10 replies to this topic

[newinfpv]

Hi

I am new to FPV. Need some advice on how to identify the type of interference appearing in this video. This seems to improve a little bit when I switch to a patch antenna.

Thank you in advance!

Link

[Kilrah]

It would help to know what equipment you have, a video alone doesn't say much...
Video frequency? power? What about R/C? etc...

[Mr.RC-Cam]

Besides the homework requested by Kilrah, I'd like to see some photos of the Rx ground station's antenna that shows how you aimed it during flight. Also would like to see the Video Tx/antenna installation on the heli.

My general gut feeling is that the interference issues are not bad at all considering that you are flying close to dwellings, offices, and an assortment of other common trouble making sources.

[dleroi]

My general gut feeling is that the interference issues are not bad at all considering that you are flying close to dwellings, offices, and an assortment of other common trouble making sources.

Mr. RC-Cam,

I was about to suggest multipath interference. That's what you're saying, right?

- Don

[newinfpv]

Hi guys

Sorry for the late reply.

This is the specification of the gear I am using

Transmission Frequency : 1.4GHz / 1.5GHz / 1.6GHz
Output power : 1W/1.5W
Modulation Mode : FM
Radio Channel : 12-CH
Unobstructed Effective : Range 800 to 1500 meters
Video Output : 1Vp-p-AT-75Ω , S/N>38dB
Audio Output : 10KΩ/200mVp-p

Edited by newinfpv, 28 January 2010 - 07:24 AM.

[newinfpv]

This is how the camera unit is mounted on the heli. Antenna is parallel with the tail boom as shown.







FPV platform

[newinfpv]

These are the pictures of the ground station setup.




Unfortunately, I do not have the photo of the ground station in the field. What available is a still footage from the video. The ground station was placed on the roof of the car. The patch antenna is in the red circle, it was placed just like the photo frame on your desk. Both types of antenna were oriented vertically during the recording.

[newinfpv]

Close up of the camera unit

[Mr.RC-Cam]

My suggestions, all equally important:

(1) The Tx's antenna must be vertical; The horizontal orientation will cause a performance decrease. The Rx's Patch antenna orientation must match.

(2) Move the patch antenna off the car roof and set it up on the grass field. Try it close to the ground, as well as test it up on a four foot tall Tripod. I suspect close to the ground will be best for your environment, but check both ways and decide for yourself.

(3) Try other video system frequencies to find the one that has less external interference.

(4) If the problem persists, perform test flights in a wide open area that is far from mankind. If you still have bad performance there, then the wireless video system is defective or very poor quality.

[newinfpv]

Hi Mr Rc-cam

Thanks for the tips.

Is it true that high power TX will cause drop out when used in build up area?

http://www.rc-cam.co...ideo-tx-system/

[Terry]

I'm not sure why it is but I get less drops with a 10mW TX than a 500mW TX when I fly from a grass area between buildings. I'm guessing the higher power just gives many more reflected signals that are strong enough to effect the wanted signal. As has been said there are other ways to minimise this apart from lowering the TX power but if you can get away with less then its a good way to go. You also get less on board interference and can use a smaller battery. If you only have buildings on one side then your patch should handle this. Could you mount your TX on a servo so it can be swung down vertical below the skids after take off? This is what I plan to do soon.

Terry