[Bdegan2]

OK, after reading Narly1's post and he mentioned Latency. I thought that it would make an informative topic of discussion.

As Narly stated...

Originally Posted by Narly1

1. "Latency" is a fixed delay between the time when you turn the wheel or pull the trigger and the time when the servo first starts to move.

I have dealt with Latency in a different respect. It was with Music. Either in a live venue or in a recording situation. It can really mess with how you hear things or timing.
An example is when you see an NFL football game. The referee presses the button on his transmitter to announce a penalty.
You see his mouth start to move and then you start to hear what he is saying. And if you pay attention, you notice that he actually has to wait in between sentences for the sound of his own voice to stop coming across the PA system before he can start his next phrase.
But then there are other annomilies at play there as well. Such as reflections and echo.
Which are also present in our radios and receivers depending on where you are.

Now that this has been said, on to the main topic here.

Radio delay. The time form when you enter an action, to the time the receiver, receives it and tells the servo or ESC what to do. And the time it takes the said item to start actually doing it.

1) Does anyone know what the delay time is of most radio systems ?
Spectrum?, Am?, Fm?
Is there a difference between brands of radios.
If I remember, the Futaba HRS system used in the 3PK radios is supposed to have a reduced latency time.

If possible, lets keep the discussions and any answers to having actual facts behind them. Not just hypothetical, ie.( "Well I used my buddies radio and it was soo much faster than mine".)

Part 2) Reflections or echoes.
Your transmitter sends a signal, the receiver receives it. But then your receiver gets a second signal causing glitching.
This signal is not from another radio. It is the same signal that your transmitter sent out, only it has bounced off of another object and has been picked up a second time by your receiver. With a slight delay from the first signal. This is in milliseconds, 1 to 4 milliseconds.
This delay is practically imperceivable by the human brain ( which by the way has its own latency )
This causes what we perceive as a glitch or twitching in our cars.

Are certain frequencies more suceptable to this fenomenon?
AM, FM, spectrum/2.4Ghz.

Lets discuss

[adam lancia]

from what i know about it (admitedly not as much as some ) i think am and fm have similar latency periods. that's not counting the futaba, airtronics, ko, jr "fast" systems. i've read that pro drivers can feel an appreciable difference between the standard spektrum system (non-hrs in futaba) vs the futaba hrs crystals system. also, they've said that the fasst 2.4gHz futaba system is faster again than the standard hrs crystal system...the spektrum pro which is almost as fast as the crystal-hrs is somewhere around there as well. i know that airtronics and ko and jr are working on their own 2.4 gHz low latency systems and nomadio's radios are (i think!) the fastest out there. but there has to be a point where fast is too fast, i just can't say for sure where that is. i think that once you get used to the time it takes for the car to respond to a signal you'll be in good shape to drive fast. i would think that only the top 10% of drivers in the world would actually benefit from super low latency.

[Speed Metal]

When going from a Spektrum DX3 to a Nomadio Sensor I saw and felt an appreciable difference. The Sensor is much "faster". It's a remarkable radio in that regards. I was surprised and very happy when I tried it for the first time. I honestly think by just switching to this radio I will chop a tenth or two off of my lap times. Especially compared to the DX3 which is a pretty basic radio when used for racing.

Don't really know how the Sensor compares with the Spektrum Pro and Futaba HRS 2.4 GHz systems as I don't recall if I've tried those systems or not. But from what I understand, the Nomadio radios transmit/recieve at a higher frequency than the rest of the 2.4GHz crowd. And it's for this reason that the Nomadio is "faster" than my DX3 was.

regards

speed metal

[Bdegan2]

Was this noticable difference using the same servos as your prior setup?
In other words, did you just swap out the transmitter and receiver. Or were the servos different as well?

[Speed Metal]

Originally Posted by Bdegan

Was this noticable difference using the same servos as your prior setup?
In other words, did you just swap out the transmitter and receiver. Or were the servos different as well?

Same servos just swapped from Spektrum radio to Nomadio radio. That's it.

regards

speed metal

[Narly1]

Originally Posted by Bdegan

I have dealt with Latency in a different respect. It was with Music. Either in a live venue or in a recording situation. It can really mess with how you hear things or timing.
An example is when you see an NFL football game. The referee presses the button on his transmitter to announce a penalty.
You see his mouth start to move and then you start to hear what he is saying. And if you pay attention, you notice that he actually has to wait in between sentences for the sound of his own voice to stop coming across the PA system before he can start his next phrase.

Hi Brad,

The effect you are descibing above is actually the difference between the speed that light travels at (in free space) and the speed that sound travels at (in air). The respective figures are roughly 300 million metres/second and 340 metres/second, so this is why you see the lips move before you hear the words on the PA system.

Radio waves travel at the speed of light in a vacuum. Thus it takes a certain amount of time for the command signals from your transmitter to get to the receiver. This is called propogation delay. Here is a link to a very good example/explanation:

http://en.wikipedia.org/wiki/Speed_o...ations_and_GPS

Latency is a different kind of delay caused by the DSS encoding used in the Spektrum radio system. To simplify, the encoding scheme means that a whole bunch of overhead occurs in the digital domain before your actual command input gets converted into a RF (radio frequency) signal and transmitted to the receiver. It all has to do with finding a clear channel and making sure that the transmitter and receiver are "synchronized" together, aspects which make the Spektrum "bulletproof".

So the total delay from end to end in our R/C systems = latency + propogation delay + servo or ESC speed. (LOL, I should have thought about this a bit more before I posted my thread about fast servos last night. Obviously I wasn't thinking clearly at that late hour!!)

Hope this clarifies,

Narly1