theclutch

iTrader: (2)

Most folks know that I am still running my KO Propo EX-5 and JR Racing XR2 AM radio. I've had these radios probably for 15-20 years. The problem is, like an old shoe or a pair of jeans, I've grown to love them. All of my other electronics are top of the line and no expenses spared.

But each time I look into upgrading my radios, I keep coming across "latency" battles between Airtronics, Futaba, KO, etc. Prior to me getting back into the hobby, I've never heard of these issues before. Also, I'm appalled by the fact that receivers for these radios are around $100 each. This is quite a bit more than the $30 AM receivers. Setting expenses aside, I'm worried that if I get a new 2.4 Ghz radio, I would suffer from latency issues. I assume I will get used to it eventually. But if these 2.4 Ghz radios have latency, is it safe to assume that the "old style" AM radios had ZERO latency? So from a pure radio transmission speed standpoint, I'm better off keeping my old radios until they finally die? Also, I've had ZERO glitching issues. So my only real question is radio transmission speed. I know there's a lot more bells and whistles with the new 2.4 Ghz radios.

Can someone tell me if the AM radios had latency and if today's newer 2.4 Ghz radios are in fact faster? Thanks in advance.

ZiG-87

iTrader: (5)

There's going to be some latency in any RF communication technology, so it's not technically correct to say your system has 'zero' latency. But yes it will have less than a 'modern' 2.4g system. Will you notice it? I sincerely doubt it. Probably Commander Data and the Terminator are the only people who could perceive a few extra milliseconds response time..

Just to give you an example, my touring car has a bls551 brushless digital servo, and with my Futaba 4pk if I release the steering wheel while it is turned slightly, you can watch the wheels on the car vibrate back and forth as the wheel on the radio vibrates slightly after snapping back to center.

howardcano

iTrader: (37)

Old AM and FM radios have latency. The maximum latency is the same as the frame rate, which was generally in the 10ms to 20 ms range. ("Frame rate" is the time required to send all information for all channels. This repeats continuously in the same sequence.)

"Which has less latency?" can only be answered if comparing particular radios. There is no general rule that says one technology has less latency than another.

If you are happy with your old radio, then there is no reason to upgrade. There is also very little chance you would notice any difference between the old and new radios due to latency.

Micah123

iTrader: (1)

I use a airtronics receiver for under $50 with my mt4. Works great regarding latency and my radio has great software and is a very stable system. Also have a mt-v which is another good alternative.

asc6000

iTrader: (15)

You are correct of course technically but I have to say that going from a CS2P to an MT4 was an eye opener. Sure seemed faster but even if they were equal I would still consider a new radio if you need all the model memories and various other features. The ability to tune the car is drastically better, both steering and throttle. You couldn't pay me to go back.

ffejrxx

instead of worrying about radio latency, get faster servos
it will make a bigger difference

howardcano

iTrader: (37)

Yes!

wingracer

iTrader: (24)

The early 2.4 stuff (and current cheap 2.4 stuff) was horrible with latency. An FM M8 or M11 was much better. The latest offerings from Airtronics/Sanwa, Futaba and KO have got it down much better.

wingracer

iTrader: (24)

true and not true. There is a difference between speed and latency. For example, a servo ten times faster than the fastest thing currently on the market would do you no good at all if your radio couldn't move that servo until a full second had passed from the time you made an input. Such a car would be impossible to drive well. Of course a fast radio but a really slow servo will give similar results.

Fortunately, none of our radios are that bad but the difference between 8ms and 20ms is quite noticeable to a better than average onroad racer and is critical. For an average offroad racer, not so much.

Also, one of the big problems with early 2.4 stuff wasn't just that the latency was long but it was also inconsistent. Drivers instinctively adapt to latency without even realizing it. If a radio is a bit slow causing you to overshoot the apex, you let off and turn in sooner so within a few laps you're hitting the line again. Unfortunately some radios might have only a 6ms delay on one corner but the next it might be 12ms then 8ms, then 20ms. This makes really precise driving impossible.

theclutch

iTrader: (2)

Ummm... NO. If it takes 2 years for the signal to get to the receiver it doesn't matter how fast your servo is....

DirkW

iTrader: (1)

"2 years"... we're talking about a couple of miliseconds here. No need to overemphasize things like that.

Unfortunately I don't remember the numbers (nor could I find them in a quick google search) but I think I remember that the nerves in our bodies probably take longer to transport a signal from the brain to the hand than that (our brain and body aren't as quick as many people believe)... never a doctor or a biologist around when you need one. So, leaving that thought aside for now...

Yes, a servo that is 0.1s or 0.05s faster has a bigger impact than the 12 ms (=0.012s) faster radio from the example mentioned above.

Again:

0.05s less delay (servo)
vs.
0.012s less delay (radio)

Of course these numbers add up in the end: the servo only starts to move after the radio has transmitted the command for it to move, but you can see where the greater gain can be made. And even a super-fast servo will be slower than a slow radio (or are there really radios out there with >50ms?).

So, yes a fast servo will in most cases bring the larger benefit. Of course if you want to max it out, you'll need both, fast servo and fast radio.

Johnnysplits

iTrader: (1)

We're talking milliseconds. If you can see the difference between 4ms and 8ms, you must be an f-ing robot!! Any 2.4g system will work fine for anyone with the exception of a few talented pro racers.

theclutch

iTrader: (2)

I absolutely agree. So having said that, is Airtronics M12 "the fastest". I know there's a point where you hit the "law of diminishing returns". The M12 is $440. Would the MT-4 SSR be good enough?

Or would I need to go the Futaba route with the 4PLS or 3PM-X?

Dave H

The servo speed ratings are for 60° of travel if I remember correctly. The time required for initial reaction (which may be more relevant?) or for smaller inputs can make the time values much closer if not overlapping.


An interesting subject, I'm on the side of these small differences being noticeable for a moderately serious racer. Thought the same back in the AM days, although the early 2.4GHz radios is where it has been most significant for me.

One of my unrealized projects is to set up a lab test and measure a variety of radios for response/latency and consistency/repeatability. Have most if not all the fixings, just need to find the time to properly setup and debug a test method. Some day maybe...

wingracer

iTrader: (24)

I have no idea since I have never seen anyone post actual test results of car radios. I do know that competition heli guys take latency very seriously and I have seen results from those tests. A Sanwa FM radio destroyed everything else but that was a couple years ago.

I have talked many times to one of the top pros in the world about this very subject. He has turned down paid offers from other companies because he has tried their stuff and found it lacking on the latency issue (he is even more sensitive to it than I am). He finds KO the best in that regard and so that's what he runs. He did let me in on a secret, Airtronics has never offered him money and that's the only other one he would use.