[AJCoholic]

Is 2.4Ghz affetced by stray rf signals such as the gasoline engine solid state ignition units?

I know I was always very cautious installing throttle and choke links (no metal, no battery or switches in close proximity to the ignition battery and wiring) when dealing with 72Mhz FM.

WHy am I asking? I was hoping to place my throttle and choke servos in my new plane up front and close to the firewall... since I am on 2.4 with this airframe for the first time in a large plane.

Anyone know for sure? (no guesses please).

Andrew

[Carl Layden]

Hi Andrew,

In practice and theory the answer is no. I'm sure there's someone out there that may disagree. In my own experience operating ignition systems with a 2.4 systems interference has never been an issue due to the ignition.

In theory the way 2.4 GHz systems work DSM2, spread spectrum, etc eliminates the potential for the interference. Two basic reasons, frequency is beyond that of the RF noise generated by ignition and the design of the receiver eliminates all signals not received from the transmitter it which it is bound.

I have seen a 2.4 GHz system experience interference. This was caused by a 2.4GHz video transmitter that did not comply with IEEE standards.

Hope that helps,
Carl

[JeffElecRC]

Originally Posted by AJCoholic

Is 2.4Ghz affetced by stray rf signals such as the gasoline engine solid state ignition units?

I know I was always very cautious installing throttle and choke links (no metal, no battery or switches in close proximity to the ignition battery and wiring) when dealing with 72Mhz FM.

WHy am I asking? I was hoping to place my throttle and choke servos in my new plane up front and close to the firewall... since I am on 2.4 with this airframe for the first time in a large plane.

Anyone know for sure? (no guesses please).

Andrew

Andrew,

Speaking as an electrical engineer, I will state that no one can tell you "for sure" that you are safe to put your servos close to your ignition. It will depend heavily on how well the ignition and wiring are shielded, the connector and signal quality between your receiver and servos, the locations and orientations of components in the system, etc. To quantify the noise in your system you have to contract a radiated emission expert and book some anechoic chamber time.

Short of that, the best answers you will get here will be "educated guesses" and personal experience. Here's my experience with my 2.4Ghz spektrum radio. In one plane I have a throttle servo within 2 inches of my gas igntion module and I do not have any issues. All I did was put an RF choke on the long wire back to the reciever. I did not use a choke servo, but I used an optical kill switch for the ignition battery.

On two other planes I have seen the igntion cause glitching in one or two servoes. This glitching I believe was caused by the servo signal wire directly (not the receiver) picking up noise from ignition because in both incidents all other servoes were rock solid. On one plane with twitching and deflecting ailerons at idle, I remedied this by shielding the spark-plug boot to the engine block and to the rest of the shielded spark plug cable (which was not previously shielded). On the other plane it was the throttle servo glitching at full throttle, I relecoted the throttle servo wire and it was fine.

Lots of people will tell you you should follow all the guidelines of a 72Mhz install because "the noise is still there and it is only hidden on 2.4Ghz, it will still cause problems you can't see, gremlins, etc...". While this advice is good because those practices of isolating components from noise will work with 2.4Ghz, the reasoning is wrong. The benefit of 2.4Ghz RF frequency with spread spektrum is that you are on a whole new playing field of noise. The low frequency noise caused by an ignition system will be orders of magnitude lower at 2.4Ghz then it would at 72Mhz. Add to that digital modulation techniques of DSS and FHSS, the noise caused by an ignition is insignificant. Of course there are other sources of noise at 2.4Ghz, but that is a whole new topic.

In short: install the components how you like. Do a range check with engine running. Ask someone to carefully monitor your servoes for twitching or random deflection.

Hope that helps,
Jeff

[BillGreen]

A personal experience was with a freinds 1/3 extra 330. Upon range checking with a 72 mhz rx, ignition noise was very apparent. We tried a PCM rx and got lockout during a running range check also. We decided to pull the 2.4 Rx out of his other gas plane, did a range check, no interfearance or lockout. Flew the airplane with great success and confidence.
I have personally have flown 2.4 on most of my planes, gas and glow. for the last 2 years.
Never had a glitch. I also use a data logger to verify the integrity of my system (spektrum) and arange satelite rx's for the least # of dropouts. My extra has the throttle and choke servo's mounted on the firewall box.

[3dflyer]

hi andrew .to answer your question.i have a wildhare extra 260 with a zdz 80,the choke servo and throttle servos are close to the firewall and so is my ignition battery.i switched to 2.4 when i bought the plane back in april.i,m running two satalite receivers and have not had any issues with any interference.i have many flights on my plane.so far so good.just my 2cts.

[AJCoholic]

Thanks for the responses, guys!

It appears that I can mount my servos up near the firewall - of course I will thoroughly range test the aircraft with the engine running - but I have confidence now that it will not cause trouble based on what I have read here.

AJC