DSM2 brownouts x4 - is something going on?

[Pete B]

Responding to the last point first, RR, and I don't want to divert the thread from the topic, I would say that we try very hard to keep this forum inclusive and welcome posts from reluctant members. It is an extension of the magazine and as such should appeal to, and have suitable content for, modellers of all ages. The fact that this forum is considered 'over-moderated' by some should be reassuring for those who don't wish to get involved in the unpleasantness and personal abuse seen frequently elsewhere. All forums have a core of regular contributors and that cannot be seen as an excuse for the 'timid' to not post. Equally, we can do little but encourage those reading in the wings to come forward and give it a try - they have nothing to lose. When I joined some years ago, it was a rather big step to take to become involved and post with confidence. Now, I try to pass on some of the valuable knowledge so freely given to me in those early days to recent arrivals, as do so many other regular contributors here. A subject for another thread, perhaps?

Back to the thread. AFAIK, HH had no option but to develop DSMX as an active frequency-hopping system as DSM2, selecting two fixed frequencies at switch-on, was no longer permissible. I don't believe it was due to HH knowing there was a fundamental flaw in DSM2. As the 2.4GHz band has become more and more widely used, it seems there may be a vulnerability with the 2 frequency system and this may be exposed by poor operating practices as mentioned earler, such as switching on at ground level. I am fortunate that I fly in a 'low 2.4GHz emissions area' and I certainly have had no loss of signal for several years which could not be explained.

I also feel that many of the published problems are those from relatively inexperienced fliers who have bought into the system, based on the availability of relatively low-cost equipment compared to such as Futaba, so it may be that, on numbers of users alone, Spektrum apparently has many more problems than other systems.

Whilst not being technically qualified, I also take great care over installation, placement and ensuring that I have as reliable an Rx power supply as I can possibly make it. Any incidents I have had have fairly quickly been traced back to shortcomings in this area. As a result of that, and the fact that I find the system reliable, I don't think it is confrontational or defensive of Spektrum to ask those who encounter a problem to describe their setup in some detail. Indeed, the frequent reluctance by those who have problems to fully explain their setup makes one wonder why? It shouldn't be any cause for embarrassment to admit to failings in the area i mention - indeed, it should be seen as an opportunity to bring those issues to everyone's notice, in order that others don't make the same mistakes.

Certainly there are instances where careful and experienced fliers encounter unexplained problems - it would be foolish to deny that. I don't know why - perhaps it is a fundamental flaw in Spektrum gear or perhaps it's any one, or a combination of, the points made above.

Finally, I can fully understand yours or anyone else's loss of confidence in a system if the cause is truly inexplicable. If it happened to me, I would certainly consider changing to another. So far, having used Spektrum DSM2 and DSMX for 6 or 7 years, I haven't felt the need to do so.

Pete

[Former Member]

[This posting has been removed]

[Dave Hopkin]

Posted by Andrew Ray on 14/05/2015 09:56:01:

I will leave you with the one thought that this is costing HH a small fortune, do any of you really think that they would be doing this if loss of signal was caused by poor installation or pilot error?

Edited By Andrew Ray on 14/05/2015 09:57:54

Actually I think they would - What would be the alternative? To send the TX back as "no fault found" every time - if they did that, their reputation would nose dive and people on forums like this would be saying "Oh dont but Speky their rubbish" - we are a small community and word spreads quickly.....

I cant see they have any choice but to replace the RF board as a "just in case" step - if there was a latent fault in there I am sure they would have pushed back at the manufacturer and demanded it be rectified - of course that may of already happened!

[Dane Crosby]

When Spektrum went DSMX there had to be a good reason - the new EU requirements for 2.4GHz being one. I changed to DSMX using various 6 and 7 ch Rx with my DSMX DX7s Tx. I take great care installing the Rx and the satellite rx to give optimum reception. I fly with a log in each model and although my gliders fly quite far away I have had no holds or fades when the logs were checked after each flight. In the crowded RF spectrum it is incumbent on us to fly with the equipment that can cope, which at the moment is a minimum of DSMX IMO. As for having to obtain new Rxs, well, compared to the costs of the model, they are worth the investment.

I have retired from being a military jet instructor, rescue helicopter instructor and examiner. Our CFS training required us to constantly question and improve our own operating skills and never assume that our top qualification and wealth of experience meant that we were perfect in every way. Just because we QHI/QFIs were good did not mean that we couldn't make mistakes or gloss over checklists and operating procedures. Arrogance was frowned upon. If this touches a nerve with anyone who thinks they know it all then don't get angry, change your outlook, debrief yourself and learn something.

[Former Member]

[This posting has been removed]

[Pete B]

Posted by Andrew Ray on 14/05/2015 09:56:01:.
Repeating myself, I only had problems with DSM2 and my DX8, the DX8 was flawless on DSMX. Since I have moved away from Spektrum I have had no more problems, my installations have not changed.

There was indeed a problem with DSM2 on the DX8 with the early production back in 2011, Andrew - it happened to me - and mine was returned for the firmware fix, since when I haven't had a recurrence. Was your Tx subject to this recall? :

Spektrum and JR DSMX Transmitter Bulletin

DSMX transmitters operating in DSM2 mode

The Spektrum Team has been investigating sporadic reports from DSMX transmitter owners using their products in DSM2 mode. We have discovered that in some rare instances, DSMX equipped transmitters with the Product ID (PID) within this bulletin, may have a backwards compatibility issue that could cause a "hold" with the following superseded DSM2 receivers: AR500, AR6100, AR6100E, AR6110, AR6110E, AR6200 and AR6300.

Note: This bulletin does not apply to DSM2 ONLY transmitters.

I'm beginning to suspect the increased usage of the 2.4GHz band may well be the problem with DSM2, so if you fly in or near an area of high levels of activity, as Dane suggests, it may be prudent to avoid DSM2.

Pete

[Former Member]

[This posting has been removed]

[kc]

Simon, yesterday I posed the question whether the AR600 which came back from Horizon was still a DSM2 Rx or whether they would have sent back an AR600 DSMX Rx. Could you let us know so we can discontinue that avenue of thought? ( photos in the AR600 manual show a Rx with an X logo on the case , but maybe they don't change the case )

( Dave thought it wouldn't bind so maybe my question is irrelevant!)

[mightypeesh]

Hi kc. The receiver went back to horizon because I noticed that one of the antenna's had got a bit of a crimp going on and even though it was a couple of years old (out of a BnF Radian Pro) I sent it back to have it tested. They did their usual and fitted new antennas and returned it too me foc, so it was the original DSM2 model not DSMX.

Just out of interest, before I had this problem I had flown gliders with my DX7 and AR7000's with a remote receiver at this site for many many hours without problems, and like I have said the PC had flown on just about every visit. most of my stuff now is DSMX, and after this episode the rest will too when my DX9 comes back.

I may be reading this wrong, but the way that I am seeing this is that Spektrum started the ball rolling with DSM2 on a protocol which rapidly became crowded as communication technology also was expanding expotentially which may be causing problems now it is reaching saturation point. Although switching between two channels was fine however long ago it was, now it is not enough to guarantee the link?

The other problem with discussing the situation as Andrew Ray pointed out is the foggying of facts due to the almost 'talking about politics' type passions that folk have either for or against XY or Z. I have always worked from experiance and observation and like to make my own mind up after reseaching how I feel about technology (or people). The conclusion that I have come to from this episode is that Spektrum is not inheriantly bad, just that for dsm2 at least, the system cannot cope with the increasingly over stretched airways that are surrounding us. For me I will stick to Spektrum and DSMX and see what happens - which I suspect will be nothing!

Cheers chaps, Simon

[J D 8]

A clubmate has been having similar problems with his new DX8 in recent months, He first set it up to fly his regular hack aircraft with hundreds of flights under its wings with DX7 TX.

While doing first range check with engine on, the motor went to idle but when he operated the sticks controls worked and engine then worked as normal. Test was repeated twice and all was fine so flying commenced all was good for about ten mins then it went in some distance away. Not sure what had happened aircraft was repaired [He is a very good traditional builder] and at the next session range tests were fine and aircraft flown until on a low slow pass right in front of the pilots box engine went to idle and controls stopped working result was cartwheel down the strip,rebuild time again.

He sent TX back to Horizon who found no problems but at the next session it failed range check again.This time "board" was replaced as a precaution but again the problem has remained,not every time you switch on, it's intermittent. Tx has gone back again this time to be exchanged.

Aircraft has been flying again with no problems on the old DX7.

[john stones 1 - Moderator]

Simon I have read your posts and build blogs, as a non Spektrum user I don't have owt to offer as to what happened, but you come over as a sensible fella and I hope soon get back to flying trouble free.

John

[Dave Hopkin]

Posted by Andrew Ray on 14/05/2015 10:50:34:

Posted by Dave Hopkin on 14/05/2015 10:05:23:

Posted by Andrew Ray on 14/05/2015 09:56:01:

I will leave you with the one thought that this is costing HH a small fortune, do any of you really think that they would be doing this if loss of signal was caused by poor installation or pilot error?

Edited By Andrew Ray on 14/05/2015 09:57:54

Actually I think they would - What would be the alternative? To send the TX back as "no fault found" every time - if they did that, their reputation would nose dive and people on forums like this would be saying "Oh dont but Speky their rubbish" - we are a small community and word spreads quickly.....

I cant see they have any choice but to replace the RF board as a "just in case" step - if there was a latent fault in there I am sure they would have pushed back at the manufacturer and demanded it be rectified - of course that may of already happened!

Really? You actually believe that? Wow!!

There are many things that Spektrum could do. I could list those I could think of but frankly I don't think it would help.

It is plainly obvious that there are thno suose who have experienced this and those that have not. To those of you who are firmly in the it's pilot error, battery issues etc. I sincerely hope it doesn't happen to you. I don't think you will get any sympathy from those it has happened to.

Edited By Andrew Ray on 14/05/2015 10:51:12

I do love these condescending replies that rely on assumptions...

a) I HAVE suffered LOS personally on two occasions, one was at high altitude so caused subsequent problems, the other was on landing approach and resulted in a crash (and I have plenty of other crashes that were 100% pilot error!!!)

From a BUSINESS perspective what else can Spektrum do? They get kit sent into them for testing, they test it and find no issues, of course they cant test it at the site it failed at, they cant test it using the installation it failed in, they cant test it with the relative attitude to the TX Antenna, they cant test it in the same interference/noise environment if failed in plus many other imponderables many of them transceint - so do they simply send each one back saying "no fault found" - That would damage the confidence in their kit and impact sales

So they replace a very cheap RF board just in case and give a degree in confidence back to the user?

We operate highly complex computerised equipment in quite harsh conditions, we have all put out TX down on damp grass, and many other things that your wouldnt do with your laptop for instance

Once you weed out the incidents that cannot be explained by causes closer to home, you are left with a number that cannot be explained, it seems to me (and this is just a gut feel) that its more common in electric planes rather that IC, it is widely suspected that Speky RX's are quite voltage sensitive, is it the case that we are simply placing too much of a load on the ESC and causing a fleeting voltage drop and causing the RX to reboot?

Again I repeat I have no evidence to back that up its simply a hunch

[Former Member]

[This posting has been removed]

[Dave Hopkin]

Posted by Andrew Ray on 14/05/2015 15:47:21:

Mr. Hopkin, I'm not quite sure where I have been condescending or where I have made assumptions. If I have offended you I apologise.

As I feel that I have experienced an inexplicable loss of control on more than one occasion using DSM2 I am quite prepared to give the benefit of the doubt to those who have been or who are in the same position as I found myself rather than constantly blame pilot error.

And DSM2 has acknowledged limitations in a ever more crowded 2.4 environment in that it uses only 2 possible frequencies, rather than 23 (I think) that DSMX uses - hence the probability of a loss of signal due to both frequencies being used by something else with enough signal strength to block your is higher - the answer is to use DSMX I am afraid

[Pete B]

Hey, steady on, chaps - we seem to to be moving towards some sort of consensus. We'll have nothing to argue about discuss soon.......

Pete

ps - if you have any spare DSM2 Rx's I can probably find a home for them.....

[mightypeesh]

Crumbs. I did not realise how deep set this all goes. Maybe questions should be asked in the house of commons......... Then again best not go there either after the last few weeks.

How about a nice gentle subject like 'should we bring back hanging?'. That should calm it down.

I'm going back in the workshop to my Pushy Vamp build where its nice and safe and smells of balsa and glue.

Cheers,

Simon.

Ps thanks John

Edited By mightypeesh on 14/05/2015 16:36:43

[graeme jones]

One thing which is a recurring theme on this and other threads is "sending Spectrum Tx's and Rx's back for checking". In 40 years of using Futaba, 27 MHz, 35 MHz and now 2.4 GHz I've never had to send anything back for checking, it just works. Have other users of makes other than Spectrum sent as much kit back for checking?

The point was made a few posts ago that "99.9% of crashes are caused by battery problems". This week at my field I've only seen one crash. It was caused not by the battery (4 cell AA NiMh) but by a faulty connector. Specifically the Futaba shaped plug fitted to the battery, as purchased, was not a good fit into the socket on the Futaba switch harness. The BMFA safety officer asked for fliers experiences of this and similar problems a year or two ago, but I don't remember seeing any results/feedback. Perhaps the BMFA should look at the reliability of 2.4 GHz in general. As several people on this thread have pointed out, the band is used much more now than when we first started using it. Perhaps we should go back to using 35 MHz, which is a band reserved solely for model aircraft. Hang on though, my club have banned the use of 35 MHz due to "unexplained crashes". Not sure what will happen if people start having unexplained crashes using 2.4!!!

Graeme

[john stones 1 - Moderator]

Now don't go starting a row Graeame, us dinosaurs on 35 MHZ are happy as we are, you lot keep away you're always rowing.

John

[graeme jones]

John - I still use 27 Mhz for one old aircraft, just not on the club field. Still works perfectly, as does my 20 year old Futaba F16 on 35 Mhz.

Graeme

[Paul Marsh]

Under DSM2, if you had a voltage brownout, it took longer for the rx to reboot itself. DSM-X is instant. Futaba and the others were all quicker than DSM2 when they came out and weak power supplies showed more on DSM2, and you likely got away with it if you used Futaba or others.

Still, power problems can be battery, switch, connections as well as insufficient power reserves on your BEC or UBEC.

That's what the thread title is - a brownout, as a power cut. Lose power for whatever reason and the model becomes a free flight model, if or when control is re-established.

In the past, I lost/broke a few models, one last year, although on Spektrum, it wasn't the power, I reckon the elevator linkage failed, Another when my AcroWot ARTF went weird at Greenacres - that was on Futaba, and the battery - a 4300mah 5 cell sub c was still fully charged and connected - even after the crash.

Another one, the battery terminal failed internally a few years ago - my Rambler 45 went free flight - smashed, that was on Futaba.

One delta crashed when the battery failed, the model was on 35 Mhz and model wasn't too badly damaged.
A Sig Wonder went in when the old 400mah battery failed after one flight and just charged up. Both were years ago and now both models have a 2500mah NIMH battery installed.

[Dave Bran]

You do have to laugh at the aggressively partisan "there's nothing wrong with Spektrum" brigade, regardless of the truth or otherwise of the matter.

A recent event caused me near hysterics. Several people were discussing their DX8's and the problems they had experienced. (which have to say did seem to me to be a worry from what was said and what I know of their years of experience with RC)

One guy then wades in with a diatribe about how they were totally to blame and the DX8 was a great transmitter that worked perfectly well if only they'd set up their systems correctly.

Now for the bit that caused me to choke and walk away.....................I know he only has a BNF Blade 300 and 130 and his flying is limited to static hovering a max of five feet away tail in.

How the heck would HE know anything valid about the quality of the radio link?? I mean................. really................

Dave (frequent user of 2xDX6i, DX7, 2x6EX, 10CG, Taranis)