JR/ Spektrum fault?

[mikeymikeymikey]

Just read this review of Spektrum based systems and thought that the points he made were interesting.... Ive flown a dx7 and now a JR-DSM system with absolutely no problems over the last few years. Do you think this is a valid problem?

http://www.rcmodelreviews.com/dsm2flaw.shtml

[jongurley]

No,,

[Fade2Black]

I read it, and my feeling is the whole artical almost contradicts everything he says. The author is finding one point to exploit. I am no Frequency Guru / Ham Guy, but I think the point is just about as valid as someone keying up a 72mhz radio while someone is flying on the same channel realized his battery pack was unplugged and pluged it in finally causing the airplane to go in. (Hope that made sense). As if there had to be a triple failure that would be a one in a million chance. The TX and RX needed to be in a medal clad building (from what I gather), the RX must have randomly choose two Frequencys very close to each other and some sort of high powered 2.4ghz equipment needed to be in the vicinity and on. For instance:

	Quote:
	On the rare occasions when the JR/Spektrum radios do choose two adjacent channels, the effect is simply that your risk of lockout is increased but only if there just happens to be strong noise on that small part of the band.

I think that is the basis of the finding are good, and I am sure a lot of research went into it. I also believe this exploit would have been "Exploited" far in the begining if it was that much of an issue. The amount of failures do to this is probabaly NIL, but jsut one more reason for someone to blame 2.4 for their dumb thumb or bad judgment.

As an FYI:

Here is a peice of equipment that will transmit 600mw 2.4ghz:

A buisness grade Access Point / Router for a 802.11 wireless (WiFi Network)

[Judge]

The amount of spectrum that the video camera occupies would cause most radios to have issues. A frequency agile radio may have less issue, but it would still see the noise and suffer either a short hold or slowed response.

In addition, if that signal was present when the JR/Spektrum radio was turned on it is unlikely that the radio would select two closely spaced channels, by default it would almost have to spread them apart.

As he said, in the real world this is very unlikely to be an issue.

Keep in mind that I am a Futaba guy, but I am also a big fan of accuracy and knowing the whole story.

The router in the photo above has our Team Colors on it!!

[mikeymikeymikey]

It's funny how people react when their "baby" is being picked apart. I just thought that if this was a actual problem it sounds easily fixed. Now i'm pretty sure its not a real world issue. The first time I read it I thought I would have to sell and buy Futaba.. ugh. Now I'm not feeling so bad haha

[classclown]

Seeing how he was doing this inside a steel building, with metal racks all around him, then flooding the space with a 2.4 video signal, led me to stop reading the rest of his gibberish.

[Fade2Black]

	Quote: Originally Posted by mikeymikeymikey
	It's funny how people react when their "baby" is being picked apart. I just thought that if this was a actual problem it sounds easily fixed. Now i'm pretty sure its not a real world issue. The first time I read it I thought I would have to sell and buy Futaba.. ugh. Now I'm not feeling so bad haha

I didnt react in a detrimental way so to speak. I only reacted to the facts of what was posted. Beleive me, "JR" isnt my baby. Although i do use the radio equipment they offer, I have had my fair share of issues.

[ScottZ]

The article states that the testing was done inside a metal shop which should inhibit outside signals. I have been flying a DX 7 in a double walled metal building with foamies all winter long without a singal glitch. Sometimes the TX won't bind to the RX and I have to shut the TX and RX off and it has always bound the second time around. I originally thought that the Spektrum would be a problem from reading its own signal in the metal building. This has not been a problem. At my field this Spektrum DX 7 is still way better than the old FM even though the PCM was better than FM for signal retention "at my field" that has a VOR tower nearby.

[Pilotpete]

Hi Scott,
I think a lot of the old timers at Coyle field liked to blame Coyle VOR for their losin it when they flew out too far in that direction. I flew Futaba AM and Airtronics FM systems there for many years with no problems, other than the dumb thumbs type
Greetings form a former member of the PBM's
Pete

[GBR2]

I think he has a valid point. The 2 "channels" that the Spektrum system choose should have some sort of minimal separation just to insure something couldn't interfere with both at the same time. It should be an easy software fix and would just make the system even more bulletproof.

[wefcisco]

	Quote: Originally Posted by mikeymikeymikey
	Just read this review of Spektrum based systems and thought that the points he made were interesting.... Ive flown a dx7 and now a JR-DSM system with absolutely no problems over the last few years. Do you think this is a valid problem? http://www.rcmodelreviews.com/dsm2flaw.shtml

I agree that when the firmware selects random channels it should ensure there is decent separation between them. However I do have a problem with the authors "test". First he ensured that there was no interference by placing the equipment in a shielded room and I assume he power cycled the radio until it chose 2 adjacent channels. Then he turned on another device that he was able to force to operate on that channel. Again specifically "not a spread spectrum friendly" device... The bottom line is that with any radio link, if you have 2 devices trying to use the same frequency, you've got problems.. Even if the radio selected 2 widely separated channels there is still the possibility that someone might be operating 2 "not spread spectrum friendly" devices nearby that happen to start operating on both of the channels selected... The only way to avoid this problem is to have a frequency hopping system, but I don't think I'm going to lose too much sleep over this issue...

Wayne

[jamesrxx951]

im curious on what outside could cause 2.4 interference on any 2.4 radio. i always thought we had these certain parts of the 2.4 spectrum all to ourselves from the fcc.

[Truckracer]

	Quote: Originally Posted by jamesrxx951
	im curious on what outside could cause 2.4 interference on any 2.4 radio. i always thought we had these certain parts of the 2.4 spectrum all to ourselves from the fcc.

Not exclusive frequencies! We share them with every WiFi device there is out there.

[rede2fly]

	Quote: Originally Posted by Fade2Black

	Quote: Originally Posted by Judge
	The router in the photo above has our Team Colors on it!!

be very carefull with that router. you cant set it next to a window, or it will overheat and shut your computor

sorry i had too

[aviti]

	Quote: Originally Posted by jamesrxx951
	im curious on what outside could cause 2.4 interference on any 2.4 radio. i always thought we had these certain parts of the 2.4 spectrum all to ourselves from the fcc.

Don't feel bad...you're not the only one to think this. Several folks at my flying field told me how we have our own dedicated 2.4 channels. As I looked around and saw others nodding in agreement, I just let them go and have their little fantasy.

Although I'm curious how these systems work and how well they reject interference, it's more important that when I push the stick, my plane responds. I've been on Spektrum 3 seasons now and so far it does what I command. I'm sure Futaba does too. Life is good.