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HelicopterRadio - Spektrum DSM › Spektrum's new DSMX
02-17-2011 02:27 PM  6 years agoPost 341
Hellsiege

rrVeteran

Colorado Springs, CO

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Is it still full range though? I think the point was it can't be full range on one antenna.

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02-17-2011 02:30 PM  6 years agoPost 342
TMoore

rrMaster

Cookeville, TN

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But Futaba doesn't use FHSS. They are frequency hopping DSSS. So then what you are saying suggests they should have multiple satellites to the extent that JR/Spektrum needs it. Why do I suspect you are just leading up to an argument for Airtronics and using Futaba to triangulate?
Because I'm not, the example could have been XYZ company not Sanwa.
Okay, I'm calling just a hint of bs. Not because this is wrong, because it is not wrong. It is because of the reason you are saying Spektrum uses satellites. You need to have spacing between the two antennas. Futaba does it with the antennas on the ends of extensions. Spektrum does it with satellites. You need the spacing because of potential blockage by carbon frames or metal parts. You also need the spacing because of reflections, especially in applications such as Giant scale Gassers. Without spacing, the reflected signal off of, say, that DA 110 can cancel out the direct signal. I suspect the Futaba system is less affected by reflections due to it's signal structure, but it is not immune to signal blockage. Having distance between the antennas is needed for any 2.4 system to be considered full range. Are there any 2.4 full range systems out there that use one antenna?
If you somehow block the signal on any radio it won't work, will it? The fact is that the antenna ends on FHSS systems only need to be 90 degrees apart and in an unobstructed location. In some of those giant scalers you sited for example I've seen a half a dozen satellites in the fuse. How many do you really need to do that job? What about CF glider bodies? With FHSS systems only the end whiskers need to be exposed. With DSM2 they predicated their technology on multiple receivers. Most FHSS systems don't require it.

Heck fellas you can use any DSM2 RX without a satellite if you want to but do it at your own risk. I would do a range check first, with the model running.

TM

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02-17-2011 02:50 PM  6 years agoPost 343
helismash

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Gloversville, NY -​Fulton

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Heck fellas you can use any DSM2 RX without a satellite if you want to but do it at your own risk. I would do a range check first, with the model running.
I would think that even if you did a range check, you would still be taking a chance. For one, the range check can not simulate all the possible orientations the RX would be in when the model is in flight.
I just don't think I would chance it.
Just my 2 cents worth.

Hey, Who put the ground there!
T-Rex 500/T-Rex 600N FBL/T-Rex 600E PRO/T-Rex 700N/T-Rex 700FBL

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02-17-2011 03:28 PM  6 years agoPost 344
Paul Beard

rrApprentice

Bigfork MT

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I read through most of this thread.

DSMx 3D spreading is achieved by:
1. Pseudo-random selection of a 23 frequency pattern
(from a possible 79).
2. Pseudo-random selection of the pattern sequence
(the order the pattern frequencies are used)
3. Pseudo-random selection of the DS spreading code

The collision immunity is improved since a system would have to collide in time, pattern, code and sequence. Even if 2 systems select the same pattern they would be on a different sequence and additionally a different code. DSMx sends the same data on successive frequencies of the sequence.

DSMx transmitters are compatible with DSM2 receivers.
DSMx receivers are compatible with DSMx and DSM2 transmitters.
DSMx and DSM2 remotes are not interchangeable.
DSM2 transmitters are compatible with DSMx receivers.

DSMx is not compatible with DSMj.

The multilink architecture improves fading performance, polarization loss and antenna null loss especially if the remotes are offset- polarized with a good separation distance when installed in the heli. Our multiple radio architecture has the additional benefit of redundancy.

DSMx has an improved RF footprint lowering it's contribution to the noise floor.

DSM2 DOES have a medium-access method. It picks the channels with the lowest noise floor to transmit on.

DSMx remotes WILL work with flybarless systems.

DSMx is not adaptive. Adaptive (AFH) schemes are fundamentally flawed in RC applications. There is a risk of being "adapted" out of the medium during flight !

Hope this helps,

Paul

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02-17-2011 03:32 PM  6 years agoPost 345
rexxigpilot

rrProfessor

Florida

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This thread has gone haywire! The news of DSMX should be something to celebrate whether you are a Spektrum user or not.

The way I see it we all benefit from a safer system. It took some pretty big cajones for Spektrum to admit their original design weakness and come out with a superior system. Kudos!

More importantly for me at least is now there is another radio option I would consider purchasing besides Futaba and ATX. I've always viewed the lock on two channel design as flawed. My earlier experience with wireless network routers showed me the limitations of 2 channel frequency locking. Anyone else remember when Super-G came out?

I think Spektrum just opened the door to many potential new customers with this change. Now I can buy a radio for use with cheap Bind-N-Fly models that can be used for "real" RC too.

Let's all look at the positive here!

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02-17-2011 03:40 PM  6 years agoPost 346
helo_chris

rrVeteran

goodlettsville, tn

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Is it still full range though? I think the point was it can't be full range on one antenna.
The XPS receivers only have one antenna and yes they are full range. Also no one has mentioned the importance of Receiver sensitivity as it relates to the discussion at hand. If you look at the data sheets the Spektrum hardware has a lower sensitivity than the other brands. So you could argue that satellites are a band-aid or its just over engineering. Either way they have to have it.

"There is a fine line between cutting edge and bleeding edge.."

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02-17-2011 03:51 PM  6 years agoPost 347
Four Stroker

rrElite Veteran

Atlanta

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Paul Beard

Are you still using the same 40 spreading codes as DSM2 or a new set of 40 orthogonal codes ?

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02-17-2011 03:56 PM  6 years agoPost 348
Paul Beard

rrApprentice

Bigfork MT

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Are you still using the same 40 spreading codes as DSM2 or a new set of 40 orthogonal codes ?
Yes but, in a different sequence. There are very few spreading codes that have good auto and cross correlation properties.

DS Spreading also improves selectivity (why cross correlation is important) adjacent channel selectivity is a product of the IF bandwidth and code distance.

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02-17-2011 04:29 PM  6 years agoPost 349
Four Stroker

rrElite Veteran

Atlanta

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Thanks Paul. Will you explain to John the difference between a logarithm and an algorithm ?

The new DSMX system should be at least as good as any other 2.4 GHz system as regards RF link. Now it's back to celebrity marketing.

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02-17-2011 06:56 PM  6 years agoPost 350
Tyler

rrElite Veteran

Chicagoland area

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The new DSMX system should be at least as good as any other 2.4 GHz system as regards RF link. Now it's back to celebrity marketing.
Didn't they tell us it was bullet proof and better than every other system up until now?

It was marketing all along, celebrity optional.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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02-17-2011 07:16 PM  6 years agoPost 351
helismash

rrKey Veteran

Gloversville, NY -​Fulton

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Didn't they tell us it was bullet proof and better than every other system up until now?
Tyler,

I think that was before all the other systems came out and now there is more noise for it to contend with.

Hey, Who put the ground there!
T-Rex 500/T-Rex 600N FBL/T-Rex 600E PRO/T-Rex 700N/T-Rex 700FBL

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02-17-2011 10:18 PM  6 years agoPost 352
helo_chris

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goodlettsville, tn

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If their marketing is to be believed it wouldnt matter how many systems there were. And it didnt say we are the best until everyone else gets into the game, it said we are the best. I will repeat what I have said before, If I were in charge at Horizon I would be looking to replace a marketing manager or whom ever it was that decided to handle this the way it has been. Regardless of your opinion on the subject itself this has been handled very poorly by Horizon.

"There is a fine line between cutting edge and bleeding edge.."

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02-17-2011 10:30 PM  6 years agoPost 353
GBR2

rrApprentice

Snohomish, WA USA

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How come they can update a DX6i or DX7 but they can't up date a module (except for the one in the 12x MV)???

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02-17-2011 10:57 PM  6 years agoPost 354
Paul Beard

rrApprentice

Bigfork MT

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How come they can update a DX6i or DX7 but they can't up date a module (except for the one in the 12x MV)???
Modules (except for the 12MV and the integrated systems) have a ppm interface to the transmitter. The ppm data does not contain the model number, so the module does not know when to switch protocols if say Model #1 had a DSM2 receiver and Model #2 had a DSMx receiver.

The protocol is learnt by the transmitter during the binding process and stored along with the model number.

This is also why modules do not support DSM1 or modelMatch.

The 12MV module has a serial digital interface to the 12X where model number information is transferred as well as the servo data.

Paul

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02-18-2011 12:00 AM  6 years agoPost 355
JasonJ

rrKey Veteran

North Idaho

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If you somehow block the signal on any radio it won't work, will it? The fact is that the antenna ends on FHSS systems only need to be 90 degrees apart and in an unobstructed location. In some of those giant scalers you sited for example I've seen a half a dozen satellites in the fuse. How many do you really need to do that job? What about CF glider bodies? With FHSS systems only the end whiskers need to be exposed. With DSM2 they predicated their technology on multiple receivers. Most FHSS systems don't require it.

Heck fellas you can use any DSM2 RX without a satellite if you want to but do it at your own risk. I would do a range check first, with the model running.
Is there anything in the installation instructions for Futaba rx's that say how far apart the ends should be? There is a reason why the antennas are out on the ends of long wires. I see people always clump them together when logic dictates you should run them far apart with the ends at 90 degrees to each other.

You can't run a Spektrum rx that uses satellites without the satellites connected.

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02-18-2011 12:09 AM  6 years agoPost 356
Discharger

rrApprentice

Perth, Western​Australia

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Paul Beard, I for one appreciate the fine leading edge radio technology products Sprektrum constantly offer and spoil us with. You must have a strong back to cop some this crap.
Illegitimi non carborundum!

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02-18-2011 12:22 AM  6 years agoPost 357
Smacka

rrApprentice

PA

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Yeah, it's cool having Paul show up. I am not sure how many companies would have their VP of Engineering weigh in on a users forum

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02-18-2011 12:26 AM  6 years agoPost 358
helismash

rrKey Veteran

Gloversville, NY -​Fulton

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Yes, thank you Paul. This will help to clear up any inacurate information.

Hey, Who put the ground there!
T-Rex 500/T-Rex 600N FBL/T-Rex 600E PRO/T-Rex 700N/T-Rex 700FBL

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02-18-2011 12:59 AM  6 years agoPost 359
Havoc

rrElite Veteran

Ky.

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Guess I'll get the upgrade. But I'm waiting until after this weekend. 54deg!

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02-18-2011 01:26 AM  6 years agoPost 360
Gehrbox

rrApprentice

Charleston,SC

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Guess I'll get the upgrade. But I'm waiting until after this weekend. 54deg!
Heck man it was in the 70's here today.

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HelicopterRadio - Spektrum DSM › Spektrum's new DSMX
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