Video interference with 3DR 915 Mhz - and 900 Mhz video

I'm not sure what I was thinking, but I had a cheap radio system that runs on 900 Mhz

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

Actually, I do not use this camera but a GoPro and I have upgraded the antennas.

And then I thought I read somewhere that it was possible for both the telemetry and video to both function in the 900 Mhz together...  So I purchased the following

https://store.diydrones.com/3DR_RadioTelemetry_Kit_915_Mhz_p/kt-tel...

Well, the telemetry seems to work fine and the video is amazingly distortion free........ until I turn on the motors.  Then the video goes black and white with a lot of distortion.  Sometimes when in the air the color comes back but only briefly.

  

So I'm thinking I need to change frequency of either the telemetry or the video .... or does somebody have a better idea?  And most likely it will be to upgrade the video system.  But then I'm not sure what would be the best frequency or system.  Any ideas or thoughts would be welcome.

Thanks,

Rick

Tags: 3dr, 900Mhz, interference, telemetry, video

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You said it yourself... video and telemetry work fine and the motors/ESC are causing interference.

So changing the frequency isn't going to help you.  More expensive gear with better front end filtering might help, but that is just ignoring the real problem.

The EMI could be coming from the motors, the ESCs, or the PWM signal wires.  You could also have power supply issues causing noise in your power.  Without a scope your only real option is to move things around and see how it affects the signal.  If moving things around doesn't change the interference then you have a power supply issue.

Somehow, need to merge the two threads. http://diydrones.com/forum/topics/question-on-frequency-interferenc...

 

We got this one solved, all it needs is the filter installed and done. Point being, this should be a good thread for those who want to know if you can run both 900MHz video and 915MHz 3DR radios, and the answer is, YES it works fine.

Just keep noise out of the video link as those transmitters are prone to common mode noise and will amplify any noise on the power wires. Standard LC simple filter on the power will stop the noise.

Vernon,

I guess I am a bit surprised that it is working so well.....again I plan to do some type of distance test tomorrow, but what I saw this evening was the difference between day and night (no pun intended).  

I have this pair of antenna on the video system :  http://hobbywireless.com/index.php?main_page=product_info&cPath...  And again I am amazed at the clarity now.

So if I started having trouble with the 3dr 915 Mhz telemetry would another set of these exact antennas work?  

I mean besides it looking very strange on the copter, it just seems like it would cause major interference .....

Thanks again for all you help,

Rick

I have used 3DR Telemetry with Hobby King 900MHz video tx, on channel 2, 3 & above, no interference.

There is interference observed at channel1.

Thanks for that info! I assumed something like that might be the case, but only testing can prove it.

what freqs are you using for your 3dr rx-tx?  I'm seeing interference with my 3dr setup with 'presumably' the same hobby king set up.  I can't get mavlink to connect when I have the video turned on. (different power sources, not a shared battery, not a shared ground).

It says tuned to 910MHz, so it may not work as well with the 3DR 915MHz . Stuff like that matters a lot. The RF energy will be reflected back to the module, rather than going out to the air. It's close so only testing will prove how far it's off.

 

I wouldn't get hung op on interference in this case, either way, you are radiating the energy. The only real problem is that if the antenna is not tuned to the frequency, then the RF energy goes back to the module and might then travel through the rest of the wiring. Being that they are out of stock anyway, contact them and ask for a set tuned to 915. Being that they obviously did the math to determine wire length and bends, they can plug 915MHz into their calcs and make one that is tuned for your radio. You could mke your own, that looks like #14 solid house wire anyway. The calcs and info are online.

Vernon,

OK I salvaged an old PC and found some interesting parts....

Here is a pict of 4 coils....not sure which would be best?

Also I found a few caps (see pict) that may work....again looking for your advice on which may be the best?

I may just solder them on a board and put a couple connectors on it and wrap it in heat shrink tubing ...yes?

Following the diagram as in the attachment.

Thanks again,

Rick

Attachments:

Maybe old answer and you already did solve...

I have same combination as you and I did add this filter and this woks fine for me.

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