So I read an interesting article about GPS antennas called "Adding a GPS Chipset To Your Next Design Is Easy".
A few points to bring up that I have concerns with dealing with my M8N antenna.
1. Active vs Passive Antennas. Two paragraphs within the article describes the difference between Active and Passive antennas. According to CSG Shop's specification for the NEO-M8N it comes with a low-noise regulator and RF filter built-in. So I'm assuming that it is a active antenna.
2. Antenna's requiring adequate plane. If I read that document correctly, these GPS modules may require a GPS plane as they are installed on a PCB that does NOT have 40mm of side to them.
Quote: "Generally, patch antennas in the 15- to 25-mm size range with a least a 40-mm (on a side) ground plane will give the best performance in portable equipment, but this may be too large for your application. This could force you to look at smaller antenna topologies such as linear chip antennas."
3. The next concern is to mitigate the noise interference from FC, ESCs, and PDB. Since my Y6B is set up with a clam shell cover and my M8N is attached under and close to the all the electronics, I may need to develop a shield "ring" connected to the shield can and then connect that ring to RF ground through an inductor at a single point.
Quote: It's common in VHF and UHF RF shielding to connect all points of the shield can to the PCB's ground plane. This can be a mistake at GPS frequencies, since the open-air wavelength of a GPS signal is so much shorter than UHF. Depending on the size of the shield can, if there is current flow across the can, the shield can will be able to resonate near GPS frequencies resulting in interference or de-tuning of the GPS RF.
By developing a shield "ring" connected the shield can and the inductor, the inductor will filter any EMI-induced current flow. The ring connected to the shield can will prevent any current flows or resonation issues.
I'm not an electrical engineer and need guidance from those out there who are. Did I interrupted this correctly? and if so I could use some help with developing the "ring".
Thoughts?
Replies
Thanks!
Pavel.
Support for UAVCAN sensors in APM is a bit lacking, so the steps described in the tutorial are needed to work-around this manually. Hopefully APM will improve in this regard in the future. For purposes of comparison, Zubax GNSS 2 can be used with PX4 as a plug-n-play device - no configuration needed.
I don't think it's possible to screw something up following the tutorial since it's really straightforward; even if you get in a bind you can always ask for assistance at the support forums.
Pavel.
Zubax GNSS 2 features an embedded SAW/LNA, a large high-gain patch antenna, u-blox receiver with TXCO oscillator (u-blox M8Q, the latest generation), and shielding which makes the device more resilient to EM interference (we successfully used Zubax GNSS 2 on a UAV with an embedded x86-64 computer where other GNSS receivers would perform poorly because of EMI).
I'm not selling hard I'm just stating known facts ;). You can always google or search this website to see some public feedback.
Doug
Do you know if the battery goes bad if the time it takes to get a good gps lock increases? My M8 used to grab 6-8 sats in just a minute or so. Seems to take more like 4-5 now I don't get it. About the only thing I can think of is the battery. Thx
Another question for you. How long has your GPS been powered off or shelved? I know this sounds peculiar, but I have observed that GPS units that have been off for a period of time (such as a week) could take longer to reacquire the satellites due to the orbit of satellites are not fixed they rotate around the earth.
Can you put a voltmeter on the battery to determine if the battery is dead or low? By the way the batteries I have on my GPS units use a MS614SE type battery and are rechargeable.
Please tell me where did you read that this batteries ARE recharging in your GPS on Multi...maybe you need special recharger not just connecting in gps...my experience tells me this small batts just discharge after some times completely,never heard of recharging.....and than GPS unit don't have logs memorized and needs more time to find satellites..
Emin,
I received an email response back from CSGSHOP. See below.
@Emin. Great find. I am a convinced user of CSGshop M8N and now looking to M8T. Using linear 5V regulator to power it and grounding the CF tube which support the "box" where the M8N is always gave me real good results. Under the "box" a self adhesive copper / aluminium improve the radiated noise from "below".
I haven't (yet) tried the M8T but very soon.. :-)
I am curious as to why 3DR continue to used "noisy" switching regulators to power "everything"? People get into lot of trouble due to "noisy" power.. Anyway...
Henri
Yes sometimes it can be off for a week at a time I kn ow it takes longer then but the thing is it seems to always take that long each time.
Cool thanks for the tip on the rechargeable battery!
I think the issue is whether the rechargeable battery has enough recharge time on the drones when it gets it's power from the flight batteries with the average flight time for most people between 8-20 minutes. I think tests need to be performed and posted showing any results in the battery to stay charged up during any flight time and another for how long it would take to drain empty on the shelf.
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