help needed - vibration with wireless cam causing breakup

[gfcermak]

Hi,

I bought one of these wireless cams ($99): http://www.web-tronics.com/webtronics/wicosy2on8g.html

The advertised camera weight of 29g is wrong, really it is 99g, unless you remove the case and antenna. But I flew it anyway in the case as a test. All my static at-home tests showed a good image with good range. But, once in the air it had a very bad picture, even near the rx antenna (I was flying indoors at a hangar, if that matters) with color shifting, static, loss of picture, etc. I can post a video if needed.

So, I took it apart and discovered that if I tap the tx board it produces static and all the other issues I saw in the air.

The tx board uses a Mitel SP5655S PLL as a 2.4GHz frequency synthesizer, driven with a 4.0 MHz crystal, and controlled by a PIC 16C54C.

What could be causing the sensitivity to vibration/impact?

1. Could the crystal be changing frequency slightly from vibration/impact and then being amplified by the PLL?

2. Loose component? (I have checked and all the SMTs look fine, twisting causes no problem, and the intensity of vibration or impact changes the amount of video disturbance).

Are there any solutions?

Do other 2.4GHz transmitters have this problem too?

Thanks,
Gerry

[Ken-Ohki]

Was your motor runin during your bench test?

Does the problem go away if you cut throttle in flight?

Did you try it at another location? Say outside not surounded by hangar? Where you fly could matter, and should never be overlooked when trying to troubleshoot a interfearance type problem.

Ken-Ohki
"I make things do what I want them too, The Hell with what they are designed to do."

[gfcermak]

No motor running during bench tests. Just hand held, or stationary.

I never tried cutting the throttle in flight, as that would cause issues with control (a small hangar with low ceiling).

I did walk around the hangar with the motor running while holding it and this caused some color shifting of the image (what causes that?).

-Gerry

[gfcermak]

I have temporarily added a short video from the flight so that someone can hopefully see what is going wrong: http://static.rcgroups.com/gallery/data/500/34746RC_Cam_Test4.wmv

Is it just multi-path problems due to the metal frame building?

[gfcermak]

Just found this, and it appears that low frequency crystall do frequency shift with small g loads: http://www.wenzel.com/documents/vibration.html

Any suggestions for a replacement crystal?

[Comatose]

Have you tried soft mounting the camera? It might help. I'd use the neoprene receiver foam that the glow guys use, mainly because you likely have some in an old transmitter box somewhere that's not being used.

[Mr.RC-CAM]

This problem has been reported before and affects some brands of wireless video gear. Basically, tiny displacement of the components can cause a severe shift in the microwave frequency. Common sources are open frame coils, unsoldered tin covers, loose or flexing PCB's, etc.

Another source is the microphone (it present). Loud sources, and certain vibrations, can overdrive the audio subcarrier and/or add additional ripple to the V+.

RC-CAM

[gfcermak]

Thanks RC-CAM. I did find the adjustable RF coil had two legs of the can unsoldered, but soldering them did not help.

I built one of your 2.4 GHz antennas and soldered that to the board, but it didn't help either (thought maybe the board banging inside the plastic antenna in the stock antenna was causing it).

You may be on to something with the microwave shift. If I touch the antenna insulation, the picture drops out.

Any suggestions on fixing this? Or should I just start over with a better TX?

-Gerry

[Mr.RC-CAM]

I did find the adjustable RF coil had two legs of the can unsoldered, but soldering them did not help. Some designs have air core (wire looped) coils inside the "sardine can." However, if your Tx's inductors are strip line (copper traces on the PCB) then perhaps the pcb is vibrating. Even some SMT ceramic caps are susceptible to vibration. With microwave RF gear, if these are allowed to vibrate then problems will occur on some designs. Have you had the can's lid off to see what is inside?


If I touch the antenna insulation, the picture drops out. That might not be related. I suspect the Tx does not respond well to impedance changes at the RF output.


Or should I just start over with a better TX?Some wireless Tx's are just not good choices for R/C use. At some point you will have to decide if yours is a keeper or not.

BTW, the retailer claims the Tx is FCC approved. What is the FCC Reg number (per label on the Tx case)?

RC-CAM

[gfcermak]

There is no FCC ID: label on the TX. There are other labels, but appear to be mfg specific stuff.

It uses strip-line inductors. Did not have the inductor's can lid off, but it looks like a normal RF can with screw slug turnable from the top. This is the only discrete inductor. I have unsoldered and removed the board from the metal case to get at various points on the underside. For some reason, they had bypassed the 78D09 regulator on the TX, and gone with the direct wall wart supply to the TX (unregulated). I put the 78D09 back in place, and added another 33uF/10V cap to the output and am running it from a 3S lipo for testing - but alas no change.

I think this tx is just junk for RC. Rats, such a nice price, and the 330 line CCD camera is good. Fortunately the camera can be salvaged. I will give it one more try mounted outside of the can and see what happens. But walking around my yard with the RX in the garage does give me much hope on it's range (at least passing through wood walls).

Would my XCam2 tx make a nice one for RC? I've seen your web page on conversion, but was worried about the lack of power/range.

-Gerry

[Mr.RC-CAM]

There is no FCC ID: label on the TX.Ahh, then the vendor did not tell the truth. That might be grounds for a refund. :)


But walking around my yard with the RX in the garage does give me much hope on it's range (at least passing through wood walls).Range testing around the house will not give you reliable range info due to the usual multipathing issues.


Would my XCam2 tx make a nice one for RC?With a Linx BBA-519 50mW RF amp on it, it works great. If you already have the X-10 equipment, and the RF skills, then this is a cheap way to create a system. Like all of the ready-to-use wireless video gear that isn't FCC Part 15 registered, or has been modified, a ham license is required for legal operation in the USA.

RC-CAM