5V SN777 (VSN505) and EzUHF, can they co-exist happily?

[DanielShutt]

Hi all, I've recently upgraded to ezUHF and have an sn777 camera that I would like to use with it.

I have the vsn505 5v type bought from firstpersonview and was told Sander had done some research on that model and found it to be relatively noise free.

I've been looking around the boards to find this original post to confirm it before I send it all up, but don't seem to be able to find it.

Can anyone confirm I probably won't drop out of the sky a mile out if I go up with this.

Thanks

Daniel
:)

Ps this is the smaller 20x20mm version not the 30x30 which is known to be very noisy.

[ssassen]

I'd like to show how to get the KPV-VSN505PHB to behave, or basically reduce its RFI to levels which are at, or below, the noise floor. The solution is pretty simple. After taking a closer look at the KPC-VSN505PHB it was clear that all of the RFI was radiated from the camera wires. Here's what the camera radiates in stock form, which is pretty nasty indeed.

http://www.immersionrc.com/images/baseline_ferrite_300_500mhz.gif

Fig 1. Baseline plot from 300 to 500MHz, KPC-VSN505PHB camera off.

http://www.immersionrc.com/images/camera_on_300_500mhz.gif

Fig 2. Plot with the KPC VSN505PHB camera turned on.

How to remedy this? Start with twisting the camera wires (which means removing the outer protective sleeving). Then feed the twisted cable (VCC, GND and VID) through a ferrite ring >4 times, this solves the problem. Below are the spectrum analyzer plots that show the results. Fig 1. is a baseline plot with the camera off showing the noise in the surrounding environment. Fig 2. is a plot with the camera tuned on, clearly there's lots of nasty peaks to be seen in the plot which raise the noise floor on the UHF band. Fig 3. is the plot from the camera with the wires twisted and fed through the ferrite ring >4 times, you'll notice Fig 1. and Fig 3. are almost identical, hence no more noise in the UHF band. Fig 4. shows the camera with the ferrite ring, it needs to be placed as close to the camera as possible.


http://www.immersionrc.com/images/camera_on_ferrite_300_500mhz.gif

Fig 3. KPC-VSN505PHB camera on, no more RFI.

http://www.immersionrc.com/images/camera_ferrite_ring.jpg

Fig 4. Twisted camera cable fed through ferrite ring >4 times.

Cheers,

Sander Sassen
ImmersionRC Ltd.

[DanielShutt]

Hi Sander, thanks for that full on, compreshensive explaination, one thing to be told that something will work, but seeing the graphs too, my confidence is even higher!

One last quick question, would it hurt to extend the wires from the camera, Im going to be mounting the VTX on the back of the skywalker, so will need a decent length to be able to string them together, im also toying with the idea of the ezUHF being in the middle of the plane.

Thanks

Daniel
:O)

[ssassen]

You're welcome!

What frequency Vtx? I would keep Vtx and camera close and not run wires the length of the fuse.

[DanielShutt]

It's one of your 500mw 2.4ghz vtx's though im toying with the idea of going back to my 600mw 5.8 and using antenna tracking.

[ssassen]

Where are you putting the camera?

Care to do a rough sketch of how you have planned to mount stuff on the Skywalker? And have you seen this?

http://www.rcgroups.com/forums/showthread.php?t=1262099

[kenkos68]

Care to do a rough sketch of how you have planned to mount stuff on the Skywalker? And have you seen this?

http://www.rcgroups.com/forums/showthread.php?t=1262099

Hi Sander,

Where is the EZOSD GPS on your Skywalker? Under the plastic on top of the wing? As for the UHF receiver and video transmitter on your Skywalker, no problems with the receiver being fairly close to the transmitter as long as the antennas are greatly separated?

Thanks!

[DanielShutt]

Hi Sander, Sorry I haven't done a sketch of my layout yet, Christmas got in the way! Love the build on your skywalker, I see on that build you did run the wires from VTX to camera through the fuse, how did that perform?

If I'm able to extend the connection from UHF Receiver to antenna as you have that would make laying things out MUCH easier, is it safe to just use an smc to smc coax extension so I can put the antennae on the wing tips, and if so, what kind of length of extension is safe to use?

Finally, when using an extension on the antenna, does it matter where the actual RX is placed in regards to RF noise?


Thanks, and Merry Christmas!

Daniel
:O)

[ssassen]

Where is the EZOSD GPS on your Skywalker? Under the plastic on top of the wing? As for the UHF receiver and video transmitter on your Skywalker, no problems with the receiver being fairly close to the transmitter as long as the antennas are greatly separated?

EzOSD and GPS are shipped as a single unit, but can be separated if you want to place the GPS elsewhere. You can see the EzOSD/GPS mounted on top of the fuse. It is always a good idea to keep Vtx and RC Rx separated as the antennas are not the only way RF gets in, servos wires etc. are another means of coupling RF back into a RC Rx. These outputs are filtered though on our EzUHF Rx, so it is pretty tolerant of RF on those pins.

[ssassen]

see on that build you did run the wires from VTX to camera through the fuse, how did that perform?

Fine, run them clear of battery/ESC and other wires running high current.


If I'm able to extend the connection from UHF Receiver to antenna as you have that would make laying things out MUCH easier, is it safe to just use an smc to smc coax extension so I can put the antennae on the wing tips, and if so, what kind of length of extension is safe to use?

I wouldn't extend the antenna cables too much. If I had to rebuild the SW I would put the RC Rx on top of the fuse and have the antennas stick up in bunny ears configuration.