RE: Rcexl Opto Gas Engine Kill Switch v1.2
I do not have any stored plots of such, but can tell you that if one looks at the interior circuitry and such of ignitions, there's very little reason to think that it could produce 2.4GHz signals. Besides, the RPM that one is running in a frequency is very low when translated to cycles and potential RF output.
One thing to understand: 72MHz technology had very little inherent noise rejection for bad data as compared to 2.4GHz which is a totally digital system and is spread across a wide band. It can filter out glitches,etc whereas some 72MHz would pass them right through to the servo outputs. PCM did a lot to mask the bad data. It was still there, but filtered out.
There are two types of interference-
1. Radiated (emitted as a radio frequency to air)
2. Conducted (sent down a transmission line)
Most of the issues 72MHz has seen are because of a signal that ends up on the same as that of the model's rf link or something that affected the internal IF circuitry,etc. 2.4GHz, while having varied types of transmission (DSSS, FHSS,etc) are a totally different system altogether. 72MHz is a very narrow signal and a very primitive transmission scheme, by comparison to the amount of bandwidth that a more complex 2.4GHz system uses, which reduces the probability of interference. If 72MHz was a frequency hopping/dsss scheme like 2.4GHz, it could be different. Think about it this way - 72MHz is less than 1MHz of available total channels and we only use one narrow channel (20kHz if memory serves correctly). 2.4GHz uses approximately 80 MHz of available channels to pick from, whether it is a hopping or Direct Sequence system (which typically spread the code over a 1Mhz or similar channel, or narrow, saw 20kHz if FHSS).
As for 2.4GHz, it is possible that lower frequencies can get into the system and affect its operation. But, one would likely not see local interference stepping on the transmission frequency. Think of it as a crowded room with discussion. The more people you have, the more the noise floor goes up. This is why separating things helps. Signal falls of with the inverse of the square of distance. The lower the noise floor, the better the hearing is. Your RF transmitter is shouting, but is further away than the noisy atmosphere near the receiver. The general rule of thumb is "he who shouts loudest wins".
Thus, without going into great detail, I stand by my statement that 2.4GHz is far superior in inherent noise rejection methodology.
Michael