Gps and Missions

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Gps and Missions

Postby pilotnbr1 » Thu Mar 10, 2016 4:11 pm

So as I continue to tune and explore my quads abilities I am so far unimpressed with my gps antenna. I get a 3d lock in about 30 seconds upon power up. Once I start flying the quad it often degrades to a 2d lock. Is this common? I feel like I had a more reliable reception with my old diopole, although less acurate... I am running-

32db High Gain CIROCOMM GPS Active Built-in Ceramic Patch Antenna 38*38*6mm

Dielectric antenna
- Center Frequency: 1575.42 ± 3 MHz
- VSWR: 2:1
- Bandwidth: ± 5 MHz
- Impedance: 50Ω
- Highest gain : > 3dBic Based on 7 × 7cm
- Gain Range : >-4dBic at -90 ° <0 <+90 °
- Antenna polarization: RHCP

Amplifier / filter
- Amplifier gain: 30dB
- Noise Figure: 1.5dB
- Filter band attenuation
- 7dB Min f0 + /-20MHz;
- 20dB Min f0 + /-50MHz;
- 30dB Min f0 + /-100MHz
- Output VSWR: <2.0
- DC voltage DC: 3V --- 5V
- Power: 10mA

Specifications:
- Weight: 7g
- Size: 38 * 38 * 6 mm
- Cable length: 10cm
- Connector type: IPEX
- Line color: black

I do not have a groundplane beneath the antenna :? ... I know I need to add one. Anyone familiar with my current antenna or should I just go buy the recommended 35mm toaglas? and of course add a groundplane..

I have another question regarding missions. I am assuming I will need to do some tuning of my nav pids. What happens when the quad misses a waypoint? Does it turn around and try again? Or loiter?

Thanks guys!!

Luke
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Re: Gps and Missions

Postby LPR » Thu Mar 10, 2016 5:13 pm

You need good GPS to fly with an autopilot. With a good ground plane and an open area I get a Hacc of less than .5 m/s.

If you are dropping to 2D lock your Hacc is over 3.0 m/s. Your antenna should work much better than it is. Just add a ground plane around 3 times as big as your antenna and be sure not to have the antenna too close to other antennas and the flight controller.

With the QGC you can see the Hacc on the data page when you turn on the Mavlink telemetry.

Larry
Last edited by LPR on Fri Mar 11, 2016 2:44 am, edited 1 time in total.
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Re: Gps and Missions

Postby Max » Thu Mar 10, 2016 10:59 pm

Add a groundplane and get the antenna as far up as possible, away from all electronics. I had the same experience with a dipole being better than a 25mm patch, simply because it is further away from interference. Once I raised it up to the limit of the cable, the patch got much better.

-Max
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Re: Gps and Missions

Postby Max » Thu Mar 10, 2016 11:05 pm

pilotnbr1 wrote:What happens when the quad misses a waypoint?


It will try to get to the wpt no matter what. If the nav PIDs are too agressive then it may overshoot and then return... worst case it would oscillate back/forth around the wpt but never really reach the acceptance radius. If the PIDs are too low, it will be very lazy in navigating and may take a long time to reach the wpt (if at all). But the defaults are usually close.

Perhaps needless to say, but make sure everything else works correctly before flying a mission -- PH is steady and RTH works well. This should ensure the mission executes as well.

Cheers,
-Max
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Re: Gps and Missions

Postby Simson » Fri Mar 11, 2016 11:15 am

If you are using a M4V2 you should use a taoglas, otherwise you will not receive Glonass Satellite's.
At the beginning I had also the cheap Cirocomm and after I changed it, I had always very good Hacc.

https://viacopter.eu/multirotor-shop/an ... pter-store
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Re: Gps and Missions

Postby pilotnbr1 » Fri Mar 11, 2016 2:11 pm

Thanks for all the good advice guys! I'll let you know how it goes.
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Re: Gps and Missions

Postby pilotnbr1 » Sat Mar 26, 2016 3:25 pm

I ended up putting the antenna on a 6 inch mast above the quad. Now my hacc is about .9 - before it used to be about 2.5. Still no shield.
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Re: Gps and Missions

Postby aBUGSworstnightmare » Sat Mar 26, 2016 9:12 pm

pilotnbr1 wrote:I ended up putting the antenna on a 6 inch mast above the quad. Now my hacc is about .9 - before it used to be about 2.5. Still no shield.

During initial testing of Linux in RPi I've put a M4r6 + 35mm GNNS + shield next to the open window: 0.8m or less
I would opt for a shield
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