RE: Futaba, or just 2.4, problems at Joe Nall?
 

You got that right...I'm so out of touch I still use cash to pay for a cup of coffee or a pack of gum :):D

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Here is a little food for thought.
How was the 4G cell phone reception at the event?
Johnny

RE: Futaba, or just 2.4, problems at Joe Nall?
 

;)

I wonder if anyone in Alexandria is jonesing for a pork chop, LOL....

RE: Futaba, or just 2.4, problems at Joe Nall?
 

To set the record straight regarding the crash of the Robart P-47 at Joe Nall.

First of all the rumor of the module falling out of the radio is completely false. I flew the aircraft Thursday morning with no issues. On my second flight after the noontime show is when the aircraft locked out. After my second lap the radio made a long beep and then the radio went into failsafe. The engine came back to idle, leveled out and headed for vendor row. I was trying to diagnose what was going on even with no control over the aircraft. I was flying the aircraft the whole time even though the radio was in lockout hoping the radio would respond. After the crash we checked the onboard flight battery which was good, the Transmitter battery which was at 10v, and checked the receiver by plugging it in to a servo and everything was working fine. Futaba determined that possibly every time I unplugged the module and plugged it back into the transmitter it could have loosened one of the pins in the module causing the loss of signal. Futaba is currently in the process of diagnosing the radio system and have not yet heard the results.

I have been flying Futaba radios for the last 22 years with no issues what so ever. I am currently flying my own and Robart’s airplanes on Futaba 10C and 12Z 2.4 radio systems.

So my recommendation if you own a radio with a module based 2.4 systems, is do not unplug and plug into the transmitter, modify your transmitter case so the radio and module fit without removing the module. If you remove your module every time like I have done, I would send your radio back to your radio manfacturer and have them check it just to be on the safe side.

Eric Karl
Robart Mfg.

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Umm, no. Actually there is a connection. When a carrier is modulated it spreads out its frequency spectrum. Once the channel spacing on 72 MHz was set, it limits the rate at which it can be modulated, hence it restricts the update rate of PCM signals.

At 2.4 GHZ the available bandwidth is much larger, and much faster modulation is possible and the new radios take advantage of it. I suppose you could design a new 72 MHz radio with very fast modulation but it would not be compatible with the existing uses of 72 MHz for RC.

+1 for bigbaggy...

Dave

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Actually spread spectrum is used to widen the bandwidth of the signal only as a means for multiple users, security, etc. It doesnt have anything to do with "more bits".

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Also he was referring to PPM and not PCM systems. And as we know some versions of 2.4 had issues with latency. That's about all I know about it LOL

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Sorry, it can be so inconvenient to bring basic science into these conversations .. back to the techno babble... please proceed :-)

RE: Futaba, or just 2.4, problems at Joe Nall?
 

+1 :D [sm=thumbs_up.gif]

RE: Futaba, or just 2.4, problems at Joe Nall?
 

LOL. Yeah, backpeddle as necessary.

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Reminds me of the saying "Never let the facts get in the way of a good argument".....

RE: Futaba, or just 2.4, problems at Joe Nall?
 

if you think that was backpedaling, then I believe you've made my point, so thanks!

and HD, you know enough about this to understand that the question was about rate of modulation broadening the bandwidth of a signal, it was not about SS techniques specifically ... it was referring to the ratio of modulation rate to carrier freq.

oh, and while we are at it (since I put the spoon in to stir the pot here), I wonder if the JR gang have a "rewards points" program for their loyalists bumping threads with titles that reflect badly on their competitors. I wonder how many points you need to get some extra satellite receivers? and, it is very thoughtful of them to state right up front that their new DSMX was introduced to fix all the problems they were having at large flyins.

:-)

RE: Futaba, or just 2.4, problems at Joe Nall?
 

I am not part of a JR gang. I just state facts. If you didnt know, I was the one who discovered the problem with JR/Spektrum radios sometimes picking adjacent channels. So yeah, I guess that makes me biased. Duh.

I just call it like I see it. No agenda here. But time and time again the same old Futaba goons usually come in and muddy the waters with nebulous statements and misinformation. Bravo to you.

Anyway, if you dont like answers to these questions then dont ask them or better yet dont spread misinformation. You can argue with me but you cant argue with physics. Well, you can but you will always lose. :) I guess this is all just "techno babble" for those who just dont understand advanced comm theory. That doesnt make it any less true.

BTW, rate of modulation can be increased without bandwidth spread. It's called M-PSK. Or even QAM. How about Trellis modulation? Look it up, read more, understand. ;)

RE: Futaba, or just 2.4, problems at Joe Nall?
 

I'll be totally blunt here: I switched to Futaba back in September due to this very reason. I was moving into turbines then, I simply did not feel comfortable with this reality.

Now, to be even more frank, I am also very uncomfortable with the Futaba antenna setup, but felt that having FASST technology was an acceptable tradeoff. However, I still do not have complete peace-of-mind with it. Having various remote antenna locations with various planes of orientation seems logically to be a better 'receptive' arrangement. But, again based on the above quote, it is moot if a bad channel selection is made by the radio.

With DSMX, IMHO, it's a whole new ballgame. Had DSMX been a little sooner in coming to market, I would have stayed with JR, dumped DSM2, and gone with DSMX. FHSS technology (DSMX) coupled with a diverse receiver antenna array sure looks like the best way to go (I know, I know, look at Weatronics), understanding that nothing man-made will ever be 100% reliable.

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Ok, HD, I was trolling on the JR thing ... You got me!

Now, since we all know that you have some actual technical knowledge, can you please explain to everyone if my original comment that the 72 MHz RC frame rates are limited by the channel spacing is correct or not? You will note that was the idea that started this conversation. See if you can manage without using any fancy technical jargon ... I am sure you can! Just simple physics or communication theory as you prefer.

Oh, and I didn't think I was arguing with you ... Actually I believe I acknowledged your insight. I suppose that it is good not to be arguing since such an argument looks like it would not have many facts in it, just boastful statements and invocations of fields of study as you just did.

Have a nice weekend!

Dave

RE: Futaba, or just 2.4, problems at Joe Nall?
 

sluggo, I concur with your thoughts exactly! I am still on JR but have a Futaba radio for my RC cars. Do I think Spektrum is trying to play the marketing angle with their new DSMX? Surely. If I had the cash to convert all my stuff I would go to Weatronics. They appear to have addressed many of these issues and have what I would call a superior solution.

ww2, hey man I agree that your 72MHz argument on channel spacing is correct - that is if they keep with FM/FSK. My point wasnt to debunk what you said, rather if modulation scheme was open, then 72MHz with a PSK scheme *could* yield higher bit rates (i.e. faster frame updates as you put it). Keeping things all the same, 72MHz would hit the wall whereas 2.4G obviously has more bandwidth to play with. Believe me, I am not trying to argue with you but simply discuss other technical aspects (sometimes that gets me into trouble).

As many have already said, I think 72M is really a backwards step. You cannot get passed radio impound and single channel operation. Nothing fixes that problem other than going to a SS scheme capable of a large number of users. And you need more bandwidth to accomplish this. As someone stated here before, a dual frequency band Tx/Rx utilizing SS would be a nice solution. Maybe 900M/2.4G or 2.4G/5.8G. Sort of the same principle which GPS/Galileo works. Think of all the fading/multipath issues that could be solved with this sort of setup along with a hopping scheme or use of longer DS codes.

RE: Futaba, or just 2.4, problems at Joe Nall?
 

For sure I was not trying to re-kindle ANY brand war with this thread. It was simply to get info on what went on at Nall with Futaba and/or 2.4g, and hopefully identify any potential gremlins lurking out there. While there is always risk of losing a plane, to lose one due to something that was totally preventable with the proper setup is especially painful. And while this is strictly my opinion, I agree with those here that have stated the 2.4 issues at Nall were highly, highly likely due to the sheer number of 2.4 transmitters in use at any given time.

I further agree, as some very knowledgeable and experienced rc-ers have stated, that the vast majority of 2.4g users, whether it be JR, Futaba, Weatronics, Hitec, etc., as long as the radio gear is installed properly and used in accordance with the manufacturers instructions, will have no issues at your rank-and-file club field, or standard 'rally' where there aren't a hundred or more radios on at one time...with the understanding that nothing man-made is fool-proof.

RE: Futaba, or just 2.4, problems at Joe Nall?
 

So, back to the original topic (and sorry for the diversion). Believe it or not, I dont see this as a brand thing either. At some point in a large flyin with multiple flight stations, we are going to have signal to noise issues. It may come from too many radios on in the band, even with good rf schemes like DSMX and FASST, or from flying too far from your own tx and too close to a cluster of others, or both.

What I would like to see is for both of the big radio mfrs start showing up at large events with some of their engineers and good test equipment. I do not know how else we are going to learn the limits and find ways around them.

And now that JR has stepped up and fixed their RF link, Futaba should offer some tools to evaluate their link performance. Up to now their position has been that 'it just works' which is pretty much true ... But again, with what margin? Now that the other guys have what I expect will be an equivalent link, they'd better get going!

Dave

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Note translated from some info posted on the Robbe German website about the S-Bus II telemetry:

Automatically when connecting the receiver is receiver battery voltage, an external voltage (up to 60 V) and the antenna signal strength the main telemetry data radioed to the ground.

Although information is scarce at the moment, it looks like S-Bus II will give indication of signal strength via telemetry.

RE: Futaba, or just 2.4, problems at Joe Nall?
 

+1 on the comment about seeing what's going on at Joe Nall - I mentioned that previously. Heck, even I have a spectrum analyzer that gives you a 1/2 way decent picture of what's going on in the 2.4 GHz band. Why aren't some of the JR and/or Futaba guys checking that out? Back in the 72 MHz days, they has a spectrum analyzer in the radio impound at Joe Nall and were watching what was going on, why not now?

I'm not sure I would say that the JR/Spek link is "fixed" - just one possible limitation of it. BTW, as I see it, DSM2 picking two channels that were too close to each other was really only a problem in the face of a broad band noise source - like a 2.4 GHz FM video link. If all of the emitters in the band were DSM2 or FASST, why would it even matter where the two channels that a DSM2 link picked were?

To me, I have reservations about the selectivity and gain of the Spek RX's and their software still seems a bit flaky to me - I haven't yet heard that the "re-bind it and it will work" type stuff is gone for good...

Bob

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Now Dave, you posted last year that you have never seen anyone at your club ever have a problem on Spektrum, so why would you try to imply their link was 'broken'? If it because some Spektrum equipped planes had issues at events like Joe Nall last year, then I would say that means Futuaba's link must be "broken' as well since some Futaba-guided planes went in last year and more notably this year.

In any event, if I were flying Futaba gear I would sure want to be able to evaluate the performance of my radio just like Spektrum and Weatronics have offered for some time.
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RE: Futaba, or just 2.4, problems at Joe Nall?
 

I did post that, because it is what I have observed .. no problems at a club field with DSM2. Still true today. But this is not where the problems have been observed.

There were lots and lots of reports over the last few years (e.g. SEFF, Joe Nall) of issues with DSM2, and lots of engineering reports here of evidence of bad design on picking "incorrect" or "non-optimal" frequency pairs that might explain problems with lots of transmitters on at once.

Then, when DSMX came out the post ON JR's OWN WEBSITE (!) said it was to address problems flyers were having at large events, so it ain't hard to connect the dots. Of course if you quote JR's website here, you get accused of being a Futaba "goon", and posting "nebulous statements misinformation". Sigh.

So I'll stand by "broken" .. just my opinion. You may not agree. I was never impressed by it from day one. I do have a DX-7 and fly it in a bunch of non-jet stuff and it works just fine.

But, you make a good point, no one is saying Futaba's link is perfect either, and we have no tools to monitor it. Clearly it's a better design than DSM2, but maybe DSMX is better than FASST .. we'll see. Heck, the JR gang can count frame losses and fades while flying via their telemetry on the new DX-8. I have maintained all along that if the Spek radios come with multiple RXs and fade counters, they must require it ... otherwise no serious engineering team would provide them.

My point is simply that we really don't know enough about the performance and failure characteristics of the 2.4 systems yet, especially at very crowded venues.

I would be very concerned to fly DSM2, DSMX or FASST at Joe Nall... but would trust any of my planes to any of them at a club field.

BTW, I love the idea of the Weatronics stuff, it's just too much of an aftermarket "kludge" to be attractive to me now.

Dave

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Eric,
When I purchased my 12FG almost four years ago, the 2.4 module was not available and when it did come out and I bought one, I realized after a few months of swapping modules that I was asking for trouble. For two reasons. One was that I might become to complacent and forget to acquire a frequency pin when going from 2.4 to 72 and end up shooting someone down and the other was that constantly swapping modules every weekend seemed like there could be connection issues over time. At that time I decided to change all the planes I fly regularly to 2.4. Sorry for the loss of your plane and I hope when and if you radio is diagnosed, you'll share the results here.

Marty

RE: Futaba, or just 2.4, problems at Joe Nall?
 

Dave - What you state above sums it up nicely: Was this a Futaba issue, a 2.4g at the Nall issue, or some combo of the two.

I am a Futaba newbie. Got a 12FG to replace my x9303 when I made the move to 12 channels. But, I have never been comfortable with the "you don't need a data logger with Futaba because it just works" mindset.

However, as you say about club fields, just as DSM2 worked just fine for me, so has FASST. Barring a bad setuo/installation, seems like the worry with 2.4g technology has more to do with the size of the event than with the method of sending/receiving the signal.

Randy

RE: Futaba, or just 2.4, problems at Joe Nall?
 

It never stops, eh? Ok, I'll bite. So when you question technical matters that arent exactly true you get labeled part of the "JR gang". See how that works?

Hell, I focus on the technical issues* and you guys still have to throw barbs. I guess no olive branch is big enough for you to toss in the garbage.

Back to reality for me**, some of this is too deep for me to wade in.


* I am sure C/No meters are no good in the real world. Why would anyone use one since the link should just work? End users shouldnt worrry about stuff like that. :eek:

** Designing DSSS systems during the day and talking techno babble to the uneducated in my spare time.