Alternative/better aerial for M+

Hello - we are using a Reach RS as a base and an M+ on a UGV for some land Autonomy projects. We are struggling with good satellite fix on the M+ and I wondered if anyone has used an alternative, larger antenna? We are not limited by size in our use case. Any advice would be very welcome - thanks. John.

A better antenna is really not going to help you much. The main source of your problem is the fact that the RS and M+ are only using a single channel to the satellites. Your best bet would be to move to an M2 and a CORS(NTRIP) correction service or an RS2 as a base station. These are all multipath solutions and will not only acquire a fixed solution faster, but will maintain it better throughout the session.

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While @chascoadmin is completely right in his statement, let’s see if we can improve your current setup:

  • can you post some pictures of how the antenna is mounted and how the M+ unit is placed?
  • to get less multipath elevation above ground is key on especially L1-only receivers. How close is the antenna to ground now?
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Hi - the M+ unit is inside a pelicase mounted on a rover

the antena is mounted just in front of the radar you can see in the picture (the white cylinder).

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If you rely on the gnss antenna for something meaningful, you should have it pri. nr 1 for placement.
Right now its getting interference directly from the radar and a second set of antennas right in front of it.
Also check if you powersupply is making some noise.
You could mount the antenna on top of the radar with a proper groundplan
Whats that white pole in the back?

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It is a Ubiquiti Wifi link - but we have now switched to Radio Mesh system - so getting it further away from other antennas is key here?

This is just sick! I have been looking into an RC monster (truggy) truck build that can go offroad, but this is just another level. You definitely want to have the GNSS radio antenna higher than any of that other gear and will want a base plan that blocks all the interference. I am guessing the base plane would need to be at least 120x120mm.

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We have added a base plate, but we will need to try adjusting the positioning.

will an alternative Anetnna help (https://www.3dxr.co.uk/sensors-c5/gps-gnss-c89/emlid-reach-c452/emlid-multi-band-gnss-antenna-reach-m2-m-ant-107-p3656) , even if the M+ is single channel?

Follow up question - our RS+ base station seems to work fine, it is the rover based M+ that struggles. Will the M2 work with our RS+ base station or will we need an RS2 as well? Thanks for all the advice

Not necessarily further away. More like shield gnss antenna from noise the other devices are broadcasting. It helps not beeing on the same frequency but they still make alot of mess.

No, its mostly designed for multi band and to pick up signals from different angles.

You are within the limits of L1 only receiver with L1 base and rover, adding dual rover makes no difference since base only transmits L1.
L1 is extra vulnerable for noise, by removing most if should help a ton.

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Hi John,

As Tore and Michael said above, Reach M+ is a single-frequency receiver that requires a clear sky view without any obstacles to provide you the best solution. It seems that the radar blocks a significant part of the sky view for the antenna. There might not be enough common sats between base and rover to calculate the centimeter-accurate position in such a case.

Also, the Reach M+ antenna requires a ground plane to reduce multipath.

So, I’d suggest starting with raising the antenna higher and placing it on a ground plane.

Reach M+ can work with a multi-band antenna. However, it can hardly improve your results a lot. You can achieve the same results with a single-band antenna placed on a ground plane.

Tore is right: Reach M2 requires multi-band corrections from the base to operate correctly. A couple of multi-band devices can indeed work in more challenging conditions. However, it’s better to place the antenna as higher as possible, especially if you work with the ground vehicle.

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Thank you Svetlana, we will give it a try.

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