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Terry

Is the end in sight for 5.8Ghz already?

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I am starting to see wifi gear with the option of using 5.8Ghz recommended because its clear!

Is it time to give up and admit defeat?

Terry

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Not in Europe at least, the band ranges between 5180 and 5700. The usual 5.8GHz band we use for video is clear.

http://en.wikipedia.org/wiki/List_of_WLAN_channels#5.C2.A0GHz_.28802.11a.2Fh.2Fj.2Fn.29

I have a dual band N router and my 5.8 video is perfectly clean. Now if it would give me more than 300m of range, with 200mW, I'd use it more...

Edited by Kilrah

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Ahhh thanks for that kilrah, not time to give up flying and take up golf just yet then :)

Terry

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All this interference stuff continues to beg the question: What can we hack to create a useful (good range, low cost) digital video link? Such technology should significantly reduce (possible eliminate) common interference issues. At this point I would even be excited by something that had latency issues if cost was low and image quality was high.

Perhaps those cool HD room-to-room video senders could be a starting point. Their range is only about 100 feet and the boxes are big. But remember the days when we took short range / bulky X10 cameras and hacked them for R/C video? Honestly, those efforts helped pave the way to what we enjoy using today. Perhaps some of that ingenuity needs to come back to the hobby. For sure, with all the cheap FPV systems out there, the hacking has come to a near stop; our laziness is starting to hurt us! :)

From what I have seen, the hacking discussions are just about dead. Would be nice to see some renewed interest in such things.

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I'd rather say the problem is that the required hacking with those new technologies becomes too expensive and complicated...

Those HD senders cost $600, and unlike our good old analog things where we can easily start poking and changing things most improvement attempts would hit the wall of closed proprietary software, in which the change might just be a simple bit to toggle but we don't have access to it...

And designing something from scratch in this field is so much more complicated than a video switch, OSD, LRS,... that nobody will want to do that as a hobby project...

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Is it not possible digital video will follow our digital rc with low power units having PAs fitted to get the range?

Terry

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From the info I have, those uncompressed HD transmitters use common 5GHz WiFi transcievers, with most of the protocol stripped and with some tweaks applied to achieve the needed ~1.3Gbps throughput.

One of the "tweaks" to improve data rate is to set a very low transmission timeout and send packets very close to each other, but it has the side effect of limiting range not due to RF constraints (power, sensitivity,...) but simply due to the time the signal takes to reach the other side, and the acknowledgements to come back to the transmitter.

If this is indeed true, you could amplify power to 1kW (providing you manage to get an amp that can handle a 1.3Gbps throughput with low enough distortion) and you'd still have your same 30m range, because beyond that packets would start timing out.

Maybe it's not the case for all such units, but at $600 per test set it's a little too much for me to bet on. At this point I'd be more open to shell out $4000 for a proven SD digital transmission system ;)

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And designing something from scratch in this field is so much more complicated than a video switch, OSD, LRS,... that nobody will want to do that as a hobby project.

I agree the complexity is off the charts. But, there is going to be someone with the desire and dedication to hack such things. We just need to encourage that fellow to get on with it. :)

Maybe it's not the case for all such units, but at $600 per test set it's a little too much for me to bet on.

When we start seeing the HD sender boxes for under $100, and their size has shrunk a bit, hopefully that will invite some hacking/experimenting projects to see if range can be increased.

At this point I'd be more open to shell out $4000 for a proven SD digital transmission system

Any chance you've played with the Teradeck Cube? It is a $1500 USD wi-fi based HDMI transmitter. Unfortunately latency is 250mS, but if it has useful airborne range (>300 meters) then that would give us hope that something cheaper/better could follow.

http://cube.teradek.com/

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Any chance you've played with the Teradeck Cube?

No, but I've had a look at it. At first they were advertising it for use with iPad, but they were using software decoding on the iPad at this time so had approx 10 second delays. Now they have the encoder and decoder pairs for $2500 that do meet the 250ms latency.

These would probably be good candidates for toying and getting decent range, but at 250ms, no flying, only live broadcast use which I don't need. Plus, the TX is heavy.

Also, it's a whole other problem to find an HDMI-equipped FPV-friendly camera.The only one that comes to my mind is the Toshiba S10, but only after modification, pan/tilt is excluded, and it's been discontinued for more than one year now. The others like the GoPro, Drift, Sonys,... only offer analog HD component signals (when they do at all). The ones with HDMI have awful form factors...

For the past few months I've been discussing with someone who's developing a small, <100gr, <50ms latency, multiple composite input digital SD transmitter with several kms of range, albeit at a higher price. They've had multiple development problems and delays, but as soon as I can I'll be throwing one in the air.

Edited by Kilrah

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At the moment I'm discussing with someone who's developing a small, <100gr, <50ms lantency, multiple composite input digital SD transmitter with several kms of range, albeit at a higher price.

That is good to hear. Even if it is high priced, it will help push things forward. Ultimately we need a Tx/Rx system that is <$500 retail with good performance and allow legal license free operation.

FWIW: Despite all the endless discussions about needing long range and ultra low latency, there are still plenty of users where these are not critical attributes. For example, there are those that use the hobby airborne video link for aiming their still camera, remote inspection/surveillance, slow moving mobile robotic applications, etc. These folks would love to see something that solves the Wi-Fi interference issues and eliminate the RF spectrum regulation limitations. So an affordable FCC / CE approved (license free) compact sized A/V system that has >15FPS performance and reliable 250 meter range is something that would be exciting to start off with. That should help transition to something with more performance to meet the needs of the common FPV user.

For the last 3-4 years I've been expecting some hint that this sort of thing will be commercially developed. Other than a brief bit of hope for nghobbies a year or two ago, nothing has happened. It is getting to be a bit disappointing and I don't expect a commercial solution will drive this forward. I think it will take a talented and dedicated hobbyist(s), perhaps aided by an open source project, to get things moving. So that is why I keep ranting and praying for relief from you hackers out there.

Besides, the Rapture was a bust and the world didn't end yesterday. So we all have plenty of free time to work on this. :)

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Ultimately we need a Tx/Rx system that is <$500 retail with good performance and allow legal license free operation.

That's what the one I'm waiting for is, minus the price thing. I don't mind, as there's simply no alternative at this point. Better than nothing.

The developer says the price could be substantially lowered, but at a batch size he doesn't believe he can sell. I personally think it's doable, but then again it's not me investing those huge amounts ;)

If demand is there and we can prove him wrong, we can hope for larger and cheaper subsequent batches...

So an affordable FCC / CE approved (license free) compact sized A/V system that has >15FPS performance and reliable 250 meter range is something that would be exciting to start off with. That should help transition to something with more performance to meet the needs of the common FPV user.

The problem is that the amount of effort in making an "average" system like you mention and a full-blown one actually isn't all that different. So better do something good from the start instead of a low end alternative that probably wouldn't end much cheaper.

Most of the effort is in miniaturising the thing and going away from the big 500gr boxes. But it seems not to be that easy if someone who actually already sells full size digital transmitters still has problems making the smaller version of the exact same after 1 year...

As we had a already discussed, there are consumer technologies that could allow such a thing and would be within the range of good hackers with all these HD cameras out there nowadays - but being consumer technologies they have such a short life cycle (barely 6 months) that the components (that are more or less plug and play) would already be obsolete and unavailable by the time someone can finish a development.

Avoiding that means full system development, and we'd need a group of very good specialists in this field to get going...

Edited by Kilrah

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The problem is that the amount of effort in making an "average" system like you mention and a full-blown one actually isn't all that different. So better do something good from the start instead of a low end alternative that probably wouldn't end much cheaper.

If creating the full blown solution is not much more work, then that is awesome. I'd love to see a perfected system make it to market, even it it was $5K. That should help end the discussions that digital video will (or won't) work fine for some of us. That will help drive what should come next.

Personally, I don't mind if the developer sets the bar lower and creates an average system; Demanding perfection at the start can sometimes derail things. Case in point: I'm still disappointed by the thread (on another forum) where ngobbies and Rotoconcept showed off their early prototype of a digital video RF link and presented a demo of it in a R/C car. Despite being a works in progress, the discussion quickly deteriorated because there was backlash from those that didn't feel it would be good enough for long range FPV. It was sort of like boo'ing the movie before it even started.

I don't think many R/C hobbyists appreciate that these types of designs rarely get the attention of the well funded developers. So those brave souls that try to develop these difficult designs are risking a lot because they are operating with fragile budgets. So when those of us in the peanut gallery start crapping all over their efforts we risk scaring them off and then everyone loses. It seems to me that sort of happened with that earlier project. Certainly anyone that helps advance the R/C model digital video revolution is going to win my boundless admiration and respect. I know it's not much motivation to offer, but I promise to cheer them on! :)

Hey Terry, sorry I took your discussion to another place. Please forgive me for the hijack!

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Interesting discussion. I've often wondered if the sheer physical limits of digital wireless transmission keep this from moving forward. The limits as i see them (and I have only the tiniest grasp of these things) are latency (due to encoding and processing) and the fact that digital video doesn't play nice when the signal gets weak. With an analog system, we just slowly get video deterioration, which we can fly through. With digital, you get full picture hangs, or worse. So, I wonder if the answer for this is a side by side system using digital for flying real time with high resolution and the analog running on a small separate screen as a back up in case the digital link fails?

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With digital, you get full picture hangs, or worse.

Not necessarily. If the encoding and protocol is "well made" (read appropriately for the purpose), you can also have a picture that first degrades, becomes blocky,...

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Also there would be no reason that the RX could not have an in built OSD that showed how strong and how good the signal quality was.

Terry

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there would be no reason that the RX could not have an in built OSD that showed how strong and how good the signal quality was.

For sure. Even that primitive digital video link I showcased a couple years ago had an onscreen RSSI feature in it. And even better, a digital video system could more easily incorporate a FPV OSD with colored graphics, not like that old-school B/W stuff the composite video OSD's offer. But baby steps, as they say. :)

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