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GPS Problems Help

PostPosted: Sun Mar 18, 2012 5:52 am
by grassiew
I am just getting into fpv and I have run into a snag. I have major issues with My GPS, I am running Cyclopes OSD 1.5 and a 400mw 1.2 GHZ video system with a low pass filter and the only way I can get any GPS signal is by removing the OSD and GPS from the plane and moving the GPS as far from the plane as its cable will allow. Even then its pretty slow to connect. I am assuming that my problem is either noise from the power system or the video transmitter. I have tried moving the GPS and transmitter further away from one another by about 6 more inches then they were positioned before and I have also installed chokes on all of the power wires. To no avail. Is there a way to fix this? Do I need to move my transmitter even further away? Its driving me mad and my OSD is mostly useless without it. Oh and this is all mounted on a skysurfer.

I really appreciate any help or information anyone can share with me.

Re: GPS Problems Help

PostPosted: Sun Mar 18, 2012 7:21 am
by RCModelReviews
This is one of the reasons that I'm not a fan of 900MHz - 1.3GHz video systems.

Most of them are amazingly noisy (from an RF perspective) and spew lots of interference right across the GPS frequencies and even the 2.4GHz RC frequencies.

You might find things work better on some of the video transmitter's frequencies than others.

Also, although the low-pass filters may help with the noise -- the GPS band and 1.2/1.3GHz video band are so close together that you won't get a total solution.

The best thing is to ensure that there is as much distance as possible between the GPS antenna and the video transmitter/antenna.

When I fitted the 200mW HK 1GHz (900MHz) transmitter to my EPP FPV plane, I found that the GPS performance was greatly reduced and the 2.4GHz RC range was more than halved. When I activated the return-to-launch function, the model took a *very* roundabout path back to the launch site!

Or, you can use 5.8GHz video and avoid the problem altogether.

Re: GPS Problems Help

PostPosted: Sun Mar 18, 2012 3:39 pm
by grassiew
Hello Bruce,

Thank you very much for your quick reply. I am a big fan of your Youtube channels and hope that one day I can make it to Tokoroa and fly with you guys. Your reviews and video continue to be a great help to me and are very entertaining. Keep up the good work!

You have confirmed all my suspicions. Unfortunately I didn't read about all of these issues until after I had invested in 2 receivers and 3 transmitters. I am going to mod my skysurfer today and move the transmitter to the tail. I hope this at least makes it usable. Then I am going to wait a few paychecks and get me a 5.8 system.

Of the 5.8 systems what mw would you recommend? I have heard several people suggest 500mw. Also do you know a good inexpensive site to pickup said 5.8 gear?

I really appreciate your help.



Re: GPS Problems Help

PostPosted: Sun Mar 18, 2012 10:48 pm
by RCModelReviews
I had hoped to have the 5.8GHz FPV backpack video/project pages up by now but I've had to make one small extra change so it will now be a few more days before those appear.

If you already have a camera then you'll be able to build the backpack and matching receiver for about US$50 or less -- probably a cheaper (and more flexible) option than the commercial offerings.

Stay tuned.

Re: GPS Problems Help

PostPosted: Sun Mar 18, 2012 11:24 pm
by grassiew
That is great. I have been waiting for the back pack build with great anticipation.

I do have a camera, in fact its the one you reviewed from security camera 2000. I made sure to mention I saw it on your channel.

Also I moved my transmitter to the tail of my skysurfer and the gps performs much better. In fact it was keeping its signal when I moved in the house. I can't wait to take it up but alas we have been having 75mph wind gust today here in New Mexico and even though I have gyro stabilyzed ailerons I figured that might be a bit much.

Thanks again.

Re: GPS Problems Help

PostPosted: Thu Mar 22, 2012 8:34 am
by Mark Hitchman
Another thing that helps heaps is to wrap all the GPS wires around a toroid, a lot of OSD units emit RFI for the GPS. I have only ever flow with 900mhz and if setup correctly you will not have any problems. I have now built a tricopter with an EZOSD and the vtx is less than 6" away from the GPS, all is working good.


Re: GPS Problems Help

PostPosted: Thu Mar 22, 2012 2:01 pm
by grassiew
Yah after my last post I was having problems again. It started working again when I faced the OSD a different directions. Which is weird. I will try your suggestion. I am building a tricopter right now and hope this works. Thanks for the tip.