Signal Loss with Spektrum?

[Denis Watkins]

It is a huge shock when the motor cuts, and your model goes in. You do look to blame everything else. But to go forward with our equipment in a confident way, we do try to ensure that we do not repeat the crash process.

Once a bullit proof set up is acheived, that care of installation should be repeated in every model. Installation instructions should be adhered too, and maintain the flight pack as you do your TX pack.

All is common sense, and well stated in publications. Just be aware that 2.4 gig is no x-ray

[Phil Green]

Posted by John F on 14/01/2016 08:55:34:

Don't forget though that folk are stubborn and won't be told that it was their errant thumbs rather than what they saw as a Tx fail in reducing their pride and joy to matchsticks!
It is much easier to lay blame than admit responsibility, in many cases.

Thats very true John but doesnt explain all the replacement RF boards...

[gangster]

Whilst we have a lot at stake with our models both in terms of financial value and safety related issues we must be prepared to accept that the link will always be fragile we use very basic mass produced equipment and are at the mercy of all the rules of physics and propagation. The wavelength at 2.4 GHz is tiny (about 4 inches in the iold money) So look at those tiny quarter wave aerials (the bare bit after the grey). About the size of a servo motor, so we have a lot of things to get in the way of the signal. Even with diversity (two or more aerials) the odds of one hiding behind a servo and one cross polarised or end on to the Tx is pretty likely at times.

It does not make any difference who made the kit it is of similar quality and depends on the same rules of propagation

2.4 was hailed as the overall panacea to all problems(most of which were ficticious anyway) it is not the case it has it's own issues. It is possible that we will just realise how much more suitable 35mhz might be. Those who kept some high quality 35 kit might be laughing cos we are unlikely to see manufacturers making it in the future

[John F]

Posted by gangster on 14/01/2016 09:33:14:

2.4 was hailed as the overall panacea to all problems(most of which were ficticious anyway) it is not the case it has it's own issues.

What issues gangster?

[gangster]

Well John just about everything that people blamed a crash on rathet than pilot error

interference was always a favourite. Whereas I firmly believe poor maintenance of batteries leads and switches and poor installation were the real culprits

Or are you asking about the 2 4 issues? In which case in addition to the old favourites we can include aerial installation and signal blocking. How many models have you seen with the aerials screwed up in the fus even careful placing may inadvertantly result in shielding on some occaissions

[Phil Green]

...again, all very true Gangster, but doesnt explain all the replacement RF boards...  

Plug-in 35mhz RF modules are still readily available, Profi and Scoonies have stock of Futaba-style Hitec HPF-M1's think they're about five or six squids including the crystal (random choice). Our s/c group have bought quite a few, they work very well, my Macgregor MR200 has used one for 4 years now with a Corona synth rx.

 

Edited By Phil Green on 14/01/2016 10:58:13

[Andy48]

Much earler in this topic I gave my experiences of three different planes all crashing in exactly the circumstances, two of them in exactly the same place with my Spektrum gear. Since changing over to Taranis I have not had a single problem for a whole year.

The Taranis does have some significant advantages in the area of signal loss, because you actually get verbal a warning of signal loss long before the signal is actually lost. Also the built in telemetry records the signal strength throughout the flight so one can check where signal strength is weakest.

I did discover that one problem often occurred at a low altitude where by accident the tip of the aerial pointed directly towards the model as it was flying quite close, and the receiver was in the aerial's dead spot.

[Pete B]

I wonder just how many of those replacement RF boards were put in just to appease the punter when no fault had been found in testing?

Pete

[gangster]

Quite so Pete I was just writing the same when my battery went flat. It is not uncommon though for a manufacturer to have a design ,component batch or a tolerance issue. With regards the Taranis telling you that sounds good however with a moving model by the time it told you it's history. However you would be foolish to ignore to many.

I have not studied the latest 2.4 kit but would not be surprised if that info is not stored on some transmitters, as standard BUT what does it mean in reality? Spektrum tell you (in the DX8 manual )that 50 to 100 fades is typical in a flight and to look at aerial orientation if you get more than 500 fades

but what the hell does that mean surely that is the whole point of having two aerials anyway

fFrom having read this thread I deduce that yes we will always have glitches but that is not too serious , and maybe not even noticeable when we have height but the phenomena that is a real killer and seems to be due to shielding is when signal is lost close to the ground with no chance of recovery this may well be a 2.4 related issue that we never had on 35

[Erfolg]

I do think that there has been a reduction in the number of claimed interference issues since 2.4 has become the predominant frequency.

I have noticed that at one club I am a member that there has been some generally unexplained crashes.

In one case it was established that it was an radio issue, surprisingly in retrospect, it took some time in establishing it was a Tx issue, as for a time there was a suspicion it was Rx issues. The radio was repaired by Spectrum.

In other cases it was far less obvious. I personally took little interest beyond helping in the model search. That is until my own model went in from a situation which seemed most usual. A random comment that a lot of models had gone in that general region, started me thinking. I observed that the general area, has a lot of trees, that it was on the far side of the patch and that many had made landing approaches from this area. In my case I never made an approach from this area as I much preferred an approach further round, avoiding most trees and providing a clear line of sight. The crash I had, was probably partly due to me being further out than usual, and the trees being partly in line, and I was pretty low. I now wonder if trees can be part of the issue.

In the case of the sets where models have gone in, they are mainly Spektrum sets. Another factor that is relevant is that the club is probably 90% Spektrum. I am a Futaba Fasst user, where to date I am only aware of the one unexpected and unexplained event. Then again I am essentially the only Futaba user.

[Martin Harris - Moderator]

It does seem odd that the only loss of control issues that I've experienced with 2.4 GHz models have been with clubmates' models using Spektrum and budget radios. I fly very regularly with my own gear in exactly the same area - hundreds of flights a year - and have had no issues. I will even admit to some models with very much less than optimal aerial installations - e.g. a foam F18 with literally hundreds of documented flights (all my models are telemetry equipped) where the aerials are floating in a bay with a 4S 2200 LiPo, the power wiring and with the servo wiring and receiver - with a 70mm EDF a few inches further back - and only a cursory attempt at orientation diversity is made while I snap the canopy on.

Lack of alarms plus regular reference to the logs confirm that there are no incidences of signal loss, poor quality or excessive attenuation of received signal strength. The model is flown to reasonable distances - often at low level.

I hasten to add that this cavalier attitude does not extend to my more serious models where I do take care to plan aerial installation.

Is the change of RF board so often heard about by one manufacturer a sop to the consumer? Who knows, but I have to wonder why would they imply blame on their own equipment so readily if it was not true?

[Don Fry]

Posted by Masher on 19/01/2015 12:18:58:

I can - all my incidents have been pilot error either "on the sticks" or installation/preparation issues. BUT, I've only been flying for 2 years!

Masher, I've been at it for 50 years, and I'm in the same situation. Sometimes I try to blame the radio, as I can't believe I can be so stupid, but have to accept I am.

[Andy48]

Posted by gangster on 14/01/2016 11:38:08:

With regards the Taranis telling you that sounds good however with a moving model by the time it told you it's history.

That's not the way it works, it gives you two warnings, low and critical, both well before the model moves out of range. Even with the critical alarm warning, the range extends about 500m beyond that point.

[ben goodfellow 1]

I wonder how many crashes have been put down to pilot error , when Infact it was a dose of dsm death ..

[gangster]

Even with the critical alarm warning, the range extends about 500m beyond that point.

If only things were that simple rf propagation especially with a moving receiver isn't that cut and dried. If it was this thread may not exist

[John F]

Posted by Pete B - Moderator on 14/01/2016 11:12:02:

I wonder just how many of those replacement RF boards were put in just to appease the punter when no fault had been found in testing?

Pete

Wasn't there a thread mid summer last year where they could not find any fault whatsoever, stated as much but replaced the RF board anyway?

Reminds me of the video whereby a flier crashed his plane, lots and lots of toothpicks all over the place, guy was furious that Spektrum is rubbish, it is the famous Spekky Glitch. Showed the video and many, many other folk furiously agreed it was a travesty and was obviously a glitch and a fast, low, inverted pass should never end in tears like that.

The video shows clear as day the guy was desperately trying to make it fly up, he even raised the Tx into the air above his head, showing everybody that he had the right hand stick all the way down!

Posted by gangster on 14/01/2016 10:33:29:

Well John just about everything that people blamed a crash on rathet than pilot error

interference was always a favourite. Whereas I firmly believe poor maintenance of batteries leads and switches and poor installation were the real culprits

Or are you asking about the 2 4 issues? In which case in addition to the old favourites we can include aerial installation and signal blocking. How many models have you seen with the aerials screwed up in the fus even careful placing may inadvertantly result in shielding on some occaissions

Poor batteries and leads would always end in an oops moment. 

Dunno about cramming a Rx in a position with aerials screwed up as being an "issue" but rather a poor installation.  

Edited By John F on 14/01/2016 16:03:45

[gangster]

nd leads would always end in an oops moment.

Dunno about cramming a Rx in a position with aerials screwed up as being an "issue" but rather a poor installation.

Indeed so John but having suffered consequences where will be the blame be laid ? Agreed it doesn't make 2.4 less reliable but introduces another pit fall.

[Andy48]

Posted by gangster on 14/01/2016 15:39:55:

Even with the critical alarm warning, the range extends about 500m beyond that point.

If only things were that simple rf propagation especially with a moving receiver isn't that cut and dried. If it was this thread may not exist

It is that simple! If you want to see the signal strength at any point in the flight simply look at the telemetry data stored on the SD card in the transmitter. You don't need any telemetry gear to do this with the Taranis, its built into the system, and all you need to do is enable the data logging and say how frequently you want it logged. If you have the £20 GPS module plugged in (which readily transfers between models) you can tell exactly where on your flying field the signal is lowest, and how high the plane is flying.

[Martin Harris - Moderator]

Posted by John F on 14/01/2016 15:59:33:

Reminds me of the video whereby a flier crashed his plane, lots and lots of toothpicks all over the place, guy was furious that Spektrum is rubbish, it is the famous Spekky Glitch. Showed the video and many, many other folk furiously agreed it was a travesty and was obviously a glitch and a fast, low, inverted pass should never end in tears like that.

The video shows clear as day the guy was desperately trying to make it fly up, he even raised the Tx into the air above his head, showing everybody that he had the right hand stick all the way down!

Sounds rather like the video of Ali's Hunter crash?

If so, it looked like to me was that the model dropped from inverted flight - down elevator (and closed throttle) seemed eminently sensible in that case!

Edited By Martin Harris on 14/01/2016 18:20:12

[ben goodfellow 1]

it amuses me when people come up with things like "Don't forget though that folk are stubborn and won't be told that it was their errant thumbs rather than what they saw as a Tx fail in reducing their pride and joy to matchsticks!.. that ofcoarse assumes we are all as pathetic as them at flying ... fly low .....but not on dsmdeath

[Simon Chaddock]

I always wondered why Spektrum when they released DSMX made a big song and dance about it ability to work with up to 100 Txs all on at the same time.

Was such a capability really so important or was it that the very popular (at the time) DSM2 was actually not all it was cracked up to be and needed to be replaced!

I have had absolutely no trouble with DSM2 (and still don't!) in my very quiet (lone flyer) 2.4 environment but it has resulted in two incidents for me (one a complete loss of control crash) in just 8 flights at a really busy field.

Does DSMX have the same sort of problems?

I suspect it is case of a reputation once lost takes al long time to recover.

[GONZO]

A comment on DSM2, not the technology but rather the required opperating proceedure. Trusting that the technology will always work no matter how it is treated is often the cause of failure of said technology. I have noticed on many ocassions that people with these sets tend to turn on their Tx when it is on the ground, some times with the aerial lying in damp grass, or with the Tx in the back of their car. It is imperative that the Tx gets a good 'RF view' so that it can select two unused channels for use(DSM2 jumps between two channel only). The afore mentioned proceedure means that the Tx is, at best, partially blind to other transmisssions. This poor and incorrect switch on proceedure could result in the Tx not seeing channels that are in use by other DSM2 users and one or both channels being selected for use. This could then result, in adverse RF signal conditions and if the channel jumping gets in sink, in a partial loss/lock out of control for either plane dependant on which plane gets the best signal. Most times, I would suggest, there is no problem. But, on the odd occasion you loose in this lottery. Just an observation. I would always seek to switch on any DSM2 system with the Tx at least at chest height so as to give it a good 'RF view'. Of course some one else could still switch on their DSM2 set using the incorrect proceedure.Can anyone, hand on heart, who uses DSM2 say that they have never switched on their Tx with it lying in the grass or in the back of their car?

[Phil Green]

Posted by GONZO on 14/01/2016 22:35:14:

A comment on DSM2... I have noticed on many ocassions that people with these sets tend to turn on their Tx when it is on the ground, some times with the aerial lying in damp grass, or with the Tx in the back of their car. It is imperative that the Tx gets a good 'RF view' so that it can select two unused channels for use ...
I would always seek to switch on any DSM2 system with the Tx at least at chest height so as to give it a good 'RF view'. Of course some one else could still switch on their DSM2 set using the incorrect proceedure.

Good point, well made.  Exactly what I've been saying for a long time Alan:

Posted by Phil Green on 30/04/2014 15:56 on RCG:

I have an issue with DSM2 users rather than with DSM2:
Every weekend I see DSM2 flyers arrive at the flight line, they kneel down to tend their models and place their transmitter down flat on the grass. Presumably this is for safety, so the tx cant fall over & open the throttle.
They then switch on the tx and from a position flat on the ground surrounded by damp grass the tx looks for a couple of free channels. From down there, all it will be able to hear is other RC transmitters in the immediate vicinity. It wont hear the things its designed to avoid, like distant video transmitters, beacons, repeaters and other ISM band hash because its aerial is right down at ground level in the damp grass. I've suggested they switch on at least at waist height, but they dont take any notice!
Cheers
Phil

 

Re the point about channels, spread spectrum ensures that any one 'channel' can happily carry several DSM2 signals simultaneously.  This is partly because of the low duty cycle but mostly because the chipping code unique to each transmitter moves each transmitter around the chosen channel in a  different pattern to any other transmitter, changing frequency several times per data bit.  Your receiver wont even see another transmission on 'your' channel, because your rx isnt using the chipping code used to send it, so it will just see noise.  I think in our sort of environment, its more important that the startup process avoids any continuous transmissions like video, analogue repeaters etc.

 

 

Edited By Phil Green on 15/01/2016 01:04:29

[gangster]

Quite so Phil. It is a very difficult concept for people to grasp we tend to think of the old concept of radio and television ie one frequency one program and anything on the same rf frequency will interfere (radio Luxembourg at night for those old enough)

digital protocols have changed all that. Digital TV is the best readily available example. Just see how many TV programs fit onto each channel. Without path sharing be it cable or radio we certainly could not have broadband or mobile phones. The bandwidth of the link feeding a mobile phone mast is a tiny fraction of the aggregate of all the high speed data links to smartphones in use at any one time also correct me if I am wrong but I believe you can safely have dozens of models up at any one time on DSM2

also I understand any issues with Dsm2 are more related to power than rf issues. Ie slow recovery However the power up and binding issues just mentioned are equally relavent and probably the only shortcoming of just 2 channels

[eejit severn]

I'd like to put a few things into the mix. Please bare with me, it's a bit of a tale!

I've owned 5 Spekkie transmitters, all bought new, a DX7, DX6i, DX8, DX7S and a gen 1 DX18. The DX7 was made by JR and was bombproof, they're still quite sought after. The DX6i developed an intermittent problem with the Ail pot which I only discovered after it put three models in (luckily not expensive ones!) Horizon replaced the pot (with a second hand one!) FOC even though the TX was out of warranty.

I did a LOT of reading and waiting/thinking before I bought the DX8 which was my next one. I bought the DX7S as a spare but it remained in its box. I had no issues with my DX8 and sold it and the unused 7S and bought a gen 1 DX18 which I still have.

I personally know 7 people with DX18s and only one of them has had a problem with them so far, however two of them bought a DX18 because their DX8 had smashed up expensive models!

Horizon may provide "good customer service" but.... Three of us in the same club all bought the same Blade Helicopters and had 4 servo failures between us, within the space of a month we each asked Horizon if this was a common issue and all three of us were told that it wasn't (even though I pointed out to them that it was all over the forums!!) Luckily for me and for some bizarre reason the servos would usually fail between flights so we could actually prove it was not dumb thumbs.

I wrote a review of this helicopter on the Horizon website and after it was submitted I received a reply saying that my review would not be published because the servo failures I'd mentioned had nothing to do with its flying performance??? EH???

As far as I was concerned this was a cowardly manipulation of the truth. Horizon are simply playing a numbers game with their customers. If the failure resulted in a crash, blame the customer's dumb thumbs, if it didn't, warrant with a smile. You do the maths about how many failures don't result in a crash....

Something which Ben has not mentioned here but I feel should be mentioned is that he is a really good flyer and when I say really I mean really. He is without doubt the best 3D fixed wing pilot I personally know and though it would only be a guess I'd think in terms of aerobatic ability and aircraft control I'd put him in the top 10% in the country. He's also not one to skimp on his setup either. He buys what he considers to be quality gear.

I witnessed Ben's Sukhoi go in and helped him pick up the bits, it was DEFINITELY NOT dumb thumbs. My guess (because I don't know for sure) was that it was a radio link issue. He was running a redundant battery setup to (IIRC) a powersafe RX.

Whilst I've not had any issues with my DX18 yet, the incidents I've observed with Spektrum are getting a bit close for comfort. Add that to Horizon's attitude/business model and it's making me think that the writing is on the wall and I too am looking at Jeti as a true quality alternative.

D

 

 

 

 

Edited By eejit severn on 16/01/2016 23:52:08

Edited By Biggles' Elder Brother - Moderator on 17/01/2016 13:57:56