drcuzo
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Post by drcuzo on Oct 27, 2008 20:35:47 GMT 10
I took my new Jaegar hotliner (From Andrew @ Falcon Gliders) to Bald Knob yesterday afternoon. Conditions were perfect to maiden it. I had TestPilot Sean all lined up. Radio: JR DSX9, receiver: Spektrum AR7000
When I powered it up, which scares the crap out of me ( - powerfull electric motor - hope the switches are off!!) the servos went ballistic. Mainly the right aileron which went full up and then a bit. The others were chattering +++. When the model was pointed at the tower the servo's went mad at 90 degrees very little activity. It was absolutely reproducible. Taking the receiver out of the fuse made no difference and the orientation of the receiver made no difference. Needless to saw I did not fly it. Sean had the good idea to take the ferrite ring off the motor lead and put it on the aileron lead, hey presto!! no interference.
This demonstrated several important points
1) 2.4 is not immune to high frequency interference.
2) the interference has nothing to do with the radio or receiver but is picked up by the servo lead.
3) the problem can be fixed with simple cheap ferrite bead filters.
It is now obvious why they put them on speed controllers - you don't want the motor starting on its own and cutting you to pieces.
Getting the small round ferrite rings is not easy/possible. The only ones I can find are significantly bigger from Jarcar.
Note to Self: Put filters on all servo leads of all planes I value.
But the jaegar looks awesome and i can't wait to fly it.
Steve
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Post by sean on Oct 27, 2008 21:26:32 GMT 10
The Jaeger is a fine looking model, quality of a Euro model IMO. Real shame we couldn't fly it.
Steve did a lot of testing and there was absolutely no doubt the interference was coming through the servo leads. I had exactly the same problem at Bald Knob while using a 2.4GHz AR7000 in my balsa electric 3D plane a few months back, only difference was it was on the elevator servo (it has a long lead thanks to the servo being in the tail). Before these incidents I had thought 2.4 was supposed to be immune to that kind of interference, but clearly not!
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Post by jirvin4505 on Oct 27, 2008 22:26:26 GMT 10
Ferite beads.... Took the Chili up to the Knob a few weeks ago and had simililar problems on 36mhz... The chili is old school hotliner (~1990's) and as routine with electrics in those days we had to be careful with interference. It has a ferrite ring (multiplex part) on each wing lead (servo's in the with HS101's ) and in my recent reconfiguration I had put the elevator servo in the tail GWS naro). Fly fine down on the flat ...up to the hill and the elevator servo goes beserk. Skyboyken suggested that the amplifyers in the servos can become overlaoded. I think this is the case and i will put a ferite ring on the elevator lead before flying at the knob. My wing has one servo that gives the same sort of greif however it is Rx dependant- on the Jr700 no worries, on the Schulze 5 chanel and Corona synth. 4 chanel the servo goes of centre which is orintation the wing is with the tower. cheers jeff PS Been coveting and desiring the Jager for some time - looking forward to seeing it go
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Post by Hamburglar on Oct 28, 2008 2:13:28 GMT 10
Thanks for the report Steve. It's really interesting!
I've heard of a couple of similar incidents.
One was of a US sailor racing an RC car on the flight deck of a carrier. He had a severe glitching problems which would come and go every few seconds. The car eventually drove itself overboard and was never seen again.
The other was almost identical but involved a RC plane.
Both were undoubtedly caused by radar. It's amazing how much RF energy these things put out into the atmosphere and the effects it can have on electronic circuits. Video cameras (the ones that use tapes) seem to pick it up really well. You can see and hear the electrical interference every time the radar makes a sweep.
This kind of interference happens every day. Vacuum cleaner interfering with the TV, cell phones interfering with the stereo, I've even seen a wifi connection that dies everytime a microwave oven is turned on. It's almost impossible to get away from RF interference in this day and age.
Putting ferrites on the leads was a great idea. You could always try and convince JR to make a fibre optic system (although I don't like your chances ;D)
I'm still a fan of Spektrum 2.4ghz. I've yet to see/hear about a problem that wasn't caused by an improper setup or operator error. I'm guilty of the latter. I specked out a glider with a AR6100e parkfly Rx in it and lost control for about 2 seconds. On Saturday I had my first chance to fly with a decent crowd. At times there were 20+ planes in the air. I saw more glitches on 72mhz radios in that one day than I'll ever experience in a lifetime on 2.4ghz.
The Jaegers look real sweet! Can't wait to read your flight report.
Jordan
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drcuzo
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Post by drcuzo on Oct 28, 2008 11:12:04 GMT 10
Jordan
I agree, I am very happy with the Spektrum/JR 2.4 radios. I cannot see me ever going to 36mHz.
I do however wish that they would make a full range receiver like the AR500 with end plugs. I use the AR7000 in my slope foamies which really is overkill.
Steve
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drcuzo
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Post by drcuzo on Oct 28, 2008 11:18:03 GMT 10
Ferite beads.... It has a ferrite ring (multiplex part) on each wing lead (servo's in the with HS101's ) and in my recent reconfiguration I had put the elevator servo in the tail GWS naro). cheers jeff PS Been coveting and desiring the Jager for some time - looking forward to seeing it go Jeff Wher did you get the ferrite rings - I cannot find a supplier Steve
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Post by jirvin4505 on Oct 28, 2008 12:20:21 GMT 10
Ferite beads.... It has a ferrite ring (multiplex part) on each wing lead .... Jeff Wher did you get the ferrite rings - I cannot find a supplier Steve Steve they were in the shed - ya just gotta understand my shed and the sickness of hoarding.... Jokes aside- They were a multiplex part - I think multiplex is handled by model engines these days. Could also try peter pine at flyelectric.com Also some leads here.... www.rcgroups.com/forums/showthread.php?t=239630cheers Jeff
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drcuzo
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Post by drcuzo on Oct 28, 2008 12:58:16 GMT 10
Jeff
Thanks for that Peter Pine was extremely helpful. He had them in stock.
Steve
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Post by thevon on Oct 28, 2008 18:29:17 GMT 10
About a month ago at Bald Knob I was getting shocking interference with my Nemesis. I thought - dang it's the Hitec RX, so I pulled out the new JR RS70 I'd just bought. Put it in, and same problem, but ... I also realized that servos were jittering when they weren't even plugged in! They had power since I have a wing harness distributing power + and - via one lead each at the wing/ fuse plug. But I had servos that the signal wire wasn't connected to the Rx, and they were still jittering! Weird.
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Post by chamm37 on Oct 28, 2008 22:32:17 GMT 10
this is all really interesting because i get nothing with my DX6.....fly it with no worries at all ae ;D
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drcuzo
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Post by drcuzo on Oct 29, 2008 10:03:20 GMT 10
Chris
It has nothing to do with the radio or receiver. I have used DX6i, DX7 and DSX9 with the same receiver on foamies - no problem (short servo leads). The issue is the length of the servo lead which acts as an antenna. The longer the lead the stronger to interference. Andrew's example is classic. The servos where powered, but the signal to drive the servo movement was coming from the high frequency EMI (electromagnetic interference). The ferrite rings filter EMI so no more interference.
The thing that worries me is the intensity of the EMI up there. It is very strong. I have not seen it anywhere else. I wonder what it is doing to the servos in our brains.
Steve
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Post by sean on Oct 29, 2008 11:33:16 GMT 10
Another thing to confuse the matter is not all servos connected to long leads pick up this EMI. For example my 3M Pike is using the same 2.4GHz receiver (AR7000) as Drcuzo's Jaeger but doesn't pickup this interference. I've seen a very mild form of it on my Carbon Bird but only when directy under the towers. Could it be that some servos pick it up but not others?
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Post by Hamburglar on Oct 29, 2008 11:44:05 GMT 10
Steve,
As a comparison you could try placing a cellphone near the lead and making a call. Cellphones put out peak power when they are ringing/waiting for a call to be answered. Once the call is established the transmitted power drops significantly. GSM phones put out about 2W and the more modern ones are usually <1W. If the interference is worse with the cell phone then you probably don't have to worry about cooking youself up at the tower. It's not a very valid test but the results would be interesting.
I've been told that the testicles and eyeballs are the first to be damaged by RF energy because of their inability to dissipate heat. I have also heard that men who are exposed to a lot of RF are more likely to father girls. I'm not sure how true this is.
-Jordan
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drcuzo
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Post by drcuzo on Oct 29, 2008 13:49:33 GMT 10
Jordan
Thanks for that. My best mate was a hornet pilot who has 1000's of hours here and with the US Navy on exchange. He points out that the radar on the fighters is so powerful that it cannot be turned on on the ground. He spent many hours leading formations of fighters with their radars pointed straight at him. He had trouble having kids but eventually had a girl. Cyclists have the same thing with increased numbers of girl babies as do older men. My mate is an old ex-fighter pilot cyclist - a miracle that he could have any children
Steve
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Post by skyboyken on Oct 29, 2008 22:41:14 GMT 10
I have over 3,500 hours flying in maritime surveillance planes with very powerful radars. Let's just say I don't need a night-light . In the old Neptune aircraft they had an enormously powerful radar. They kept track of births in the Squadron over a 10 year period. 98% girls. As for servo problems, here's my take on it as an old Electronic Warfare guy who used to know this stuff pretty well: The servos aren't picking up 'interference' in the normal way we use that term. What we call interference is when a signal which doesn't come from our transmitter is picked up by the receiver, processed by the receiver along with/instead of the proper signal, and causes random or unwanted servo movement, or a lockout. When a single servo moves without being commanded in the presence of a strong RF field, usually dependent on aspect to the 'interfering' signal, the receiver is not involved at all. Thevon's experience demonstrates this. Instead, the signal is conducted by the servo wire directly to the servo amplifier which then causes an uncommanded servo movement. Ferrite rings will almost always be effective in stopping this 'servo interference'. Sometimes simply disconnecting the servo wire from the receiver, twisting it as many times as possible and re-connecting it will be sufficient. It's worth a try anyway as it can often be done at the time. The other thing to try at Bald Knob is simply to move the plane away from the towers to where you intend to fly it, and try to repeat the uncommanded movement there. A little separation goes a long way with this kind of 'servo interference'. If it isn't already clear, 'servo interference' has nothing to do with either 36MHz or 2.4GHz. It only has to do with the servo(s) in question. I'm looking forward to seeing the Jaeger as well Steve ;D . Ken.
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