Espritmodel.com Telemetry Radio
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Old Oct 28, 2012, 03:32 PM
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Just a note here on terminology. Jamming is a term used to denote intentional disruption of electromagnetic signals by swamping the frequency band with high level signals. Inadvertant disruption of electromagnetic signals, as being discussed in this thread, is called interference.

Larry
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Old Oct 28, 2012, 04:02 PM
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United States, NJ, Frenchtown
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Corrections

Police do use 2.4 giga hertz on a lot of equipment..

Do a web search of...........police equipment on 2.4 giga hertz. Plenty of their gear is on that frequency.

I may be old at 75. But I do know & check out what others are saying is not correct.
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Old Oct 28, 2012, 04:28 PM
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K BC company sells 2.4 giga equipment part 90 of FCC requirements. super hih power that will reach out 3 to 130 miles in good conditions. Federal, state, local, Police ,fire, Bombsquads & anybody else can apply for the station license to operate.

You now realize that triple triple secret agencies can do what ever they want with any transmission frequencies & power levels they can afford. If their beam meets your receiver antenna. Glitch that is not recoverable in time. Yet after the crash has everything working fine again.
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Old Oct 28, 2012, 05:28 PM
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Originally Posted by cyclops2 View Post
You now realize that triple triple secret agencies can do what ever they want with any transmission frequencies & power levels they can afford. .
Tin foil hat time

And remember that 2.4Ghz is a wide band and within that band RC systems can operate on maybe 100 different frequencies. Any signal no matter how powerful wont block them all. Even if the interference coincided with a frequency your Tx is using that wont cause a problem because you either have two frequencies working together (DSM2) or hop between many different frequencies (FHSS type systems)

And the strangest thing.. After these mysterious signals shoot your model down they invariably vanish as quickly as they appeared so that by the time you walk to the crashed plane everything is working fine again... funny that!
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Old Oct 29, 2012, 12:24 AM
I think I'm inverted. Maybe.
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Can't help it:

I'm having trouble with the radar, sir (1 min 38 sec)
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Old Oct 29, 2012, 06:46 AM
Taranis Tyro...
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Originally Posted by cyclops2 View Post
K BC company sells 2.4 giga equipment part 90 of FCC requirements. super hih power that will reach out 3 to 130 miles in good conditions. Federal, state, local, Police ,fire, Bombsquads & anybody else can apply for the station license to operate.

You now realize that triple triple secret agencies can do what ever they want with any transmission frequencies & power levels they can afford. If their beam meets your receiver antenna. Glitch that is not recoverable in time. Yet after the crash has everything working fine again.
...and yet despite this hundreds of thousands of modellers manage to operate 2.4GHz systems from every brand without issue every week. Why? Because in the real world the cross-band interference you speak of is somewhere between incredibly rare and non-exixtent - I've never seen it, and I suspect 99.99% of modellers haven't either (the model boats example Andy cited is the only time I've heard of something like that, so I think we should consider it the exception that proves the rule!).

So what is important in the real world? Resistance to narrowband interference (be that from other TXs or other commercial/consumer kit that operates in the 2.4 waveband). The good news is that the hopping functionality of all the latest 2.4 systems renders them far superior to the older 35/72MHz kit, which has zero capability in that respect - if something intereferes with your frequency, you're going down. Even DSM2 (which just grabs two free frequencies when switched on) give an order of magnitude better resilience. And remember, we've already proved in this thread that the authorities you are so worried about also have plenty of kit that operates in the MHz band too.

Ultimately success with 2.4 is about understanding - understanding how the tech works, it's power requirements and how to install it in your model. Most important is understanding that standard good practices with 35/72MHz won't guarantee success with 2.4 - that doesn't make it a worse system, but does mean you need to learn some new rules of thumb. I strongly suspect the latter point is at the root of the huge majority of 2.4 "issues" that get reported on the forums (I'll admit that many modelling issues I've had over the years have had their root cause somewhere else in the control system... )

PS - If you want to learn more about 2.4 technology I recommend this video from Radio Carbon Art. I bought it for a fiver on a whim at our club sale, but it's already paid for itself many times over by allowing me to avoid the 2.4 "gotchas" that often occur when experienced modellers adopt the technology for the first time.
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Old Oct 29, 2012, 08:56 AM
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If 2.4 is subject to jamming, will 72 PRESERVE their planes????

Ahahahahaha.

howell
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Old Oct 29, 2012, 02:08 PM
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All Spektrum air systems are now DSMX which has frequency hopping and is arguably the most robust system currently out there, or at least as good as any other. It's certainly every bit as secure in high traffic environment as FASST.

There is nothing wrong with DSM2 unless you are in a massively high traffic area such as a big flying meeting where there may be in the order of 100 DSM2 Tx's all transmitting together, and so a real risk of grabbing the same two frequencies. If you don't fly at big meetings then it's no issue because the Tx will always grab two free frequencies when it's turned on.
Funnily enough the fact that all Spektrum systems are now DSMX frequency hopping should I think mean that the older DSM2 systems are more secure than they used to be in those big flying meetings. There is less and less chance of enough DSM2 Tx's being active to cause issues.
I'd venture a guess that 99.9% percent of all 'interference' issues involve a thumb to knob interface issue..

DSM2 can NOT grab a freq already being used as I understand it. Upon activation it scans for an unused band and using that...BUT didn't you state that here." then it's no issue because the Tx will always grab two free frequencies when it's turned on." So how can there be two xmitters on the same freq?? I'm confused, but have never been interfered...
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Old Oct 29, 2012, 02:13 PM
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Originally Posted by rtbates View Post
DSM2 can NOT grab a freq already being used as I understand it. Upon activation it scans for an unused band and using that...BUT didn't you state that here." then it's no issue because the Tx will always grab two free frequencies when it's turned on." So how can there be two xmitters on the same freq?? I'm confused, but have never been interfered...
Yeah, the problem comes when there are so many transmitters operating that the Tx cant find a free frequency and so ends up being forced to take one that's already occupied. This could only occur if there are very many transmitters operating simultaneously, like some of the biggest flying meetings.

If you just fly alone, with a few friends or at regular club fields then it's a non-issue.

I fully agree with your first point. The vast majority of so called interference is user error either in poor set up or most likely dumb thumb error. The fact that the 'interference' can hardly ever be reproduced after the crash speaks volumes.
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Old Oct 29, 2012, 02:22 PM
Brett
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Originally Posted by JetPlaneFlyer View Post
Yeah, the problem comes when there are so many transmitters operating that the Tx cant find a free frequency and so ends up being forced to take one that's already occupied.
Seems like an odd failure mode. Should it just not grab any frequencies if it's can't find one (so, obviously, it wouldn't work, but that's better then crashing).
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Old Oct 29, 2012, 02:23 PM
I think I'm inverted. Maybe.
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Supposedly (they say 'theoretically'), about 500 Tx's (some say 1000) should be able to operate on 2.4 at the same time. I don't know the channel resolution of most 2.4 systems, but I wouldn't be surprised if that number is true.
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Old Oct 29, 2012, 02:29 PM
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Seems like an odd failure mode. Should it just not grab any frequencies if it's can't find one (so, obviously, it wouldn't work, but that's better then crashing).
It was a real issue (albeit in very limited conditions).. That's why Spektrum moved to DSMX

To get the full details you would best ask over in the radios forum as the guys with the real in depth knowledge live there.
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Old Oct 29, 2012, 02:41 PM
Fly it like you STOL it!
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Beat you to it! but the video helps haha
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Raspberry jam....must be Lone Star!!!
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Old Oct 29, 2012, 09:59 PM
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I fly on 72mhz. No one around me flies so I ain't to worried about someone turning something on and bringing my stuff down lol.
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Old Oct 29, 2012, 11:55 PM
Brett
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Nice thing about 72mHz these days is that there are so few people flying it that the chances of getting shot down are pretty low. I still use 72 for my slope gliders, and now I worry a lot less about someone down in the valley below my hill flying some other aircraft, because most likely it'll be on 2.4,
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