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I think I have a TX/RX problem

Old 11-27-2008, 04:10 AM
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michael7810
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Default I think I have a TX/RX problem

I'm looking for some advice on the best way to protect against signal loss with a Spektrum system. I've had 3 planes just fall out of the sky over the past 4 month for no obvious reason. All were larger park models (48-52") and flying around 75-100 feet above the ground and around 400-500 feet away. I'm using a DX-7 with AR6100 and AR7000 receivers. I don't use a separate BEC and have not been particular about receiver placement. I've never had a problem with small foamies flying at close range. Range checks before and after crashes were OK. I read the best practices on Spektrum's website about receiver and antenna placement and will pay attention to that in the future. Is anyone out there having/had similar problems? Thanks for any advice you can give me.
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Old 11-27-2008, 05:17 AM
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Rabbitcreekok
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Mike, range would not be a problem. The DX7 range is farther than you can see to fly. There has been some discussion about servos drawing too much current and dropping the voltage below the LVC. Digital servos draw more current than analog. Most recommendations are that with 4 or more servos, use a separate setup for the servos.

You might post more information about the setups in each plane that went down.

This is a long thread about DX7 problems. The end result was a problem with the transmitter, which was replaced by Horizon and he has had no further problems.

Hope this helps.
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Old 11-27-2008, 06:36 AM
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MaxAdventure
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For $30US, you can pick up the spektrum flight logger to check the AR7000 for frame loss and fades. That would let you rule out interference/loss of signal. (AFAIK, it doesn't work with the AR6000) Really, this is what a logger is perfect for. I've seen several for $50-$60 that can record servo movement, pack voltage, Spektrum signal, among other things. Very valuable if you add up what it may save in one crash, including your time. (I love my Eagle Tree!!!)

I had a similar incident about a month ago, after much thinking and equipment checking, (I didnt have a logger on this model at the time) I'm suspecting my voltage regulator had an issue and cut power to the system.

As for pure signal redundancy, on my most expensive models I'm running the JR R921 and two remote receivers for four total, maximum path diversity! If it saves me one crash in the models life, it probably paid for itself. Heck, it just saves me some stress every time I fly!
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Old 11-27-2008, 06:47 PM
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michael7810
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Rabbitcreekok: The latest crash was a eFlight P-38:
2 Park 450
2 eFlight 25A ESCs (I disconnected the BEC on 1 ESC)
3 Heads-up RC 9 gram servos
Hobby King 3S1P 2200 25C
The crash occured about 8 minutes into the flight. I usually fly for 10 minutes and the battery voltage is ~11.35V
Spektrum AR6100 with antennas facing forward/aft
DX7 with antenna pointing close to vertical

I'll get a flight logger and see if that reveals any signal anomolies.

Thanks
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Old 11-28-2008, 05:10 AM
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Rabbitcreekok
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Mike, two things come to mind.

How do you have the LVC set up on the ESC that is being used for power?

Secondly, is it possible the battery did not have a full charge and ran low earlier than you anticipated?
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Old 11-28-2008, 05:22 AM
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ministeve2003
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hmm, 2 park 450's on a single 2200 3cell.... and 10minute flight time.... that doesn't sound right.... maybe if they are underproped and you are only using half throttle 90% of the flight....

any Idea what amps that is drawing?

SK
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Old 12-02-2008, 04:32 AM
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michael7810
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I can't remember exactly but the max amps is somewhere around 35. I fly at 1/2 throttle most of the time. I even takeoff with 1/2 throttle. The only time I use full throttle is to enter a loop from horizontal and only for a short time. I don't know what the LVC is set at; whatever the factory setting is I did not change it. The battery was fully charged but it was near the end of the flight which usually means around 11.3V with no load. In thinking how the plane was oriented when it fell I believe the left motor/speed control was between the TX and RX. Could the motor have blocked the signal? Any thoughts on which is better; a separate BEC or a small 2S Lipo to power the RX & Servos?
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Old 12-02-2008, 06:35 AM
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ministeve2003
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If I'm figuring it correctly...

2.2x60/35 = 3.7 minutes full throttle or 7.4 minutes half.... so that sounds right...

I'm going to guess that you normally fly slower... but that time you were juicing it a little more than usual, even if you were only juicin it slightly....

SK
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Old 12-03-2008, 04:04 AM
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michael7810
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Hmmm! Now that I think about it I was using an 1800/20C when it went down. I suppose low battery could have been the problem but I've flown it many times with an 1800 and no problems. It seemed to loose control and not just motor juice. Although I guess it could have lost motor juice first, then stalled and lost control. I'll never know what happened but I'm learning a lot of things to do different next time.
Thanks
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