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Home✈️Aircraft🚁HelicopterAerial Photography and Video › Jr9303, XPS 2.4 system, cell tower interfered...
02-23-2010 10:46 PM  10 years ago
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Disciple4123

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Jr9303, XPS 2.4 system, cell tower interfered...
Did a session today. Flew 300+ feet away from a cell tower several times with the heli (equipped as a gasser, DJI autopilot, 900mhz downlink at 1/2 watt). When I came to do some shots at 600 feet from it, about 100 feet up (equal to tower) I began to lose control and DJI was taking the slack. I landed thinking something was afoul with the engine, as when DJI goes to auto-hover from transit there is some sudden engine loading as expected. I found all things good, and approached again. In the same spot at the same altitude it began the same interference.

Although DJI has been flawless to take over, I try to cover all bases; especially considering that the client is ordering me back for periodic re-shoots)

I have been using the XPS (xtremepowersystems) 2.4 system on a 9303 Jr radio. Any other similar reports? Would the JR 12x unit carry itself differently? It is hard to fish for objective answers with RF, which is a very unpredictable field of study, but some experiences may point me in the right direction.

For clarification I was about 800 feet from the heli, antenna on the rear side of heli facing me, and cell tower was on my right slightly closer to the heli (measured on G-earth to be 600 feet)

Thanks,

Eric
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02-23-2010 11:03 PM  10 years ago
Vortex Aerial

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Heard nothing good about the XPS system.

I fly the 9 channel Rx that comes with the 9303 2.4 radio set along with an additional sat Rx over and above the one that comes with the radio set (so it runs 4 descrete Rx at one time) and the JR/Spektrum Data Log device that gives good useable info as to reception performance.

Thing doesnt even flinch.

Advise either all JR or all Futaba and nothing else.

My 2 cents
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02-24-2010 02:16 AM  10 years ago
Disciple4123

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I will eventuall get the 9505 jr system, as i agree it seems better. I had gotten the XPS back when other options were not available and i had need for a 2.4 system to mitigate twin engine EMI.

For temporary I am relocating certain components to improve things.

thanks.
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02-24-2010 04:43 AM  10 years ago
Vortex Aerial

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Was going to get the 9505 as well but once i saw that it only does two more things than the 9303 (barring the huge and useless 50 model memory) does i went out and bought two 9303s at the discounted blowout rate. They were just over 400.00ea if i recall.

You may be able to find an ebay vendor if your interested.
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02-24-2010 06:06 AM  10 years ago
theslayer

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Add a spektrum module to your 9303 and you will be set.
XPS wouldn't be my choice, for sure

Daniel
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02-24-2010 06:27 AM  10 years ago
SeismicCWave

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I used a JR 9303 2.4 GHz Tx and I flew right next to a cell tower on one of my assignments. I was skeptical at first but after a few minutes I realized that the cell tower had absolutely no interference on my radio.
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02-24-2010 07:46 AM  10 years ago
Ghia

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Nothing wrong with XPS. They have data logging also where you hook the XPS telemetry module to a laptop for things like signal strength etc...

What version of xps do you have? They have version 3 now which is a full hopping FHSS system, way more robust then a DHSS Spektrum which, by the way, is having lots of problems of their own and soon to be replaced by JR's DSM2 FHSS.
It would be a downgrade to switch from XPS (unless to a FASST/SANWA/Hitec/MPX of equal FHSS performance)

Was it going into failsafe? Why is it a prob with radio if you are flying right next to a cell tower?? Any SS gear, MAYBE even a FHSS hopper, would have issues with brown out especially a DHSS spektrum because with the power those towers put out would affect the whole band.

There is a video out on version 1 XPS hopping from a interference normally encountered real world by a RC craft at a sanctioned field. Its a special algorithym that states EXACT parameters of band noise must be met to affect a hop....

now that FHSS version 3 is out, no one uses version 1 XPS taht I know of and I upgraded 2 years ago. Havent heard of one issue in real world conditions.

Alot of folks who dont really know any better will spout the general "Get a spektrum" line but that would be the LAST system I'd pick for cell tower duty.
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02-24-2010 10:25 AM  10 years ago
Disciple4123

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Well I trust JR is probably marketing a competant system. Is it better than XPS for my machine, only time would tell. Ghia your post seems to contradict opinion on this thread, and to a lesser degree, opinon that I have read on in other forums. Since I am only marginally qualified in electrical sciences, I thought it best to ask it here where some degreed individuals could offer meaningful knowledge. What are your qualifications Ghia, not a challenge just a question?

I understand that multiple receivers are a valid concept, makes a lot of sense to me, at least the remote(s) are far from all gizmos on the machine, great idea JR. Not to mention that diversity systems are used in Wifi, etc.

I will say that my dealings with XPS in 2007 were nice, their engineers talk to customers, they care. Now if they are state of the art in 2010, I cannot assume that. Their niche, to put a 2.4 system on old 72 mhz TX's is fading fast. My XPS gear is the late 2007 version.

Seems I can get a JR module and AR9000 RX for about $180, good deal if you ask me. I have use for a second TX for one type of operation, but will refrain from the $800-1400 route for now if a module and RX can be had.
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02-25-2010 09:31 PM  10 years ago
JuanRodriguez

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Disciple4123 ,
If the XPS gear you're using is 2007 vintage, then it's "old technology" and would explain __possibly ?__ why you are having some difficulty.... If you were to update your equipment to their current version, as Ghia has pointed out, that should resolve all of your issues.....

Their "upgrade" package is about $40 bucks for ALL of your XPS modules and receivers. Not a bad deal if you have multiple receivers and modules....

Sorry, I can't offer any "qualifications".....other than to offer "real time" experience. I'm just a satisfied XPS customer. I "converted" my JR 9303 last year and have 4 models flying their system. So far, no issues.

I can also tell you from being on this and other forums as well, that many "opinions" are given as "fact" and in many instances, the person offering the opinion has had no hands on experience with the equipment.... Rather, they "heard it" from a "friend, a relative, a friend's friend's third cousin", etc..... you get my point.

Lastly, I'm not going to debate that XPS is better than X brand or Y brand...... I can only tell you that it works and works well for me. But, I'm not flying around cell towers.....

And no, I'm not a stock holder nor am I associated with them in any way.
Been there, done that and old enough to know better.....
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02-25-2010 10:46 PM  10 years ago
Disciple4123

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Appreciate your opinion, Juan, and all the others. I am not here to give anyone a hard time. It is just that Ghia's last sentence was a bit strong for me, that is all.

My opinion on XPS: It was a good option when JR and Futaba were first starting to offer microwave gear for this application. They may have been a trendsetter. Now that JR and Futaba have been in it for a few years and proven themselves to the community, the retrofit XPS gear in 2010 may seem less neccesary to me than it did in 2007 because of the options. Multiple receivers just seems like good principle, regardless of my limited understanding of RF engineering. "We see thru the glass dimly..."

I appreciate Jim Drew's (XPS owner) speaking with me about one issue I had back then, they seem like a caring, honest company, wish them well, they'll probably hash out some patents in the coming years, I wish them well. But JR probably has a clue as well.
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02-26-2010 04:51 AM  10 years ago
Ghia

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sorry If I came on strong

No expert by any means and like others I didnt want to jump on a bandwagon when 2.4g hit the market, so I read ALOT. All are good systems, and if DHSS is so great like the bandwagon folks claims why did the companies late to the 2.4g party ALL come with FHSS hopping?

Multi Rxs is a good Idea but when is the last time your aircraft held a stationary position in the air long enough for its "blocked" antennea to lose signal?? You fly right through. For certain models with a high CF content, Satellite Rxs are good I think, and most the popular companies offer them (version 3 XPS). Non issue as everyone has them.

XPS does have their own integrated radios along with modules. They are the new Graupner US dealer. You can buy a integrated MX-16/MX-22/MX-24 radio right now with XPS Rx.

JR now has DSMJ FHSS coming out so Im not sure how that will mix with the DSM2 DHSS spektrums.

I say buy what ya like but realize DSM2 is having alot of issues right now.
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02-26-2010 02:33 PM  10 years ago
Rafael23cc

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Sorry, I have no further input on the Cell tower issue, but the XPS vs "the rest" debate has spiked my interest. I got a Spektrum module for some of my birds and I "inherited" an XPS module with a couple of receivers. So this discussion has me interested.

I am a JR guy, have been for over 10 years. I might be living in a cave, but I have read this statement twice in the last 6 months, and I know nothing about it:
JR now has DSMJ FHSS coming out so Im not sure how that will mix with the DSM2 DHSS spektrums.
Would you please state a source? Seems like for an XPS user, you are more informed about JR products than JR users.

I apologize if I'm hijacking the thread in a direction that the OP did not intend.

Rafael
Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com
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02-26-2010 04:09 PM  10 years ago
jgoodsell

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Not very explicit explanation but I guess it's a start point for a source of information

http://www.rcjapan.net/tx/dsmj-vs-dsm2.html
It seams that Gravity is worst around here !
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02-26-2010 06:26 PM  10 years ago
Vortex Aerial

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I decided to switch from 72 Mhz to 2.4 gig after a number of tail control incidents occurred on my 21.5 Lbs. Maxi Joker video ship that were traced to both intentional and unintentional narrow band interference on two separate occasions.

I chose JR (specifically 9303) ONLY because i like the interface and ease of use.
Did much research on my own as i have heard that in a real world application, both DSSS and FHSS have their limitations but are FAR superior to Narrow band 72 Mhz PCM systems.

It may be comforting to some to have multiple receivers on board in a JR system but the biggest reason they are there is because DSSS technology demands it. But the upside is also hardware redundancy.

As far as being more robust in real world applications, to my knowledge and based on my own research, neither is better than the other for keeping in constant contact with your aircraft. It’s truly a matter of personal preference.

In a hobby application the two technologies are wonderful as they not only reject signals from each other but are totally immune to guys who still fly 72Mhz.

In an AP/industrial application both are susceptible to broad band noise as is guaranteed to be present in an environment that uses ANY kind of wireless network, be it cell phone, routers, or any wireless network that uses either technology. (most use DSSS)

To put it very simply, if the noise level across the band of channels your 2.4gig system is flying on gets loud enough, your receiver won’t be able to decode its incoming data, regardless of its level of encryption or rejection.
What is the likely hood of this ever happening? IMO it’s very slim as your aircraft never really gets far enough away from your transmitter to get swamped by other devices in the area. But, as with the case of newer autonomous hardware that enables long distance fully autonomous flight i could absolutely see a problem, but only if one was stupid enough to fly autonomously at a great range (like out of visual range) in a metropolitan area using a radio link that doesn’t transmit at a high enough amplitude for that kind of task. Out in a rural area though, it would most likly be ok IMO.
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03-03-2010 04:40 PM  10 years ago
Rafael23cc

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Not very explicit explanation but I guess it's a start point for a source of information

http://www.rcjapan.net/tx/dsmj-vs-dsm2.html
You are abosultely correct. It is not very explicit, and not at all reliable. Although we would like to think that the RC hobby is a worldwide industry, it is not. JR / Horizon clearly delineate the boundaries of where cetain products are allowed.

I'm not saying that you are wrong, you could be correct in the long run. At this point, this information is hear-say from a forum in a non-US JR market area, is not the best place to look for information for the US market.

Now explain to me where do you extract that JR is coming out with a frequency hopping system from those 3 lines on the top paragraph.

Rafael
Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com
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03-03-2010 05:03 PM  10 years ago
jgoodsell

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Now explain to me where do you extract that JR is coming out with a frequency hopping system from those 3 lines on the top paragraph.
I don't think it says it's a frequency hopping. I interpret it has a power difference due to regulations
From RCJapan
You can think of DSM2 USA and DSM2 Europe as brothers. Virtually the same, just the frequency is a little stronger in the USA.
Jeffrey Goodsell
It seams that Gravity is worst around here !
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03-10-2010 03:22 AM  10 years ago
Rafael23cc

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I don't think it says it's a frequency hopping. I interpret it has a power difference due to regulations
That is the way it is right now. Different countries have different power outputs due to regulations. That is a well know fact of 2.4 technology.

I want Ghia to explain this:
JR now has DSMJ FHSS coming out so Im not sure how that will mix with the DSM2 DHSS spektrums.
Rafael
Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com
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10-02-2010 01:39 PM  10 years ago
Disciple4123

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Been using an AR9000 DSM2 system for a long time now near the cell towers; flawless contact every time. FYI.
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10-02-2010 04:15 PM  10 years ago
lele

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italy

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I never flew close to a cell tower, but anyway I prefer Jr-spektrum and I placed as many as possible satellite receivers all over my heli.
Also I do not like Futaba style with only 2 antennas as I would be afraid the heli itself could shade the signal from some directions.

I also have the small device from spektrum that you plug in to the receiver after a flight and you can see if any of your receivers ever dropped a bit of information during the flight, I used that only in first flights to test the system and it showed everything was working right even at great distance.

Lele
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10-02-2010 09:46 PM  10 years ago
rerazor

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Mich.

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Don't bother with the 9303/9503 if buying a new JR Tx. The JR 11x is the one you want nowadays. Great radio for the money!!!!Robert
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