dickhoover`

Where can I get Ferrite Beads or Ferrite Rings?

Thanks, Dick

exeter_acres

My Feedback: (2)

http://www.horizonhobby.com/Products...ProdID=JRPA029

TFF

You can twist or braid the servo wire too.

BarracudaHockey

My Feedback: (11)

What does that do?

Other than make the wires twisted?

TFF

The errant signals and voltages can cross to another conductor that runs parallel to it. They radiate out 90 deg from the path. Braiding is the best as the wires do not run parallel anywhere along the run. Twisting is not as good because the pathe is not broken as much but I have had to do it and it works. All older radios had braided wires, but now we run off the shelf wire and connectors from computers and the better electronics dont emit as much.

dickhoover`

Thanks guys, I appreciate the answers. I'll post the results when I get them on. BTW, I did wind a 3 turn coil in the excess servo lead, and it didn't help at all. The extensions are already braided.

Dick

TFF

How long are the runs? Radio shack has the beads sometimes. I try to get as many turns that will stay on the wires.

dickhoover`

Update on ferrite rings.

I ordered some ferrite rings from Mouser Electronics (http://www.mouser.com/) They are Wurth part nr. 7427012, they are $1.22 each. They certainly do the job, but they are larger than I expected. They are 15/16� OD, ½� hole, and are 9/16� long. They weigh 34 g (1.2 oz). I ordered that size, getting the one that had the highest Z (impedance) with a hole big enough that I wouldn’t have to cut the servo lead to get it on. With this one, just passing the servo lead through the ring would not cure the problem but one turn around the ring did the job, no jitter no matter how close the transmitter.

I think the next time I can get a smaller one, Wurth 74270121, and I will have to cut the servo lead, and put a couple of turns around the ring. These weigh less than 3 g.

Just for info, the ship is a Rascal 40 with FMA servos and receiver. The transmitter is a JR 8103. I am using the separate aileron setup so I can have differential. I have the receiver buried, and have a couple of 3� servo extension to bring the ailerons up to the bottom of the wing. The aileron servos are about halfway out the wings, so I have a 12� extension there, plus the regular servo pigtail. I put the rings on the extensions where they leave the wing near the center, over the fuselage interior.

I have had this type of problem with larger sailplanes in the past, but not nearly as severe. Besides, I cheated on the sailplanes, I collapsed the antenna to reduce the transmitter power, and the jitter went away. I would launch, and as soon as it got away, I would pull the antenna out on the transmitter. Not good procedure, I nearly lost an unlimited when the transmitter antenna became unscrewed, and I pulled it off the transmitter. I did figure out my mistake, and got the antenna screwed back into the transmitter before the sailplane hit the ground.

The Rascal would not just jitter, the servos would go wild or even freeze up. But these rings cure it, no jitter no matter how close with the transmitter.

Dick

Gray Beard

My Feedback: (-1)

There is also another product called a servo choke that plugs onto the lead that dampens things down too. Don't know if it would help out. I had to use one on a gassers throttle servo to get rid of the little bit of RF I was getting, it removed the jitter I was picking up. Not as cheap as the chock rings though. Mine was made by JR and sold through Horizon.

JPMacG

My Feedback: (2)

Allied Electronics www.alliedelec.com has a good selection of ferrite beads. You should be aware that ferrite beads come in many different material compositions. Some compositions are effective at 72 MHz and others are not so good. Fair Rite Products Inc www.fair-rite.com is a major U.S. manufacturer of ferrites. You can read about their materials on the website. Their Type 31 and 43 materials would probably be a good choice for 72 MHz. These materials are commonly available, through Allied and elsewhere.

No ferrite has much effect above 1 GHz, so don't bother using them if you are using spread spectrum.

dickhoover`

I decided that having the ferrite ring hanging by the servo lead was not a good way to go, so I put it down on the floor of the cockpit. The receiver is mounted on the bottom of the floor. I also used just one ring, and ran both leads through the ring, made one turn and back through the ring again. It works fine, absolutely no jitter. I will be test flying tomorrow, and I’ll post a report after.

Another question, how do you put a picture in a reply? Is there someplace on this forum that gives some help? I would put a picture of this if I knew how to do it.

Dick

BarracudaHockey

My Feedback: (11)

Twisting is great for phone and network cable where multiple signal wires are running next to each other to prevent cross talk.

For servo wires its a sugar pill.

Robotech

My Feedback: (9)

When you are in the post editing box you will see a blue link on the bottom left that says "Click here to upload images".

dickhoover`

Well, I wanted to test fly today, but I found out I still have the problem. And it seems to not be just at close range. So the next step is to change out the receiver.

Here is a picture of the toroid as I installed it, with both servo leads going through the toroid. I'll change out the receiver tomorrow, and test some more.

Thanks to Robotech for the picture upload info

Dick

oceansfiftyseven

Dick,
I use ferrite rings also. I have found that they work better when I wrap the servo leads at least 3 to 5 times through the ring. I also locate the the rings on the wires as close to the receiver as possible. Rich

FILE IFR

For servo wires it's a 'sugar pill'?.... incorrect assumption.

dickhoover`

I was going to change out the receiver, but I ran a bunch of tests this afternoon, and the receiver I was going to change out to did no better than the one I had in the Rascal 40. So I think I am going to follow your suggestion and put 4 or 5 turns. I am also going to use a separate ring for each servo.

What rings are you using?

Dick

oceansfiftyseven

I use these as they are cheap.
http://www.horizonhobby.com/Products...rodID=AGNR1000
The hole is small so I have to remove the pins from the connector. Easy enough though.

dickhoover`

Here is the answer. I added a ring on each servo extension and put 2 turns on them. I did leave the first one on, Totally eliminates all servo jitter. I could get no jitter or any non commanded movement with the transmitter antenna at any distance or orientation. These are large things, but there is no effect on the Rascal 40 performance. Next time, I will get some smaller ones. I hope this helps someone, and I want to thank everyone who contributed.

Dick