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Mr.RC-Cam

5.8GHz / 500mW Wireless A/V System:

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If you had multipath problems using lower frequencies then 5.8Ghz may not be for you.

No, I drive out to a flying field in a more rural area now. I used to fly at a park closer to the city, although I think the problem I had was more related to having an insensitive receiver and/or strong adjacent interference than multipath because it didn't exhibit picket fencing.

Just trying to get a feel for how much of an issue it is. But it sounds like its not too bad at a typical semi-rural flying field.

Edited by kc6f

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Hello,

I have one more question. Can the Airwave 5.8GHz A/V Receiver with Patch Antenna receiver be powered using a 3S LiPo?

Thank you

Cyb

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Can the Airwave 5.8GHz A/V Receiver with Patch Antenna receiver be powered using a 3S LiPo?

Yes it can.

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Just trying to get a feel for how much of an issue it is. But it sounds like its not too bad at a typical semi-rural flying field.

Correct, its not a huge problem at all if your RX is away from buildings and metal objects. Infact I fly from a point 50ft from large electic pylons and using a 14dBi patch I get no multipath issues at all.

Terry

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That is very good news. I checked out the video you sent me (test results look great!) and I recognize the field as the one you've flown at many times before. So, comparing the 5.8GHz 500mW to your 900Mhz and 2.4GHz systems, what sort of differences have you observed in performance at that location?

Some more basic questions:

Can you post a photo of the Tx installation on the model?

Which camera was used in the video?

What exactly is your ground station?

What antennas did you use on the Tx and Rx?

Was a diversity system used in this test flight?

And more importantly:

Any chance you can post the video clip for others to see? :)

Finally a chance to reply! So sorry about all the delays. On to answer your questions: The 5.8 systems perform very well at my field compared to the other frequencies. Less dropouts, better signal. Since I don't fly out that far, distance hasn't been an issue. I was somewhere in the 1000 ft altitude range with the DPCAV 5.8 500 mw transmitter. The dropouts occur consistently over a known bad area of the field regardless of frequency. There are a lot of houses/buildings around. Perhaps interference on the other bands.

Camera used is this one http://www.123securityproducts.com/kpcvsn500nhb.html

Ground station is an Iftrontech 5.8 diversity receiver hooked up to a Sony MiniDV recorder.

The antennas I used were the stock dipoles provided by you and Iftrontech.

The transmitter and camera were taped to the top of the Funjet with the antenna pointing straight up.

And more importantly...video!

Edited by docphi

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That is an impressive distance! Time to add headlights to your model and fly it out further. :)

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... Camera used is this one http://www.123securityproducts.com/kpcvsn500nhb.html

Ground station is an Iftrontech 5.8 diversity receiver hooked up to a Sony MiniDV recorder.

The antennas I used were the stock dipoles provided by you and Iftrontech.

The transmitter and camera were taped to the top of the Funjet with the antenna pointing straight up.

And more importantly...video!

Wow! That is very impressive video. (and flying is also outstanding)

OMM

Edited by Old Man Mike

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OK the weather was fantastic this morning so I went for a long distance flight, I didnt push it to the limit but still got out to 3.53 miles. I dont intend to try and beat this any time soon so thats my limit for now anyway.

I used a 14dBi patch that was pointing way too high so 4 miles is not out the question.

Terry

Edited by Terry

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That is fantastic! For sure, thanks for performing the 5.8GHz/500mW system range testing.

The common buzz in those other forums is that 5.8GHz doesn't work for FPV and you'll be burned at the stake if you claim otherwise. So, we should keep this a secrete. :)

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I have the vids of both the onboard HD cam and the downlink with the OSD range on it but I must have faked it some how, Nigel will be shot as a collaborator! I wont post them in fear of my life...

Terry

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So be it - **looks around** - I have the same VTx :o

@ Thomas,

Do you know the RSSI pin on the VRx?

http://www.rc-cam.com/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=1672

I have an RC-Cam RSSI meter I'll fit to it and then in the next couple of weeks, I'll get some testing done (weather permitting).

EDIT

I've found the RSSI pin as when I opened it, I realized it has an Airwave 698 Rx.

/EDIT

Nigel

Edited by Devonian

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Do you know the RSSI pin on the VRx?

It has a AWM682RX Airwave receiver module in it, which has RSSI. The module's datasheet can be obtained at www.dpcav.com

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I have finally gotten around to putting the VTx onto a plane.

I'm finishing the build of a Skywalker with the new FY21AP and want to use this VTx.

I have noticed that I get some 'herringbone' lines in the received video when the VTx is powered by a 3S Lipo.

If I power the VTx from a 2S Lipo, the lines are all but gone.

I'm assuming the lines are from the inbuilt switcher (I'm not using the VTx to power anything else and I have powered the VTx by a seperate battery as well as from the main flight pack during testing - the result is the same).

I first thought the heringbone lines were from something else in the setup, but if I simply replace the 500mW VTx with my own homebrewed 100mW VTx, the clarity is great and no lines.

Any ideas where I should go from here and any improvements I can make to the 500mW VTx?

I can make a short video and put it online if it will help.

Nigel.

Edited by Devonian

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Well this is a strange one. There are two stages of LC filtering on the internal VReg and so the ripple is very low. Plus, 3S LiPO power more efficient than 2S, so it should have less DC-DC noise.

But I have a hunch. What happens if you power the camera from another battery? That is, Tx on one battery, camera on another, with only a common ground between them. And to make it a fair test, both should use a 3S.

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I have done that.

I have tried powering it all from one pack and powering each item individually (as my cam is 12v) and the result is always the same.

I narrowed it down by just using the VTx and cam in 'stand alone' mode - in other words, only the VTx and cam on the bench and not in the plane (again powered from one source or individually). Tried with another 12v cam as well.

It's got me beat...

Nigel.

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It is a strange problem. Let's check the DC-DC for basic operation. On the top of the 5.8GHz Tx, near the power LED, are two pads labeled 5VDC +/-. Using your digital voltmeter, what is the measured voltage (x.xx format) when a 2S battery is used? What is it with the 3S battery?

Due to the DC-DC operation, the switching currents from the battery are high. So a good performing LiPO is needed. Do you have another freshly charged 3S LiPO, that is higher capacity rated, that you can try? If the lines change with a different 3S battery, then that may tell us something.

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OK I made several tests with just the VTx and camera.

I used a couple of good 2S and 3S LiPo's.

I also powered the VTx from a variable voltage, regulated PSU capable of 20A constant.

When the camera is seperately powered the results are:

On 1000MAh 2S it reads 5.08v and a 2300MAh 3S reads 5.11v

At all times the 5v I measured was pretty much rock solid at 5v whilst the camera was powered from the VTx.

The video I've attached shows my results whilst varying the VTx input voltage, with the camera powered from the VTx (the video result is the same when the camera is seperately powered).

It appears to get visibly bad at around 9.6v+, below that, it's quite acceptable.

Vimeo has done a job on it and it is not too easy to see the real problem, although it is evident.

The original appears much worse, but you can see what I mean...

Nigel.

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Thanks, that is good information. It suggests that the supply filtering needs attention. But the odd thing is that the symptom would normally occur at the lower voltage, rather than at higher voltage. But, let's ignore that for now.

Do you have any caps in your parts bins? Small value ceramic and large value electrolytic would be nice. If you have some, what values do you have to pick from?

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I thought a short video would show it better than I could explain.

I have a whole bin full of old circuit boards that I can scavenge components if I don't have them new.

What do you suggest?

Nigel.

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(1) On the side with the LED, install a 0805 size SMD ceramic cap across the 5V +/- pads. The value can be 0.047uF to 0.1uF. Do not use wire leads, install a SMD cap directly to the pads.

(2) On the side with the heatsink, install a electrolytic across the 5V +/- pads. For the initial test use a large value, such as 1000uF (10V or higher). Leads must be as short as possible (do NOT extend them with wires).

Note: If you don't have the recommended caps then tell me what you do have so that we can decide what to use instead.

If the additional caps solve the problem, then you can try reducing the 1000uF to a smaller value to see what you can get away with. Or, stick with the 1000uF if you don't need to reduce its physical size.

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OK, finally got some time to add the caps as suggested.

Used a 0.047uF SMD ceramic as in point 1 and a 1000uF 16V elecrolitic as in point 2 above.

No noticable difference I'm afraid :(

Nigel.

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Thanks for trying the cap mod. It was a long shot since the DC-DC power supply is heavily filtered (much more than necessary).

I spent a few hours over the weekend trying to duplicate the problem. It wasn't until today that I was able to reproduce it. The lines are caused by the DC-DC circuitry's close proximity to the RF module. I could not reproduce it at first because my engineering Tx has the two boards separated with about an inch of extra space (so that I can make easy test measurements). On a hunch I remounted the two boards in the normal configuration and then I saw the lines when a 12V power was used. Even so, they are hard for me to see. I suspect that not all of the Tx's will have the problem since it will depend on component variations.

Unfortunately it looks like it will require a new board layout to fully end the issue. So, other than reducing the input voltage, or using an external VReg or BEC for power, I don't have any simple electronic solutions at the moment. I'll continue to think about it, but please PM me so that we can work on a backup plan.

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