Futaba 2.4 GHz FASST Service Advisory

... | >> I just bought a 9C. What failings can I expect? | >> mk | > A fairly sizeable latency for one:
| >
http://www.runryder.com/helicopter/gallery/8588/latency_pcm13.gif
| >
http://www.runryder.com/helicopter/gallery/8588/latency_pcm13_avg.gif
... | I didn't see my TX there, are we on the same TX? Fut 9C ?
Futaba 9C - R149DP is the 2nd to the last item on the first page, and the last item on the second page.
In any event, a few things to consider here --
-- this is CCPM, where the 9C is known to be slower. In other modes, it's faster than this. Also note that this is a helicopter mode -- for planes, things are not so bad.
-- this is PCM, where everything is known to be slower. Using a PPM RX will give considerably lower latencies. (Though to be fair, the spread spectrum gear generally has similar features to PCM receivers, without the additional cost or latency.)
-- I doubt anybody who reads this group has a 120 ms reaction time (approximately the maximum measured latency of the 9C + PCM RX) and most of us probably couldn't tell the difference between the worst case 9C at 85 ms and best case 12Z + R5114DPS at 20 ms.
Yes, it's a shortcoming of the 9C. But it's a pretty minor one. And this chart is basically set up to give it's worst case scenario.
My 9C has a problem with V-tails and 4 servo wings. This problem was fixed, but I have one of the first ones made, so it still has the problem. Newer ones should have this fixed.
Either way, I wouldn't buy a 9C new now. But not because it's a bad TX -- it's not -- but there are better ones out there now. And any new gear I buy would be spread spectrum. My next TX will probably be a JR X9303, unless something better comes out.
--
Doug McLaren, snipped-for-privacy@frenzied.us
Talking with you is sort of the conversational equivalent of an out of
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Doug McLaren Wrote:

Doug, I agree that a 120 mS reaction time to a sudden one-time externa stimulus is exceptional - but you're overlooking a major factor. Ther are many situations where we input periodic (rhythmically repetitive control inputs for RC models, a classic example being a rolling harrier In these cases, it may take a lot longer than 120 mS to implement th first finger movement, but the subsequent rhythmic movements can easil be timed to considerably greater accuracy than 120 mS by anyone - n need for special super-fast reflexes.
There are also many situations when we anticipate an upcoming contro input in advance, and therefore can time it to much higher precisio than 120 mS. For instance, if you put your model into a snap-roll o spin, you anticipate the point at which you need to input correctiv control inputs to stop the roll or spin at the desired heading.
Several years ago I worked as an engineer on a team designing a hig quality loudspeaker system with internal DSP processing. We wanted t find out if such a speaker could be used as a live monitor by musician while they played their music. In order to find out if the latency/dela from the processing in the speaker would be an issue in this situation I took one of my electric guitars in to work one day and did some quic experiments playing scales and groups of sixteenth notes through a pur delay line (with adjustable delay) to see how much delay mattered.
What I found surprised me. A mere 20 mS of delay was quite detectable and had a deteriorating effect on my ability to play. 15 mS was abou the threshold where I couldn't quite be sure if I could detect the dela or not. Below 10 mS, I couldn't feel the effect of the added delay Anything over 30 mS was really nasty - it became increasingly impossibl for me to play the guitar at all as the delay was turned up beyond thi point.
Keep in mind I'm no Van Halen. My guitar playing is amateurish and m top speed is not particularly fast as guitarists go. And even so, 20 m was unacceptably large for me. Surely 15 mS would have been too much fo someone with better guitar technique than myself.
So is 120 mS delay in an RC transmitter an issue? Perhaps not whe we're using slow servos with 200 mS delay of their own, and almos certainly not if the transmitter is being used to fly a sedate mode with inherently slow responses. But the guys who fly twitchy 3 helicopters with lightning-fast 70mS tail rotor servos say they can fee the difference. And I can see no reason not to believe them.
I CAN say for sure that I can feel the difference in latency between model flown with 5 V DC power to the servos and the same model flow immediately afterwards with 6 V DC to the servos, because I tried thi on a .40 size electric model with a switching BEC that let me try bot voltages by simply moving a jumper. If you look at typical servo specs they often pick up about 40 to 50 mS of additional delay at 5 V compare to 6 V. And I could easily feel this difference when, for instance flying snap-rolls or spins: at 6V the model would stop snappin noticeably sooner after I neutralized the controls. If in doubt, highly encourage you to try it yourself - I was using a $8 switching BE from United Hobbies, so there is not much cost outlay in trying th experiment.
-Flieslikeabeagl
-- flieslikeabeag ----------------------------------------------------------------------- flieslikeabeagl's Profile: http://www.rcgroups.com/forums/member.php?u303 View this thread: http://www.rcgroups.com/forums/showthread.php?t 331
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flieslikeabeagl wrote:

Interesting stiff. Thanx beagle. echo style delays are MOST disconcerting if you play to what you hear..rather than just finger the notes.
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The Natural Philosopher Wrote:

I play by ear, which might have something to do with it. But don't al musicians, even when reading from a score, listen to what they'r playing so they can create the tone and emotional context they're tryin for?
One of the weird things I discovered from that experiment was tha there was a delay setting where the guitar strings felt like they wer covered in grease. I don't mean sounded like they were covered in greas - they actually felt sort of sticky/slippery to the fingers of my lef hand. I think my brain was struggling to understand the delay betwee touching the string and hearing the note, and chose to interpret it i this way. Weird, a bit like one of those optical illusions we've al seen, only this one was an auditory illusion with a crossover to a th tactile sense!
I don't remember exactly what delay setting caused the "greasy" feelin (it's been few years), but I think it was around 30 mS or so.
-Flieslikeabeagl
-- flieslikeabeag ----------------------------------------------------------------------- flieslikeabeagl's Profile: http://www.rcgroups.com/forums/member.php?u303 View this thread: http://www.rcgroups.com/forums/showthread.php?t 331
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On Thu, 24 Jan 2008 09:28:07 -0600, flieslikeabeagl

That's gotta be tough.
Most of the people I know either use their fingers or a pick ;-)
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Bob Cowell wrote:

Coffee/keyboard alert! Bastard ;-)
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Too late! ;-0

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MJKolodziej wrote:

Well, there are quite a few. Someone else has mentioned high latency (near the worst of all txs available when used in PCM mode), a few of my pet peeves are as follows :
1. Broken throttle-controlled airbrake design means trims are dangerous in acro mode. (This was fixed in glider mode from the 9C to 9C Super so why they couldn't have fixed it in acro mode too beggars belief). This means that an intermediate plane like the H9 Ultrastick cannot be completely programmed on a 9C as it can on the JR equivalent. And before you point me at the howto on the Futaba website, it doesn't work. And when I say the howto doesn't work I mean hopelessly, uselessly, laughably doesn't work, and stands no chance being made to work whatever you do.
2. Side-control sliders can't be set up to allow eg flaps to be controlled with neutral flap at slider full up and full flap at slider full down. Best that can be done is to have no flap movement from slider middle to slider up and full flap at slider down. This is a problem with the sliders and no amount of mixing will cure it.
3. The only servo that can be slowed is (bizarrely) the throttle servo. The manual alleges this to be so an IC engined plane can be made to perform like a turbine with a slow engine spool up. It's just plain weird IMHO, much more useful would be a servo slow that can be used on other things like retracts.
4. Futaba's advertising states the 9C to be a 9 channel TX. It's not really : even if you do splash for a Futaba PCM dual conversion RX it is not possible to set the ATV for the 9th channel. And the key downside of a dual conversion RX is if you stack the plane you can't just discard the crashed XTAL, you have to send the RX away to get the internal XTAL replaced by a service engineer.
5. The rotary dial turns the wrong way cf the way the display selection changes. Or maybe that's just me :-) I did ask Ripmax but they said there's no way to alter it.
6. There are others...
Having said that and got it off my chest, my 9C Super has been reliable in the 18 months I've had it and it's not a bad TX for all that. I just get more and more tee'd off with the programming style that seems to be designed to permit exactly those facilities that Futaba deem suitable for a mid range TX and to prevent anything more adventurous from being tried. Oh for a mainstream TX with the kind of flexible programming model shown by the Profi 4000, now demised.
Hth,
--
Boo





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