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Old Feb 02, 2010, 03:58 AM
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Originally Posted by oakman7004 View Post
Well, I was under impression that FASST uses 72 channels...giving 5 times redundancy. ie. even better!

Is this correct? http://www.flyelectric.ukgateway.net/24scanner.htm

/Jonas Ekman
I've run across that one before, it's a nice read.

as to Spektrum, the resistance of DSSS to interference is related to the chip rate of the pseudonoise modulation(how "wide" the signal is spread out via encoding), and the processing power on the receiver side to perform the de-spreading process can limit this.

Futaba is performing a DSSS transmission process, and that transmission is actually over a wider part of the band than the Spektrum transmission, so Futaba must therefore be implementing a higher bandwidth pseudonoise scheme, and employing more processing power on the de-spreading side. so Futaba is performing DSSS in a more robust fashion than Spektrum is, and then taking their show on the road, so to speak, by shifting their DSSS stream around the band. Then, to really put the icing on the cake, the data is being transmitted at 5x the bandwidth the receiver is actually outputting it at, meaning there are 5 update cycles the receiver decodes for every 1 output cycle at the servo leads, so a dropped frame is very nearly insignificant.

but I'd still recommend an A9 or an SD-10G for most sport fliers, all the 2.4 protocols are VERY MUCH capable of reliably transmitting the minuscule amount of data we use to control our models, and Airtronics and Hitec are giving you more features/programming and better gimbals for your dollars.

I think Spektrum compete reasonabley in the low segment (being eclipsed rapidly though), but I don't generally recommend JR systems because their features are terrible for the price, their RF link is A-ok

-Danny

(I've got a 12FG, and will probably end up with a 10C as a 2nd unit for compatibility reasons, would probably prefer an SD-10G for a backup FWIW)
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Old Feb 02, 2010, 04:47 AM
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Originally Posted by DannyZRC View Post
(I've got a 12FG, and will probably end up with a 10C as a 2nd unit for compatibility reasons, would probably prefer an SD-10G for a backup FWIW)
Well, I have the same thoughts...but the other way around since I started with 10 CG.

BUT, it would be nice to have the SD card memory on the 10CG...Now I have to use CAMpac. And just copy/past model memories between the radios isn't easy I guess. Maby this works ok between 12 and 8 FG sice they "have" same setup in programming and utilizing SD card.

I will probably in the end of the day have 2 10CG just for the simplicity in transferring model memories. We'll see!

/Jonas
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Old Feb 02, 2010, 05:46 AM
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Originally Posted by oakman7004 View Post
Well, I was under impression that FASST uses 72 channels...giving 5 times redundancy. ie. even better!

Is this correct? http://www.flyelectric.ukgateway.net/24scanner.htm

/Jonas Ekman

I go by the Futaba and FCC docs:
https://fjallfoss.fcc.gov/prod/oet/f...ive_or_pdf=pdf

Also when I turn on my spectrum analyzer you can see how the signal is spread across the band.

For what I've seen; Futaba FASST is a Hybrid system. If you look at the FCC documents shows FASST uses a DSSS modulation (core).
Futaba makes there own IC chips, so they decided to add “channel shifting” using 36 channels instead of holding to two channels like DSM2.
But the core modulation for FASST and DSM2 is DSSS; both systems will check the band at boot and spread the data across the band (DSSS)

Doug.
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Old Feb 02, 2010, 06:29 AM
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Aha! So, I should interpret this to 36 channel used and one unused channel inbetween each used channel. Hence the tested channels 2, 38 and 72 which gives used bandwidth of 72 channels. Correct?

/Jonas
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Old Feb 02, 2010, 07:22 AM
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That's how I see it.

DSM2 and FASST, to me... For what we do, both designs are good.

Doug.
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Old Feb 02, 2010, 08:48 AM
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Originally Posted by DougV View Post
That's how I see it.

DSM2 and FASST, to me... For what we do, both designs are good.

Doug.
Not really, I had problems with DSM2 and never any with FASST. The main problem with Spektrum is that it locks onto only 2 channels and does not continually scan the band. I have never understood how you could call a 2-channel system Spread Spectrum but that’s a topic for another thread.

Since Switching from Spektrum to FASST (I have a 7C-2.4 and 8FGH) I have never had anymore radio related crashes.


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Old Feb 02, 2010, 09:34 AM
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Originally Posted by RC Man View Post
Not really, I had problems with DSM2 and never any with FASST. The main problem with Spektrum is that it locks onto only 2 channels and does not continually scan the band. I have never understood how you could call a 2-channel system Spread Spectrum but that’s a topic for another thread.

Since Switching from Spektrum to FASST (I have a 7C-2.4 and 8FGH) I have never had anymore radio related crashes.


Hi RC Man,

Ok, that's interesting. I use both systems and prefer FASST, but I’ve never heard about issues with the DSM2 link, I know about the lock-out/brown-outs with the batteries and or receivers, but never with the RF link.

Can you please elaborate on how you determined that it was LINK related? It will be good info.

Regards,
Doug.
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Old Feb 02, 2010, 11:38 AM
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Originally Posted by DougV View Post
Hi RC Man,

Ok, that's interesting. I use both systems and prefer FASST, but I’ve never heard about issues with the DSM2 link, I know about the lock-out/brown-outs with the batteries and or receivers, but never with the RF link.

Can you please elaborate on how you determined that it was LINK related? It will be good info.

Regards,
Doug.
For me it has been issues with AR6100's, I've had a couple times now when I've been locked out of controls without a brownout indication (relink blinking light, these are v1.6 AR6100's). Most of the time that it has happened to me, it was preceeded by a increasing amount of lag to the controls.
One specific time, was a few indoor club meets ago, while flying with some R/C car racing guys (carpet track, inside an old naval base hangar), I was flying along, then the heli started getting jerky (give a control input, give some more, then suddenly it would catch up).

I brought it in for a landing and as it was coming in along the flightline hit throttle hold. It didn't shut off the motor instantly (took about a second), then came sliding in without any control (I was holding full forward on the stick to try to stop it).

It luckily touched the skids first and slid to a stop, I was still holding the cyclic forward waiting for when it would catch up, I said to the guys standing near me that it had locked out, they walked closer to where the model was and watched with me as suddenly the swash went from level to full forward finally following my controls again (this was about 5sec or so after it had landed, and the AR6100 light was still solid, not blinking)
The only way that I can explain this issue, is that the RF traffic by other radios (digital, on the channels my AR6100 was using) were bouncing around the hangar and the RX wasn't able to buffer all the data properly and was probably seeing clipped packets on both the channels and fell behind. There were about 15 guys on the drivers stand, and as I mentioned before, this is an enclosed metal building so RF will reflect everywhere.

I never once said that simultaneous channel utilization will always cause problems like it did on 72mhz (as Onewasp suggested I was saying), if there is another spektrum on even one my RX's channels that it's listening to, it still has to read the packets for the header information before rejecting it based upon not matching the TX coding. And as you add more to the mix it has to handle significantly more (which I believe is the failing of the AR6100 specifically, I don't think the processor is up to the task when a certain level of saturation and packet clipping is reached).

I unfortunately have mostly AR6100's because of when I converted to Spektrum (had a lot of models to swap, so I bought a whole bunch of them). So that's much of my decision to segmented swap to FASST starting now with my helis (I also fly planes and even a Y-ufo).

-Kai
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Old Feb 02, 2010, 12:11 PM
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Kai,

I am really interested to hear your view in comparison with the new FASST system when you finally get it operational.

Marko
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Old Feb 02, 2010, 12:43 PM
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Kai,

I am really interested to hear your view in comparison with the new FASST system when you finally get it operational.

Marko
I'm bouncing up and down in my chair here at work right now, UPS tracking shows it's out for delivery so it should be here at any moment .

I have an indoor club meet tomorrow night in the same hangar, another meet with the car guys next wednesday, then the hobby show that weekend (IMHO, the meet with the car guys, and the hobby show will be the real areas that will test FASST reliability vs DSM2/AR6100v1.6 for me).

I should be flying my main indoor heli on FASST by tomorrow (I took tomorrow off work to program it all up and to play with it). The limit of my hopes for the report is just to report no issues , that will make me happy enough. I have no special measuring equipment, all I can do is theorize based upon empirical behavior (Occam's razor and logic are what I choose to try to apply).

I have no illusions about being able to feel the faster heli response, but if I do notice it I'll mention it . FASST HS latency is 14.1ms vs DX7/AR6100 27.5ms latency averages are honestly so quick that the difference might only be noticible by computer analysis. I did feel the difference when I went from 9CHP PPM 64.9ms latency to Spektrum, but there are only so many times that you can slice latency in half and feel the difference in wetware .

-Kai
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Old Feb 02, 2010, 01:13 PM
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WooHoo, the package arrived, it's now sitting on my desk here at work charging

I wanted to get it the day before I fly on it so that it will have time to fully wall charge overnight, after that I'll switch to charging the batt outside the TX. Now I think I'm bouncing in my chair even more, impatient to turn it on for the first time, LOL

Edit: First impression, it's no wonder so many people don't notice the difference to the bearing gimbals right away, mine was out of the box set to the strongest stick tensions (I like my sticks set a bit softer since I like to do a lot of piroetting flips).

-Kai
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Old Feb 02, 2010, 03:23 PM
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From the Futaba site, the latency with the R600HS is 7ms not 14.
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Old Feb 02, 2010, 03:31 PM
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Originally Posted by Greybird View Post
From the Futaba site, the latency with the R600HS is 7ms not 14.
7ms is the framerate in HS mode, not latency.... (too many numbers flying around, hehe)

That's why I put the link to runryder with JKos's latency testing in eCCPM modes (ie. this is specific to heli mixing), framerate means that every 7ms updates are sent to the servos by the RX, latency means that when stick inputs are given, there is approximately a delay of 14.1ms to the outputs on the servo channels (truthfully from JKos's testing environment, min and max of 11ms to 17.7ms).

Edit: Another way to put it, is that for every input at the sticks, the analog pot position from the sticks are converted to digital, mixed together in the TX processor, encoded into digital packets, then transmitted (and the cycle starts over again), the RX is receiving, decoding, filtering, then sending signals to the servos. All that processing adds latency, by the time the servos get their PWM to move, the TX has already sent the next position updates (so the servos are technically around 2 cycles behind what's happening at the sticks in 7ms framerate mode, but even 14.1ms is still plenty fast considering human reactions are involved).

Of course, I'm pretty sure those tests are rather ideal circumstances, but fairly composed for comparison purposes.

-Kai
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Old Feb 02, 2010, 04:54 PM
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Thanks for contributing to my state of confusion. Unscientifically, when I went to a 10CHG with an R600HS and BLS451's, from a 7CHP/PCM with 3151's, I became very happy....
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Old Feb 02, 2010, 04:59 PM
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Originally Posted by Kai_Shiden View Post
7ms is the framerate in HS mode, not latency.... (too many numbers flying around, hehe)

That's why I put the link to runryder with JKos's latency testing in eCCPM modes (ie. this is specific to heli mixing), framerate means that every 7ms updates are sent to the servos by the RX, latency means that when stick inputs are given, there is approximately a delay of 14.1ms to the outputs on the servo channels (truthfully from JKos's testing environment, min and max of 11ms to 17.7ms).

Edit: Another way to put it, is that for every input at the sticks, the analog pot position from the sticks are converted to digital, mixed together in the TX processor, encoded into digital packets, then transmitted (and the cycle starts over again), the RX is receiving, decoding, filtering, then sending signals to the servos. All that processing adds latency, by the time the servos get their PWM to move, the TX has already sent the next position updates (so the servos are technically around 2 cycles behind what's happening at the sticks in 7ms framerate mode, but even 14.1ms is still plenty fast considering human reactions are involved).

Of course, I'm pretty sure those tests are rather ideal circumstances, but fairly composed for comparison purposes.

-Kai
Would you be posting videos of you flying with the futaba 8fg?
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