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  2. FWIW, video level issues, like the bad FR632 vRx in this discussion, affect other FPV systems too. Not everyone recognizes that their video image's problems are due to incorrect video levels; Instead they blame other things. The only way to know if the video level is correct is to measure it. That's easier said than done! The problem is caused mainly by the lack of respect for the composite video standards. These industry documented specifications are often ignored to save manufacturing cost, other times it's due to the ignorance of the video circuit designer. Our cheap imported FPV products have been big offenders of this. To help combat the problem I've created a DiY built tool to check the video levels. It can also be used to calibrate the video level. The project is simple to build and replaces expensive/complex test equipment. Any FPV hobbyist that cares about their video signal level can now easily check it. Details are published here:
  3. Firmware flashing comes next. So come back soon for the details!
  4. Assembling the vTx and vRx video generators requires basic soldering skills. And in case I have not been clear, there are two (2) MinimOSD's used in this project. First you need to connect some ground and power pads that are on the two MinimOSD boards. Just add a blob of solder across the pads shown below (Grounding pads on bottom side, SJ2 pads on component side). Some suppliers have already done this for you, but if the pads are not bridged then you must do it. The new firmware (to be flashed later) includes an optional battery voltage monitor feature. This requires adding a jumper wire, as shown below. If your MinimOSDs are the old/original version (not "KV Team") then the voltage monitor feature will require adding some 1% 1/8W resistors, as shown below. Each boards' Power and Video connections are available on the stacked 3-Pin headers. The pins are labeled on the bottom of the MinimOSD board. The vTx OSD only uses VOut and +12V power pins. The vRx OSD needs VOut, VIn, and +12V. I used 3-pin servo plugs to connect the MinimOSD boards, but direct soldering can be used instead. The video connectors you use are up to you. I installed RCA phono panel jacks and made some simple adapter cables that connect them to the FPV system. How you do this is your choice. As a reminder, the vTx's MinimOSD does NOT use the VID-IN signal, so be sure to omit it.
  5. So it's time to gather the parts to build this cool tool. As mentioned before, you need two video target pattern generators; One for the FPV vTx and another for the vRx. The target patterns are provided by low cost Arduino based FPV OSD boards. Here's the Parts List: 2 pcs, MinimOSD (KV Team version recommended). Approx $8 USD each on eBay and AliExpress. To flash the custom firmware you'll need one (1) of these: FTDI FT232RL USB to TTL Serial Converter (6-Pin version) for Arduino. Approx $3 on eBay and AliExpress. Keep in mind that there are several similar looking Chinese clones of the MinimOSD on the market. I recommend the "full size" board that has the KV Team Mod (built-in voltage attenuation resistors). Here is what the KV Team version looks like: How to tell the difference in board versions: The KV Team version will have the JP6 8-Pin header area (8 empty solder pads across the top). See photo above. It's important that both OSD's have identical video signal characteristics. Therefore, I recommend that you purchase both boards at the same time from the same supplier. This should reduce the chance of any component variations that might cause unmatched video levels. You can use your existing 7-12VDC FPV batteries (3S LiPO is fine) to power the boards. No other components need to be purchased. But if you want a power switch, A/V connectors (I used RCA phono chassis panel jacks), or plastic enclosure, then feel free to add these things to the shopping list. Although you can simply protect your OSD board with some heatshrink or duct tape, the 3D printed plastic case gives it a professional appearance. Here's the STL files for it. Case Base: case_base1.stl Case Top: case_top1.stl Case Hole Plug: case_plug1.stl Printing recommendations: ABS filament, 35% infill, 3 layer shell, 101% size scaling (shrinkage correction). There's room for a mini toggle power switch, Alkaline 9V battery, and RCA panel jacks. The "Case Hole Plug" file is a small piece that covers an unused RCA mounting hole on the vTx pattern generator (Vid-In is not needed on the vTx side). Here's how everything fits inside my vRx target generator: BTW, the vTx looks the same, but has only one RCA jack.
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  7. FPV Video Calibration Tool: DiY -- Low Cost -- EZ to use. The calibration of our FPV system's vTx / vRx composite video signal level (amplitude) matters a LOT. Unfortunately many are incorrectly adjusted out of the box. There's a number of reasons for this -- marginal designs, poor manufacturing QA, compatibility problems due to brand mixing by end users, cheap component drift, and just plain bad luck. Hold on you say! You are convinced that your system's video is fine. But perhaps that's wishful thinking. Here's the cold hard reality -- Many FPV systems have marginal video levels and this invites problems that are often blamed on other things. For example, the random "weak signal" blackouts we all hate are not always directly RF signal related. Poorly calibrated video levels will cause those random blackouts too. Plus a host of other image quality problems that are simply victims of marginal video levels. Checking the composite video signal normally requires an oscope (oscilloscope). Ideally a test pattern generator is also used to provide the 1Vpp standard video signal that is measured with the oscope. Not many hobbyist have access to this equipment or know how to correctly perform the measurements. So I experimented with video level testing using simpler tools than a oscope. My goal was to have something that worked well, but was cheap and simple to use. After a bit of head banging a clever DiY solution was born. How does ~$20 USD and a couple hours work sound to you? Yes, really. Here's what my DiY FPV Calibration Tool looks like. Spoiler alert: Inside the small 3D printed plastic box is a $8 eBay circuit board and a 9V battery. To calibrate a FPV system you'll need two of them. Both boxes will use identical hardware but with different firmware. Oh you guessed it, Arduino is involved. Come back soon. I'll show you how to build and use it. Your FPV system will thank you. The world will be a better place.
  8. 5.8GHz seems to 'need' diversity less than 2.4GHz in terms of dropouts, but even so I thought I'd try the new FR632 diversity receiver for a local plus high gain arrangement. Bench tests seemed okay, but on fitting it into a real system I found picture roll on some screens, intermittant 'interference' across the middle of the screen on others. Swapping the part out for an Airwave module or a 5.8GHz single-input 'scanning' receiver gave a perfect picture, so I suspected a sync problem in the FR632. On the 'scope' the outputs are different (see attached) - FR632 - Airwave - Scanner. Everything else was the same - okay, there was a OSD message flashing on and off in all three cases, which probably explains the slight extra 'detail' in the video trace for the Scanner. The Airwave and Scanner outputs, although at different references to earth, look fine, with a clear sync pulse at the beginning. In practice these receivers perform well. The FR632 looks odd, and is awful. Any suggestions how I might fix this? Online reviews of the FR632 are full of praise, so presumably it's just this one...
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