Stick 40

I was in the LHS and saw these metal rings and the idea is, they reduce RF. The servo wire is warped in/around it and that is to reduce RF.
Are they of any help, the guy in the shop was a little dubious about it he said a good set up was a good idea.

sticks

ahicks

My Feedback: (2)

I would have to ask myself if the RF reduction is necessary before considering anything that might reduce it. Reducing something just 'cuz is overkill from where I'm sitting.

All Day Dan

My Feedback: (5)

They are useless at 2.4 Gigahertz. Dan.

av8tor1977

My Feedback: (6)

Dan, could you explain how they work for 72mhz and why they don't for 2.4 gig? Just curious and love to learn.

AV8TOR

castlebravo

They are small ferrite rings that when you wrap your servo wire around them creates small chokes. On especially long leads...they can help reduce induced interference. I disagree that they are useless on 2.4ghz systems.....its not the signal to the receiver that they are there for....its the induced ignition noise.
Now...with that said.....I've never had the need to utilize them...even in several 40% airframes where I've had 5ft+ servo leads. Ignition noise on most modern engines is due to the plug cap being loose or the shielding being compromised....both easily preventable. With ignition noise....you'll see certain surfaces acting funny....but not all of them.....with interference to the carrier signal to the receiver...it's all or nothing....and I agree that 2.4Ghz is nearly immune to this.
Make sure all of your ignition related connections are rock solid and you wont have to worry about it...


CB

av8tor1977

My Feedback: (6)

My 28% Extra had a problem the first time I started it up for a test run. Hitec Aurora 9 2.4 gig radio system. It wildly fluttered ALL the controls to the extent that I thought it was going to damage the servos and/or the controls! What I found was the metal cap on the spark plug hadn't been crimped shut properly, and there was a hairline opening in it. About the width of an Exacto knife blade. I crimped it shut properly, and the interference went away. In all fairness, I had a non-resistor plug in it just for the test run only, but still, it goes to show how important that ignition shielding is, even to 2.4 systems.

AV8TOR

Zeeb

My Feedback: (41)

A loose spark intended for the sparkplug is about the only thing that can zap a 2.4GHz system.

The ferrite rings usefulness or effectiveness is an Urban Legend only supported by anecdotal evidence that cannot be confirmed. If using them makes 'ya feel good, go for it.....

wnewbury

The ham test study materials said the ferrite rings are good for something but I don't remember (or understand) what.

ltc

My Feedback: (3)

Ferrite cores come in both split and ring (toroid) styles.
Thry work by dissipating high frequency signals (noise) into heat (very very low levels)
They are used in many products, usually on cables and come in hundreds of different compositions, which work over different frequency ranges. They are inexpensive and you can find lots of information on the web/wiki.
They can be useful on long leads in an RC plane if you have certain conditions present or used on the throttle lead between an ESC (SBEC) and receiver port.
For the vast majority of cases, you shouldn't need them, but if you use them 'just because' they won't harm anything.

Stick 40

OK,
that goes along with the guy at the LHS, hard not to believe him when he says not to buy something (not the owner).

Thanks for all the input, I will keep the spark plug caps on tight and call it good. I am not flying 1/4 scale yet.

sticks

All Day Dan

My Feedback: (5)

AV8TOR, 2.4 Gigahertz is in the microwave region. Normal circuit theory does not apply. Those torroids or inductors are meaningless blobs. Dan.

Lifer

My Feedback: (1)

The assembly manual of my Hangar 9 109" Cub called for them on the aileron leads. They are fairly long. I can't say as they are necessary but there has been no interference issues. The wings do have large metal struts attached and this may have been a case of prevention rather than a cure.

ltc

My Feedback: (3)

I wouldn't call them useless blobs.
I agree that most of them don't have effective impedance at 2.4GHz, but they are designed to suppress frequencies below 1GHz, which is the usual source of radiated emissions or immunity problems. They prevent the wire leads from acting as antennae. Again, they are very common and well understood in electronics.
Again, they have a specific purpose on when/where they should be used. Even if applied when not needed, they will not cause any problems.

Stick 40

I was thinking of the throttle servo mainly.
on one of the threads a person with a giant scale had a throttle servo go full throttle on him. Lucky it was on a stand and he was not close.

I don't fly the big 1/4 or giant, and if a plane "goes in" I can live with that, but I like my fingers a lot.

sticks

ltc

My Feedback: (3)

Throttle servo likely due to proximity to ignition module/wiring.
Similar situation on some ESC's SBEC.
The issue is conducted noise on the (long) leads causing internal interference in the servo or receiver.
By installing the ferrite core on the leads, the unwanted high frequency noise voltage is reduced (dissipated as heat at an inmeasureable level) and the interference is eliminated or improved.
You see ferrites everywhere ... mainly on computer cables, power supply charger cables, etc ... they are normally overmolded in plastic on the cables.
In RC, the only thing we need to do is secure the mass of the ferrite so it doesn't cause the wire to move around.

Stick 40

that is a good point, making it secure and not flying around. pun intended !! I guess I won't get involved with them as I have very short leads, not over about 15" long.

thanks for all the input, great help.

sticks

castlebravo

That was me....and it was scary.........It was a loose plug cap on a DA-50. Fixing the plug cap (adding a small hose clamp around it) resolved the issue. I have doubts a ferrite ring would have helped but in the end it was not needed....fixing the issue with the plug cap resolved the bigger issue....unfortunately it cost me a severely damaged plane to figure it out....

CB

Stick 40

I was impressed with your post, safety is a big thing with our hobby, when we share issues like this we make others think about it.

a severely damaged plane is nothing , compared to a severely damaged hand!!

your post was what made me bring this up, I am always looking for the safe way. I don't think they are the answer, but had to ask.

thanks

sticks

dirtybird

My Feedback: (5)

There is a lot of BS still floating around about interference on 2.4.
The fact is the only way you will get interference is if the entire band is wiped out. That can happen if there is an unshielded spark somewhere.
An external ignition depends on the shield to provide its ground. If you break the path you will get that spark. The way to fix it forever is take a bare wire and wind it tightly around the shield then ground the other end to the motor. Then you wont have to worry about a loose cap.
BTW a toroid is very effective on 2.4.
.
It is even more effective than on 72. It is just not needed

ltc

My Feedback: (3)

I am going to have to disagree on the effectiveness of a ferrite at 2.4GHz. Most ferrites will peak below 1GHz and will be falling off as you go past 1GHz.
If we are talking about a wound torroidal core ferrite, the interwinding capacitance will shunt any effective impedance that the ferrite can possibly provide.
If you merely extrapolated your simple equation, it would imply that you can get any impedance you desire from any inductor at any (high) frequency. It does not take into account parasitics or any other model parameters.

dirtybird

My Feedback: (5)

It is still very effective
Its a moot point,though,capacitive reactance will have everything shorted out between the leads at that frequency before it ever gets there.

Lifer

My Feedback: (1)

The pair of torroids weigh about 1/2 ounce. Use them. Nothing negative about them on long leads.