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Old 07-16-2006, 08:00 AM   #31
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Does anybody really understand how the total latency of the transmitter adds up?

Here is what I think, lets discuss it:
total latency= radio latency + module latency

I think BOTH FM and DSM modules has latency. The radio's latency is constant independent from what type of module we are using.

We discussed this with a couple of guys and here is what I think about the latency on my 3PK:
- the radio has an inside latency of ~3ms

Futaba modules
- the PCM module's latency is ~30ms
- FM module's latency is ~18ms
- HRS module's latency is 7.8ms

Spektrum Modules
- Spektrum module's 5.6ms
- Spektrum Pro module: 3ms
- Spektrum HRS: 2ms

So the TOTAL latency ranking will look like this:
PCM - ~33msec
FM - ~21msec
HRS - 10.8 msec
Spektrum - 8.6msec
Spektrum Pro - 6.5msec
Spektrum HRS - 6msec

I'm not sure about the 3PK 3ms internal latency it may be much lower than this.

Is this make any sense or I'm way off???
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Old 07-16-2006, 08:35 AM   #32
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Well, here's my 2 cent on this subject. Latency wont be a problem I think, no-one will feel 5ms...

The only difference I felt when going from my KO Mars to the Spectrum was the following and I can understand that Pro drivers could have a serious problem with this.

Since you are transmitting the position of the trigger in code you are limited in the minimal difference, to put in a ridiculous example, if they were sending 2 bit you would only have 4 positions for servo movement.
I think here lies the difference while PPM or FM would have an infinite number of positions (its analogue) the spektrum is limited.

The slowest I could drive with the spektrum or with the Mars is a lot of difference!! -> with the mars I could lets say go 1m/h, no way I can do that with the spektrum, my lowest speed is a lot more -> same speedo...

Just something more to think about, hope someone agrees...
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Old 07-16-2006, 08:50 AM   #33
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Default No...I cant feel the difference

But I can tell you...not having to carry a pocket full of expensive crystals when I go to a race is well worth buying the DSM!!!
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Old 07-16-2006, 08:56 AM   #34
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Quote:
Originally Posted by apexraceway
But I can tell you...not having to carry a pocket full of expensive crystals when I go to a race is well worth buying the DSM!!!
And peace of mind.
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Old 07-16-2006, 09:09 AM   #35
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Default Hey Gix...

Couldnt have said it better!!!!
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Old 07-16-2006, 09:10 AM   #36
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I had DSM in my Futaba and after switching to my new KO Helios with Super HSR FM I noticed a HUGE difference. The speed in radio response was noticable on the first lap I used it. I would not trade my helios for anything.

Before with the Futaba and FM I would get glitches at my local track. However with the KO and 27mhz FM I've had zero glitches since I bought it. It also allows me to run Japan 27 half freqs which most non-pros don't know about.
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Old 07-16-2006, 09:34 AM   #37
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Just by not having to wait for a clip to practice with or being able to work on your car in the pits is worth the money for a DSM!!!!!!!!!

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Old 07-16-2006, 09:47 AM   #38
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i had my radio glitck in my nitro while i was taking a 60kmh corner that ended up with the car's steering twitching and putting itself into a fence pole
$250aud worth of damage later it realy made me wish i had'nt been such a tight a$$ and got the dsm earlier.
since getting it i'd rather put up with the odd glitch from time to time than have to fork out the $$$ because a fm radio glitch caused the front of the car to be destroyed
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Old 07-16-2006, 09:49 AM   #39
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Originally Posted by eforer
Many high level drivers have tried spektrum and switched back to FM due to feel issues. So the response time, or some other factor does influence the way the car reacts to the radio. A friend of mine, who is also a current national champion said it made his car feel broken!

I ran spektrum in my M8 at the carpet nats along with EJ Evans in the 12th stock main. My car felt okay, but the M8 is a slow clunky radio anyways. EJ was running an M8 too. We were the only spektrum users in the main. Its possible that the slow ol' M8 isn't really affected by the spektrum issues. Its also possible that I'm a total hack and can't tell the difference.

I will say this, if spektrum offered more advantages than liabilities for top drivers with newer radios. You can bet they would use it.

I'm planning on getting a new Helios or M11 in the near future. Based on the feedback from the fast guys running new radios that have tried spektrum in them, I'll be running FM.
I do think that sponsorship is a big reason. You have guys that are sponsored by Airtronics or KO. Do you think they want their drivers using an add on system that performs as good or better than their FM stuff? I think they think it looks bad. Like, WOW look how good our radio is when you use Spektrum....

Also, I have seen pro's use the system. Some have said they had issues. I bet most of those latency issues came from low BEC, but who knows. Maybe it is. Maybe when I get that good, I'll notice it too.

Also, I am pretty sure the spektrum has something like 4096 steps of resolution. I don't understand why anyone would want to use only 1/4096th of their throttle. Why are people so concerned with how SLOW they can make their car go?
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Old 07-16-2006, 09:57 AM   #40
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Quote:
Originally Posted by PitCrew
Why are people so concerned with how SLOW they can make their car go?
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Old 07-16-2006, 10:31 AM   #41
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Well, trust me, Spektrum rulez... For my level of driving, the latency or speed or steps is the least of my concerns.

I'd recommend it to everyone

Just gave my thought about perhaps its not the response time but rather something else
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Old 07-16-2006, 11:22 AM   #42
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I used to run spektrum in my 3pk. In stock and 19t I was always as fast as the fast guys but when I put a mod motor in the car I was alwasy 3-4 tenths slower and I couldn't figure out why.

Well none of those guys were using spektrum. So I did an experiment where I ran 2 battery packs. One with and one wtithout the spektrum. I found those illusive 3-4 tenths immediatly and have not gone back to spektrum again and had a wicked race weekend qualifying second in mod and actually picked up some time in 19t as well.

This has been my experience but it sounds like there are many successful runs with spektrum as well but I am going to stay with what I am using for now.
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Old 07-16-2006, 11:30 AM   #43
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I went from a Ko Propo ex-11 to a spektrum dx2 and couldn't be happier. I've never had such responsive steering. I truly believe all this latency is a mental game. If there are so many problems associated with DSM and all these pros have issues with it, then why is every manufacturer working on their own system? I have no doubt that the top of the line radio's all feel great,they should, you paid $300 bucks for them, but the question is, which is more susceptable to glitches,and time has proven that traditional systems are.

If you think you've never had a glitch on your traditional frequencies,you're fooling yourself. A while back when that eagle telemtry company ( I think they were called eagle) intoduced their telemetry pack,rc car action did a review. The telemetry pack recorded glitching that he had no idea about. I would liken that mystery glitch to the latency everyone is so worried about,but I doubt can really feel. I'll look for the article,but I'm pretty sure my wife chucked it.

I will admit that I do miss steering exponential,but I definitely don't miss glitching--Al
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Old 07-16-2006, 11:57 AM   #44
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Quote:
Originally Posted by Quante
Well, here's my 2 cent on this subject. Latency wont be a problem I think, no-one will feel 5ms...

The only difference I felt when going from my KO Mars to the Spectrum was the following and I can understand that Pro drivers could have a serious problem with this.

Since you are transmitting the position of the trigger in code you are limited in the minimal difference, to put in a ridiculous example, if they were sending 2 bit you would only have 4 positions for servo movement.
I think here lies the difference while PPM or FM would have an infinite number of positions (its analogue) the spektrum is limited.

The slowest I could drive with the spektrum or with the Mars is a lot of difference!! -> with the mars I could lets say go 1m/h, no way I can do that with the spektrum, my lowest speed is a lot more -> same speedo...

Just something more to think about, hope someone agrees...

might be true BUT, the speed control is digital so no matter what number you transmit the esc will convert that to the closest digital, same as the spektrum module...you either do the conversion in the transmitter or the esc...
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Old 07-16-2006, 12:04 PM   #45
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Quote:
Originally Posted by JoeGlover
I used to run spektrum in my 3pk. In stock and 19t I was always as fast as the fast guys but when I put a mod motor in the car I was alwasy 3-4 tenths slower and I couldn't figure out why.

Well none of those guys were using spektrum. So I did an experiment where I ran 2 battery packs. One with and one wtithout the spektrum. I found those illusive 3-4 tenths immediatly and have not gone back to spektrum again and had a wicked race weekend qualifying second in mod and actually picked up some time in 19t as well.

This has been my experience but it sounds like there are many successful runs with spektrum as well but I am going to stay with what I am using for now.
3-4 tenths per lap? Holy smoke. Well, in that case I should try my FM gear again. If I pick up that kind of time, Travis S and Peter Robinson will be chasing me.
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