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Old Nov 01, 2012, 06:26 PM
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United States, UT, Salt Lake City
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Originally Posted by jasmine2501 View Post
At my old company, we had the problem where people in the accounting department would start telling the computer programmers how to code stuff...

The policy that finally worked was "If you don't understand what the other person is saying, you have two choices: either learn to do their job, or trust their expertise and shut up."

Problem in the RC world is everybody is an expert on everything. We are highly intelligent people for sure, probably most of us are above average. However, if you're not a radio engineer, it's pretty damn ballsy to be commenting on the reliability of something that was designed by actual radio engineers. I think from now on, my response to that kind of assertion is just going to be "please post the data that the Spektrum engineers didn't know about" because those assertions are really saying "I'm smarter than the Spektrum engineers"

Seriously - if you're going to say Spektrum did it wrong, you need to be prepared to explain yourself, in terms that are scientifically accurate.
I thot they got it right - and how it works is on line available to all who will bother to read .
But if the CONCEPT of how 2.4 works is a mystery - it is easy to convince one that unless a lot of hopping takes place - the system is no good.
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Old Nov 01, 2012, 06:35 PM
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United States, AZ, Mesa
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Originally Posted by richard hanson View Post
I thot they got it right - and how it works is on line available to all who will bother to read .
But if the CONCEPT of how 2.4 works is a mystery - it is easy to convince one that unless a lot of hopping takes place - the system is no good.
True, I've seen people actually say Spek isn't spread spectrum because it doesn't hop.
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Old Nov 01, 2012, 06:52 PM
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Upstate NY
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Originally Posted by jasmine2501 View Post
.... I think from now on, my response to that kind of assertion is just going to be "please post the data that the Spektrum engineers didn't know about" because those assertions are really saying "I'm smarter than the Spektrum engineers"

Seriously - if you're going to say Spektrum did it wrong, you need to be prepared to explain yourself, in terms that are scientifically accurate.
Don't mean to step in this one - but do you know whom patented the concept behind spread spectrum? It wasn't an engineer!

http://en.wikipedia.org/wiki/Hedy_Lamarr

Engineers don't always produce the most technically capable system - but what they are trained to do is to produce a system that meets a whole set of criteria (requirements) that includes availability of parts, ease of manufacturing, life cycle support, and of course a COST bogey which drives the design and complexity of the solution. Never assume that what is being marketed is the best solution - it represents a compromise to the business - will it meet market needs, will it meet business needs, does it have an advantage in the market that enables likely profitability and captures market share.

So, I won't comment on Spektrum other than to say that they pushed a new concept (that became affordable through commercialization of common chips), took over the market and ultimately changed our expectations to the plus and hopefully they made money doing it.

There is a tremendous amount of information that talks about how the systems work. In any case, I think all of the systems work just fine for ordinary conditions and allow each of us to enjoy this fine hobby!

Get out and fly before the snow comes!
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Old Nov 01, 2012, 07:23 PM
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Originally Posted by ScottSails View Post
Don't mean to step in this one - but do you know whom patented the concept behind spread spectrum? It wasn't an engineer!

http://en.wikipedia.org/wiki/Hedy_Lamarr
Yes I'm VERY familiar with the links I've been posting!

I'm not saying that regular folks can't have great ideas, what I'm saying is if you're going to bash the decisions of commercial engineers who are getting paid good money to do what they do, you should have the experience and the data to defend your position. I've only ever seen one case of someone presenting that data, and it had to be carefully contrived in order to prove their point.

Think about the difference between saying "I have a great idea!" and "your idea is crap" - one thing only requires creativity, while the latter requires knowledge and experience.
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Old Nov 01, 2012, 08:02 PM
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It does makes me chuckle when people worry so much about 2.4GHz interference when they are flying out in a field in the middle of no-where. Even in a park, to be able to fly, there has to be sufficient space to actually fly the aircraft without risk hitting something! Unless your flying dangerously close to areas of possible interference (i.e. buildings) and any local transmitters are legal (i.e. within power limits and collision avoidance) there should never be a strong enough signal to cause a problem.

Walk in a busy city street, you see hundreds of people listening to their music through Bluetooth headphones, talking to people on Bluetooth headsets, browsing the internet using WiFi at a Coffee shop, sending data over Bluetooth, nearby office blocks full of laptops talking over WiFi, etc, etc. Every one of those is a transmitter all running at different power levels, all vying for the same very crowded band, trying to get their data through when there is a brief moment available to transmit on. Yet you don't see or hear people moaning because their headphones are stuttering, their WiFi has dropped out or they can't pair their device. Ok, generally speaking, the distances between the devices is small however the combined surrounding noise is likely to be large and they are transmitting at much higher data rates than RC kit. It's testament to how good modern modulation techniques are.

I'd love to see the noise floor on the ISM bands in a busy city street!

Si.

P.s. I always think it would be interesting and cool if transmitter manufacturers implemented even simple 2.4GHz spectrum analysers in their radios. It would put a lot of myths to bed about interference.
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Old Nov 01, 2012, 08:17 PM
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Upstate NY
Joined May 2005
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Quote:
Originally Posted by jasmine2501 View Post
Yes I'm VERY familiar with the links I've been posting!

I'm not saying that regular folks can't have great ideas, what I'm saying is if you're going to bash the decisions of commercial engineers who are getting paid good money to do what they do, you should have the experience and the data to defend your position. I've only ever seen one case of someone presenting that data, and it had to be carefully contrived in order to prove their point.

Think about the difference between saying "I have a great idea!" and "your idea is crap" - one thing only requires creativity, while the latter requires knowledge and experience.

Whoops - sorry, i would never had quoted that if I had read that.. Mea Culpa...
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Old Nov 01, 2012, 08:24 PM
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Originally Posted by SimonChambers View Post
It does makes me chuckle when people worry so much about 2.4GHz interference when they are flying out in a field in the middle of no-where. Even in a park, to be able to fly, there has to be sufficient space to actually fly the aircraft without risk hitting something! Unless your flying dangerously close to areas of possible interference (i.e. buildings) and any local transmitters are legal (i.e. within power limits and collision avoidance) there should never be a strong enough signal to cause a problem.

Walk in a busy city street, you see hundreds of people listening to their music through Bluetooth headphones, talking to people on Bluetooth headsets, browsing the internet using WiFi at a Coffee shop, sending data over Bluetooth, nearby office blocks full of laptops talking over WiFi, etc, etc. Every one of those is a transmitter all running at different power levels, all vying for the same very crowded band, trying to get their data through when there is a brief moment available to transmit on. Yet you don't see or hear people moaning because their headphones are stuttering, their WiFi has dropped out or they can't pair their device. Ok, generally speaking, the distances between the devices is small however the combined surrounding noise is likely to be large and they are transmitting at much higher data rates than RC kit. It's testament to how good modern modulation techniques are.

I'd love to see the noise floor on the ISM bands in a busy city street!

Si.

P.s. I always think it would be interesting and cool if transmitter manufacturers implemented even simple 2.4GHz spectrum analysers in their radios. It would put a lot of myths to bed about interference.
+1 ...well said.
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Old Nov 01, 2012, 10:09 PM
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Originally Posted by jasmine2501 View Post
Spread spectrum is a whole lot more complicated than using multiple channels - that isn't even spread spectrum, that's transmitter diversity or something like that.
There is a spread spectrum technique that employs frequency hopping for modulation (called FHSS) but I'm pretty sure no RC 2.4 systems use it (possible exception of Airtronics). Bluetooth uses it.
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Old Nov 01, 2012, 10:19 PM
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Originally Posted by jasmine2501 View Post
However, if you're not a radio engineer, it's pretty damn ballsy to be commenting on the reliability of something that was designed by actual radio engineers.

Seriously - if you're going to say Spektrum did it wrong, you need to be prepared to explain yourself, in terms that are scientifically accurate.
Are you a "radio engineer"? You sure *try* to sound like one. If not, please take your own advice.
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Old Nov 01, 2012, 10:33 PM
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Illinois
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Originally Posted by jasmine2501 View Post
Yes I'm VERY familiar with the links I've been posting!

I'm not saying that regular folks can't have great ideas, what I'm saying is if you're going to bash the decisions of commercial engineers who are getting paid good money to do what they do, you should have the experience and the data to defend your position. I've only ever seen one case of someone presenting that data, and it had to be carefully contrived in order to prove their point.

Think about the difference between saying "I have a great idea!" and "your idea is crap" - one thing only requires creativity, while the latter requires knowledge and experience.
Keep up the good works, Jasmine. We all appreciate your posts! Not just from the engineering side, but also from the common sense side.

You too, Simon!

Andy
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Old Nov 01, 2012, 10:34 PM
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Well, maybe not ALL of us, but at those of us who understand do appreciate you!

Andy
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Old Nov 02, 2012, 12:49 AM
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Originally Posted by jsipprell View Post
There is a spread spectrum technique that employs frequency hopping for modulation (called FHSS) but I'm pretty sure no RC 2.4 systems use it (possible exception of Airtronics). Bluetooth uses it.
Doesn't Futaba have new system called that? Is it strictly frequency hopping or is it a combo with DSS like FASST is?
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Old Nov 02, 2012, 07:06 AM
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Quote:
Originally Posted by jasmine2501 View Post
At my old company, we had the problem where people in the accounting department would start telling the computer programmers how to code stuff...

The policy that finally worked was "If you don't understand what the other person is saying, you have two choices: either learn to do their job, or trust their expertise and shut up."

Problem in the RC world is everybody is an expert on everything. We are highly intelligent people for sure, probably most of us are above average. However, if you're not a radio engineer, it's pretty damn ballsy to be commenting on the reliability of something that was designed by actual radio engineers. I think from now on, my response to that kind of assertion is just going to be "please post the data that the Spektrum engineers didn't know about" because those assertions are really saying "I'm smarter than the Spektrum engineers"

Seriously - if you're going to say Spektrum did it wrong, you need to be prepared to explain yourself, in terms that are scientifically accurate.
Is this ok for you?

http://www.rcgroups.com/forums/showt...=5#post9492828

http://www.rcgroups.com/forums/showp...1&postcount=29
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Old Nov 02, 2012, 09:51 AM
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As for good old 72 mHz, I recall that the band was shared with pagers, crane controllers, and railroad communications. By FCC regulation, those services had priority and could legally interfere with RC frequencies. But not the other way around. IIRC, in our club's area, we stayed away from Channel 20.

I'll take 2.4 gHz, rumors notwithstanding.

Jim R.
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Old Nov 02, 2012, 10:16 AM
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I remember this discussion- but since then four years have elapsed and real world experience says "DSM2 does work just fine" and interferrence on th two channel setup in minimal at best.
My first argument was that real world interferrence is not likely to be a tiny spott on the 2.4 band which would -in some scenario- nail ONLY a hapless Spektrum flier who somehow(?) got two adjacent channels which some how were killed by some highly localized interferrence. Also the "less prone to voltage argument - I simply can not buy-
In doing a lot of testing with small -large - high C and low C batteries - the problem is state of charge and C ratings - when these finally start to respond to loads -the voltage depression continues to rapidly cause lower and lower voltage.
ANY 2.4 radio gets knocked off.
Anyway - the real problems with 2.4 that I have seen since that 2008 running argument go right back to original problems
A- incorrect power setup
B- poor electronics which supply power
C- incorrect reciever /antenna/ placement/ orientation.
A rx just quitting on it's own hook and then starting up again (it's a miracle!) as some others claim - I just can't accept as a real scenario.
I fly with lots of Spektrum users -some Futaba users and some users of other types
All have had some problems or quirks - all were resolved -
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