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5.8GHz / 500mW Wireless A/V System:


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Hi,

I am interested in this package! Would it be possible to provide an antenna for the simple Rx with SMA ?

Do you know if this receiver can easily fit on the headband of the fatshark goggle ?

Cyb

Edited by Cyb
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Would it be possible to provide an antenna for the simple Rx with SMA ?

For the simple Rx, I'm leaving the antenna purchase up to the user. To combat multipathing you'll need something directional like a patch. But Terry has good results with ducky dipoles that were fashioned with a Windsurfer type reflector behind them.

Do you know if this receiver can easily fit on the headband of the fatshark goggle ?

The simple Rx's dimensions and other useful stuff is shown here: http://www.dpcav.com...productid=16559

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OK thank you. So it's better to go with the receiver with patch antenna.

One more question : I see in the TX datasheet that there's a +5v output on the board, can it be used to power a camera ?

For the simple Rx, I'm leaving the antenna purchase up to the user. To combat multipathing you'll need something directional like a patch. But Terry has good results with ducky dipoles that were fashioned with a Windsurfer type reflector behind them.

The simple Rx's dimensions and other useful stuff is shown here: http://www.dpcav.com...productid=16559

Edited by Cyb
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I see in the TX datasheet that there's a +5v output on the board, can it be used to power a camera ?

No. The 5VDC is provided on the audio cable to power an amplified microphone like the dpcav Tiny-Mic. Using it to power a camera will probably result in frustrating problems similar to what Terry encountered. To keep things simple, consider using a 12VDC camera and power it all with a small 3S LiPO pack.

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As far as I know he is powering his KX131 from the Tx's 5V, which is not something this design is expected to support. As you can see by several postings regarding his frustrating intermittent loss of signal, this may be what is punishing him. So, don't do it; If you must use a 5V camera then install a R/C BEC type 5V Vreg on it and power it from the LiPO.

BTW, how are you powering the KX131 on your current wireless video system? This camera needs 5VDC, so I suspect you have a VReg on it.

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I am currently flying with a 2.4ghz TX from Aeropix on which there's a 5V output (out of a 7805 I think).

So, don't do it; If you must use a 5V camera then install a R/C BEC type 5V Vreg on it and power it from the LiPO.

You mean that I can take another Motor controler to get the 5v for the camera ?

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Yes, the 5V BEC output on a retired ESC can be used to power the KX131 camera. Not elegant, but functional. Some ESC based BEC's can't handle much continuous current with 3S LiPO voltages and may need to be limited to 2S packs (just review the mfg data sheet).

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I think its pot luck if you get noise on the picture using the BEC to power the camera. With good cooling I think the TX will handle the camera power but I agree that a separate 5v reg is a much safer way to go. I will make up a simple SMT 5v reg to glue to the TX for this when I have time.

Terry

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As Terry warns, avoid DC-DC switching BEC's since they can cause noise in the camera image due to their excess ripple. Fortunately, common ESC BEC's use a dumb-as-a-rock linear VReg. So, they are decently noise free. Even so, don't use the BEC to power anything but the camera. Otherwise, a LM2940T-5.0 Vreg IC, two caps (per data sheet), and a small finned heatsink can be used to create a useful 5V camera VReg.

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As per my findings with my homebrewed VTx and VRx, I used allegedly 'good quality' UBEC's for the VTx and VRx.

Ironically, the VRx was adversely affected by the supposedly, well filtered 5/7.5A UBEC.

http://www.giantcod.co.uk/hobbywing-575a-ubec-lipoly-p-402620.html

I made an LC filter to put in line with the 5v output line and the ripple was improved enormously (as proven in the before and after video tests).

Oddly, the small 3A UBEC I used on the VTx was quite good and needed no alteration - go figure !

http://www.giantcod.co.uk/hobbywing-3amp-ubec-p-402342.html

Nigel.

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Thank you RC-CAM, I understand it. I have a couple of 7805 Vreg, I guess they can also be use to get the 5V for the cam ? Otherwise I also have some ESC that I don't use anymore, I guess it'll be the best choice.

Regards,

As Terry warns, avoid DC-DC switching BEC's since they can cause noise in the camera image due to their excess ripple. Fortunately, common ESC BEC's use a dumb-as-a-rock linear VReg. So, they are decently noise free. Even so, don't use the BEC to power anything but the camera. Otherwise, a LM2940T-5.0 Vreg IC, two caps (per data sheet), and a small finned heatsink can be used to create a useful 5V camera VReg.

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The plane slipped from my hand during launch (Darn this girly arm!) and splashed down in a huge puddle of water. I've let all the components dry out for several days and tested them on the bench. All looks fine. Back in the plane and we'll try again!

Docphi, have you had a chance to try again after the swimming accident? If it has problems now then please contact me so we can get it fixed. For sure, next time use your other non-girly arm to HL the plane! :)

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  • 2 weeks later...

I just flew my 100mW 5.8Ghz out to 9100ft (about 1.75miles) using a 14dBi patch, I had 30% on the RX meter. I could have gone a little further but the flight battery was getting a bit low. I will have to get a bigger flight battery and put the 500mW TX on, I guess 3.5miles should be possible with 500mW.

Terry

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Docphi, have you had a chance to try again after the swimming accident? If it has problems now then please contact me so we can get it fixed. For sure, next time use your other non-girly arm to HL the plane! :)

Thomas,

Just got back from a successful flight. It took a while to find some time after the U-boat incident! LOL! The transmitter works perfectly. It runs cool even in the Florida heat. I ran the Funjet back and forth and up and down. The signal stayed very strong. Nice work Thomas! I'll send some video your way via YouSendIt shortly.

-K

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How is the 5.8 Ghz 500 mW TX package coming? When do you expect it to be for sale on your website?

It won't be available at any other website. In a nutshell, this is a short-run (limited) special project for the forum members. The goal here is to establish if 5.8GHz is practical for FPV. That is, we would like to know if a quality 5.8GHz FPV system is thoughtfully installed, will it provide reasonable performance for a typical FPV'er? Honestly, it would be grand to have an alternative RF band for those 900Mhz-2.4GHz users that are getting hammered by external RF interference sources at their favorite flying field.

I ran the Funjet back and forth and up and down. The signal stayed very strong.

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? :)

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It won't be available at any other website. In a nutshell, this is a short-run (limited) special project for the forum members. The goal here is to establish if 5.8GHz is practical for FPV. That is, we would like to know if a quality 5.8GHz FPV system is thoughtfully installed, will it provide reasonable performance for a typical FPV'er? Honestly, it would be grand to have an alternative RF band for those 900Mhz-2.4GHz users that are getting hammered by external RF interference sources at their favorite flying field.

I am currently using 500 mW, 910 MHz video in addition to a 900 MHz ISM band XBee telemetry downlink and a 2.4 GHz Futaba FASST controller. The problem is that the spread spectrum XBee interferes with the 900 MHz video. I would like to try 5.8 GHz video to solve this interference problem.

For what its worth, I also have access to a fair amount of microwave test equipment, if you need some tests performed. I have a 40 GHz network analyzer and a 26 GHz spectrum analyzer and a 50 GHz sampling oscilloscope.

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I would like to try 5.8 GHz video to solve this interference problem.

Your situation is exactly why some of us hope 5.8GHz proves to be useful. In case you are interested, I have a couple of 5.8GHz/500mW systems left. Details/prices are in the earlier posts.

For what its worth, I also have access to a fair amount of microwave test equipment, if you need some tests performed.

That is very kind, but I am fortunate to have microwave test equipment too (and have collected all the useful test bench data). So now the practical aspect needs to be validated, which means trying 5.8GHz in many diverse FPV installations.

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How well does the diversity setup help with the multipath?

Very hard to say as it depends on the exact area. I get no multipath issues when flying in open fiels with only one patch aerial. Generaly the more directional the RX aerial the better as it ignors the reflections. When using a 4 way diversity with 4 dipole aerials it was hit and miss, moving my RX just a few feet could kill or cure multipath.

The diversity system helps but where you fly is the big question. If you had multipath problems using lower frequencies then 5.8Ghz may not be for you.

Terry

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