There is no the second MCX plug 
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Haha thanks for the reply 
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Can someone from Emlid explain to me how to set up the antenna and how to know where the 0,0,0 point of the GPS observation? I plan to use the M2 as a backup static base. I have 2 options that I can think of but one of those needs to know the 0,0,0 of the antenna or how to place the antenna over a known point. The other option is to just place the M2 anywhere in the open and process the data as a redundant fixed rover point.
I hope I was able to make my question clear.
Thank you.
The antenna would be a separate component like below and your would need to mount it on a ground plane of 80-100mm. The 0,0,0 is in the center of wherever you put the antenna 3mm above the bottom of the antenna (top of ground plane).
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So it’s the geometric center of the antenna? Aren’t there any kind of mark on the antenna for the geometric center?
Yes, but not the exact geometric center on the z-axis. Both of mine are mounted so I don’t recall if there is a mark on the bottom or not, but I used a micrometer to score mine.
The picture 2 posts above is the antenna for the M+ receiver. It is fine for an example, but I just want to make sure that we’re clear that it is L1-only and not a multi-band antenna.
The question about the center of the antenna is valid. Where is the center?
I think for this tiny antenna, you just use the bottom-center of the antenna and that is good enough and easy to measure. A ruler or tape measure will be fine to determine the center. If you want to do it in a more precise way that is fine too.
At the top of the page is a picture with a helical antenna. They are a bit taller so it may be harder to ignore the height for that one. I am not familiar with where the center (phase center) sits on those, but I would imagine it would be near center or a bit higher (please correct me if someone knows). Horizontally, just measuring the center should be fine for that one too.
After all, the reference to the antenna center from something else (the drone camera, or the bottom of the rover pole) - it is just a relative measurement anyway. As long as you do it in a consistent way, then your results will be consistent.
The only warning I can think of is if you were using an antenna reference point that was not well centered on the antenna itself, like the point where the cable exits the side, then you should always keep the antenna oriented in the same direction when recording points (e.g. always facing north).
To make a long story short, just center it as best you can and it will be fine.
What do you guys think? Is that a fair statement to make when talking about these tiny GNSS antennas?
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Good points. Thank you for clarifying the specification of the Tallysman that I used as an example. Now we are talking about the differences between the geometric center and the phase center of an antenna. Most of these antennas in a commercial setting are provided with a reference point, which may or may not be the actual phase center. Indeed, dual-channel antennas can have two different phase centers which is why manufacturers will provide a reference point which is then used as a calculation in the software. The phase center of a helical antenna is particularly tough because you would need to know the gauge and pitch of the helix. Power and frequency obviously change this as well. From what I have read the phase center is closer to the feed so a generalization of 1/4 to 1/2 the length of the helix it’s probably as close as you are going to get without field calibration. If you are really trying to nail down measurements to the hundredth of a foot then a field calibration is mandatory. Using two leveled points with known elevations start with your theoretical phase center, create a reference point and adjust the reference point until your measurements match. You then have the antenna height to be entered into your software.
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Will this new device support can(uavcan) protocol? Can you provide any info about the device?
Hi Matthew,
I am afraid in the meantime we can’t share any info on M2.
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