How many 2.4gHz at the field are too many?
08-09-2007, 07:29 PM
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How many 2.4gHz at the field are too many?
Danny, here's the question that I'm sure a bunch of us have in our heads. Has JR determined what the "saturation point" is at the flying field before there are simply TOO MANY Spektrums there? A regional fly-in type event was brought up earlier today between a few of us, and the possibility of that issue came up. IS THERE a number that has been determined? Also, we can't ignore the presence there of other 2.4s like Futaba who are bound to be on the band wagon before long. Are there any special issues or considerations concerning them (other than simple increased numbers of them) that would speed up the onset of the "saturation point"? Sorry to coin a phrase that might be troublesome, hopefully it will simply be irrelevant. We've had four Spektrums at once flying at our field, not a single issue, flawless performance from all.
Jim
Jim
08-09-2007, 08:35 PM
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RE: How many 2.4gHz at the field are too many?
G'day Jim,
There are 80 available slots in the 2.4Ghz range, that means, 40 Spektrum radios can operate together, the 41st radio won't do anything, ie, it can't grab a pair of channels to operate with, until 1 radio is turned off, then there will be an available pair.
There are 80 available slots in the 2.4Ghz range, that means, 40 Spektrum radios can operate together, the 41st radio won't do anything, ie, it can't grab a pair of channels to operate with, until 1 radio is turned off, then there will be an available pair.
08-10-2007, 09:03 AM
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RE: How many 2.4gHz at the field are too many?
Thanks, Allan.
It would have to be a REALLY happening fly-in to have that many 2.4Ghz Tx's fired up at once! So, what you're saying is that it cannot interfere with another one because it does nothing until it searches and finds an available pair of channels. So I would be safe in assuming that when a 2.4Ghz TX is turned on, the first thing it does is search for an available pair of channels, if it does not find an available pair it simply won't work, and once it DOES find a pair it will claim them both and the other 2.4Ghz Tx's scan and know those channels are occupied.
Jim
It would have to be a REALLY happening fly-in to have that many 2.4Ghz Tx's fired up at once! So, what you're saying is that it cannot interfere with another one because it does nothing until it searches and finds an available pair of channels. So I would be safe in assuming that when a 2.4Ghz TX is turned on, the first thing it does is search for an available pair of channels, if it does not find an available pair it simply won't work, and once it DOES find a pair it will claim them both and the other 2.4Ghz Tx's scan and know those channels are occupied.
Jim
08-10-2007, 09:30 AM
#4
RE: How many 2.4gHz at the field are too many?
There isn't such a thing as too many systems. For JR DSM and Spektrum aircraft systems, the highest number of systems that will link at once is 40 (80 channels available, each system operates on 2), but any number of systems can be on, they simply will not transmit and hence not link w/ a receiver if a channel is not available. Simply put, there is no need to worry about too many systems at the field, as there is no such thing.
08-10-2007, 10:44 AM
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RE: How many 2.4gHz at the field are too many?
Danny
How will the Futaba Faast system work in relationship to your DSM? If I understand correctly the Futaba changes channels constantly. Does it bypass frequencies in use by other systems? I curios to see how the different formats will “play together†at a large fly-in like Joe Nall.
I’m anxiously waiting to see the 12x before I purchase a 2.4GHZ system.
Danny
How will the Futaba Faast system work in relationship to your DSM? If I understand correctly the Futaba changes channels constantly. Does it bypass frequencies in use by other systems? I curios to see how the different formats will “play together†at a large fly-in like Joe Nall.
I’m anxiously waiting to see the 12x before I purchase a 2.4GHZ system.
Danny
08-10-2007, 01:15 PM
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RE: How many 2.4gHz at the field are too many?
The Futaba and XTM will hop past the Spektrum locked in. If there are a large number of radio's on this may cause the other two systems to slow down, but still maintain a good signal path to the plane. Spektrum with the lock-in will not be affected in this manner. I can never see a situation where this could ever happen. Even at the JoNall with 500 pilots I can't see even 100 guys having their radio's on at the same time. Dennis
08-10-2007, 01:55 PM
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RE: How many 2.4gHz at the field are too many?
If Joe Nall is one example, IRCHA (going on right now in Muncie) will be another example. NO IMPOUNDING OF SPEKTRUM RADIOS! during an event that draws more than 500 pilots.
[link]http://www.runryder.net/helicopter/t365144p1/[/link]
Rafael
[link]http://www.runryder.net/helicopter/t365144p1/[/link]
Rafael
08-10-2007, 07:47 PM
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RE: How many 2.4gHz at the field are too many?
If 40 Spektrum radios are transmitting at once what will the Futaba do when powered up? I can see this happening at a large event with no impounding of 2.4's!
08-10-2007, 07:55 PM
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RE: How many 2.4gHz at the field are too many?
I want to go to the event where there are going to be 40 aircraft in the air at one time, or 30, or 20... protective headgear required.
08-10-2007, 08:23 PM
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RE: How many 2.4gHz at the field are too many?
The Futaba changes frequency 50 times a second. All brands "label" their transmissins so they will only be "heard" by the correct RX. I don't believe (but could be wrong) that Futabas listen before XMIT. Data buses have multiple "words" floating around constantly that do not bother each other because of things like the GUID Spektrum uses.
08-11-2007, 12:35 AM
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RE: How many 2.4gHz at the field are too many?
I was supposing a hypothetical scenario. You would never see 40 flying at once but without impounding 2.4’s at very large gatherings, this scenario in not impossible.
08-11-2007, 06:16 AM
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RE: How many 2.4gHz at the field are too many?
ORIGINAL: dsnyder
There isn't such a thing as too many systems. For JR DSM and Spektrum aircraft systems, the highest number of systems that will link at once is 40 (80 channels available, each system operates on 2), but any number of systems can be on, they simply will not transmit and hence not link w/ a receiver if a channel is not available. Simply put, there is no need to worry about too many systems at the field, as there is no such thing.
There isn't such a thing as too many systems. For JR DSM and Spektrum aircraft systems, the highest number of systems that will link at once is 40 (80 channels available, each system operates on 2), but any number of systems can be on, they simply will not transmit and hence not link w/ a receiver if a channel is not available. Simply put, there is no need to worry about too many systems at the field, as there is no such thing.
Jim
08-11-2007, 07:37 AM
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RE: How many 2.4gHz at the field are too many?
From what I have read, and I claim no expertise. The radios turned on when the frequency band is full, will hunt for an empty spot to use. The question is will they transmit, or just keep changing frequency in search of empty space?
I am under the impression that there are no specific channels allocated by the fcc or agreed upon by the various manufacturers developing 2.4 gHz equipment. I understand that it is all in a somewhat broad frequency allocation designated as "unlicensed by the fcc.
Spectrum/JR claims 40 channels, apparantly their own designation. Xtreme power claims over 100 (I believe their website says 120) channels. I have found no claim by Futaba.
One would conclude that Xtreme power uses a narrower band for it's designated channels than Spectrum/JR.
The next question is what other developers are developing products, and for what purposes, in the unlicensed 2.4 band.
This is totally different than the 50 allocated 72 mHz channels designated by the fcc for rc aircraft, channels 10 - 60. In this case all manufacturers are required by law to use these specific frequencies by channel allocation, and restricted rc aircraft, only.
I am under the impression that there are no specific channels allocated by the fcc or agreed upon by the various manufacturers developing 2.4 gHz equipment. I understand that it is all in a somewhat broad frequency allocation designated as "unlicensed by the fcc.
Spectrum/JR claims 40 channels, apparantly their own designation. Xtreme power claims over 100 (I believe their website says 120) channels. I have found no claim by Futaba.
One would conclude that Xtreme power uses a narrower band for it's designated channels than Spectrum/JR.
The next question is what other developers are developing products, and for what purposes, in the unlicensed 2.4 band.
This is totally different than the 50 allocated 72 mHz channels designated by the fcc for rc aircraft, channels 10 - 60. In this case all manufacturers are required by law to use these specific frequencies by channel allocation, and restricted rc aircraft, only.
08-11-2007, 08:17 AM
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RE: How many 2.4gHz at the field are too many?
As I said before, Futaba and XTM will skip past Spektrum. Only Spektrum uses two "channels" and holds them with a GUID to keep other radio's out of your planes. Now if and only if the other two systems skip a lot it may slow down their link with the plane but in no way will it cause a loss of signal. Both XTM and Futaba have a way to block outside signals from getting in. With all three systems in use you could have more planes in the air then LAX, it's just not going to happen. The systems are self limiting, if there is no "channel" they won't transmit. At this point you may think you have a radio falure will the radio is smatter then you. Dennis
08-11-2007, 09:06 AM
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RE: How many 2.4gHz at the field are too many?
Think of it like this:
The 72 mHz system is like fenced in ranches with each ranchers cattle on his own ranch.
The 2.4 gHz system is like the old "open range" days. All the cattle run together, anywhere they stray, and each rancher knows his cattle by the brand that's placed there by the branding iron.
The 72 mHz system is like fenced in ranches with each ranchers cattle on his own ranch.
The 2.4 gHz system is like the old "open range" days. All the cattle run together, anywhere they stray, and each rancher knows his cattle by the brand that's placed there by the branding iron.
08-13-2007, 08:26 AM
#18
RE: How many 2.4gHz at the field are too many?
Spektrum uses 2 wide band channels, where hopping systems use a very narrow band channel for a very short time. This narrow band signal for a very short time will be completely ignored by a Spektrum system even if it happens within the Spektrum systems 2 channels. Also the Spektrum system uses a GUID (Globalally Unique Identifier) stored in the receiver while binding, any noise on the channels used will be ignored without the GUID code from the transmitter. Long story short....there isn't such a thing as too many systems as I said earlier.
