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Old 05-12-2006, 03:27 AM   #1
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Default 40mhz RF interference help needed....?

does any one have any good ideas how to cut down on rf interference.
i have a hitec pro car 40meg fm trany which is fantastic but keep getting interference. the car is a xray t1fk05 with metal gear servo. receiver is mounted upright on top of the servo so the crystal is up away from servo in top corner.

last week there was either interference from another driver that was 40.745 (i am on 40.985) or somthing to do with where the transponder pickup wire was. every lap as soon as i got to the tracnspoder wire my car would stop like the motor had reversed (and i have no brakes set at 0%) or it would dart left or right in to the hoses. getting really frustrated with this now as i have tried everything i can think of to sirt this i also used to get this in my tc3.

one of the things i tried was changing the motor. it was better but next heat after the change it was back directly on the transponder wire ......at this club we dont run personnels so nothing else plugged in ...

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Old 05-12-2006, 04:01 AM   #2
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Ei, Subzero,
Does you motor have capacitors? If it doesnt have, try to install three non-polarized capacitors (0.1uF 50v). Install the first by soldering the capacitor leads to the positive(+) & negative(-) terminals of the motor. Install the second one by soldering the capacitor lead to the positive(+) terminal of the motor and the other to the ground (motor can). Install the third one by soldering the capacitor lead to the negative(-) terminal of the motor and the other to the ground (motor can). Try to install your receiver at least 2 inches away from your ESC and power wires. Graphite can also cause interference so use thick mounting tape in your receiver.
Hope this helps.....
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Old 05-12-2006, 01:53 PM   #3
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Mixing and mathcing on RC components can throw up some unfortunate combinations. Try using all Hitec parts with your Tx and see if that helps. Also, a high-power servo may take too much from your Speedo BEC and starve the receiver of power just when you need it. I think the fact that it happens over the loop may be a red-herring.

Capacitors on the motor, and use all Hitec RC gear, and see what happens then. HTH
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Old 05-12-2006, 02:19 PM   #4
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A few ideas:

- check your speedo and servo plugs. Sometimes you can get them to short each other out if the part where the metal bits face each other once plugged in.

- try another receiver/transmitter. Hitec aren't the best brand and they tend to be prone to glitching.

- try using caps on the receiver. If you plug a 1000F and a 0.1F in parallel on the 3rd channel you'll have a HF filter that should help sort glitches out.
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Old 05-12-2006, 02:31 PM   #5
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Finally my job can help somebody in RC racing!!
The 40Mhz band is a highly used band and is a very noisy band. By saying noisy I mean that anythign electric can cause a intermodulation within that freq. The spacing that you described between you and another racer looks good though you might want to see how old the crystals in your set-up are. After a year the crystal can actually loss the tuning characteristics that it had when it was new, causeing your radio and reciever can drift. that's why a Synth radio is A LOT better then the crystal system because you have a small diode that simulates the freqs. bandwave and allows you to stay cleaner longer. But they age just like crystals and need to be "tuned" and cleaned up.

Small electric motors need caps to clean their signature, electric, up and keep spikes out of the 40Mhz band. Your ESC can create small electric inteference if it's cheap or damaged. Check out your crystals and cap up your motor and you should be just fine.
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Old 05-13-2006, 08:28 AM   #6
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Raced at a different club last night and made one change the the car ....

i removed the servo and laid a peice of lexan allong the chassis up to the motor re mounted the servo on top so that it was screwed as such in place.

re mounted the speed controller on to the lexan sheet with double sided.

now didnt have any interference all night had one glitch with the motor but suspect that was heat build up car ran excelent

i shall also fit a cap to the receiver to clean up the power supply anyway.. i shall post the out come..

just to let you know all the gear is newish :-
hitec fm40mhz 40.985 40.715 40.815
element std end bell 19 turn 2mths (built in caps )
vega factory speed controller 5mths old

thanks for adivse given shall give the cap ago tonight.....
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Old 05-26-2006, 04:04 AM   #7
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WELL i have sorted out my interference finally

i have since purchased a sektrum and boy it ACE

i now can race with confidence nothing else seemed to work.
nothing i have tried managed to sort it out.

thanks for all your help BUT i can now well recommend the spekturm

all though i need to learn how to drive it as in other threads relating to the spektrum state that they are faster and turn in quicker than normal RF units.

BUT WAHT A PEICE OF KIT...... well done spektrum .......
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