Strange GPS behavior, 3d Fix, but always HDOP of 100.00?

I’m running dual GPS on my cube on AP 3.6.5. Everything was working great last I flew, with excellent position hold. Now I’m getting some very conflicting information on mission planner. I can’t arm in loiter or poshold due to high HDOP, despite the fact that the HUD says 3d fix and my position is correct on the MP map. Even after leaving it in clear view of the sky for 10 minutes it only picks up 7 satellites and gets to 1.1 on HDOP. Previously it’d pick up 15 sats and average a HDOP of 0.7 in a minute or so. Any idea on things to check? I’m feeling somewhat discouraged as it had the best GPS performance I’ve seen so far on this rig. I’m using an MRo GPS on gps1 and Matek M8Q on gps2.

I forgot to mention I’m running GPS blending.

This might not be much help, but recently I got a new GPS, and for over a week couldn’t get any lock, or just 4-6 satellites… I thought it was defective… Then suddenly a few days ago it started working great! 12 satellites in a few minutes, inside!
And, I’ve had that happen other times in the past. I don’t know if it’s local interference or the coverage of the satellites on the days I was trying to fly…
But basically, I have had vastly different results on different days or weeks, with nothing on my end changing. And strangely, different GPS’s have different results on different days… Some days GPS A might only get 4 sats and GPS B gets 12… Then the next day they both get 18…
I’d say don’t get discouraged if it’s just been a day or two of poor results.

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Thanks for the kind words. It’s been a couple weeks of poor performance. Prior to that I had no problems for the couple months since I installed the second gps.

Has else changed on your copter? A different camera or other electronics could cause interference…
And if it is interference or cloud cover weakening the signals, ground planes actually help. On my small copters where the GPS is mounted to the top of the frame, I cover the top of the copter w/ grounded copper foil and mount the GPS in the middle. On bigger copter w/ a mast, I’ve cut out disks of thicker copper foil or unetched copper clad PCB.

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