:thumbsup:

http://www.horizonhobby.com/Explore...?ArticleID=1423

This is the best thing to come out since the R/C vehicle! I just ran a race with 40 others and never had a glitch, never had to leave my radio in the pit, never had to use a clip for practice, Will never have to worry if someone is on my channel ( unless there are more than 79 DSMers racing with their radios on), and was only one of 3 guys to have one.

I did a competition distance run with a couple of MHz guys and I could barely see my maxx before I turned around the others lost it within a 1/4 mile. Just unbelievable!

My M8 has never been happier :)

a vdk, I have been reading about this and I am very interested in it. I have a couple of questions. Do you have to run a receiver pack with it? And do you notice any “extra” power draw from your race pack?

Another question is, where is it available at? Horizon says not available yet.

The local hobby shop for the snowbirds, had them, the xmit modules sold quick, they had received left over. The shop was Superior Hobbies in Orlando. They seem to be out there eventhough Horizon said they would not be. They even had a give away, if you filled out a survey form.

only problem is not one pro driver used theres at the birds. something to do with being indoors and a slow response time from radio to reciever?

That's the word I got from Don Rice also, that with a lot of people racing together, the responce time is slowed down. Personally, I don't understand how but that is what I was told.

I assume we are talking about this spred spectrum stuff... I'm no expert, however that kind of stuff typicaly has to spend at least some time listeing to the airwaves to decide exactly what or how much of the spectrum it can use.... the more activity in that spectrum, the more it would need to make changes, etc... So, it's not too surprizing that there is some change in response time... what is somewhat surprizing is that you can notice it...

Yeah, that is surprising to me too. Once the freq. is locked in I can't see how the response would change. The only thing that I could see is if the receiver is busy filtering out the signals that belong to other transmitters so some of it's time is being taken up by finding the one it should respond to.

You know, I might be able to understand that if all of the drivers were on DSM but even at that, why would it cause a slow down if you are almost 2.4 "Khz" away and from the regular band and a whole Mhz away from anyother DSM frequency and locked on your own frequency?

It must be a lot about spread spectrume that I still don't understand.

Think I will give this one some more time before I jump.

not to mention names but i was hearing changing out the dsm to a regular reciever was good for almost 2 tenths a lap for the on-road guys. the switch back section was where they could realy notice a difference. sounds like a killer system for us oval heads?

What if you have more than 1 car.Will it adjust frequency to each car?What if you have 4 cars with 4 different recievers?

I suspect it was the DSM systems interacting with each other and not any problems from the 75/27MHz stuff.

My understanding is that the receiver waits for a signal with the signature of the mating transmitter before it will react on that signal. Now I guess that if many signals are received that don't match, it may take it some time to filter through those signals to find one that matches.

What I don't understand is since each transmitter is on a different frequency why it would have to sift through the garbage.... unless there is a lot of bleedover from the other frequencies. Maybe I'll email them and ask.

Here is a link about the system: http://www.spektrumrc.com

I never really understood spread spectrum stuff that well, but it's my understanding that you use more then one frequency at the same time, that is, your signal is spread somewhat across the whole spectrum... Just how much you have access to, depends on how many other things are also using that same spectrum.

Their web page seems to indicate that it picks a 'channel', so I could be wrong... on the ohter hand a channel could be just a small chunk of spectrum and not a perticular frequency.

Some where I also read that it will move, if things get busy on it's 'channel' so, clearly it is monitoring things and will move if nessasary... Moving might take a little time I supose, and might cause a small delay.

One thing I still don't understand about this perticular spectrum... 2.4Ghz... Is that spectrum public ( I assume it is ), and not dedicted specificly to RC? If that is the case, then it could get stomped on by what ever else can legaly occupy that space. Maybe the radio issues aren't directly related to other users of this product.

Yup, it is deffitnely public... and I think it's likely to be quite heavily used in some locations. I guess phones have used it, wireless data devices have use it, etc... The more stuff using this spectrum near you and your car, the more problems you will have.

Kind of a nice concept... but is changing crystals really that bad? or using a synthisied receiver/transmiter and turning the dial? At least then your only limited to dealing with other RC users...

Here is just one of many interesting things you can find with a google seach of 2.4Ghz and FCC.

http://www.bwianews.com/2001/11/part-18-rf-lighting-potential.html

Not just other radios you have to contend with, but micro wave ovens, lights, etc...

If you do a Google search for spread spectrum, there are many, many articles concerning it in the category of communication. (Boring, but informative.Just be sure you read the ones about DSSS NOT Hopping) NASA uses it for the space vehicles because of its reliability. The military use it because it is nearly imposable to jam or intercept. So it “seems” that it would be ideal for what we do, however, I could not find anything about using it for remote control usage.

The 2.4 GHz section of the band is also allocated for the use of cordless phones but the best that I understand it, they are not in the spread spectrum mode and because of that, they should be barely detectable by our radios and should not even be notice by them.

Our FM and PCM transmitters use “narrow band” technology, with only a few KHz separation between channels. Spread Spectrum is extremely wide band with data being transmitted spread over the entire section your transmitter will lock onto. In addition, the separation between “channels” is a whole MHz. Because of that alone, interference between two radios should be “zero” and because of the transmitted data being spread over such a wide area, other users of the band that do not use the spread spectrum mode (cordless phones) could be right on top of you and your receiver would not even notice it.

Now, all of that is well and good for the interference part but I still can’t see why the data is slowed down when there are a lot of radios being used at one time. PLUS, if that was the deal at the Birds then obviously, all of the radios that were in use WERE NOT spread spectrum, only the one or two that noticed the problem. It just “don’t make no since” to me! Unless, the equipment that is available is not transmitting fast enough but even that is a stretch.

Could it be a power issue and you need to run a receiver pack?

I emailed them to ask about the problem... we'll see if they get back with me.

OK, here is the info I got back from Horizon.

The response time is only a few milliseconds slower than most standard configurations. It's physically impossible to notice.

I then referred them to this thread and they replied.

The prototype units that the Losi team used in Cleveland are very different than the production units. The Losi team found an issue that we previously hadn't discovered in testing outdoors. This issue caused the response time to be inconsistent as some packet information was being lost. The following week through further testing we discovered the specific problem and it was simple to correct. All production units will have corrected programming and hardware changes that prevent this issue.

So I guess the question is where the pro drivers using preproduction units that had this inconsistancy?

Good question.

It is great though that you got a responce so quickly. Sounds like they are really trying to make it right.

Yeah... nice to get a quick response... doesn't happen much these days.

more complaints:

"Regarding the Spektrum. It doesn't seem people used it there, but remember racing is trendy if one person thought crapping in your motor made you faster and wearing your boxers on the outside of your pants then next week you'd see everybody doing it."

"I think they are still a little cautious at big events about new technology. If they use something new and have an off week then it must be the equipment."



I know I bought a Spektrum system just for this race. Got there on Wed. tried it in my first practice and the car had a VERY BAD LAG. You turn and then 2ft later the car turns, going down the straight the car just felt very sluggish, like it was hitting a Rev-Limiter. I pulled the system out and went back to crystals and had no more problems like this. I talked to a few Factory drivers about the system, everyone of them ask me what I felt while using it. I explained it to them and they said that was exactly what they felt. none of them offed there opinion first, They all ask what I thought then after that explained that they too felt teh same thing.

So if an "average joe" can feel the lag why would you think it was just a trend for them to pull the system?

I saw one person using the system all weekend and watching the car ans the kid drive you could tell he was having the same problem.

I got one and ran it last weekend at my home track had no problems like that. In fact I had my best lap times ever.

TJ

I've been using my Spektrum for a month now in 4-cell stock indoors, I did add a reciver pack for my own piece of mind and had no problems and did not notice any responce issues at all, went to a track indoor in Nebraska and had no problems at ALL. Love mine everybody will have one of these soon.

Shane
www.fastlanehobby.com