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2.4ghz lockout/shootdown

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Old 05-15-2010, 05:37 PM
  #1  
Big Oakden
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Default 2.4ghz lockout/shootdown

Hey all,

Are there any other clubs experiencing a high rate of 2.4ghz aircraft losses?

Our Club has lost 6 aircraft in two weeks, and two of them were mine.

My losses occured at approximately 8:30am both times.

Both times there was someone else flying on 2.4 and we were the only two flying on 2.4 at our club at that time.

My first loss was with a AR7100 receiver on a JR9303 2.4 only Xmitter.

My second loss (today) was on a JR 9303 usijng the Extreme Link 8 channel with a current update. I had already had one 9 minute flight and all was well.

I checked the battery prior to flight and still had 6.5volts prior to take off. I had been flying for approx 4 minutes when it locked out.

The first aircraft was lost on the takeoff roll. As she broke ground, the plane went to full throttle, and a slow roll to the right, with no chance of recovery.

Todays lockout occured at 200 ft and never came back.

Both times, I checked the receivers and batteries. the first crash's battery still showed 6.7 volts and when I hooked the servos to the receiver everything worked normally.

The second crash (todays) the wires were pulled out the batttery so I was unable to test it to see what the voltage was. When I borrowed someone elses rcvr batt and hooked it all up, everything worked fine again.

Any suggestions from those out there flying 2.4 or the MFR's?

Thanks,

Dave


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Old 05-15-2010, 05:53 PM
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Default RE: 2.4ghz lockout/shootdown

Dave, last year, we had a series of 2.4 failures, but all turned out to be antenna problems, One was with spectrum receivers, The guy lost two planes in about the same spot on the field. It turns out that one antena wire was broken clean from the PCB and the second fell off in his hand when he wiggled it. The other receiver had a broken antenna wire also. Another guy lost two planes, before finding out his TX antenna wire was broken. The little coax wires don't take viberations, and when you loose one on the RX, you can get in a position that the good one is being blocked by the plane. I'm not sure how the TX wire broke, unless the guy was shakking at a fast enough rate that it wasn't obvious. Actually, he is one of our better pilots,

Don
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Old 05-15-2010, 06:21 PM
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Big Oakden
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Default RE: 2.4ghz lockout/shootdown

my first crash was in a hanger 9 P-51 that had about 900 flights on it and still flying well. I switched to 2.4 to avoid eing shot down, after my Futaba Transmitter (8uap) took a dump on me and fried. The antenna wires were not stretched between the two receivers and had about 1 1/2 inch of play.
The P-51 had a Saito 125 in it.

The Extreme Link was behind the canopy of my Goldberg Obsession and not near any other wires, batteries, etcetera.
The Obsession was powered by Storm 63-74 200kv and a 5s2P 4350 battery pack and an MGM 90 Pro Speed Control.

In either case, vibration wasnt an issue. as the electric was very smooth as is the Saito and will be again after it gets repaired.
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Old 05-15-2010, 06:53 PM
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Default RE: 2.4ghz lockout/shootdown

The problem could be the play of antenna wires. I always add a cushion (a piece of rubber foam glued to a wood post) at the middle of antenna wires so they can not "vibrate".
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Old 05-15-2010, 08:02 PM
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Default RE: 2.4ghz lockout/shootdown

Three of the four plane I was talking about were electrics.The plane doesn't have to shake your socks of, just the normal flipping back and forth with control movements will stress the wire to failure if it isn't supported corectly. Something as simple as a small spot of silicone adheasive locking to the covering to the PCboard is enough. The early spectrum RX didn't do that, just the hard solder joint and it failed. This may not have anything to do with your problem, but it's an easy check just to make sure.

By the way, I've got four Saitos from the 91 to the 180. That 180 will shake your socks off, at least in the Twist 150. The 91 and one of the 150s are smooth as silk. don't know about the other as I've yet to fly it.

Don
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Old 05-15-2010, 08:23 PM
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Default RE: 2.4ghz lockout/shootdown

Big Oakden, Did you range check your JRX9303 before you flew? I don't know if your Tx antenna is the problem or not, but I had to send my X9303 in for lack of range as I could only get about 30 or 35 ft from the Rx before I lost the signal. They replaced both the antenna and antenna pc board.

It now has above normal range (in excess of 120 ft) when doing a range check

Jim
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Old 05-15-2010, 09:55 PM
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Default RE: 2.4ghz lockout/shootdown

Wow. What a drag..........[sm=thumbs_down.gif]
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Old 05-15-2010, 11:43 PM
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Big Oakden
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Default RE: 2.4ghz lockout/shootdown

HAULING A,

I took the trnsmitter to over 90 feet as this was the 2nd flight on the 2.4 system. Everything worked just fine, as did the first flight.

I had also flown two other aircraft that morning on the X9303 before the mustang went in, so I know that it wasnt an issue with the Xmitter.

The Extreme Link had just flown about 30 minutes before and all was well on the first flight. I checked the voltage of the rcvr prior to the second flight and all was well again.
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Old 05-16-2010, 12:21 AM
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Default RE: 2.4ghz lockout/shootdown

its something in the air fellas, I swear... I fly at a private field, maybe 10 guys total ever make it out there... its usually me, the owner and a few close friends and everyone of our 2.4 guys lost planes some back to back

out of the failures

new 9503
tried and true 9303
dx6i
and 12x

thats why I love my 72

RACE
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Old 05-16-2010, 09:51 PM
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Default RE: 2.4ghz lockout/shootdown

i think, that, IF i were a JR guy, i would be looking to replace all my DSM/DSM2 stuff with the DSM3 stuff they only sell in Japan. it hops.
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Old 05-16-2010, 10:54 PM
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Default RE: 2.4ghz lockout/shootdown

Is the antenna on the 7000 a solid core? It sticks out either side of the unit, and I had to bend it straight. It seemed almost like I was work-hardining it!
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Old 05-17-2010, 07:12 AM
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Default RE: 2.4ghz lockout/shootdown

We've had no 2.4G issues at our field. With my AR7000's I put some 2-3mm heat shrink on the antennas. Just slide it over the plastic base, hit it with some heat to stick it on. Keeps it from getting bent up in snap rolls.
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Old 05-17-2010, 07:49 AM
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Default RE: 2.4ghz lockout/shootdown

You did not mention a couple of important things.

First, what type of battery are you using? Just because you had 6.5 volts after the crash does not mean that power was acceptable. Nimh and Nicad batteries can show acceptable voltage at no load or even a small load (half amp or so) and still get drawn down under any significant load.

Early on with all the JR/Spektrum stuff planes were falling out of the sky because the receivers are very sensitive to voltage drops and people did not understand this. Battery packs need to be maintained and checked under real loads from time to time. BY a real load I mean the power that would be drawn by your plane in the worst case. A 50cc size plane can pull over 10 amps in a hard snap, your power supply (including all switches and wiring) must be capable of supplying this much power for at least a few seconds without dropping below about 5 volts.

You did not mention if your receiver lights were blinking after the crash, assuming power was still on. This is important, it indicates that there was a power loss in flight.

Is anyone in your area having trouble with anything besides JR/Spektrum gear?

TF
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Old 05-17-2010, 08:44 PM
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Default RE: 2.4ghz lockout/shootdown

rctom:Both batteries were Nimh. the first crash happened on the first flight. I tested the battery after the crash with an 8ball tester under a 1amp load and still had 6.5volts. the abttery was seperated from the receiver by about 5 feet so there was no way to see the rcvr blinking.

The second crash was from 250ft up, leaving a 6"crater in the desert floor, and had to go back to the crash site to find the rcvr (Extreme Link) it was 25-30 feet away from the center of the impact point. along with the battery without any wires left in it. so no way to test that battry.

The other issues lately were all spectrum or JR.

We did have an isssue with a Futaba Fast 14mz that was on Fromeco Relions a voltage regulator, and a power expander board. (cant recall the name of the board.) this was a 100cc plane that just went dark on him during IMAC Maneuvers, about 8 months ago.
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Old 05-18-2010, 09:41 AM
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Default RE: 2.4ghz lockout/shootdown

I have to agree with rctom on the batteries. Checking the voltage under a 1 amp load may only be a marginal test. One servo can pull one amp under peak load.

Now here is the part where it gets complicated: If the problem was a voltage drop at the RX it may only have to be 10mS long. The only way to see that is with a scope to see what is going on right at the RX. You will never see it with a volt meter, they just are not fast enough. Also it would be nice to know the resistance induced by the switch so we can calculate voltage drop it causes. Again the best way to see this is a scope and better yet a storage scope.

Do most people have this lab equipment...NOPE. But as our systems and planes get more complicated it is the only way to prevent failures or point to the cause without speculating.

My guess is you are about a 7 hour drive from me....if you lived closer you could stop by my shop and I could show you what I have seen on a scope.

Good Luck,
Pete
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Old 05-18-2010, 06:06 PM
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Default RE: 2.4ghz lockout/shootdown

I am about 61/2 hours closer and I have a scope. In fact its battery powered so I can take it out to the field if I have to.
With the number of people flying on 2.4 I think we can safely say something else besides the frequency he was on caused the crashes.
The bandwidth on 2.4 is 85mhz. There is more room there than about ten times what 72mhz has. It would take a lot of sets on the air to fill that up and cause interference.
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Old 05-28-2010, 08:27 PM
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Default RE: 2.4ghz lockout/shootdown

Hey Joe

that comment is a joke ....right ?

You are going to "bend up" a 1 1/2" antenna doing a snap roll ?

Please guys - get real .
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Old 05-29-2010, 08:49 AM
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Default RE: 2.4ghz lockout/shootdown


ORIGINAL: Big Oakden

rctom:Both batteries were Nimh. the first crash happened on the first flight. I tested the battery after the crash with an 8ball tester under a 1amp load and still had 6.5volts. the abttery was seperated from the receiver by about 5 feet so there was no way to see the rcvr blinking.

The second crash was from 250ft up, leaving a 6''crater in the desert floor, and had to go back to the crash site to find the rcvr (Extreme Link) it was 25-30 feet away from the center of the impact point. along with the battery without any wires left in it. so no way to test that battry.

The other issues lately were all spectrum or JR.

We did have an isssue with a Futaba Fast 14mz that was on Fromeco Relions a voltage regulator, and a power expander board. (cant recall the name of the board.) this was a 100cc plane that just went dark on him during IMAC Maneuvers, about 8 months ago.
You still have not said if the receiver lights were blinking after the crash. JR/Spektrum receivers, if they have up-to-date firmware, will show rapidly blinking lights if there was a power loss to the receiver without the transmitter having been turned off.

Nimh batteries are particularly bad in this respect, especially the high capacity versions. In order to get more capacity they have increased internal resistance, this means that they will supply a small amount of power for a very long time, but if required to supply a large amount of power the voltage drops significantly. This is why A123 batteries became so popular, they are able to supply large currents any time.

Also, Nimhs must be taken care of. If allowed to sit around for months, or if abused by over discharge or over charge they can lose a lot of their capacity and not show it. The only way to really know is to duplicate the environment.

I built a tester out of an electric motor and ESC with a whatt meter and an old 72mhz receiver. I can plug in a battery pack and put whatever load on it I want. I'll bet you that if you try to pull 5 amps from your two packs the voltage drops down to about 3 volts.

Fooling around with spectrum analyzers and scopes is probably a waste of time until you verify whether you have enough power which I am 99% certain you don't.

Get some A123s and a good switch and the problems will go away. You can always call me for advice, 817-430-0107.

Tom Fawcett
Wild Hare R/C
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Old 05-30-2010, 09:22 PM
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Default RE: 2.4ghz lockout/shootdown




ORIGINAL: Big Oakden

rctom:Both batteries were Nimh. the first crash happened on the first flight. I tested the battery after the crash with an 8ball tester under a 1amp load and still had 6.5volts. the battery was seperated from the receiver by about 5 feet so there was no way to see the rcvr blinking.

The second crash was from 250ft up, leaving a 6''crater in the desert floor, and had to go back to the crash site to find the rcvr (Extreme Link) it was 25-30 feet away from the center of the impact point. along with the battery without any wires left in it. so no way to test that battry.
ORIGINAL: rctomYou still have not said if the receiver lights were blinking after the crash. JR/Spektrum receivers, if they have up-to-date firmware, will show rapidly blinking lights if there was a power loss to the receiver without the transmitter having been turned off.
Actually he did state that he couldn't see them blinking because both of the batteries had become separated from the receiver or the wires pulled out of the battery in the crash. While the feature is great for helping figure out what went wrong, it's worthless if the plane doesn't survive the landing.

Tony
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