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HelicopterRadio - Spektrum DSM › Spektrum's new DSMX
02-14-2011 04:45 PM  6 years agoPost 301
helo_chris

rrVeteran

goodlettsville, tn

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Power is 300mw, antenna gain is 2.1db. According to the Cypress data sheet sensitivity is -90dbm, not sure if that takes into account processing gain.

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

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02-14-2011 05:44 PM  6 years agoPost 302
Busher

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Manchester, England

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negelected to mention that overall system latency went from 24.5ms down to 9ms with FHSS3 so that was a big reason for the change.
Those are very good latency figures. I would consider Sanwa but the support over here is less than good, and looks like its going to get much worse.

So for now I will have to stick to what I have until it gives me the messages I require to change.

I will say reading through this thread has opened my eyes to the litigious society we live in today and how ready people are to defend their chosen system. I have learnt a bit more about fhss and dsm2/x, and that there are some very intelligent fliers out there. I hope one day I can get to IRCHA and see the spectacle unfold and perhaps meet some of the fine fellows here.

Im off to my shed now to Dope off a tissue covered model, (lovely smell) and contemplate the flying season ahead. I wish you all happy and safe flying in 2011.

PS I wonder if MrMel could have dreamt that posting a link to that video would have prompted such a diverse response

Good luck
Busher

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02-14-2011 05:56 PM  6 years agoPost 303
Juggernaut

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Canada, Great White​North

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300 mW is about 24.8dBm
free air loss at 2.4GHz for
5 yards = 54dB, remaining margin = 36dB
10 yards = 60dB remaining margin = 30dB
15 yards = 63.5dB remaining margin = 26.5dB
20 yards = 66dB remaining margin = 24dB

if you were 5 yards from your heli and another pilot is 20 yards away
you have 36 dB of margin minus the other radio at 20 yards now leaves about 12 dB of margin.
Now if you have another pilot 20 yards on the opposite direction
your margin how becomes 9dB (basically doubles the power by 3dB)
now as you fly farther away your margin reduces, especially if you get close to another pilot using the same frequency (channel).

As long as the heli is close you will have some signal strength to fly, but don't go to far you will lose any remaining signal margin.
This does not take into account antenna polarization.
Note this applies to multiple radios in use at the same frequency (channel)

Hope I did my math right



Finally learned to fly inverted, Helps if you stand on your head

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02-14-2011 06:56 PM  6 years agoPost 304
helo_chris

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goodlettsville, tn

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According to Radiolabs performance calculator based on the available data at .1 mile (it doesnt do yards and .1 is the smallest value) Rx Power would be -57.29dbm and theoretical margin would be 32.71db. For reference .1mi is 176 yards. You also have to consider that just because the signal from one is stronger than the other doesnt mean it is automatically going to lock out. The Rx may still be able to see the signal. It will just have a harder time picking it out, because again they dont transmit 100% of the time. You would likely see packet losses but wouldnt necessarily suffer a complete loss of control.

http://www.radiolabs.com/stations/wifi_calc.html

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

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02-14-2011 07:28 PM  6 years agoPost 305
helismash

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Gloversville, NY -​Fulton

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If I understand DSM2 correctly, because your RX is looking for the GUID of your TX it will ignore the other TX and as long as it can see some of your transmitted signal, it will at least function somewhat. However, if the RX has lost the signal from it's TX due to another signal overpowering yours, then you would be locked out.
I think that's how it works. Someone correct me if I'm wrong please.

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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02-14-2011 07:38 PM  6 years agoPost 306
Four Stroker

rrElite Veteran

Atlanta

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The 10% duty cycles would have to overlap. Additionally, there is a 64 bit spreading code (see chip spec previously) that provides roughly 18 dB gain over the other signal.

All of this speculation about how someone can shoot you down is getting a bit rediculous. These probabilities are difficult to compute even when you know the coding details. In all cases the coding details are proprietary.

Just assume that DSMX (DSMJ.2) works much better than DSM2. Buy it if you want it. There are other choices.

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02-14-2011 08:25 PM  6 years agoPost 307
Adam Henley

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Puyallup, WA. USA

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Just assume that DSMX (DSMJ.2) works much better than DSM2. Buy it if you want it. There are other choices.
This is the most sensible post here yet. I love it! Buy it or don't. Any radio on the market is much better than anyone on this forum could build on their own. Can you imagine trying to make your own? Would cost thousand, look like a hunk of junk and would have no programing. Let's learn to do the best we can with what we've got. We can keep giving input and I'm sure the radio company's will continue to innovate. Someday we will all have thought Guided models that will go into brain safe mode and continue the rest of our projected flight on artificial intelligence if we lose radio contact.

I've never met a helicopter I didn't like :)

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02-14-2011 09:28 PM  6 years agoPost 308
Juggernaut

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Canada, Great White​North

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I think the best way to understand noise or interference.
if you are in a large room with some else (say your buddy), standing at opposite ends of the room, now add a few more folks in pairs talking to each other, not a real issue, as we can make out the conversation.

Now keep adding more folks talking, at some point you will have trouble understanding your buddy. the only way to improve the situation is to talk louder or more closer, but as more enter the room, you get more noise making it even more difficult to hear clearly.
radios basically have the same problem.

Telecom equipment also have a CRC (cyclic redundancy check) this is used to verify the data received does not have any errors, this does not correct the errors, only indicate there are errors, and reject the data.



Finally learned to fly inverted, Helps if you stand on your head

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02-15-2011 06:02 AM  6 years agoPost 309
JasonJ

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North Idaho

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If I understand DSM2 correctly, because your RX is looking for the GUID of your TX it will ignore the other TX and as long as it can see some of your transmitted signal, it will at least function somewhat. However, if the RX has lost the signal from it's TX due to another signal overpowering yours, then you would be locked out.
I think that's how it works. Someone correct me if I'm wrong please.
That's pretty much it. That and the fact that it has linked to two channels is why you can actually go over the 40 tx maximum. The downside to going over the 40 tx maximum is there is channel overlap but there is still the unique GUID to help filter the desired signal from extraneous signals. It would take a strong signal to completely overpower both the tx signal channels and render the GUID useless.

Someone will say "What about all the wifi and mircowaves and prostate examination tools in use at the same time?" Okay, show me the hard data that shows this big overpowering signal happening at Ircha.

That is the point of those who are defending DSM2. There are several factors that have to occur to cause an actual true lockout. As I see it, we can prattle on about "dead zones" in Ircha and all that nonsense but the reality is there were no strategically placed analyzers set every 50 feet out there showing saturation and signal strength throughout the flying area so it's all speculation.

Just because someone says they had a lockout doesn't mean they had a lockout. I have watched people stare at their aircraft as it crashes to the ground, doing nothing with their tx because they brainfarted, then claim "lockout". Again, I am not saying it can't happen, I believe it can happen. I am just saying that no one has brought forward hard data showing that the crashes that were blamed on Spektrum were caused by Spektrum or bad setup/dumthumbs. Never underestimate ego, unless you really believe everyone there would never blame their dumb thumbs or bad setup on the radio. That is downright naive.

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02-15-2011 06:16 AM  6 years agoPost 310
TMoore

rrMaster

Cookeville, TN

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Someone will say "What about all the wifi and mircowaves and prostate examination tools in use at the same time?" Okay, show me the hard data that shows this big overpowering signal happening at Ircha.
Call the AMA and ask them about their Wifi setup at the Muncie facility. If you actually go there and use a Spectrum monitoring system like WiSpy or use a phone with suitable software you can see the networks in operation there and they have enough power to cause issues.
It would take a strong signal to completely overpower both the tx signal channels and render the GUID useless.
That's exactly what happens and it doesn't take that much power to do it.

TM

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02-15-2011 01:31 PM  6 years agoPost 311
TmMugen

rrKey Veteran

Tiny Little Red Dot​aka Singapore

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Just curious if I can send in the radio for an upgrade?

I am a noob flyer from Singapore! Team Nitro Magic

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02-15-2011 01:36 PM  6 years agoPost 312
helismash

rrKey Veteran

Gloversville, NY -​Fulton

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Yes, if it is listed on Horizon's web site you can send it in for the upgrade.

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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02-16-2011 08:42 PM  6 years agoPost 313
Smacka

rrApprentice

PA

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Just receievd my Wi-Spy..it could not be any easier to install the software and run the program. You used to have to jump through hoops to install the USB device driver. Now, you go to their website, download the software...plug in the Wi-Spy, then launch the software. The driver(s) are automatically loaded.

On another note, if you plan to upgrade to the full blown version of Channelzyer software, be ready to dig deep into your wallet...it is $499

Happy Flying,
Smacka

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02-16-2011 10:00 PM  6 years agoPost 314
helismash

rrKey Veteran

Gloversville, NY -​Fulton

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How's the Wi-Spy working?

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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02-16-2011 10:07 PM  6 years agoPost 315
Smacka

rrApprentice

PA

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I used it to monitor my Wi-Fi network and it does a great job...it shows a section about 60dbm from around 2.405 to 2.42X in width being utilized...I give it two thumbs up

It would efinitely show you what the floor looks like at an event like IRCHA

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02-16-2011 10:29 PM  6 years agoPost 316
helismash

rrKey Veteran

Gloversville, NY -​Fulton

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Smacka,
Great info thanks.

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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02-16-2011 11:25 PM  6 years agoPost 317
TMoore

rrMaster

Cookeville, TN

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Ruh-Roh Futaba's at it again.

Watch at YouTube

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02-16-2011 11:37 PM  6 years agoPost 318
helismash

rrKey Veteran

Gloversville, NY -​Fulton

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LMAO! That's funny as hell.

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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02-16-2011 11:39 PM  6 years agoPost 319
Hellsiege

rrVeteran

Colorado Springs, CO

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LMAO! That's funny as hell.
+1 LOL

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02-16-2011 11:43 PM  6 years agoPost 320
TMoore

rrMaster

Cookeville, TN

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At least they didn't say Spectrum rhymes with Rectum. That was a good thing.

TM

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