Due to the poor GPS performance of the Iris and issues on some of them where the GPS presses down on the Pixhawk causing a wide array of other issues, i just ordered a mast kit for the Ublox GPS.

It will take custom cuts int the top cover so it will have a slot for removal but I'll figure it out when I get all the parts.

My GPS has been sent back for replacement and I have asked 3DR not to remove the protective cover from the new GPS. If they don't follow those instructions I won't be able to use the mast kit.

Anyone else tried this? 

Mark Prince

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Since installing the mast on the Iris I have had 25 completely trouble free flights. Many of them autonomous missions. Every single flight maintained DOP values of less than 2. Sometimes values as low as 1.2. 

No compass issues either. IT now flies the way I would have expected it to out of the box over 100 flights ago. The Ublox module pressing down on the Pixhawk causes MANY random problems.

Even though 3DR has yet to provide advice for a fix after several queries I can say that support otherwise has been excellent. They have a replaced a motor and a GPS free of charge and without question as well as the longer motor bolts. All other purchases I have made have been delivered and handled in an expedient and professional manner.


Did you recalibrate everything after putting the GPS module up on the mast? Getting the mast today. After the last firmware, I was suddenly unable to take off in my garden. DOP about 2.7.

Looking forward to trying out the mast solution of yours.


After installing the mast it was totally different. I always get HDOP less than 2 and sometimes as low as 1.2.

pic is attached.

Hi Mark, I'm following your guidance and mounting the primary GPS (and compass) to a collapsible mast on my IRIS+.

I have a question when mounting the GPS mast to the frame that will help me, did you use screws or epoxy to secure the mast to the frame? I ask this as the screws must be very shallow so not to interfere with the LiPo battery below.

In my case I've reduced the length of some plastic screws I have on hand and used that in combination with epoxy to secure the mast. Thanks for the inspiration, I'll post some build photos once my new GPS arrives! :)

I used the screws and nuts that came with the mast. They do protrude slight into the battery compartment but do not interfere at all with the IRIS+ 5100mah battery. Eventually the pivot pin vibrate out of the mast. thats why you see the hose clamp


I am thinking of doing this mod on my Iris+... looks pretty straightforward and the mast is only $10.  I assume that the GPS modules in our birds don't have the protective cover so where did you get one of those without buying a whole new UBLOX GPS compass unit?  Does anyone here have one of those covers from a replacement laying around that you would part with?

At the time I was making the modification I was having so many GPS related problems that I had swapped my GPS module for a new one. When I got the new one the cover came with it. Otherwise I was in the same boat as you. Seems like 3DR would have some of these laying around since so many IRIS+ have been sold unless they are buying the model without the shell.

My IRIS was one of the original consumer versions sold in late 2012. It has since been upgrade to the Iris+. I still have the mast on it and I am running 3.2. The bird is very stable and reliable.


hi Mark:

I also have an IRIS + (actually replacement IRIS+ from March 2015) and haven't had many GPS issues and my Hdop is typically low 1.4 to 1.7.  The caveat here is I usually have 9+ sat.  I like the idea of the GPS on the mast and may do this to mine as well to improve communication.  Do you know if there is a similar mod to enhance my FPV range & Quality?   I'm usually only 100m out before my video craps out.  which is scary when you can't see where my bird is.

Mark T,

The only way to improve FPV range is to get better gear.  One relatively easy thing to do is replace the FPV transmitter with a more powerful unit.  Take a look at Boscam or Immersion RC 600 MW transmitters.  I just got the Boscam but havn't installed it yet as I need to get a couple of wires and connectors to make it work without too much cutting and soldering.  Also make sure to use the cloverleaf antennas and not the little staright plastic ones for FPV TX and RX. 

Mark T is correct. I use the Immersion RC 600 MW transmitter and Fatshark googles with the IBCrazy Blue Beam antennas. I mounted the transmitter in front of the battery door with 10 lb velcro. I'm not sure of the range but I have never needed more with this setup. I use the exact same setup on my qav250 but the range is not as good since the 250 is always much closer to the ground and sometimes near a lot of trees.

I did have to make a custom connector or two but it's worth it for the extra range. I use the Gopro video cable 3DR and I got the transmitter from getfpv

Thanks Mark, and for the tip on the pivot pin, here's the mod with the mast pointing forward. Just waiting for the wind to die down before connecting my T-2D gimbal back up :)


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