9Z compatibility - RC Groups
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Oct 15, 2007, 01:16 AM

9Z compatibility

After spending quite some time with our 9Z transmitter, we finally were able to record the transmitter outputting invalid PPM data. It requires that the sticks are wiggled just right and released. Then we see periodic "blips" of data with the XDP as Chris has shown in his video. A capture with a logic analyzer clearly shows that this is a problem with the 9Z's PPM output stream. The same results were recorded with the stock 9Z RF module in PPM mode. What I observed is a long or short pulse, followed by a good pulse, followed by another long or short pulse, followed by thousands of valid pulses. The sequence is random, but the invalid output is almost (but not 100% always) two bad pulses with a good one between. Why this occurs? I do not know. I do know that simply holding the sticks from center results in no invalid data ever. We had one customer report problems only when the elevator stick was at its extreme up position (full down elevator).

I can add a glitch eliminator easy enough into the PPM stream capture. Basically, any pulse that changes more than 600us between frames would have to wait for the next frame to verify the change was valid. This should not affect stick movements as I don't think it is possible to move the stick far enough within 22.5ms, but it would hold off switch throws one full frame. I will add this filter to the "Modulation" option in the transmitter module's programming because it is apparent that no other transmitter needs this. The only real issue this has caused with our 9Z is an occassional blip for a few frames, not enough to make a servo even twitch, but it is definitely there and easily shown with the XDP.

Since Chris (Testpilot) is a beta tester, has an XDP and all in-field upgradable devices, he can also test this with his 9Z and verify this fix.
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Oct 15, 2007, 09:02 AM
You can call me FANBOY!
Just let me know what you need me to do and I will set it up and start testing tonight.
Oct 17, 2007, 05:36 PM
Registered User
Drew, do you have any idea when the testing for the 9Z modules will be finished? Because I placed an order with your company for my 9Z (order 2974) 2 weeks ago, and now I'm starting to think of changing my mind about going XPS (cancelling my order) and going Futaba... But I like your products, A friend of mine does beta testing for you and he is very happy with his set up... So I can wait a bit more but I'd like to know how it's going on your side...

Thank you for reading me,

Oct 17, 2007, 05:56 PM
All orders are current as of this morning, so your unit was already shipped. Not all 9Z radios have this problem. We have received a lot of emails from people using 9Zs a little concerned that people have reported a problem when they have experienced none. We are still doing some testing and will likely be through the weekend with a conclusion on Monday.
Oct 17, 2007, 06:03 PM
Registered User
Thank you Drew! I'll wait patiently and I will let you know how it goes with my radio when I receive my combo.

Thank' s again!

Oct 19, 2007, 07:39 AM
Registered User
ricoalonso's Avatar
In another thread which I follow, someone reported:

"My 9Z had the XPS pulse problem. It does NOT have the problem with the TM-7 FASST module. Both systems worked fine (when XPS didn't pulse)..."

And also, I understand that 'Dustflyer' who had the same problem with 9Z while using XPS is now using Spektrum module and had not encountered the same problem he had with the XPS module.

Just a thought (and this is only a suggestion)... why not try to invest on the competition's module and have the 9Z PPM pulse traced (while the competitor's module is used) to compare with that when the XPS module is installed... and as Julez suggested in another thread, use a scope at all times.
Oct 19, 2007, 11:58 AM
Using a stock 72MHz RF module, you can clearly see the PPM output "skip" periodically. It doesn't matter what module is plugged in. There are no problems with PCM mode, but even in FM mode, the Futaba receiver will also do the same thing. The issue with the 9Z affects many other receivers (probably for the same reason). We can filter this out, but it significantly reduces the response to, perhaps almost to the level of our competition's system.
Oct 19, 2007, 03:10 PM
Registered User
ricoalonso's Avatar
I see. Thanks for further clarifications and informations.
Nov 17, 2007, 01:44 AM
Registered User
Hi Jim,

I plan to order your system for my 9ZWC2, but I am a bit concerned about this issue. Do you have any update here?

Another question: I see that you offer a 10ch Rx combo for Futaba (9Z&surface+Hitec). I understand that the 9ZWC2 cannot output more than 8ch in PPM mode, am I missing something?


Last edited by chipichape; Nov 17, 2007 at 04:28 AM.
Nov 19, 2007, 11:54 AM
We had a nice chat over the weekend with one of the top USRA racers. These guys fly the 200+mph huge pylon race planes. A few weeks ago in Parker, AZ there was one of the national races. Two pilots used our system. One pilot was the points leader until Sunday when he had a bit of problem with tuning due to a climate change and ended up 3rd place overall. A bit bummed, but he was able to make extremely fast passes and was clocked at 264mph.

He reads these forums, and uses a 9Z with ZERO problems on these planes. I think these are absolutely worst case scenarios, where ANY amount of twitching would result in a high speed crash. He believes that the only problems that exist are with the pots in these radios as they are carbon plates and they just get dirty over time.
Nov 19, 2007, 11:56 AM
You could use a 10 or 12 channel receiver with an 8 channel radio, and use the additional channels for duplicate channel outputs.
Nov 19, 2007, 12:04 PM
You can call me FANBOY!
I am using a 10ch in a GP Super Stearman with smoke. Will be using 7 chs with smoke and ignition kill and will use channel mapping for the top ailerons. So will be utilizing 9 channels total, I have a 9Z also.
Nov 20, 2007, 06:28 PM
Registered User
Hi Jim!

I finally took my Hirobo Evo 50 to the club All rigged-up with the XPS system for my 9Z and I have to say it flew great, the heli feels crispier, more precise. So I am very happy with that.
But at one moment the swash plate twitched, nothing dramatic, I was about 15 feet in the air, the heli just wiggled to the left and went back level in a second.
So now I'm a bit concerned, how is it going with your testings, will you update the software of the modules so that those signal output errors get filtered out like you were saying a few replies ago?

I love the performance of the system but I also feel scared of flying my helis again... Please let us know what happening.

Here's a couple of pics of my 2 set ups.

Thank you,

Nov 20, 2007, 07:26 PM
Make sure that what you experienced was not a low power situation where the receiver rebooted. Some servos will glitch when a reboot occurs.

I am not sure what needs to be done about the 9Z. We have had a couple of guys email us saying that their Spektrum module did the same thing as our module, so it helps to confirm that what we are seeing is not isolated. It makes me wonder if this is a problem that only affects PPM, or are people losing a lot of data in PCM mode...
Nov 21, 2007, 02:55 PM

Another 9Z problem

Received yet another letter from someone trying to use their 9Z with a module system. We are definitely not alone in this matter...

Hi Jim

My name is Thomas and i'm from Germany a few weeks ago i tried to order the XPS system for my Futaba 9zWCII but your sales guys refused to send it to germany because of global distibutor graupner who is not delivering at all.
Finally i got a Spektrum DM8 and AR7000 for my 9z and last weekend i discoverd exactly the same problems with the ppm stream and servo jumping for a few miliseconds.
Any news on this what has to be done on the radio to fix this issue ? Any update on your modul to fix it ?
any chance to get the xps to germany ?

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