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ssassen

RF downlink or local storage?

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Hello,

As this is my first post here, allow me to briefly introduce myself. I'm 33, have had RC modelling as a hobby since I was a kid and am an electrical engineer by profession.

Here's what I've been trying to get some clearcut answers to. I plan on building a new RC video/photography platform for serious hobby purposes, based on the MPX EasyStar. I used to simply ducktape a Sanyo Xacti camera to my RC planes, the majority of which flew well with the added 170-grams of weight. However, for the EasyStar I want to make every effort to mount the camera properly, possibly with tilt and pan options.

Now I have the option to use the Sanyo Xacti and just make a bracket that will allow me to use it as such. However, before I go to all these lengths the lingering question in my mind is whether a CCD camera with RF 2.4GHz downlink will provide image quality which is on par, or maybe even better, than the Sanyo Xacti? The Sanyo has 640x480 @ 30fps recording.

Here's some footage directly from the Sanyo Xactie, no processing whatsoever, it uses H264 MP4 encoding in camera to reduce filesize.

Sanyo Xacti footage, raw data, unedited (76MB download)

http://rapidshare.com/files/61559033/su27_...7_xxl_part3.MP4

Can anybody tell me if a RF 2.4GHz solution will provide a similar image quality? Esp. considering these Sanyo Xacti cameras are priced at about $350. Hence if $350 doesn't get me similar IQ then why bother?

Alternatively I can use the Xacti's A/V output and a RF 2.4GHz transmitter to downlink the image, so I can fly real time using the onboard camera, or just get a general impression of what the footage looks like. Going forward it then obviously is pretty simple to just add two micro-servos to the Xacti and control zoom and photo and video trigger.

That might prevent accidents such as happended to me this monday, where I lost control of my RC plane with the camera mounted. A real time onboard view might have prevented that crash, although it probably was due to being out of range, so that would not have helped much either.

SU-27 XXL, riverside rescue

Any suggestions would be most helpful!

Best regards,

Sander Sassen

http://www.hardwareanalysis.com

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Nobody? Could someone that has a 2.4GHz RF downlink on their plane of decent quality at least let me know if it offers better or worse image quality than below noted footage? It is a free download, you just need to click a few things, sorry I can't offer another form of hosting for this file.

Sanyo Xacti footage, raw data, unedited (76MB download)

http://rapidshare.com/files/61559033/su27_...7_xxl_part3.MP4

Ps. I might add that you need Quicktime player for this file to play on most PCs as Windows Media Player doesn't have the right codec for H264 encoded MP4 files.

Cheers,

Sander.

Edit: fixed broken URL

Edited by ssassen

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That clip is very good, you won't get better than this without going for the expensive MiniDV recorders on the ground.

I'd keep that and add a transmitter for live view. But that's if it interests you of course.

I'd also get a wide angle converter for it, and not put it for a downward vertical view ;)

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Thanks Kilrah,

I'll stick with the Sanyo camera and local storage then and just use the A/V output for FPV flying. For those of you wondering what the camera is that I use, here's the manufacturers website, it weighs just 180-gram with battery and SD card and is waterproof!

Sanyo Xacti CA65

http://www.sanyo-dsc.com/english/products/...ca65/index.html

Cheers,

Sander.

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Nice, I just saw a CA6 yesterday at a friend's, cool small things :P

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Hi Ssassen, nice to hear from you on the forum.

I flew a Xacti C5 a couple of years ago. I thought I'd avoid dropouts and get nice 5Mpixel stills. Not to mention zoom.

I found, in practice:

1) Putting a 180g camcorder on a 2-axis mount, that isn't so bulky it interferes substantially with the airflow enough to make even a 3m electric soarer close to un-flyable, was _much_ harder than mounting a <20g board camera!

2) The mount I had (carbon fibre & aluminium) despite seeming pretty stiff still allowed in-flight wobble that really rather killed the stills, too. There was a rotational axis moment that was clearly visible in all shots.

3) Zoom isn't any use if the camera's too narrow to start off with, and I couldn't find a wide adaptor for the C5.

I did try taking the camera/lens assembly out, to put it on an umbilical lead, but this stopped working after one test on the bench. Permanently. Take apart something with 80-way ribbon connectors 8mm wide at your peril! I also found it would only record AND give a composite out feed in NTSC, not PAL, although NTSC-PAL converters are tiny and cheap these days.

The recording quality was every bit as good as you'd expect for that data rate, although quite edgy/choppy compared to miniDV.

I've since had a lot more success with small cameras and dedicated receivers; I'm very happy with my current setup of 2x RC-Tech receivers feeding an Oracle diversity controller. You've got to get a quality downlink for it to be usable at all, so I'd recommend getting that right first, rather than accepting poor results; you'll just end up putting something more expensive into the water!

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Thanks Doofer,

Those are some helpful suggestions! Alright, I'll drop the idea of putting the Sanyo Xacti on a pan/tilt mount, I had my doubts about that already. I can however simply put it in the nose, or in the fuselage. I just picked up my EasyStar today so I'll have a look what works and what doesn't. My power system will weigh around 200-grams, so that's about 400-grams already set in stone. Now I still need to add a 2.4GHz Tx and hopefully the IFOSD with GPS. Total weight of all this equipment should be around 500-grams, which will make the AUW about 750-grams, which is doable for a 1.4-meter wingspan EasyStar.

Cheers,

Sander.

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Sounds like a good starting point. Start, try it, modify, improve etc...

See if the CA6 has the 'No PAL output when recording' problem, if so you'll need a NTSC IFOSD if you're using the Xacti as your video source.

(PAL->NTSC conversion is more difficult than NTSC-> PAL, the converters are bigger + more expensive, so you probably can't fit a NTSC->PAL converter into the airplane. If you want to record your downlink e.g. that 'world-record altitude' attempt, it's wise to think ahead about this issue; digital recording will be fine, but if you're going to want to keep the video interlaced - it looks nicer - it's worth thinking this one through)

I'd also consider putting in a brushless motor from the outset - this is one thing it's a pain to change after building. I found a range of speed 400-style inrunners + ESC for $50-60 or so! - you may want some extra poke hauling an Xacti about. There are endless discussions about alternative motors on this & other forums...

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Doofer,

Indeed, as a matter of a fact I already laid out a plan for the motor and esc. I actually haven't used a brushed motor in a long-long time, so not even touching the stock motor. But frankly this EasyStar will not get a 1:1 thrust:weight ratio. I plan on using a 2200KV motor with a 6x4 prop on 3S LiPo, which will yield about 650-grams of static thrust at full throttle. That will get that ~750-grams EasyStar going upwards quickly. When I use a 1/4 throttle setting that should be enough to stay up there for about half an hour without too much headwind. In the meantime I'm ordering parts left and right and by the looks of it I should be able to get this EasyStar off the ground in about two weeks time.

Cheers,

Sander.

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