bubbleboy

I am building a 1/6 scale Polikarpov I-152 which has a 67" wing span. It has a Super Tigre 2300 engine. The radio is a JR 5 channel with 577 servos for rudder and throttle and 539 for elevator. A JR mini servo for each aileron. The problem I am having is that when I get about 3 metres from the plane with the radio on, all the servos start to "Jitter". I have never had this before and have used this same radio in other models without this problem. I have changed the receiver with the same effect still there. Tried unplugging each servo individually to eliminate any interferance. Still does it. By moving the receiver aerial around can improve it but not eliminate it or can make it worse. I am scratching my head??? There are no substantial metal parts on the model that could cause interferance. Can any one offer any help????????[]

The Ghost

You don't say where you are running the areial. Try it out the top of model to rudder.

Cheers.

bubbleboy

I was running the aerial through the centre, inside the model. I took it outside to try it and it still does the same.

Rodney

The first thing I'd suspect is the wiring. Either to small a gage, bad switch, poor connections etc. or a battery with a high internal impedance (not likely but possible).

Montague

To add to what Rodney said, if you haven't already, try to make sure that the antenna stays as far away from other wires as possible.

If you take the wings off the fuse, does it still happen? When you unplugged the ailerons, did you unplug them at the RX, or did you pull the servos from an extension in the wing?

redfox435cat

After triple checking the wireing and all the connections

try another newer battery

if that doesn't work try putting a 3" extesion on a couple of your longer servo runs. I've run in to this twice with my thermal gliders. The servos leads were close to the reciever antenna length and was messing with the reception. by adding 3" to the leads mismatched the length enough to aleviate the problem

bubbleboy

Thanks guys...I will certainly try these suggestions, I appreciate your help.

Montague

Btw, if you find the problems are related to the aileron extensions (assuming you are using some), you might make the problems go away if you cut the servo leads and solder in the extensions. There is a small, but non-zero voltage drop in each connection, so if you can eliminate some of that, it can help.

Kaos Rulz

Is your TX antenna fully extended when you're 3 meters away and the servos jitter? If so, do they jitter when the antenna is collapsed? It sounds to me like you're swampping the receiver. This usually happens with freshly charged (healthy charged) batteries. See if the jitters stop after a partial draining of the RX and Tx batteries. Usually the equivalent of one flight should tell the story. Also the servo jitters are more prone when using a 6 volt receiver battery.

Bottom line is that this type of servo jitter is not harmful at close range. You just need to be aware of it and compensate by collapsing the TX antenna. I'd only worry if the servo jitters at distance. Then you have a problem.

Montague

Ed,

Good point. I've seen this exact thing myself.

I read the origional post to imply that he was starting in close to the plane, and jitters appeared as we went out from the plane and reached about 3m. But he could have meant coming in and getting to 3m.

bubbleboy

Thanks guys........I have soldered the connections as much as I can. With the TX aerial collapsed it starts to jitter at about 3 metres walking away from the model. No jitter when next to model. Extend the TX aerial and it is not too bad. I am running 6volt NiMh battery pack for the first time with this radio set.

Kaos Rulz

OK now I understand. You definetely have a range problem. Don't fly until it's fixed. You have swapped receivers with the same results and this points to the TX, or the install layout.
I would take the receiver, battery and a servo out of the plane and range check it. This should isolate the install as being the possible culprit. If the range check (outside of the plane) is OK, you then know the TX and receiver are good.

Rodney

If you can, get another battery (4.8--4 cell) and plug it directly into the receiver; i.e. bypass the switch and switch harness and see if the problems dissappear. If they do, try it with a 5 cell battery. If it still works, put a NiCad battery in place of your NiMh, some NiMh have to high an internal impedance if you are using high current servos. Doing a direct plug in to the receiver, bypassing the switch harness, will tell you whether or not the switch is a problem.

Blixsim

take care of that 539 servo. The guys in South africa have reported a trend in 539 servo failures and expensive crashes

BillS

Fresh charged 6v batteries will often create a jitter problem. Multiple servo connectors for a servo will make the problem worse. I found Futaba 1/4-scale servos to be very jittery around neutral with a fresh charged 6v battery and Hitech 1/4-scale servos to be very quiet. I found connector resistance as small as 0.5 ohm to create jitter. The jitter always went away when the edge comes off the 6v battery. A full charged battery would sometimes be almost 7v. With 4 cell batteries the jitter was not seen.

Hope the information helps.

Bill

jaka

Hello!
Sounds as if you have a range problem.
With my JR radio(s) I have had 100m in range with the transmitter antenna totally collapsed. This is what all my JR radios have had since I first started using them in 1980.
My club's Futaba radios (Skyward and 7ch Gold series) also have 100m range with the antenna fully collapsed.
I personally always have my receiver antenna inside the fuselage and despite often using wire pull-pull systems to control rudder and elevator, next to the antenna, I have never seen any ill effects of having it that close to other metallic objects.
Once, in 30 years, I have noticed that the range of my JR radio was down to about 50m with the antenna collapsed...it was the receiver that needed trimming.
Having returned it the range was 100m again.

Regards!
Jan K
Sweden

ballgunner

My Feedback: (1)

I replaced the TX 4.8V battery in my Fairwind sailboat with a 6.0V
and immediately got the jitters. Of course the boat only has two servos but the important one is for the rudder. Took out the 6.0V and no more jitters.

Garret H

My Feedback: (15)

This same thing happened to my brother with his JR radio. He had a 4.8 volt receiver battery in his plane and it did not jitter; as soon as he went to a 6.0 volt battery, it started jittering.

speedster 1919

My Feedback: (3)

This is an old post . Did you get it fixed? Two club members had the same problem as you and both turned out to be servo extentions. I had a simular problem , but a new switch solved my twitches............

shogunmst

My Feedback: (3)

Had a guy at out fly feild with a simulor problem, after loosing a 2nd plane in one day he sent his radio off to get checked and they changed out some sort of filter and WALA, problem solved. Maybe you should send the radio off for a check up.
Good Luck
Shawn

acam37

My Feedback: (16)

I had that problem once and after extensive troubleshooting I found that a metal clevis connected to the carb throttle arm was vibrating (metal to metal) and causing the interference. I now only use nylon clevis's.