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HelicopterMain Discussion › Ircha: How is impounding working with Spread​Spectrum radios?
08-08-2007 07:23 PM  10 years agoPost 1
MooneyDriver

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Kent, Ohio

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Anyone there yet?

-Neil

Hey man, why does my lipo get bigger every time I charge it?

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08-09-2007 07:44 AM  10 years agoPost 2
w.pasman

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Netherlands

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I read something about the max number of spectrum radios being on at the same time on the field, it's about 40 if I remember it right. Also, there seems uncertainty about what happens when you get over that maximum. So still reason to have an impound.

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08-09-2007 08:07 AM  10 years agoPost 3
IYKIST

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London united​kingdom

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I read you could have up to 3000 on without getting conflicting signals.

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08-09-2007 08:34 AM  10 years agoPost 4
ARMSMASTER

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spokane, wa

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Not true. Just read on the Sprctrum web site. There are only 80 channels allocated to this application. The Spectrum systems uses two channels per radio at a time. You could have all 40 spectrum radio's turned on and #41 would just not activate untill one of the other 40 turned off. That is what makes spectrum so nice. It will not activate untill it finds two open channels. Now the issue is the Futaba Fast system. It uses one channel at a time and then channel hops or skips. But the more 2.4ghz radio's that are on the longer it takes for it to hop to the next available channe. There was a big article in last months Model Airplane News on the two different systems. You should read that article if you have any questions. Hope this info helps.

Life is like a box of chochlates!

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08-09-2007 12:29 PM  10 years agoPost 5
DS 8717

rrProfessor

Here wishing i was​somewhere else

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SS is 40 channels,XPS is over 100 channels. Dont know how many Fubar will have,i guess we'll see next year some time.

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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08-09-2007 02:09 PM  10 years agoPost 6
Pistol Pete

rrProfessor

Seffner, FL

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as per the AMA they are also supposed to be impounded in order to maintain safety protocol throughout all flying sites equal.

Indeed interesting question...subscribed.

~~Enjoying the hobby one flight at a time~~

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08-09-2007 03:12 PM  10 years agoPost 7
BarracudaHockey

rrMaster

Jacksonville FL

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If nothing else I'm sure they will impound for flight line access control.

Andy
AMA 77227
http://www.jaxrc.com

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08-09-2007 04:40 PM  10 years agoPost 8
tadawson

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Lewisville, TX

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Not true. Just read on the Sprctrum web site. There are only 80 channels allocated to this application. The Spectrum systems uses two channels per radio at a time. You could have all 40 spectrum radio's turned on and #41 would just not activate untill one of the other 40 turned off. That is what makes spectrum so nice. It will not activate untill it finds two open channels. Now the issue is the Futaba Fast system. It uses one channel at a time and then channel hops or skips. But the more 2.4ghz radio's that are on the longer it takes for it to hop to the next available channe. There was a big article in last months Model Airplane News on the two different systems. You should read that article if you have any questions. Hope this info helps.
Where the fun is going to start happening is where over 40 systems are active in an area, simply because they were powered on out of range of each other, and thought it was safe, and then folks walking to the flight line (or whatever) bring all of them into range of each other. What happens then? They are all transmitting, so none will "fail to activate" . . . and none can safely just shut down, since there might be a model in the air . . . so, having a hard limit makes a lot of sense, and myself, I would make it LESS than 40, just to be sure that an occasional "stray" that is ignoring the impound doesn't get in the way . . .

- Tim

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08-09-2007 05:10 PM  10 years agoPost 9
Micro-Maniac

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Pasco,Washington​Formerly: Captain​Chaos

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Spektrum systems also use Global Unique Identifying (GUID) for just such a situation - It's the same as with cell phones - Each has it's own unique ID encoded with the signal so several can all operate on the same channel and use GUID to filter the correct signal - Anything that doesn't contain the GUID is ignored - So in reality there could actually be a lot more than 40 Spektrum systems operating at once - Spektrum really thought things out to make a near bulletproof system

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08-09-2007 05:18 PM  10 years agoPost 10
tadawson

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Lewisville, TX

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GUID or no GUID, if there are only 40 sets of frequencies and a 41st transmitter somehow is on air and comes into the mix, RF interference is RF interference - somebody is going down. The GUID does NOTHING to help in this situation . . . . the interference makes either masks the "correct" signal, so that the aircraft only sees the wrong one, and goes into lockout, or both signals corrupt each other so badly that neither aircraft can get a clean bind. It would be interesting to see what happens in this case, though . . . would they just start frantically frequency shifting, "passing the problem around", as it were, or ? ? ?
Since Spektrum binds to a pair at initialization, how do they deal with the corner case where some other signal that is already on that frequency comes into range?

- Tim

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08-09-2007 05:19 PM  10 years agoPost 11
Micro-Maniac

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Pasco,Washington​Formerly: Captain​Chaos

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Does your cell phone go down when you're around others talking on cell phones or you hear their cell phone conversations on your cell phone? Because it's likely you're all sharing the same channel and using GUID same as Spektrum

About the only problem would be like a downlink operating too close to the RX or being drown out by something operating at higher power than these systems

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08-09-2007 05:22 PM  10 years agoPost 12
tadawson

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Lewisville, TX

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Actually, cellphones DO drop calls when they move into cells that already have all channels in use . . . they can't get an assignment, and ***thud***, call gone. The Cellphone system is not a terribly good comparison, though, since the land side gear controls the frequencies in use by the phone - the phone does not just "choose at random" when it comes on . . .

- Tim

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08-09-2007 05:22 PM  10 years agoPost 13
pgoelz

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Rochester MI

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Only responding to the correct GUID merely means that I can't cause uncommanded servo movements on your radio. I can still cause your radio to fail to respond if I camp on both of the channels you are using. Or make it a lot less reliable if I camp on one of the two.

What I am not sure about is what happens to the channels I am using with my Spektrum system when a lot of Futaba (or Xtreme Link) frequency hopping systems power up. Do they actively avoid my 100% occupied channels as they hop around or do they each create momentary loss of signal as they randomly transmit on my channel(s)? If the latter, it could get interesting if enough of them are on at the same time. Not a factor for normal use at the field but it could well be at a large event like IRCHA.

Paul Goelz
Rochester MI USA
http://www.pgoelz.com

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08-09-2007 05:25 PM  10 years agoPost 14
Micro-Maniac

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Pasco,Washington​Formerly: Captain​Chaos

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True a channel can become saturated but it's not likely going to knock your system out - At worst your system may just seem to become a bit sluggish - High power or close vacinity signals can drown a system out though (can't hear it's own signal at all) (video downlink mounted next to rx - not sure about likeliness of high power as I think all 2.4 systems are limited to 1 watt)

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08-09-2007 05:34 PM  10 years agoPost 15
steve9534

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yakima, wa.

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Tim

This discussion is based on the premise that you can be out of range in the pits and by walking to the flightline come into range with other radios. Not too likely that is going to happen. The distance from the pits to the flight line is small compared to the range of the radios. Worry about it if you like, but I'm not going to lose sleep on this one. steve.

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08-09-2007 06:08 PM  10 years agoPost 16
Carey

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Allentown USA

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I am surprised more wasn't taken from existing wireless network technology.

We already have PLENTY of unique identifiers in the 48 bit mac address field (multiple trillions), so that is not an issue. What is left is the segmentation of the media, which would be the same as ad hoc wireless networks. Right now I can make tons of 1 to 1 pairings with wireless ethernet over ip between 2 nodes.

Someone help me understand the limitations here, as I am not a radio expert.

Thanks

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08-09-2007 06:59 PM  10 years agoPost 17
Juggernaut

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Canada, Great White​North

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Ever wonder why the 2.4GHz spectrum is open.
Every one now has a microwave oven, for your interest, it operates at 2.4GHz, not one frequency, but a large spread. I work with radios,including the unlicensed bands. we use 2.4 GHz bands to beam signals from site to site, to send information and telemetry.
who else uses 2.4Ghz. Cordless phones, personal walkie-talkie, Microwave ovens, toy RC anything, radio telemetry systems.
Attached is a screen capture using a spectrum analyser, with a DX7 and a microwave, Yellow is the microwave oven, green DX7, I placed arrows to help you see the DX7 signals.
I'll stick to my 72Mhz radio, it's a licensed band, used strictly for RC aircraft

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08-09-2007 07:02 PM  10 years agoPost 18
Micro-Maniac

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Pasco,Washington​Formerly: Captain​Chaos

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Let's see if I myself understand Spektrums use of wide-band and GUID - Unlike our 72mhz systems operating on narrow-band Spektrum operates on wide-band which allows for way way more information transmition than a single Spektrum system needs - While everyone is worried about interference which could be the case with narrow-band as there becomes too much info flooding a channel while wide-band allows for more information and GUID filters that information - More information (from multiple systems) doesn't necessarily drown out a channel but is simply more info transmitted on that channel and each Spektrum system just uses the info addressed to itself and disregards the rest

I got hits and interference on 72mhz all the time (lost more than one aircraft to it) but not a single noticable hiccup in 2 years of using 2.4ghz - It's quite proven itself to me

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08-09-2007 07:16 PM  10 years agoPost 19
w.pasman

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Netherlands

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Someone help me understand the limitations here, as I am not a radio expert.
The limitations with wavelan wifi and other existing wireless computer networks is the lack of guaranteed REAL TIME behaviour. These networks may drop out, delay, and whatever.

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08-09-2007 07:22 PM  10 years agoPost 20
cessna151

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Missouri...​Originally Indiana

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Sounds like the best thing to do is use synthesized 72mhz, pick a channel not in use and go fly!

--Eagles may soar high, but weasels don't get sucked into jet engines!--

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HelicopterMain Discussion › Ircha: How is impounding working with Spread​Spectrum radios?
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