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jalves

wireless video, types of interference, could you chime in?

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Hello all,

To tell the story short, I need your help (knowledge) to figure how to remove some nasty interferences from my video system, in order to increase my FPV pleasure.

So, Thanks in advance!

I fly today my Easyglider, the video section has a MSH36 camera, a switching type bec to provide 5,5V to a Fatshark/aeropix 500mW video Tx and a 3 (2?) dbi whip on the Tx. The power to this combo is provided by a 3s dedicated lipo (12V to camera, 5.5V via bec to Tx).

The Tx is in the EG rear, almost in the tale, coaxial video line, coaxial power line, camera in the front (canopy), bec in line with trailing edge of the wings, lipo in the middle(in the battery tray), no osd or gps.

In the ground I use the Fatshark goggles integrated receiver, also with the same 3dbi whip.

You can see here http://www.vimeo.com/2622926 the type of interferences the system suffer.

What is odd to me is that I didn't go to far (maybe 1000m) and the video glitches just happen without warning, even when the image is clear.

What are your opinions regarding this type of interferences?

multipath?

nodes?

bec EM noise?

esc noise?

...?

jalves

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For the type of flying you are doing, a 3dBi whip on the Rx is not the best solution. I think you should use a 5-8dBi patch antenna. For best results, use a diversity Rx with both a patch and whip together.

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If you are flying overhead then signal tranfer will be at its worst. Try a circular patch on the RX or a helical. Maybe worth putting your TX aerial on its side at the same time.

Terry

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For the type of flying you are doing, a 3dBi whip on the Rx is not the best solution. I think you should use a 5-8dBi patch antenna. For best results, use a diversity Rx with both a patch and whip together.

Thomas,

I know your connection to the oracle, I am leaning towards it. But, it will the oracle plus two receivers solve this kind of interferences?

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Maybe worth putting your TX aerial on its side at the same time.

Terry,

Could you elaborate more the idea above?

Yes, the signal comes from the sides of the aerial not the end so if you mount the tx aerial horrizontal then the maximum amount of signal will be sent down to the ground. This will only work if you have a circular polarized aerial on the RX or use 2 aerials set at 90 deg polarization to each other with a diversity switch (oracle).

I only say this as it seems you fly very high above yourself and not way out to one side as then a different set up would be better.

Terry

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A popular way to help reduce the multipath nuisance is to use a 5-8dBi patch on the Rx. These have a narrower beamwidth than an omni and that helps to mask the issue. A diversity system like the Oracle will help even more because of the advantages of spatial diversity from twin antennas.

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I agree the interference appears to be multipath, if you are flying high overhead then the signals bounced off ground objects will be worst with an omni as Mr RC-CAM says. Thats why I say go for the setup I said as it will reduce multipath a lot while giving the best pick up of the direct signal.

I take it you were flying high overhead ?

Terry

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I agree the interference appears to be multipath, if you are flying high overhead then the signals bounced off ground objects will be worst with an omni as Mr RC-CAM says. Thats why I say go for the setup I said as it will reduce multipath a lot while giving the best pick up of the direct signal.

I take it you were flying high overhead ?

Terry

Only in the beginning and in the final approach to land, I almost always approach twice to land in the end.

Terry,

I understand your idea (putting the Tx antenna horizontal spread the "donut" over my head/video receiver), but what happens when the plane is 1500m away from my location?

My idea is that the receiver will only "see a point" as a transmitting antenna, thus decreasing the signal trough the receiver. am I wrong?

Is the GP patch a good solution ?

I did a GP patch for 1,2GHz in the past with great success, I may build one for 2,4Ghz.

Is it important to build it with different materials as plates, or may I use the same type of foil?

Is the thickness of the foil important?

Thanks for your valuable help

jalves

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but what happens when the plane is 1500m away from my location?

Ahh, in that case its best to keep it vertical but as mr RC-CAM says a patch will help.

Is the GP patch a good solution ?

Yes a very good place to start, it may very well cure your problems.

Is it important to build it with different materials as plates, or may I use the same type of foil?

Is the thickness of the foil important?

Yes and no, build it with whatever you can get your hands on, any changes will have an effect but the good news is its hard not to get a good improvment over the basic aerial.

Terry

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As said, start by getting a nice patch antenna. Note however that if you want to fly at such altitudes you'll have to point it about 45° towards the sky for best results, which isn't what the fatshark are the best for with their integrated receiver if you don't want to have to be looking up all the time (can get hard to mount the antenna on it, need to fix it to a cap and link with a coax cable or something).

From the reports I've seen about it, people seem to agree on the fact that the integrated receiver is fun for beginner / easy short range flying, but less suitable for long range due to antenna mounting and low sensitivity, at which point they change for a better external receiver and proper antenna setup.

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I use today a separated receiver (airwaves 634 based), put a alu reflector over the whip and the video quality reception increased a lot.

What kind of receivers (make and model) are you folks using with good results?

And in the Tx, are you using a 3db whip or a ground plane antenna (the one with 4 spikes 45 degrees down)?

Recommendations?

TIA

jalves

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Not sure what make mine is as it seems to be unbranded, I just use a basic 3dBi dipole type whip for best all round signal.

Terry

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Jalves,

a switching type bec to provide 5,5V to a Fatshark/aeropix 500mW video Tx

That BEC might the cause for the interference, have you tried a linear regulator just to see if that fares any better?

Cheers,

Sander.

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Jalves,

That BEC might the cause for the interference, have you tried a linear regulator just to see if that fares any better?

Cheers,

Sander.

I will replace the bec with a 2s lipo, The fatshark has a internal linear regulator (it does build heat with ease).

We shall see then, when the rain here stop...

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From what is seen on the example video, the symptom does not seem to follow traditional BEC noise characteristics. But a failing BEC could cause intermittent voltage loss and perhaps short lapses in video.

Because the problem appears to be common multipath interference, I'd recommend trying the DiY GP Patch antenna on your Airwave Rx (direct connect, no coax) at some point. Keep in mind that you'll probably need someone to casually aim it if you fly directly overhead or behind your flight line.

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HEllo all,

Solve my video problems!

Bought a 8dbi patch and mounted in a tracking device.

Now have clear video except above my head.

You're right regarding the use of a patch.

Thank you all for your valuable help.

Jalves

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