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Old 04-27-2005, 10:38 AM   #46
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Quote:
Originally posted by nimble
Yes, FHSS is Frequency Hopping Spread Spectrum. Many existing off-the-shelf FHSS radios designed for Wireless LANS or serial modems like SCADA wireless industrial controls, they switch channels very slowly.

Our system was designed specifically for the real-time control demands of R/C racing, we can switch channels in 200ns, that is nanoseconds, 1/1000000 of a second,
we switch channels 100's of times a second! By the time you pull the throttle from neutral to full-on, it has probably changed channels dozens of times.

Expect to see a review of the DART system in one of the R/C magazines soon.

DART is ROAR approved, no worries.

The good news is the pricing will be very competitive, VERY competitive, as we intend to win.
FHSS does have data security in its favour, however, it will become restricted once more people are using 2.4GHz, as the more channels "assigned" to Spektrum and Nomadio systems will limit its ability to "hop"....

Admittedly, it wont be an issue in a race, but it will be an issue if there are no TX impounds and people are using their radios in the pits...

I would certainly be happier with a system that stuck on a single frequency and didnt move.... But thats my PERSONAL preference not based on any rational analysis...

However, your system has many other advantages that some will prefer without a doubt... especially the ability to hardwire it to non-module radios, thats gonna make it a killer IMHO...

Glad to see its launched, I am doing a 2.4GHz roundup for a UK based RC magazine, the first article comes out next month, would be great to include the DART system as well...

I am also championing the BRCA (UK ROAR equivalent) vote for acceptance of 2.4GHz into the racing rules (its currently outlawed and not insured ) BRCA website here



PS. I think you will find a nanosecond (ns) is one billionth of a second ie 1/100000000 a Microsecond (us) is a millionth 1/1000000


Last edited by Galifrey; 04-27-2005 at 10:44 AM.
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Old 04-27-2005, 10:59 AM   #47
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Quote:
Originally posted by STEALTH
At huge races Personal Transponders are a requirement... this type of technology may one day become one too!?
Man, how cool would that be??? Everyone with personal transponders AND 2.4ghs radios!!!!!!!!

The ULTIMATE race directors dream.......:sigh:
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Old 04-27-2005, 11:38 AM   #48
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impounding does little to help. How many guys do you know have multiple radios? (i do.. backups!) Are you going to take all their radios? Most manufacturers include a direct connection cable in the kits anymore. Who uses that? I have anyways. (works great for virtual r/c too :P). Are you going to impound cars also as some of the new systems use a transceiver? Is this going to turn into f1?

Do we really need to treat people like babies before they act like one? Is common sense that far gone?


Maybe its time we start investing in RF Signal locators and just start disqualifying people.
..If you're going to be serious about toy car racing.


What we really need is a transmitter antenna array where drivers walk up to the stand, plug into one of the provided radio link locations and then bind the car, have it placed on the track. yadda yadda yadda, this would be for serious racing only as initial costs for clubs are already enough. and guess what, people might still have their modules back at the pits. (guess we could call a gents' agreement on a set of freqs for drivers stand.. but how many? most places run up to 10 at a time... but i would do 15 if the racers could handle it. The lap counting software does)


In the end, You will have to rely on the people who race for a good race. Its just like a football/baseball field - any place can be a field but the players make the history.

So start educating the unenlightened and let's race.
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Old 04-27-2005, 01:06 PM   #49
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Quote:
Originally posted by Mason

Do we really need to treat people like babies before they act like one? Is common sense that far gone?


Maybe its time we start investing in RF Signal locators and just start disqualifying people.
..If you're going to be serious about toy car racing.


So start educating the unenlightened and let's race.
Funny you said that.........quote & unquote"......do we really need to treat people like babies before they act like one?. We racers turn to Jekyl & Hyde when we head for the track and "race" our toy cars.

Poeple will keep their DSM/FHSS etc...system "ON" all the time in the pits or else where when they can and they will just to make sure they can "tinker" their toy car to get that little advantage. I myself will be guilty until proven innocent. LOL ...Heck...we spend $$$$ on dynos so we can get the juice out of that damn motor.....spend more $$$$ on magnet can zapper to reverse the polarity & reverse it back to get 1-2k more rpm.....more $$$$ on 3700,3800 whats next 4100 mah batts to jack rabbit start??? For what.......? to get that 6" trophy or that plaque......oh well...this is part of this thing we call racing toy car that we are all addicted.to...so whatever new is out there...we will buy it & use it. SO THERE BETTER BE SOMETHING TO MANAGE/CONTROL IT......IMPOUND IS THE ANSWER.

just my 2 cents.

Henry E.
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Old 04-27-2005, 01:39 PM   #50
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just make it uniformed across every form - whether running crystals, DSM, Synths, Nomadio, Nimble's thing (which you did a nice shameless plug for your product all thru this thread)

Treat them all the same...if you impound one, impound them all...if not, your staff will be dealing with nothing be headaches having to answer the same questions over and over again "why can that dude keep his radio and I can't?" or you'll have the jerks that just dont care and keep theirs in the pits too...


make it uniformed for everyone, its just easier!!
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Old 04-27-2005, 04:18 PM   #51
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Originally posted by k_bojar

make it uniformed for everyone, its just easier!!
Agreed, and fairer..

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Old 04-27-2005, 11:52 PM   #52
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Originally posted by Galifrey
Agreed, and fairer..

the only advantage a DSM/Synth/2.4G has is that any time they want to work on the car set-up, they walk to impound, ask for their radio and do what they need too...Impound staff doesn't need to worry about what's on the track at that moment...

keep it fair and uniformed for everyone...allowing exceptions breeds problems
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Old 04-28-2005, 10:49 AM   #53
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Man, how cool would that be??? Everyone with personal transponders AND 2.4ghs radios!!!!!!!!
That was the vision for DART from the beginning, we hope by next summer it will come true, I mean the "everyone" part.

We also have the Leader Light, no more excuses from slow cars they didn't know the leader was trying to lap them.
Seeing your laptimes as you practice and your race position during races..



p.s. thanks for the correction on nanoseconds, switching time is 200uS microseconds, 1/millionth, not 200nS 1/billionth.
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Old 07-13-2005, 10:52 AM   #54
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Default Some Digital Radio Issues that may not be obvious

A couple of things you all might want to ponder.

Far as the 2.4GHz spectrum goes, there are exactly enough slots for 80 1MHz channels, which are used by most conventional narrow-band radios, such as the DSSS radios Nomadio and Spektrum use, or typical 2.4GHz FHSS technology, such as Bluetooth. Different technologies use the 1MHz channel space in different ways. Most FHSS systems use a simple modulation technique, which offers more data throughput; the DSSS systems use a large number of smaller, parallel radio slots within the channel slot, which contributes to reliability and range at the expense of speed.

So while there are tricks that might technically allow more than 80 channels (we know of several different techniques), you're going to pay for them somehow. Chances are, anyone implementing such a thing would run into reduced range, more frequent data collisions/loss, or increased latencies, depending on how you do it. The FCC isn't adding actual space to this band.

With that said, it's also important to realize that the world isn't perfect. For one, every digital system needs one or more rendezvous channels. Basically, when you power up, say, a Nomadio system, the transmitter and receiver (yes, both are TX/RX, but you know these terms) have to find each other. We implement three rendezvous channels, just in case there's noise enough to make one or two unreliable (if all three fail, there's a pretty good chance you're in an area that's just too noisy for radio communications -- we've never seen this). We actually built early military prototypes using Bluetooth, which only has a single rendezvous channel, and learned from the experience.

So in reality, you have a few channels not used for racing. Then, there's another smack of the reality stick -- there could be noise on other channels, just as there could be in any radio band. When a Nomadio system goes to pick a channel, it tries to find a nearly perfect, clear channel. When it can 't, it starts to accept slightly worse channels. There's no telling if the worse channel will actually be any kind of problem in practice, particularly in the short ranges usually used in racing, we simply want to provide the best channel available.

The thing is, the more folks connected, the more often a possibly worse channel will be used. In a race, you would tend to want the racers to get the best channels, assuming you are in an area with any interference. In a normal small to moderate sized race, it's probably not an issue, but in a larger race, I would consider it sensible to let the racers start up before anyone in a pitt.

With an FHSS system, you have another problem -- radios will eventually collide with one another. Each TX/RX pair follow a pseudorandom hopping sequence of their own, not coordinated with any other operating pair. As you increase the number of radios, you increase the possibility of collisions. FHSS protocols should be designed to work with collisions or bad channels being selected from time to time (Bluetooth 1.2 adds an AFH option, but that limits the number of devices that will peacefully coexist by effectively blacklisting noisy or otherwise occupied channels), but you can get to a point where, in practice, everyone's operation starts to suffer.

How quickly? Well, the probability equation is given by:

Pno_collision = (1-1/79)^(2n-2)

Let's assume (as would be in a single race) that collisions pretty much trash both packets, and that you'd like to get 50% of your packets through without collision. Solving for n in the above equation, that puts the limit at 28 devices. If you only need 1/4 of the packets to get through, you could have 54 simulataneous devices. With all 79 devices going, you'll only get slightly better than 1/10 of your packets through, under a Bluetooth-like FHSS system. Statistically, of course, if you sent each message 20 times, that wouldn't seem to be a problem, but in practice, I suspect the system would get unusuable at high numbers of vehicles. This wasn't the primary reason we dumped Bluetooth, but it was a concern.

Oh, incidently, FHSS wasn't invented by the military. Various kinds of spread spectrum were, in fact, used in military devices long before consumer devices (Bluetooth, cellphones, WiFi, etc), but FHSS was actually invented in 1942 by actress Heady Lamarr and composer George Atwell (US Patent 2,292,387).
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Old 07-13-2005, 11:25 AM   #55
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Quote:
Originally Posted by Nomadio_Dave
Oh, incidently, FHSS wasn't invented by the military. Various kinds of spread spectrum were, in fact, used in military devices long before consumer devices (Bluetooth, cellphones, WiFi, etc), but FHSS was actually invented in 1942 by actress Heady Lamarr and composer George Atwell (US Patent 2,292,387).
I knew FHSS wasn't created as a military application, just wasn't 100%
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Old 07-13-2005, 11:55 AM   #56
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Default FHSS Origins

Quote:
Originally Posted by k_bojar
I knew FHSS wasn't created as a military application, just wasn't 100%
Actually, Ms. Lamarr and George (I've seen "Atwell" and "Antheil" as his surname) had a military application in mind. This was during WWII, after all. She thought they could use this concept to guide torpedos, then radio guided rather than self guided -- this techique could prevent jamming. She had the idea of jumping around in frequencies; George had done a series of musical bits with coordinated player pianos, and figured his technique could be used to coordinate both sides of the radio broadcast.

The military did read this patent, but reportedly balked at the suggestion of "player piano" as mentioned in the text. In the early 60's, they dug deeper and actually did implement FHSS, in the technology of the day, but well after the patents had run out.

Anyway, one of the weirder invention stories I know of.
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