Strange behaviour... Phoenix Models Extra 330s EP

Ed Cregger wrote:


But sadly not on 36Mhz, where all shifts are the same.
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Rats! Just when you think you've learned something, you learn something else. And that metal on metal thing you mentioned was eye-opening, too. Care to expound?
Harlan
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H Davis wrote:

OoH. Its the oldest issue in the book. Dissimilar metals - the classic is a brass throttle arm and a steel pushrod - make a tiny battery, and as they rub together you get micro sparks.
Get an AM radio, tune it to a weak station and try it. You will hear all sorts of stuff.

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Thanks for the explanation. I admit that the reaction of dissimilar metals isn't complete news to me, but I didn't know the mechanics of the corrosion.
Harlan

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| OoH. Its the oldest issue in the book. Dissimilar metals - the classic | is a brass throttle arm and a steel pushrod - make a tiny battery, and | as they rub together you get micro sparks.
That's not the way I understand it, or at least that's not the entire story. Well, sure, dissimilar metals can create a voltage, but the effect that causes metal rubbed on metal to create RF noise is somewhat different or at least there's more to it. For example, two similar metals rubbing on each other will cause the same effect -- you don't need dissimilar metals.
As I understand it, the effect is caused by a non-linear interaction between the two pieces of metal, which causes it to re-reradiate the RF signals it receives (including the one created by your TX, but also signals from FM radio stations, TV stations, cell phones, etc.) at different frequencies (the frequency change is caused by the non-linearity.)
If the two pieces of metal are connected somewhere else (like a single wire soldered to both pieces) then they won't make this noise, even if they're rubbing against each other.
| Get an AM radio, tune it to a weak station and try it. You will hear all | sorts of stuff.
That much is true. It makes a lot of noise.
To see it on your plane, just remove your prop (if it's an electric -- you don't want it roaring to life) and turn your TX and RX on and then go near your plane and rub two pieces of metal together -- two metal pushrods works very nicely. If you have a PPM (not PPM/DSP or PCM) RX, you'll generally see your servos chatter.
--
Doug McLaren, snipped-for-privacy@frenzied.us
Oh, spiteful one! Tell me who to spite and they shall be spoten.
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Similar problems sorted by moving ESC as close to motor as possible and moving battery connector to opposite side on plane to RX. Definite glitching when battery connector was moved close to RX as could happen during some flight manoeuvres. Wires and connector now restrained with lightweight nylon ties. Some Phoenix, VQ and similar ARF were covered with a three layer peel & stick material (not solarfilm) of which the bottom layer was a metalised material which caused mayhem unless RX aerial was routed shortest way out of model to top of fin and trailed out. (care during range tests that the RX aerial is not close/touching ground) Good article on avoiding interference at: http://www.friedrichwuerth.de/scale-models/RX-gb.pdf and more on my web page under "Radio Systems, Accessories, Alterations and FAQ"
Regards Alan T.
Alan's Hobby Model & RC Web Links http://homepages.ihug.co.nz/~atong /

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OK, I have just replaced the JR RX with a Futaba PPM RX and all is well. Not a single jitter!
I have also spoken with a couple of hobby shops about this matter and they both said they have had nothing but problems with HS55 servo's jittering with JR RXs.
Very strange because my mate is running a 3D foamie with HS55s and JR610 with no problem at all.
Thanks to everyone for their input. Much appreciated.
Regards,
Troy.

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Well my excitment was short lived....
In my earlier post I mentioned that all is well now that I have swapped RXs for a Futaba but didnt realise I had mentioned that the RX was PPM when it is infact PCM. The PCM was just masking the jitters, they are unfortunately still there as bad as ever!
I have now swapped out all HS55 servo's for cheaparse S75 Spektrum servo's and low and behold. Problem solved! Definitely!
I have also found many more posts on the net from others having the same problem with HS55 servo's.
I had previously removed each HS55 servo one by one to see if it was just one of them causing the jitters but they all done it. Two of them are old from a mates plane and two of them brand new purchased 2wks ago.
Regards,
Troy.

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Troy wrote:

Mmm.
The odd thing is that I use these pretty exclusively, and its only some from this year that have been problematic. Possibly,. Not gotten to the bottom of that one yet.
Anyway, glad you have fixed the problem.
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Troy wrote:

My uncle bought this same plane. He had the same problem. He called the company and tthey said about the first six hundred were going to have problems. They sent him a new one for free.
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Do you have the contact info for Phoenix?
Not worried about getting a replacement now because this one is flying fine. But I would like to discuss the problem with them to hear what they have to say about the matter....
Regards,
Troy.

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I found their contact info but have since had the HS55 servo's out on a bench nowhere near the plane and they still jitter when I walk away with the TX antenna down at around 5 feet which is terrible. I have tried countless RXs, TXs, batteries and crystals with no luck. I have tried with and without Y Leads and Ext Leads and still no luck. I swap the servo's out for JR and Futaba and the problem is solved. I can get easily 100feet or more without a single glitch!
I have sent Hitec an email to hear what they have to say about this issue. I don't expect a reply though..... Sent them a query a few days ago and no reply as yet. So I have sent another one tonight with my findings.
Troy.

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