Vector GPS and Lawmate v3 1.3G (intl) interference. - RC Groups
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Nov 19, 2016, 05:05 PM
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Vector GPS and Lawmate v3 1.3G (intl) interference.

Hello, when I start the vector with my Lawmate v3 1.3G video tx plugged in, the GPSdoesn't get a fix.

If I unplug the video tx, the GPS immediately gets a fix. I then plug in the video tx to monitor the number of satellites on my FPV monitor. Within a few minutes, the number of satellites drops back to 0.

The GPS is fixed on shelf on top on my dragonlink receiver at the back of my plane (MyTwinDream), while the video tx is near the front of wings in the middle of the plane.

What could I be looking at in terms of GPS interference? Do I need to shield some cables, and if so which ones? Place copper tape underneath the GPS? Would switching to a different video channel help?

I'm looking for ideas or feedback from people with similar hardware or difficulties with the Eagletree and the Lawmate video tx. Any tips would be much appreciated.
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Nov 21, 2016, 09:04 AM
JohnET's Avatar

1.3ghz is known to cause interference with GPS receivers. You will either need to separate the 2 devices as much as possible and/or add a filter such as one of these (no guarantee this will fix the issue);

It is also possible there is an issue with the video TX.

Regards, John
Nov 21, 2016, 03:09 PM
Registered User
Hi John, thanks for the reply. I will get my hands on a 1.3Ghz notch filter and let you know how it goes. I will also try adding a few ferrite rings here and there to my setup.
Nov 21, 2016, 05:04 PM
Registered User
I wrapped the GPS cable four times in a ferrite ring, and I immediately got improvements (rings that are often on ESC cables). I added one to my VTX cable as well. Within 2 minutes I acquired 7 satellites, which is not awesome, but way better than having no satellites at all.

I will pursue my investigations to see if I was just lucky or if this is actually going to be a solution for me.
Feb 15, 2017, 08:42 AM
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Hey! I'm currently looking at buying the lawmate v3 but having a hard time finding review about it. How does it work for you??
Feb 20, 2017, 03:34 AM
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wazoo22's Avatar
Originally Posted by Kija
Hi John, thanks for the reply. I will get my hands on a 1.3Ghz notch filter and let you know how it goes. I will also try adding a few ferrite rings here and there to my setup.
Not a notch filter. A low pass filter cuts the transmitted signal above the intended frequency. A notch filter takes out whatever frequency the notch is tuned for.
Not being picky. It matters.
What you need is a LPF, most likely.
I'm surprised that you are having this much trouble. It's quite possible to design the transmitter to do the filtration internally, and that should be the case here. Failing that, the toroids are an excellent idea.
We are gradually graduating from the world of outdated surveillance equipment- cameras, transmitters and receivers, etc.
and it can't come too soon for me.
Feb 22, 2017, 07:59 AM
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I finally get my hand on a lawmate v3 t1012-pro and unfortunately, it is really underpowered. I don't recommend this product at all :/
Feb 22, 2017, 07:49 PM
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sdigrazia1's Avatar
Originally Posted by marcus le renard
..."unfortunately, it is really underpowered."

I assume you tested its output, or is this based off range experience flying with it? Just curious, I have one that is part of a build that I haven't tested yet.
Feb 23, 2017, 12:53 PM
Registered User
Don't have a RF meter on the ground so it was up in the air at 1000m . I've been out 7.4km and it just became unflyable.
My setup:
in the air: TrueRc singularity
on the ground: RMRC vrx with comtech tuner and madmushroom.

With my rmrc 800mw vtx, I can go up to 10km with that setup so I expected a bit more with the 1000mw :/ (didn't expect much, just replacing the 800mw because well, it handles a couple of crash and some swimming in the ditch, not reliable anymore)

Let me know if yours works fine!
Mar 13, 2017, 03:22 PM
Registered User
Update: getfpv exchange the 1st one I got and this one is working better. Been out to 10km, witch is enough in my opinion for a 1000mw vtx (with omni).
The unit is very lightweight!!
May 16, 2017, 09:01 AM
Registered User
So the season started a bit late here in Canada, and I was finally able to continue troubleshooting my GPS fix issue. In the end, changing vtx channel from 1280 to 1360 seems to make a huge difference. This weekend I flew with 22 satellites! On 1280 I would get between 5 and 9 stats, and would lose fix when the plane was banking.

Next step for me is to troubleshoot the limited video range.
Jul 19, 2017, 05:00 AM
Registered User
deleted. sorry