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First FPV crash - diagnostics

lobstermash

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#1
For those in Canberra today, you'll call me crazy for flying in this wind. But I couldn't resist. I got out to Yarralumla this morning, which is a picturesque, ritzy little suburb by Lake Burley Griffen. There's a big paddock next to the water that's great for flying RC planes, as it's not a sports oval.

This was my first fly with the cp antennas and also running the systems off the same battery. I've got a lc filter in the line too, as well as a FMA copilot. OK, I should be making one change at a time. First mistake. I took off without too much issue. It was pretty bumpy, but as I reached about 20m I flicked on the stabiliser. It made a huge difference, and the plane was locked in nicely. For the first time, I was also sitting down, on the nice warm grass. With the rubber ducky antennas I put the gear in my pockets, but thought I'd lay the gear on a box instead, which required me to sit down to make the cables reach.

After a couple of circuits, mostly in front of me, I thought I'd go out over the lake a little and get some scenery. All was fine, until suddenly I lost control. Video feed was crystal clear, and the plane was only about 200m away. The plane stayed straight and level, and it made its way over land and onto the roof of a boatshed. The landing wasn't gentle, but as I got closer to the plane I could see that it was in one piece. Someone gave me a boost onto the roof, and I was amazed that the only damage was the hinge on the elevator on one side, which had obviously hit a corrugation in the roofing.

I'm trying to diagnose what went wrong... I've flown this receiver out much further without any sign of signal loss. The 900Mhz vtx (I use 910) hasn't interfered with the rx range before. I also run a UBEC (5V 4A) to power the rx, so in spite of 7 channels being in use, as well as the stabiliser, it'd be hard to put it down to brownout. The battery was also pretty fresh off the charger. I've also flown behind myself before without issue. I'm wondering if me sitting down on the grass, hunched over the tx might be the cause...

In any case, I'm very lucky to have the plane in one piece and dry...
 
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lobstermash

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Haha, you wouldn't catch me dead on that one!!! ;) I was so comfy in the nice, long, mossy grass. Too comfy...

Just had a thought... There UBEC didn't have a ferrite ring (I just added one a minute ago). It's probably not the cause, but perhaps a contributor.
 
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#6
I lost rc-signal one time when I was crouched to view a small screen on my Sony Handycam lying on the ground.
I had clear FPV view all the time - no video issues(was watching the screen - no goggles)
I quickly moved the radio as far up as I could reach and still have control and it helped me out.

Distance to home was well within my normal FPV area...


Not really much help - but try to avoid ground to get a clear signal.

On my modified TGY9X I have a connector so I can change antenna - and add an extension to mount the antenna on a pole.
3 meter cable and 9bdi ;)

//UndCon
 
#7
Haha, you wouldn't catch me dead on that one!!! ;) I was so comfy in the nice, long, mossy grass. Too comfy...

Just had a thought... There UBEC didn't have a ferrite ring (I just added one a minute ago). It's probably not the cause, but perhaps a contributor.
Well I dont think that the ferrite ring could be the problem. Was it your first time flying in that field? In europe 900 mhz is used for mobile phones, maybe there was someone with an (europe) mobile which shortened your range.
 

lobstermash

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#8
Yeah, hopefully it's just that. I'll find myself a nice fold-up chair. Likewise, it was all crystal clear video. I didn't think to stick my radio up at the time, but thought that would have been a good idea as soon as I saw exactly where it was when it lost signal. It was in an exactly straight line between the tx antenna, my spine and the plane.

Never mind. I've got a G-OSD and FrSky telemetry combo on the way, which should be in time for next weekend. It'd be horrendous bad luck to have a 3rd weekend of strong wind...
 

lobstermash

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#9
Well I dont think that the ferrite ring could be the problem. Was it your first time flying in that field? In europe 900 mhz is used for mobile phones, maybe there was someone with an (europe) mobile which shortened your range.
Video feed was perfect. We have 900Mhz phones here too, but I've tested my phone on a call right next to my video rx and tx and got no interference on 910 (channel 0 on the vrx).
 

lobstermash

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#10
On the ferrite ring issue, often UBECs can create a lot of noise, which may reduce range because the noise is being pumped directly into the rx. Ultra cheap UBECs often don't have any filtering, but decent ones usually do.
 

lobstermash

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#14
Flew from a hill today. No range issues at all, but the Copilot was on the whole time, just in case. I thought this spot would be ideal for FPV, but it was hard to spot where we were on the hill. Had some eagles flying with us today too. I need to get my HD wing camera up and running!
 
#15
Flew from a hill today. No range issues at all, but the Copilot was on the whole time, just in case. I thought this spot would be ideal for FPV, but it was hard to spot where we were on the hill. Had some eagles flying with us today too. I need to get my HD wing camera up and running!
Eagles?!?!? Thats so cool, cant wait for the footage when you will fly again. Chasing/filming birds is one of the things that I would love to do but if we post that on youtube I think that I will get allot of angry mails from bird spotting clubs.
 

lobstermash

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#16
Yeah, was pretty cool. I'd been holding off getting a micro SD card for it until I started FPV. Unfortunately I forgot about it! Hopefully I'll have it up and running next weekend (if I can sneak out - wife's birthday on Saturday...)
 

dusk

Junior Member
#18
Video feed was perfect. We have 900Mhz phones here too, but I've tested my phone on a call right next to my video rx and tx and got no interference on 910 (channel 0 on the vrx).
910MHZ is GSM Vodafone. I believe that only Optus is using parts of that spectrum for 3G. What provider is your phone with?

The 900MHz spectrum in Australia is a highly contested bit of real estate. Even the AFP use bits of it. Have a look at the ACMA review for a breakdown. Chapter 2 is the most relevant part.
 

lobstermash

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#19
I'm using Virgin (Optus network). I'm not too worried about Vodafone interference in Canberra (those who live here will smile). I've had a look at spectrum use in Australia and even did a brief article on it. I anticipate that I'll be shelving my 900Mhz system in the near future in favour of 5.8 (600mW IRC tx). Until then I'm keeping in pretty close range to avoid the issues that come with greater distance (keeping it under 500m away). I've now got an OSD up and running and my FrSky system SHOULD be here this week, so I might get more adventurous over bushland in the near future (hopefully this weekend).
 
#20
I'm using Virgin (Optus network). I'm not too worried about Vodafone interference in Canberra (those who live here will smile). I've had a look at spectrum use in Australia and even did a brief article on it. I anticipate that I'll be shelving my 900Mhz system in the near future in favour of 5.8 (600mW IRC tx). Until then I'm keeping in pretty close range to avoid the issues that come with greater distance (keeping it under 500m away). I've now got an OSD up and running and my FrSky system SHOULD be here this week, so I might get more adventurous over bushland in the near future (hopefully this weekend).
Yea 5.8 GHz 600 mw with cp antennas will be great. You can always upgrade it with a helicall for longer range.