harmsal

My Feedback: (49)

I have a new ARF, a ModelTech Formula 3D with a GMS .76 two stoke engine with a Pitts style muffler. All servos are Futaba with a Berg receiver. Here is the problem, with the engine off, all control surfaces remain rock steady. As soon as I start the engine, all control surfaces go crazy moving in all directions including the throttle servo. If I stop the engine, the control surfaces go back to normal. What gives?
I have changed and balanced the prop - routed all servo wires away from the antenna lead - tried a new glow plug - moved the antenna lead away from all servos - tired a different receiver and crystal - non change - what am I missing?
Thanks
Al Harms

pmw

My Feedback: (1)

Sounds like metal to metal vibrating somewhere. I had this happen once and found it was a metal clevis I had used on the metal carb arm. Also check anything else that's metal such as gear, axles, metal servo arms, tail bracing wires, etc. Make sure the receiver is not vibrating or hard mounted. Good luck.

MinnFlyer

My Feedback: (4)

Yep, a metal clevis on the throttle was the first thing that came to my mind too

PMAXX

My Feedback: (5)

Pushrod rubbing on the muffler maybe?

spitfire66

I lost an airplane because I had throttle linkage running in between the muffler and the engine. When the engine was running the throttle rod touched one of them and caused the same problem. I recommend using a ball link for the throttle setup and make sure you don't have metal on metal. Good luck.

zbird

Can someone please tell me how metal to metal contact can interfere with a radio signal, or the problem harmsal is having?

flaminheli

No explanation. It just happens. You don't want any metal to metal at the throttle arm, control rod with a z bend is another problem as is the metal clevise mentioned earlier. If you have a metal to metal contact on any control, which is used at the carb more than anywhere else you need to replace it with a plastic clevis.

zbird

Thank you for your reply, I was hoping there was some science behind it.

harmsal

My Feedback: (49)

I want to thank all those who answered my question. I did have a metal control rod to the throttle and I replaced it with a golden rod and the problem vanished. Now I need to figure out why the GMS 76 caused radio interference and the Tower 46 did not. Both had metal rods to the throttle. After today, the Tower engine will now have a golden rod instead of the metal rod. Thanks again for the response!!

jetmech05

Could you be using a metal engine mount? Is the engine tight in the mount if you are?...Did you check the resistance on the aircrafts switch in Rx10000 range...it could be that the vibration of the engine is causing a problem inside the switch which is setting up interference......good luck in your search

Deadeye

There is. Everything on this planet generates (or has the capability to generate) a radio frequency. Metal to metal vibration creates a high frequency radio wave that sometimes matches our 72 mhz band close enough to cause the interference.

That's the science in layman's terms.

vertical grimmace

My Feedback: (1)

You can also experience this if you have a cracked RF filter in your RX. This usually because of a crash. I have sent many RX's back to Hitec for this and they fix it cheap. I know this from flying a lot of combat. A lot of times, the RX is fine until throttling up to full throttle and then it goes crazy.

StevieLWells

What Causes My gas to keep running from my tank to my exostpipe or in to my moter when its not running? This keeps flooding my moter so I cant start my car and also waisting my gas.

jaka

Hi!
Are you sure that you use lots of soft foam around the battery and receiver...?

-pkh-

My Feedback: (2)

Many guys that have had glitching with 72MHz radio systems due to metal on metal vibration, carbon fiber components, ESC noise, etc. have found that going to a 2.4GHz spread spectrum system eliminates their problems.

Deadeye

I'm going to have to disagree with you on this point. 2.4 ghz is STILL an FM radio frequency. 2.4 ghz IS prone to radio interference just like 72 mhz. If their problem magically went away with SS, then they are just masking the problem like PCM does for 72.

-pkh-

My Feedback: (2)

The argument is that the higher frequency gets you out of range of most of the noise energy put out by those noise sources, AND the transmitter's spread spectrum signal is spread out over a much larger bandwidth than FM, so noise source spikes are less likely to cause problems on the receiving end.

The military uses spread spectrum precisely for this reason, the signal energy is spread out over a large bandwidth, making it difficult to detect and/or jam.

No form of spread spectrum can be considered "FM".

Robotech

My Feedback: (9)

However you want to say it but it does not eliminate the problem. It might eliminate the symptom though.

Robotech

My Feedback: (9)

Heres some thing to check. I can't because I don't have either engine. See if one engine has a metal throttle arm and the other a plastic arm. That would explain it.