Many people are under the impression that radio receivers, while being tuned to specific frequencies, are "brick wall" devices that will "hear" nothing but their tuned frequencies. This is absolutely not true.

Ever drive your vehicle near a broadcast FM station while having your radio tuned to a different station? Chances are you experienced interference from the "off frequency" local radio station. This situation is even worse with AM broadcast receivers and stations.

Model ignition pulses are generally in the frequency range of the human voice audio range. Radio signals do not begin to radiate effectively until they reach 15 KHz (15,000 cycles per second). However, at close range, such as the interior of a model airplane and even large model airplanes, electromagnetic energy can radiate far enough to induced voltages in the receiver, battery, switch harness and servo leads.

Our old systems (non SS) had problems much more frequently than the SS systems because the encoding data rate of our transmitters is right in the audio range of the human voice, meaning it was of a relatively low frequency that was serendipitously close to the same data frequency used in the older radio systems. It is my suspicion that the coupling occurred inductively, much like how a transformer functions.

The relatively narrow bandwidth of the system data stream of the older systems made it much easier to couple to the internal wiring than the much broader data rate used by the 2.4 GHz SS systems. While not immune to this type of ignition interference, it takes considerably more energy (field strength) to interfere with the SS system than the old single frequency radio systems. Also, the SS system data rate is significantly higher than the old R/C system data rate, meaning that it is not a close match between the ignition interference and the SS systems data rate.

No radio system in the consumers' hands will have brick wall filtering. It is simply too expensive to employ in our systems at an acceptable price. Meaning that we still have to pay attention to installing our ignition systems and our R/C systems carefully and we must employ good engineering practice. Once again, there are no absolutes.


Ed Cregger

Plus there is the harmonics effect.

Frequencys thar are multiple of others.
Such as our 72 mhz system is the harmonic of the 144mhz band or the 2 meter amature raido / Ham band.

And so on. There are less problematic multiples of the 2.4 ghz than the 72 mhz band.

Ralph our old field had lots of hits due to high voltage towers arcing across the insulators. The poping from the arc would cause rf and planes would go in. After the helo crew repaired the insulators the problem went away. So rf and hits come from many sources. Hopefully the 2.4 will be much better in this area.

Capt,n...FWIW, I put the Futaba FASST TM7 module in my 9C transmitter last August and have five planes on the system. All my planes are gassers from 100cc to 38cc and I have had zero problems with interference of any kind. I think you will be pleased with 2.4 when you make the change.

I was the one who originally asked the question and I ended up making the change. I found some problems in my servo extensions (cracked insulators around the wires in places) and replaced all of those. Almost all the interference went away but there were still random glitches that occasionally occurred for no apparent reason. I also found a crack in the insulation of the receiver antenna. I taped that up but it didn't seem to help.

I bought a 2.4 GHz Futaba 7C and since then things are rock solid. I'm not sure if the problem is being masked or if there was possibly a problem with the old 72 MHz receiver, which was about 2 years old (Futaba 7 channel dual conversion). I have flown the plane several times since the conversion and have been ecstatic with the performance. I finally have confidence in this plane not losing control due to servo glitches.

Gary

That is called splatter.

Before frequencys were set up that is how all raidos worked.
And it covers a wide spectrum of raido frequencys.
Of course it was all morse code and no voice communication back then.

73's

Nothing seems to beat trial and error
http://www.rcuniverse.com/forum/ques...l#post12223897

Nothing like digging up and updating an 8 year old string.

First, the Groupner system modified the XPS system and had problems. If you get the genuine XPS system you will have no problems.
2.4 is very resistant to interference. It employs spread spectrum that was developed for that purpose. However if you wipe out the entire band it will be interfered with.
The gas ignition system in use depends on ground connection thru the shield. If you have an intermittent connection in the shield you will get a spark there that will wipe out the band and kill your system.Mag systems were grounded internally and the spark plug wire required no shield as long as you used a resistor plug.
To guard against any interference, wrap a bare wire around the plug cap and ground it to the engine.

I've had an XPS Nano in one model for 3 years with no issues. This one operated fine last year and then stopped working properly this year. Lots of glitching and the off switch stopped working. Order was restored by swapping in a cheap Futaba FHSS receiver. It also works on channel 48AM

https://m.youtube.com/watch?v=3C5SnjLAKY0