RE: Scorpion -6 for both 3S A123 and 3S LIPO / max beginner flight time
Not sure which 2.4GHz Tx you have now so cannot comment. Yes, IMO an 11T pinion would be a good starting point for you using 3S A123 with a 2221-6 motor. Spektrum DX6i has everything you will need to get started and for some time to come. The DX7 feels better in the hands and for most folk will last a long time before they out-grow its features, if ever. If your budget is tight then the DX6i is a good candidate IMO. If you can stretch a little further to get the DX7, you will be glad you did in the long run. Flight duration is influenced by many things, with headspeed being dominant. For the same headspeed, the stock motor and 3s 2200 20C lipos will probably give longer flights than the 2221-6 and 3s 3200 A123. But you would need a lot more lipos to get the same total flying time per hour so the A123 still come out ahead if you have the right charging setup.
Posted on: 4/5/2009 9:43 AM by Author "kgfly" in the forum "T-Rex heli"
http://www.rcuniverse.com/forum/fb.asp?m=8650309

RE: Scorpion -6 for both 3S A123 and 3S LIPO / max beginner flight time
The Scorpion 2221-6 is an excellent choice for flying 3S A123 but not well suited to 3S lipo, even with a smaller pinion and especially for a learner. It is inherently less efficient than less powerful motors like the 430L or even the 430XL and is very hard on lipos. For learning IMO 2600rpm is better than 3000rpm. The heli is less jittery, accelerates less aggressively, does less damage when encountering terra firma and flights are much longer for any given battery. Unless you are flying a Kontronik Jazz, getting 2600rpm with a 2221-6 using 3S lipos would probably require an unreasonably low throttle curve which will in turn be inefficient, heating up the batteries, ESC and motor even more. The 2221-8 might be a compromise worth considering if you are sure you want to fly both A123 and lipo. In the end you might not find a combination of motor and pinion that suits both battery types equally well for your preferred feel in the air. I would suggest you commit to a battery choice first and then select the appropriate motor. I think 3S A123 + 2221-6 has many advantages but it is less "off-the-shelf" than going with 3S lipo. I love the safety factor, the very fast charge times and the robustness if the A123 packs.
Posted on: 4/4/2009 11:24 PM by Author "kgfly" in the forum "T-Rex heli"
http://www.rcuniverse.com/forum/fb.asp?m=8649527

RE: 2300 3S Hypersonic Turbo Pack - Align T-Rex 450
Well 3s A123 on 3380kv/15t should be about: 3 x 2.8 x 3380 x 15 x 0.9 / 150 = ~2500rpm. That should be OK for sport flying but most would consider it unsuitable for 3D. If you want higher headspeed you would have to go to 4s and 13t which with the same motor would be closer to 3000rpm but of course then you would have the extra ~80g to deal with. Certainly A123 is not a high performance option for a 450-class heli, lipos definitely win out in this size range. In terms of power/weight lipos always win out. However in larger helis the tradeoffs start to shift and high power A123 configurations become viable, just with shorter flight times than equivalent power lipo setups.
Posted on: 9/24/2007 12:57 AM by Author "kgfly" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=6406273

RE: 2300 3S Hypersonic Turbo Pack - Align T-Rex 450
I live in Glen Iris. I cannot return the compliment, I have not yet been to Vietnam. Be great to see a comparison between your results on the two different HDX500 setups so please do try it on the SE first and then the SA. [;)] Yep, I know about the weight issues but there are numerous reports of folks happy doing sport flying with 4s A123 on TRex450. Some make a split pack, 2 cells up front and two strapped under the main shaft or one each side like saddle bags. Some drop the battery tray to near vertical and simply stand a 4s brick up the front. 3s A123 will be low headspeed (hence hairylama's need for a bigger pinion) and short flight times, but may still be the better compromise. I won't see my A123 packs for a month or two so plenty of time for more research [:)]
Posted on: 9/19/2007 1:32 AM by Author "kgfly" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=6386850

RE: 2300 3S Hypersonic Turbo Pack - Align T-Rex 450
Thanks for sharing that info. I have 3 DeWalt packs on the way and have been wondering about running 3s or 4s on my T450 (430L-3550kv, 12t). I will be *very* interested to see the results of your testing 6s on the HDX500, I have my eye on that heli ;) I plan to try 6s in my Logo10 where I am currently running 5s emoli.
Posted on: 9/17/2007 11:38 PM by Author "kgfly" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=6381870

RE: What do you guys think about the Scorpion Motors
[quote]ORIGINAL: captinjohn Hey thanks Guys for the fast reply!! I plan on flying the Cap on low throttle to conserve the battery pack. I hope to get 12 + min flights. I cannot wait to try it. Capt,n[:D][:D] [/quote] I'll be interested to hear how that turns out for you. Running brushless motors at low throttle is very inefficient and will tend to cause the ESC and motor to run hot. You might find this FAQ from www.castlecreations.com interesting: [quote][b]2. Can I control how much current passes through my speed controller by limiting full throttle travel on my transmitter with endpoint adjustments/trim? In other words can I use a 25 amp speed controller with a motor that will pull 45 amps but lower my top throttle endpoint on my transmitter so my watt meter only shows 25 amps at full throttle? Will this be OK?[/b] NO!!! A speed controller controls power to the motor by turning full throttle current on and off really fast, 11 to 13 thousand times per second (Pulse Width Modulation or PWM). The percentage of each on/off pulse that is off compared to the part that is on determines how much power the motor sees. I.E. With a pulse that is 50% off and 50% on the motor will see 50% power*. Because each on pulse is 100% of full throttle current, a system set to pull 20 amps at full throttle through a Phoenix 10 will not last if you are throttled back to the point where you only see 10 amps on a wattmeter. The ESC in this case is still switching 20 amps, which it can’t do for long. Actually it is worse than the simple example above. Because an electric motor will always to try to pull as much power as is available to get to its rpm (volts times Kv), when you are running the motor below its Kv speed by switching power on an off, each on pulse will actually be way over the full throttle amp draw. That is why ESCs work harder at partial throttle than full throttle and why we underrate our ESCs. We underrate not so they can handle more current than their rating at full throttle, but so they can handle extended partial throttle operation with no problems. [i]* Actually, electric power is not linear as in this example, but you get the idea.[/i][/quote]
Posted on: 8/23/2007 9:09 AM by Author "kgfly" in the forum "Brushed/Brushless motors, speed controls, gear drives"
http://www.rcuniverse.com/forum/fb.asp?m=6276167

RE: DX-7 crash
IIRC the promises were: For the technology: 1) Forget about waiting for a frequency slot (Tick) 2) Immune to shoot-down from other R/C users (Tick) 3) Immune to model-generated noise (Tick) 4) Most robust RF link (open to interpretation but demonstrably a very robust link indeed) 5) Conveniently short antennae on the Tx and Rx (Tick) For the DX7: 5) Exceptional performance (Tick) 6) Long Tx runtime (Tick) As far as I can tell the product has lived up to all these promises. While it has proven to be more susceptable to under-spec. power supply, this can hardly be characterised as a failure to meet the claims of the manufacturer. If you ensure that the power supply meets the manufacturer's specifications then the product works very well indeed. As you point out, all products suffer a certain number of initial problems (eg AR6100 firmware bug) and inherent failure rate, but I don't see any failures to meet the original claims nor an unusual or excessive failure rate.
Posted on: 7/4/2007 8:20 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=6069203

RE: DX-7 crash
Failsafe would not have saved the plane but for safety it should be programmed to cut the motor. A side effect is that you can always tell when a LOS-failsafe or reboot event occurs because the motor cuts out. So it sounds like this sad event adds to the list of crashes tracked down to a power-supply failure, in this case it seems the Rx pack was undersized for the application. FM Rx are more tolerant of low voltage since they don't have the same reboot behaviour and hence can mask a weak Rx power supply which causes trouble after an upgrade to a Spektrum setup. You could consider running a 2s A123 setup. 6.6V nominal, 150g, 2300mAh, 4.6V@50A so very little risk of a brownout and about $12-$18/cell.
Posted on: 7/3/2007 2:54 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=6064731

RE: DX-7 crash
4.8volts - do you mean a 4 cell NiCd/NiMH Rx pack ? How many 8611 servos ? Did you setup the failsafe and if so, with what settings for throttle and control surfaces ? From your description the motor did not cut-out when you experienced loss of control, is that right ?
Posted on: 7/3/2007 2:00 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=6064617

RE: DX-7 crash
hics3968 - Ouch, sorry about the crash. What was your power supply setup to the Rx ? What servos and how many ?
Posted on: 7/3/2007 1:13 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=6064533

RE: DX-7 crash
[quote]ORIGINAL: tsyssa I have a DX7 also....never had a problem with it...until now. I love the system and think it is great. Never one glitch or operational problem. It's not a big problem, but more of an annoyance that will have to be fixed. I have read about the insulation coming off the main rx antenna, but the whole wire just came off on mine..and fell into the plane. It was carefully wrapped in foam and mounted nicely...nothing is contacting, or is even close to either antenna. The Funtana 100x must have been flying for at least some time with only one antenna attached. It may have even happened on the first flight/!??!>!>! I had no problems during flight and did not know until I was putting the plane away. My question is...is each antenna on the main rx a separate antenna...or are they part of the same single (antenna) unit? It seems to me that each one is an antenna by itself for a back up. or....I believe the dx7 transmits on two frequencies at the same time...so are there two rx's in the main rx and two in the secondary rx? Thus...the four separate antennas? Curious...but Horizon will still get my AR7000 soon... [/quote] The AR7000 main Rx contains one receiver with a dipole antenna (the two wires you see are two parts of the one antenna). Same for the satellite Rx. Both Rx receive on both channels so the system normally receives four copies of every frame. Odds are you have been flying primarily on the satellite Rx since you lost your antenna on the main Rx. Redundancy is a good thing ! For comparison: AR6000 - Two Rx, one monopole antenna each, one channel/rx = 2 copies per frame, AR6100 - One Rx, one dipole antenna, two channels/rx = 2 copies per frame but less physical redundancy AR6200/AR7000 - Two Rx, one dipole antenna each, two channels/rx = 4 copies per frame with physical redundancy AR9000 - Up to four Rx (2 in main, 1 in each satellite), two channels/rx = either 6 (one satellite) or 8 (two satellites) copies per frame with double physical redundancy
Posted on: 6/16/2007 12:03 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5993679

RE: DX-7 crash
[quote]The secret is to keep buying new ones without your wife finding out. This is in fact the real ultimate challenge with RC.[/quote] [:D] Right On! Wouldn't you know it, I bought my 8th heli in just over a year this afternoon. She doesn't know yet [8|] Of course it's "Spektrum Inside" [8D] = BCX2
Posted on: 6/15/2007 9:49 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5990468

RE: DX-7 crash
[quote]if they did nothing to the DX7 why does it no longer recognize the AR6000's [/quote] Probably because they bound that model to a DSM2 Rx to check it was working.
Posted on: 6/14/2007 7:47 PM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5988613

RE: Spread Spektrum and F-100 ( heads up )
No worries Doug :) Sad that thse two impressive machines were lost. Seems two lessons were learned. (1) Ensure your power supply is up to the job and (2) reduce your total risk level by moving to 2.4 and eliminating the risk of a shootdown.
Posted on: 6/4/2007 3:32 AM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5941893

RE: Spread Spektrum and F-100 ( heads up )
[quote]ORIGINAL: dougl fly the thing that started this thread was someone turned on an other radio on 72 mhz on same freq he was on...nothing o do with 2.4.. [/quote] Well perhaps I missed something Doug ? In Post #80 on this thread Mark Taylor (owner and pilot of the F100 as I understand it) said (highlighting is mine):[quote]ORIGINAL: Mark Taylor I would like to set the record straight on the crash of my F-100 at TG this weekend, as it seems many are drawing conclusions based on limited information and speculation. First and foremost, [color=#3333FF]I am 100% confident in the Spektrum RF link, and my next jet will also have a Spektrum system in it.[/color] I have been waiting my entire modeling life for a radio system to come along that offers the safety from someone turning on my frequency and shooting me down. Let me, also, state that I am 100% confident that pilot error was not the cause of the crash. Through the [color=#3333FF]use of the Spektrum flight log data, we know that the RF link was completely solid in all 10 flights prior to the crash, not to mention extensive range testing to verify solid operation in the Flite-metal environment.[/color] The flight log provides performance data on each of the 4 receivers in the airplane, as well as total frame losses and whether a failsafe occurred. The worst data we ever witnessed (during the initial flight) was 25 frame losses for an entire flight. We were able to use the data to optimize one of the receiver's location and were regularly seeing between 0 and 6 frame losses in an entire ten minute flight. To put this into perspective, they tell me it takes 44 consecutive frame losses to get a failsafe--slightly less than 1 second. [color=#339933]The fact that another F-100 went in on 72Mhz earlier[/color]--reportedly due to a single regulator that was not delivering good voltage under load, had us looking at other elements within the system. Through further discussion with the guys at Spektrum, I was alerted to the fact that the AR9000 receiver stops working much below a 3.5 volt threshold, a so called "brownout", and will go through a re-start once the voltage climbs back up. The bootup would have put the engine at idle (the smartsafe position)--a lockout would have killed the engine. We quickly started to realize that we, too, may have been getting away with a very marginal power system with the 72meg Rx when we started adding up all the servos (19 of them) going through a single 7.5 amp regulator. Considering that we were about half way through the flight and that we had just completed a dirty pass and were in the process of cleaning up the airplane, starting to G-load for the base turn, we were certainly at a point in the flight where the regulator was likely at peak temperatures and most likely to start giving up. Add the fact that this was the hottest day and hardest we flew the system to date, [color=#3333FF]I would conclude that the single, undersized voltage regulator is the root cause of the crash[/color]. I consider this matter closed. [/quote] That seems pretty definitive to me. Is there some confusion between two events being referenced here ? If indeed somone was shot down on 72MHz that rather poignantly illustrates why 2.4 is inherently safer than FM.
Posted on: 6/4/2007 3:01 AM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5941852

RE: DX-7 crash
[quote]ORIGINAL: caltrop Wow, can you imagine a 90 size helicopter with carbon fiber V-Blades sailing uncontrolled into the spectators because the DX7 lost contact with it? [/quote] Wouldn't that be just as ugly as a 90 size helicopter with carbon fiber V-Blades sailing uncontrolled into the spectators because the FM-radio lost contact with it? Nobody should expect a 0% failure rate with any system. Spektrum and the other 2.4GHz spread spectrum solutions offer safety advantages over legacy FM systems, like protection from causing or experiencing shootdowns, higher RF sensitivity and noise rejection and operational advantages like easing of frequency controls. If those benefits don't seem worthwhile then don't use the technology. The question to consider is this, if you were to take 20k FM users at random and 20k Spektrum users, which group would report more (suspected) radio-related incidents ? It hurts when someone loses a model for whatever reason (short of their own deliberate stupidity) and I can understand the sense of frustration and anger that results when this happens with a brand new technology. However each user will have to assess the risk/benefit tradeoff based on a consideration of the whole picture. It is possible there is a design or manufacturing problem with any new product and we all want to see them worked out ASAP.
Posted on: 5/30/2007 4:11 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5920016

RE: DX-7 Defect
[quote]ORIGINAL: Jumpnjoe Passion, are you still around? If so, what did you ever find out? Same thing just happened to me with my 3DHobbyShop's Extra 300 SHP. Here's my setup, which closely resembles yours: Torque 2818/900 Airboss 45A Elite ESC (with 2amp BEC, rated for upto 5 cells) ThunderPower Extreme 3cell (25C) 2200 4 HS65(HB) servos [/quote] Sorry for your loss. Most probable cause is BEC overload. You have 2A linear BEC driving 4 HS65 servos on a medium size acrobat with large control surfaces. HS65 are rated at 400ma (@4.8V) operating at no load. Easily double or triple under load. Wouldn't take much to push the ESC to thermal shutdown, particularly on a hot day. One thing we know for sure is that microprocessor-based Rx are far less tolerant of voltage dips. I have no doubt your BEC checked out OK post-crash, it had ages to cool down and was under almost no load. Time and time again reports of Spektrum control failures have been tracked down to power supply problems that were masked/tolerated by FM Rx but not by the Spektrum Rx. A brief shutdown on the FM Rx may not be noticed or might be felt as a glitch. Even a sub-second shutdown will cause the Spektrum Rx to reboot and then scan to reacquire the Tx, a process that takes seconds. Is this a downside to Spektrum Rx ? Definitely. You have to decide whether the advantage of flying Spektrum outweigh the disadvantage of having to provide a more robust Rx power supply. My bet is that your radio was fine but in a plane like that a 3A switched-mode BEC would be a good idea.
Posted on: 5/30/2007 3:54 AM by Author "kgfly" in the forum "JR Radio & Spektrum Radios"
http://www.rcuniverse.com/forum/fb.asp?m=5920000

RE: DX-7 crash
I have been flying Spektrum in my helis for about a year with no problems in hundreds of flights. I have also been monitoring a number of forums for flight reports and crash reports. The vast majority of failures have been tracked down to issues other than the RF link, with most being Rx power-supply weaknesses. The AR6100 was found to have a bug and the problem quickly fixed. Perhaps the AR7000 has a problem too, time will tell. There is little evidence of a systemic vulnerability of the new spread spectrum R/C solutions, indeed, quite the opposite, with many, many reports of models and sites previously experiencing problems with FM finding them completely gone with spread spectrum. There seem to be factual problems with some of what NikolayTT is writing. [b]Mobile phones[/b] - The mobile phone bands used around the world are 800/850/900/1800/1900 MHz. Even harmonics from most of these would be way out (although clearly the 3rd harmonic of 800MHz would be in the ballpark). While front-end overload can occur on any Rx and in the very unlikely event that a malfunctioning cellphone would or could output 1W sustained RF power, unless that phone was within meters of the R/C aircraft the chances of it swamping the Rx are extremely low. The real risk from mobile phones is very small. NikolayTT please explain specifically how a mobile phone could cause serious and long lasting interference to a moving R/C Rx which is likely to be at considerable distance ? By what mechanism could such interference occur and be sustained long enough to significanty affect control of the aircraft ? [b]Alternatives to Spread Spectrum[/b] - It is odd and incorrect to use ZigBee as an example of alternatives to spread spectrum when it is in fact explicitly a Direct Sequence Spread Spectrum (DSSS) technology! Indeed, the XPS XtremeLink R/C solution is based on the MaxStream xBee/xBeePro modules. There have been many self-professed RF experts proclaiming why the new generation of R/C systems cannot work, will fail mysteriously or are inherently flawed. As mentioned by others, no system is perfect, no RF solution 100% reliable and no electronic product immune to manufacturing defects and runtime failures. What matters is whether the new generation R/C solutions are likely to provide greater security and performance than the ones they seek to replace. I would say that the great weight of evidence so far is that they do indeed out-perform FM overall. Early adopters will be exposed to higher risks of bugs and problems in immature products (eg the AR6100 bug). However these will be flushed out quickly and even nervous Nellies should be comfortable to buy a spread spectrum R/C solution by 2008.
Posted on: 5/29/2007 8:55 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5915720

RE: Spread Spektrum and F-100 ( heads up )
[quote]As for Lipos in a JET, I am waiting for safer technology...[/quote] I think you will find it is here already. Consider taking a look at the A123/M1 LiFe cells: http://www.a123systems.com/html/products/ANR26650M1specs.pdf * Near zero fire risk from short-circuit, overload, overvoltage or puncture * Physically robust * High current capability (30A continuous, >70A burst) * Fast charge (10A/4C) * 500 to 1000 cycles if the cells are kept below 140F/60C * Relatively cheap (2S1P 2300 16c/33c = ~160g, ~$30) * 3.6V/cell nominal, 3.1V @ 10A * Short-circuit protected (cell will vent and go open-circuit) * Tolerates 100% discharge (so you won't kill your pack if you forget to turn your plane off one time) * Environmentally friendly and non-toxic (unlike NiCd/NiMH) Seems ideal for a regulated system. There are also the LiMn "Magnum" 20C packs from Apogee that are also inherently fire safe. 2s1p2300 20c = ~170g, ~$60 Times they are a changin...
Posted on: 5/15/2007 9:30 PM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5860052

RE: Spread Spektrum and F-100 ( heads up )
[quote]The Specktrum system of locking onto 2 of ?? channels does seem to build in the random chance for either one or both of channels being used by another 2.4GHz radio at the same time. I wished someone from Specktrum would address this issue in some detail so we all might understand better the chance for that type of interference to occur. Is it possible and if so will that lock up either radio? [/quote] The 2.4GHz ISM band is not specifically channelised. Equipment manufacturers decide how they will partition it for their application. For example WiFi defines about 13 overlapping wideband channels, some video senders define only 3. All spread spectrum R/C radios share certain characteristics including: * They use packet-based communications and low duty cycle transmission. This means they only transmit R/F signals for a small percentage of the time, just enough to get a packet out when needed. This has two advantages. It significantly reduces Tx power consumption (eg the DX7 consumes only about 160mA in DSM2 mode) and it also reduces the incidence of signal collision/overlap. * They use unique codes for each Tx (or Tx+model) to encode their transmissions. This means that signals from anything other than the bound Tx can only ever look like noise to an Rx and it is (virtually) impossible for another Tx to take control of your model. * "Failsafe" occurs when there is signal loss. Now since, unlike legacy FM Tx, there is no continuous carrier wave, signal loss cannot be based on the presence or absence of an R/F signal. Instead, it is determined by missing a threshold number of packets in a row. Typically this is something like 50 to 100 packets which corresponds to 1 to 2 seconds. When the Rx has been unable to successfully decode a packet for this time it determines a logical LOS condition and goes to its failsafe settings. Recovery from failsafe occurs when 1 or more packets are successfully received. * Loss of power to the Rx will tend to have more serious consequences than for an FM Rx due to the longer reboot and reacquisition times of the spread spectrum Rx. This is particularly accute for Spektrum where the Rx has to scan the band for two channels before declaring the link flightworthy. Numerous crashes blamed on "failsafe" have later been demonstrated to be brownout or other power related problems. This has been true in models where the faster recovery time of an FM Rx was masking the marginal power system setup. Note that even a freshly charged 4.8V NiCd Rx pack can be inadequate for driving multiple high power servos and will dip below the 4V safety level under load. If you are flying a spread spectrum solution you *must* ensure a rock solid power supply that will never dip below 4V under any circumstances. [b]Spektrum[/b] They define 80 x 1MHz channels and use two separated by 50MHz for each air link. At power up the Tx scans the band looking for two suitably low noise channels. If it cannot find two it simply will not start transmitting and it will not be possible to fly. Having found two it starts to transmit. With one channel reserved for binding, this is why they are limited to 39 simultaneous users at one site. On the Rx side: AR6000 = 2 Rx, 1 channel each = 2 copies of every frame AR6100 = 1 Rx, 2 channels = 2 copies of every frame AR7000 = 2 Rx, 2 channels each = 4 copies of every frame AR9000 = 3 or 4 Rx, 2 channels each = 6 or 8 copies of every frame So to enter failsafe there has to be sustained noise on both active channels sufficient to cause enough packet loss to trigger the threshold. Recovery should happen as soon as the noise level on at least one channel falls low enough that some packets can get through each second. Note that just someone else turning on another 2.4 ISM device nearby, even on the same logical channels, is not necessarily enough to swamp the signal, it takes a lot of excess noise to get there. Spektrum systems have been tested and shown to work successfully by end users immediately adjacent to WiFi nodes and bluetooth equipment. One guy even jiggered a microwave oven to operate with the door open and had his AR6000 working fine in the presence of 1.5kW of noise. However any RF system can be overwhelmed and there have been user reports of some video Tx swamping nearby Spektrum systems. It is a *potential* weakness of the Spektrum approach that it cannot avoid noise once the air link is established. [quote]Futaba SS system is advertised to never lock onto any one channel but rather scan through every channel, sending data virtually on all channels. The only problem with that system might be a delayed recapture during a fail-safe event... the only problem is what would cause a fail-safe event with the scan system? [/quote] [b]Futaba[/b] They have not published technical data AFAIK but based on some spectrum analyser traces the speculation is that they too use something like a dozen 5MHz channels. This is not confirmed. Their frequency hopping gives some potential benefits in avoiding narrow band noise, especially if it is somehow adaptive and can skip noisy channels. AFAIK they have not stated how many simultaneous users they support but we can expect it to be in the range of 20 to 100. It is not clear how their reacquisition algorithm performs, but with few channels to scan and only a single lock required, I would guess it is faster than Spektrum's. [b]XPS XtremeLink[/b] This product is based on the successful off-the-shelf XBeePro module from MaxStream and divides the band into 12 x 5MHz channels. At powerup the Tx selects a single channels and starts transmitting. This system is is unique (so far) in that it is a fully bidirectional system with the Rx being fully active Tx as well. The Rx sends an ACK back to the Tx for each packet received. Along with the ACK it sends information about the signal strength and the noise level in adjacent channels. The Tx monitors the packet loss and signal strength reported by the Rx and can initiate a switch to a lower noise channel if it sees the need. The switch takes less than 1ms. What's more, if the Tx does not receive an ACK within 862us it retransmits the packet (or sends the new frame data if that has arrived). This makes it much more likely that a packet will get through for any given frame. Again, with fewer channels to scan and only one to lock, reacquisition after a brownout should be faster than Spektrum's. ================= The bidirectional link of XPS, with its retransmissions and ability to dynamically shift to quieter channels in flight makes it seem the most robust design of the three. Whether this proves to be the case in the field and the many debates backwards and forwards about these systsem will make for a very interesting year ahead.
Posted on: 5/10/2007 8:16 PM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5821116

RE: Spread Spektrum and F-100 ( heads up )
[quote]ORIGINAL: Flying Arrow I have mentioned before, Why didn't JR affix its name on the specktrum if it is very reliable??????? I have the specktrum X7 ( didn't use it yet) and I am a user for the JR 10X both the plane and heli versions (35Mhz). Regards, [/quote] Because JR don't own Spektrum. Spektrum is owned by Horizon who are also the US distributor for Japan Radio (JR). Spektrum/Horizon were able to negotiate an OEM deal whereby they purchased the X622 and 7202 Tx platforms from JR to which they added their RF technology and a few modifications to create the DX6 and DX7 for sale under their own brand. However now, [b]JR have adopted "Spektrum Inside"[/b] as their 2.4 technology and their new 9303/2.4 and 12x/2.4 do indeed use Spektrum solutions. These are effectively the DX9 and DX12 products but now JR is integrating technology from Spektrum instead of the other way around. [8D]
Posted on: 5/9/2007 6:32 PM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5833368

RE: Spread Spektrum and F-100 ( heads up )
[quote]ORIGINAL: bevar Guys, I have heard the new Futaba 2.4 system will be able to "jam" the Spektrum system so word on the street is. Any idea if this is true? Beave [/quote] Unless you have some hard data I suspect this is the same baseless rumour that keeps coming back to life. The AMA recently tested a combination of 16 mixed systems at once including Spektrum, Futaba and XPS without a problem. Similarly there are many end user reports of parallel operation without a problem. And of course Spektrum, Nomadio and Futaba 2.4Ghz terrestrial systems have been working side-by-side on the R/C car tracks for ages now. Consider whether Futaba's engineers (or lawyers) would really bring out a product without rigorous testing against Spektrum, imagine the liability cases!
Posted on: 5/9/2007 11:46 AM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5831865

RE: Spread Spektrum and F-100 ( heads up )
BTW, in case you are unaware, both the Spektrum and XPS solutions already support multiple Rx in the one plane. Only one Rx provides servo outputs but the extra Rx provide path/polarisation diversity, significantly reducing the (already low) risk of losing the link. For Spektrum the AR7000 has two physically separate Rx and the AR9000 supports up to three. For XPS you can have up to 255 Rx in the one aircraft if you like and they can be independently powered [:D]
Posted on: 5/8/2007 6:39 PM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5828740

RE: Spread Spektrum and F-100 ( heads up )
[quote]A more appealing (ego trip for me) idea would be to make it "open source". [/quote] Here you go, a perfect venue for you to share your wisdom: [link=http://www.rcgroups.com/forums/showthread.php?t=651255]Discussion - OPEN SOURCE 2.4GHz (or perhaps 900MHz) SS SYSTEM [/link]
Posted on: 5/8/2007 6:13 PM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5828643

RE: Spread Spektrum and F-100 ( heads up )
Vlamgat, Clearly you have experience with the domain, certainly more than I do. A $100k R/C jet, that must be one heck of toy :lol: The reality is that these new generation R/C systems are already being flown in all kinds of aircraft, including jets, giant scale, foamies, helicopters and almost anything else you can mention. There are thousands of hours of safe and reliable operation. I certainly hope that nobody ever gets hurt or killed as a result of choosing this technology but so far it seems less likely than with legacy FM. After all, we are not trying to achieve milspec or even reliable operation in the presence of aggressive jamming. I have no doubt there will be failures. Some due to quality/infant mortality issues (like any other electronic product), some due to improper installation, use or operation and even some due to interference. One thing we can be fairly sure of is that there will be almost none due to shootdowns or false starts from forgetful/ignorant/careless pilots turning on their Tx when they shouldn't. I have no doubt the new technology will be a huge boon in the ParkFlyer domain where the astonishing drop in the cost of entry for R/C has brought a massive influx of new and inexperienced folk into the hobby and where frequency control is becoming virtually impossible. Should they be used in larger, more dangerous models like helis and nitro planes ? The manufacturers (and their lawyers) have enough confidence to say "yes". Time will tell whether these new systems supplant legacy FM or are short term blip in the hobby.
Posted on: 5/8/2007 6:34 AM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5826443

RE: Spread Spektrum and F-100 ( heads up )
[quote]ORIGINAL: VLAMGAT KGFly, Good post. Looking at the specs of Zigbee and the XBee pro module (which I presume they use) output is 100mW but a max legal output is 10db. A good wifi usb stick has 16dB and probably 10dB at the antenna. Maxtream THE SUPPLIER of XTREMELINK rf hardware quotes max 1 (ONE) MILE range with a good antenna under optimal conditions. Somehow they claim 5, yes FIVE miles
Posted on: 5/7/2007 7:34 PM by Author "kgfly" in the forum "RC Jets"
http://www.rcuniverse.com/forum/fb.asp?m=5824297

RE: Spektrum DSM2 2.4Ghz modules for Futaba and JR announced
[quote]ORIGINAL: rajul How much battery power is the 2.4GHz module going to consume compared to the standard 72MHz module for the Futaba 9C? [/quote] It should be considerably less. It is a 100mW RF module rather than 1W (I think) for the FM modules. Don't get worried about the range implications of that reduced RF power, the Spektrum systems have been tested by users to over 5000ft on the ground and 14000ft in the air.
Posted on: 2/25/2007 6:09 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5471093

RE: Spektrum DSM2 2.4Ghz modules for Futaba and JR announced
[quote]ORIGINAL: sillyness Ethical debate aside... 1) Can a 7000 and a 9000 be used at the same time in the same plane? 2) Is there any reason to use 2 x 9000s vice a 9000 and a 7000 if my channel mapping works out? I have a set-up for a 40% so I can do just this without using matchboxes or Y's. K.I.S.S.. Thanks [/quote] So your goal is to have multiple servos on the same channel or redundant control? Either way, you certainly can bind two Rx to the same Tx module and they don't have to be the same model Rx. The channels will all be mapped identically so if you only need parallelism on 7 channels you could use two AR7000 or one AR9000 and one AR7000.
Posted on: 2/24/2007 4:16 PM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5468373

RE: Spektrum DSM2 2.4Ghz modules for Futaba and JR announced
[quote]With the latest 14mz software update the 14mz has 12 channels on PPM, so why am I only able to use 8 of them?[/quote] Well the rumour is that Spektrum didn't have the latest 14mz software and since the earlier software only had 8ch on PPM that's what their MZ module supports. I imagine they might be able to adjust it before release to handle more channels or else perhaps more likely will release a more expensive "12M" module some time down the road when they also have a 12-or-more channel Rx. Just my speculation here.
Posted on: 2/24/2007 12:25 AM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5466117

RE: Spektrum DSM2 2.4Ghz modules for Futaba and JR announced
[quote]ORIGINAL: KenCClark [quote]ORIGINAL: kgfly d) Drop-outs (nulls), multipath issues and reflections are all part of why Spektrum spent years developing their air solution and why they use multiple antennae and multiple interconnected receivers to ensure the security of the RF link. As mentioned above, the no-shootdowns-ever aspect of this new technology makes it inherently safer than legacy
Posted on: 2/23/2007 7:46 PM by Author "kgfly" in the forum "RC Radios, Transmitters, Receivers, Servos, gyros"
http://www.rcuniverse.com/forum/fb.asp?m=5464859