

Thanks for that hint, i fortunately read about this while in the final stages of my case design, it should only be 2 walls around the GPS antenna now :slight_smile:

I’ve got a Beitian BT-18A (18185mm) antenna on the way, as that may be possible to fit into my case with a small bump on the side, but the 28mm version will be too large…

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I just received these yesterday.

They are roughly twice as wide about the same height and depth as the GPS antennas that come with the TBeam.

From a cold boot, I had a lock inside of 10 seconds. When you swap the antenna though, be sure to apply quite a lot of pressure to get it to seat. When I first attached it, I was not seeing any satellites. When I picked it up and applied a little pressure I had 9 satellites, removing pressure it went back to 0.

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Is there any difference in accuracy, or just speed of picking up satellites?

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It improves the signal received from the satellite network. With improved signal, you get a lock on more satellites which would result in better accuracy, faster location acquisition and faster almanac downloads.

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I got a new GPS antenna to replace the default one; it is ceramic and about one inch squared. However, it’s got a metal underside, and I put that on top of the T-Beam (when trying to fit it into a PET tube), and I got a metallic smell and now the battery doesn’t work anymore (the board works fine when plugged into the USB port). Is it possible that I have fried some component by having the metal bits on to of the board? Or does it draw more power than the original one and this damaged something else? I want to avoid a repeat when I try this with another board… :frowning:

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Hi,
better antennas are always an improvement. Although i had no obvious problems with the stock patch antenna. I do mostly track flying. I also observed some differences with projects i’ve tested so far. As i use always the same device in its case, i think i should have comparable results. PAXcounter, Airwhere, SoftRF, and GXaircom have better and stable fixes. I think it has to do with the extended powersave tasks in meshtastic. Sometimes i see PPS blinking which need a valid fix. But display says “no Sats”. Or PPS is blinking but if i wake the device up it stalls and does also claim “no Fix” Resetting or better ON/OFF gets immediately a fix again. Maybe there is still some fine-tuning needed. Actually tested with 1.1.7/T-Beam1.0 and 1.1
Made a Video: See PPS blink, then after waking up the display, there is no fix and PPS LED stalls.

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Hello!
I am sorry if this is a stupid question, I am certain it is, but would it be possible to hide location data altogether? Say if someone communicates but wants their location to remain as secret as possible (it will of course be able to assess the location through triangulation).

So if I am in the forest somewhere, transferring a message, where no location data is “shared” with my message, to a node which then repeats it to a receiver. Is this possible?

Say for example that you’re testing LoRa Meshtastic connections with a larger group of people you don’t know and you find it intimidating if they knew your exact location.

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100%. I imagine as people continue to build out publicly accessible networks of static repeaters, the ability to maintain privacy on untrusted networks is going to become increasingly important.

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I bought a T-Beam V1.1 with NEO-M8N and SX1262 because I wanted to have the flexibility of the antenna placement, which other boards don’t have. My GPS antenna is also really bad and I decided to order a BEITIAN BT-25C patch antenna as replacement. It also covers the GLONASS frequencies and I hope that I can receive GPS, Galileo and GLONASS with it, once it arrives.

It’s really a pitty that there are no cases that could fit such an antenna yet. I thought about trying to modify an existing case but I have no experience with something like that and from what I see I would have to design it from scratch and I don’t even have a 3D printer. From looking at various cases I also think most of the cases where adopted from cases where the antenna is fixed to the board and therefore can’t have an optimal orientation if you want to have access to the buttons and the USB port. The antennas of some cases are even placed in a way that either the GPS antenna or the LORA antenna has a suboptimal placement.

This is how I think a case should look like:

  • Do not solder the display directly to the board. This allows the USB port to be placed at the edge of the case.
  • Have the GPS antenna face the sky, probably place it in the middle (does this minimize interference?)
  • Have the LORA antenna and an optional external WLAN antenna at the top, so they could radiate 360°
  • Place the LORA and the optional WLAN antenna as far away from each other as possible to avoid interference)
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I think you’re cause a short circuit from the shell of the antenna and the positive of the battery, i think the main power ic it’s death.

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My case I designed a few months ago was specifically for use with a larger GPS antenna.

once there is an easy way to “activate” the Wifi antenna I will be updating the design for that too.

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@b8b8 interesting design! I like the special 90 degree power cable but I think it’s kind of pricy. Is the case still usable with a normal micro usb cable? There are also 90 degree micro usb adapters and cables available but only a few ones that allow routing the cable to the back. What I don’t like about your case is that you enclosed the lora antenna. It would be nice to have a second top with the connector accessible.

Regarding the wifi antenna: It’s not that hard and you need to solder the display anyway.

btw.: You should upload the images from this thread to thingiverse so people get a better understanding.

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Design updated for exposed antenna and standard USB cable. I find the magnetic USB cables quite handy so have slowly transitioned all my devices to using them but I can see some merit in using a standard cable.


image

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The replacement GPS antenna arrived today and now it works really well indoors. I placed it next to an outside wall and it picks up 4 to 6 satellites most of the time. Now I only need a proper case designed for the external Lora antenna and the larger GPS antenna and access to a 3D printer.

Yes, I still have the protection foil on. :wink:

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