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Old Mar 08, 2011, 07:29 PM
Oopss. Oh well.
borneobear's Avatar
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Video Receiver RSSI overlaid in OSD

There are products that show video receiver RSSI such as this one:
http://www.dpcav.com/xcart/product.p...2&cat=0&page=1

But this doesn't help when you've got goggles on during flight.

Is there any manufacturer that produces anything that can overlay the Video Receiver RSSI into the video display?

Or something even simpler - a warning buzzer if the RSSI drops to 50%?


Cheers,

BB
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Old Mar 08, 2011, 07:31 PM
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Quote:
Originally Posted by borneobear View Post
There are products that show video receiver RSSI such as this one:
http://www.dpcav.com/xcart/product.p...2&cat=0&page=1

But this doesn't help when you've got goggles on during flight.

Is there any manufacturer that produces anything that can overlay the Video Receiver RSSI into the video display?

Or something even simpler - a warning buzzer if the RSSI drops to 50%?


Cheers,

BB
Check out the FrSky transmitter modules with telemetry receivers.
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Old Mar 08, 2011, 07:38 PM
NDw
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You mean the Video rssi rather than rc rssi right?

I was thinking the RMILEC was $10 - (now a bit more!) OSD could be used on the vrx side to display that, particularly if you bought a few whilke they were $10. As I think it can be used to display the rc rssi.
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Old Mar 08, 2011, 08:05 PM
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Any voltmeter will do:

Poor man's RSSI monitor
Since the video receiver has an RSSI pin, and I figured that sort of information would be helpful, I hooked up a cheap multimeter I had laying around to the RSSI. For my receiver a strong signal reads <1V while no signal is 2-3V. Now I can monitor both background signal as well as signal strength coming from the plane without having the video cut-out first.

0.98V when the transmitter is on and nearby


2.29V when the transmitter is unplugged. (Likely the antenna is still picking up emissions from the BECs and monitor as when it is away from all that it reads >3V...again even more useful info).


Besides, it let's my spotters feel more like co-pilots when they get to monitor RSSI voltage and other data. Spotters also are voice activated so you can get an audio feed of your RSSI data in real-time, on command .

Otherwise, you'd need a second OSD on the receiver side over-laying the RSSI info onto the video stream. Not sure if anyone is doing this yet.
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Old Mar 08, 2011, 10:17 PM
Oopss. Oh well.
borneobear's Avatar
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Quote:
Originally Posted by NDw View Post
You mean the Video rssi rather than rc rssi right?

I was thinking the RMILEC was $10 - (now a bit more!) OSD could be used on the vrx side to display that, particularly if you bought a few whilke they were $10. As I think it can be used to display the rc rssi.
Quote:
Originally Posted by llamero View Post

Otherwise, you'd need a second OSD on the receiver side over-laying the RSSI info onto the video stream. Not sure if anyone is doing this yet.
Yes, I was thinking of along these lines.

But don't quite know how to do it. ... like, how do I tap into the Video Receiver video stream?
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Old Mar 09, 2011, 12:59 AM
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It's pretty simple to overlay video RSSI with the rmilec OSD. At least on my Fox 800 VRx, there's an RSSI pin coming out of the internal tuner (metal box) in your video receiver that you can connect to the 2nd voltage input on the Rmilec OSD. One downside is that the 1st voltage input of the OSD requires at least around 6.5 volts to power the OSD, so you'd need to connect it to the DC input of your VRx or similar. The 2nd voltage input on the OSD registers from around 0.3v to 18v so it can go to the RSSI pin. The result will be 3 values from left to right (V1=VRx lipo voltage, timer, V2=RSSI voltage). You will not be able to turn off V1 or the timer, but can position the on-screen info at several places from the top to bottom of your screen. You could easily install the OSD inside your VRx.

With that said, I feel that on-screen video RSSI is all but useless. During FPV, there are essentially 2 conditions where video signal becomes degraded, and an RSSI indicator doesn't really help in either circumstance. If your plane goes down and if your very, very lucky enough to still be getting a video signal at ground level, then RSSI might help you locate it.

Condition 1 - You fly behind an RF attenuating obstacle (be it a building, the ground, or your plane's lipo). On-screen RSSI won't in anyway prevent you from doing this; nor will it help after the fact.

Condition 2 - You gradually fly away until video signal is lost. The slowly increasing level of graininess and static in your picture will be a much larger indication that it's probably time to turn around, than an on-screen RSSI value. RF propagation isn't linear, so RSSI voltage won't be as helpful as you'd think in gauging remaining range either.

I am a big believer in having an RSSI indicator of your R/C control link because it's something that often shows no sign of weak signal until it fails. Even my best analog 72Mhz Corona RD802II receivers won't glitch and simply loose link when out of range.
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Old Mar 09, 2011, 01:01 AM
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Quote:
Originally Posted by borneobear View Post
Yes, I was thinking of along these lines.

But don't quite know how to do it. ... like, how do I tap into the Video Receiver video stream?
Maybe you could use a second osd on the ground, after your VRx but before your goggles? Set up a screen on that OSD with only one parameter, perhaps for instance, an ET osd and use the RSSI parameter. Instead of the RSSI from RC Rx, you use the RSSI from the ground station Vtx. I think they have similar values. Set it up in the wizzard as you would normal, presto, Vtx RSSI on video overlay. Only thing is I dont know what will happen running video with overlay (off plane) through another osd. I dont think it would be a problem provided any telemerty is already used.

I have the spare gear for this, maybe I have a go and let you know if it works.

George.

EDIT: ^^ What Patrick said!
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Old Mar 09, 2011, 01:12 AM
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would be great eagle tree osd pro support it, i think that isnt so hard to do it, we could connect rssi pin wires from receive to eagle eyes ground station, then it would add these informations (rssi) on video out, its possible ?
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Old Mar 09, 2011, 09:49 AM
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basically you'd like to know when it's going too low, so maybe an audio indication can be sufficient ? a beep when the signal is weak should be quite easy to do.

or if you are looking for a complicated way to do it, connect somehow the rssi to a channel of your RC TX. This will control a servo which moves a needle or small flag which is seen by the camera...
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Old Mar 09, 2011, 11:36 AM
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Use something like Remzibi OSD on video line of your groundstation - you can display what you want, where you want.
Or one of the MAX OSD projects boards and do your own.
But really your eyes are best RSSI ! If picture is crap time to turn around and come home!
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Old Mar 09, 2011, 12:22 PM
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^ +1

I second Shikra's post. Most video drop outs are due to multipathing, not lack of signal strength. RSSI does not indicate mutipath intereference and thus is of no practical use.

On top of that, RSSI is logarithmically scaled. It is very hard to get a definite "turn aruond at weak signals as the RSSI is not well defined in the lower ranges.

-Alex
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Old Mar 09, 2011, 08:52 PM
Oopss. Oh well.
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Thanks for all the great input guys.

If the Video receiver RSSI is not linear to strength and distance, than it is certainly useless for anything (other than maybe antenna modding ).


Back to the drawing board.

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Old Mar 10, 2011, 12:12 AM
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Here is an article studying the feasibility of using the rssi to measure distance, it doesn't work well, but you can be interested by their study of the relationship between rssi and distance.

http://www.docstoc.com/docs/26290971...ion-Algorithms
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