Signal Loss with Spektrum?

[extra slim]

Haahaa...check that out... Very darth vader Ben...now with stealth signal we hope... Does it talk to you in a Darth voice...awesome if it did....."binding...grrroooorrrr...binding"....

may the signal be with you young padawan....

[Martin Harris - Moderator]

i will have signal shortly.. after telling hh how much i hated the look of the normal dx 18 s chrome /silver finish ,which i do..i am getting one of these http://www.spektrumrc.com/Products/Default.aspx?ProdId=SPM18200 ..fly low

 

Stealth edition?

Will that mean that its transmitted signals will be undetectable?

I thought that was how this thread started!

Edited By Martin Harris on 09/02/2015 23:40:02

[ben goodfellow 1]

it may mean that the tx is stealthed from the rx , but theres alot of spekky gear like that already... fly low

[Peter Jenkins]

I had 2 instances - one a 6 Ch DSM Spektrum Rx and one a 5 Ch DSM Spektrum Rx - with a JR DSX9 Tx of losing aircraft. In the 6 Ch Rx case, it was in a Seb Art Wind 110 and in the 5 Ch case an old Trainer. The Wind suffered a glitch on take off, that was momentary, then a further glitch on the early climb so I decided to fly a circuit and land immediately, Having carried out a 180 deg turn onto base leg, the Wind pitched 90 deg nose down and did not answer the controls again. Vertical dive into the ground from 150 ft!

I sent the Rxs back to HH UK and the JR Tx to MacGregor Industries. No fault found with Rx or Tx! MacGregor implied in their response that the JR Rxs (the DSM2 ones) would be a better bet than Spektrum ones! I therefore used my RD921 9 Ch Rx and a Spectrum 9 Ch Rx and had not bother with either. I've since gone to JR's DMSS XG system which has a very rapid connection time both when switching on and after a failsafe check.

[Dave Hopkin]

DSM2 has known vulnerabilities in that its only capable of utilising two frequencies, so if you have any sort of signal contamination that hits both frequencies then you loose signal - DSMX uses many freuencies to reduce the chances of this happening - and dont forget in the 2/4 band we are competing with a wide array for devices not just RC (WiFi, Door Bells, Printers, cameras all sorts....)

[Nigel Herron]

Joining the band wagon and similar issues my system spectrum TX- DX6i Rx-AR610.

I've just lost my second plane with the above setup, two different planes and two diff setups 1st was a Seagull Super Tucano with a Sc91a Took a dive on its maiden flight during takeoff uncontrollable dive at about 6ft off the deck. I thought i had it bound correctly at the time and just put it down to P/E.

2 nd one was an electric setup Hobby King AT6 Texan flown before on a Futaba set up I Changed to Spectrum due to easier setup for flaps and mixes' etc but no mix's setup for this flight thou.

I did check binding at the time of the spectrum installation and thought was ok (now thinking other wise) as same thing same place happened again end of runway 6 ft of the deck and a nose dive.

After checking binding etc on the field at the time couldn't find any problems.

But got the bible out tonight and checked again when checking the range check again i noticed at about 40/45 yd that i was getting an intermittent signal with a hunting noise coming from the motor and note from Instructions that there are two different ways to bind an Rx 1st with receiver battery and 2nd with the ESC battery.Sadly to say i did not do this until tonight any body else had the same issue as I'm in the process of building one of the chippies and will not risk this setup we've spent to much time and effort to see it go the same way any thoughts Guys.

[onetenor]

Can an old codger put in an oar here. My radio days go back to valve sets and 27 meg transistor sets.. Anuthing could upset the apple cart .Starting a car with unsupressed ignition as was the norm in those days was quite common and virtually anything that could make !Electrical noise ! Metal to metal linkages was one . Sloppy aerial sections another. and others too numerous to mention. Single channel of course then. When 35 Mhz came along things were much better as long as peg board sorting and your X tal pennant was flown on the aerial If all x tals were different no probs. I have stuck with 35 Meg owing to having no cash to spare on my small pension. The point of this is that I can fly whenever i want as everyone else is now on the 2.4 and do not affect my kit or I theirs. I have never actually lost an aircraft through radio problems as such but wind gusts on landing or a lost linkage or hinge have done me in a few times my kit is Futaba and Graupner with a few different Rxs. Hoping I haven't gone too far off topic.

[Nigel Herron]

Sorry onetenor valves and chrystels before my time thats why i use 2.4 on both my sets and i know the spectrum Tx is good as i use this for BNF so i dont think there are any issues there.

So back to the original Q would/could the 2 different binding methods have affected the performance of the setup has anyone else made the same mistake and resulted in catastrophy. I was under the impression that once a RX was bound to your trani hey ho away you go.

Nige.

[Paul Marsh]

Regarding crashes, what about your batteries? On the case of the Super Tuccano, what battery were you using. Was it charged? A 6v, 5 cell pack and in good condition?

On the 2nd crash - the electric plane, does the ESC BEC have enough power to drive the servos and the receiver? I've had an issue with a BEC on an Orange rx, where the voltage dropped when the servos were moved and the rx shut down until it rebooted. I cured that by putting a small battery just on the rx side, and disabling that particular BEC.

[Pete B]

If you've bound correctly, there should be a solid LED showing on the RX at the end of the procedure. If there isn't, the bind hasn't worked but, tbh, binding is a work/won't work procedure, so that may not be the problem.

Is your Dx6i DSMX or DSM2 protocol. If it is DSM2, and you had a 'brown-out' or power loss, the LED would have been flashing slowly when you reached the wreckage.

Assuming this isn't a power supply problem - and encountering that on two different models in the same flight attitude would be stretching credibility - then I'd consider Tx aerial orientation a possibility.

Do you have the aerial projecting vertically from the Tx? If so, could you be inadvertently pointing it towards the model, which would be the weakest radiated signal direction. Tilting the aerial to run parallel with the top of the Tx would improve matters.

Pete

[gangster]

On the subject of brownout, something suddenly occurred to me whilst installing an ESC with a BEC

This claimed to be a 5 volt 5 amp BEC. The power is supplied from this, as with most other esc/bec devices down a pathetically thin piece of 3 core servo lead, about 10 inches of it, then though a couple of thin pins and a piece of tiny PCB track before the receiver even gets a look at it. Modern servos can be thirsty beasts and large and stiff control surfaces, and enthusiastic flying can push up the current draw considerably. Surely a recipe for a little voltage drop from time to time.

Now I know this is probably equivalent to having a traditional set up with a switch harness and a mucky old switch with either oil or black lead contamination, however our old 27/35 Mhz set ups were much more tolerant to voltage drop than some 2.4Ghz receivers, indeed many have landed safely with one cell down.

There is a school of though that suggests some Spektrum receivers are particularly susceptable to voltage drops.

Now whilst this bears no relavance to the OP but it has always struck me how paranoid modellers are about interference, yet are very negligent of the DC side of things,and fly with poor DC maintenance including that greatest sin of all that is leaving a battery installed in a model that is stored in a cold shed or garage.

So my question is..Is there an issue of excessive voltage drop on that pathetic piece of wire from the bec to the RX?

[Nigel Herron]

1st plane Tucano yes battery was a 5 cell and fully charged.

AT 6 Texan yes battery was fully charged and Arial orientation as always at 2.o'clock my system was set to Auto so I'm assuming DSMX-2. light was steady on Rx when retrieved at the field and tested again for signal strength/binding.

Texan now repaired and ready for test flight again i have a Futaba Rx so I'm going to try this one 1st then will switch back to Spectrum the Texan has a built in sound system so will try with /with out on both setups to see if this has any interference possibilities.

Nige.

[Frank Skilbeck]

Posted by gangster on 17/03/2015 22:42:18:

So my question is..Is there an issue of excessive voltage drop on that pathetic piece of wire from the bec to the RX?

I run telemetry on my systems, and when using the ESCs SBEC on reasonably high powered planes (500w to 1800w) on 3,4,6 and 8s systems with 5+ servos the Rx battery volts are remarkably stable, much more so than on other models using a battery. So I'd say the wire is not a big issue. Note on the Multiplex safety switches they rate the single wire safety switch at 6 amps, they do a 12amp version but that has two leads to plug into your Rx.

Mechanical switches are another matter though!

[Johan]

Hi, I have had several crashes since I got my new DX6 transmitter. Could not pinpoint exactly what caused it but finally worked it out and now no more crashes.

What happens is that the speed controller BEC voltage to the receiver drop too low and then the receiver reboots. This then appears as a signal loss to the pilot. If the plane is too low it cashes before the receiver has rebooted.

[Johan]

The solution is two-fold:

1. Buy a good speed controller with a BEC that can deliver at least 3 Amperes.

2. To replace all speed controllers that do not satisfy the above specification can be very costly. The following can then rather be done: Fit a 4700uF (10V) capacitor over a spare channel of the receiver (positive pin and negative pin). This will prevent the receiver from rebooting with voltage drop on the BEC to the receiver - thus no signal loss can occur either,

Since I have fitted all my receivers with this capacitor I have had no further crashes,

YOU MUST AT ALL COST PREVENT THE RECEIVER FROM REBOOTING

[Chris Bott - Moderator]

I'd suggest, Johan, that by using the capacitor you're covering up for a BEC that isn't adequate.

OK it's better than not having the capacitor, but if you are running the BEC right on the edge, then there's a chance it will fall over for longer than the capacitor can hold the volts up.

In the worst extreme, the BEC could overheat and shut down completely until it cools.

Of course then, it appears perfectly fine again and folk are often left blaming the radio.

[Dave Hopkin]

Posted by Johan on 28/04/2015 17:51:57:

The solution is two-fold:

1. Buy a good speed controller with a BEC that can deliver at least 3 Amperes.

2. To replace all speed controllers that do not satisfy the above specification can be very costly. The following can then rather be done: Fit a 4700uF (10V) capacitor over a spare channel of the receiver (positive pin and negative pin). This will prevent the receiver from rebooting with voltage drop on the BEC to the receiver - thus no signal loss can occur either,

Since I have fitted all my receivers with this capacitor I have had no further crashes,

YOU MUST AT ALL COST PREVENT THE RECEIVER FROM REBOOTING

Of course signal loss can reccur! fitting a capacitor across the power pins simply prevents rebooting in the event of a transcient voltage drops - it will have no effect on a prolonged voltage drop (that cap will have discharged and become ineffective) Nor will it protect you against TRUE signal loss, if the antenna are not collecting a signal no capacitor anywhere can do owt about it......

[gangster]

The other issue is how long is the reboot time. Does it vary? I recall watching a video on you tube which suggested up to 7 seconds with some receivers I have not done much experimenting but did have to have a little play.

on my bench was a model with a Spektrum AR 6210 DSMX receiver and 5 standard hitec 422 servos. I powered this from a variable bench supply. At 3.2 volts the servos were very slow but still responding to the TX . I was not interested in range here. On turning the supply down further and also switching it off altogether control was instantly restored as soon as the receiver got its power back. When I am bored one day I will try this with other spekky receivers as well as orange and Futaba fhss

[Chris Bott - Moderator]

We have a very long thread going back to 2008 about power supplies, Spektrum receivers and brownouts etc.

[Chris Bott - Moderator]

...and here's one of Tim's videos on the subject.

[Phil Green]

If you'll forgive me repeating myself yet again...

The idea of a capacitor as some sort of reservoir to supply servos during transient current demands is just unfeasible. Take for example the 4700uF capacitor popular wth Spektrum users.
How much energy will that store?

F = C/V, and V = 5 Volts, F = 0.0047 Farads, thus C = 0.0235 Coulombs = 0.0235 Amp*seconds = 0.00653 mAh

A 4700uF capacitor has a A/H capacity of point nough nought six of a milliamp-hour.

A perfect 4700uF capacitor would supply 3A for just 7.8 milliseconds. Thats discharging it down to zero volts, not the 3.5v (?) minimum we need, which from BEC voltage would be reached in 2 or 3 ms. Once discharged, it contributes nothing, in fact actually absorbs more current if the voltage recovers, which will very slightly extend the time the supply takes to get back to working voltage.

Extra decoupling is usually good thing & wont do any harm, but a small capacitor across the power rails is not a magic bullet, and will not 'take over from the BEC' if the voltage sags.
Smoke & mirrors, placebo... IMHO of course...

Cheers
Phil

[Paul Marsh]

I have a electric plane, a Radjet with a Orange Rx and electric set-up. When I was powering the servos - wiggling the sticks, the rx would shut down, restart until I did it again.

Put a Cap on and it seems ok, flown the model, but the first time I chucked it, went dead and couldn't control it. Found out it was that.

It's probably not the amount of power it stores, I think it prevents a fluctuation in voltage, which overloads the esc and thinks it overloads and the voltage drops. Much like a Power factor Correction Unit does in a switchgear panel - takes the load and averages out the power over given time, although not on three phases as the above.

[Tim Mackey]

Horizon hobby themselves do NOT advise using a cap on airborne systems - they do sell ( at stupid prices ) a capacitor for ground based vehicles.
However at the risk of boring regular forumites with the same old advice for the zillionth time....
USE A SUITABLE POWER SOURCE.
Spektrum are absolutely no worse for brownouts than any other 2.4G system - extensive testing has proved they operate perfectly well right down to around 3v !

[Paul Marsh]

On a few of the larger electric planes, I'm using a seperate Life battery, easy to do on Hitec Optima rx's as I'm using the SPC input, as well as the battery input.

Using the SPC connected to the Lipo pack will display the pack voltage in real-time on the Hitec telemetary system, and the Life pack into the input to power the servos.

Other tha that,I'm using a 8A Ubec and a 2s Lipo on a couple of others but most smaller stuff, such as Parkzone Bind n' fly esc's seem to be up to the job and the model is not taxing the servos/rx anyway.

[ben goodfellow 1]

shops now sitting on stock . and after being promsed one as soon ast hey came for the last 3 months ive still not got one ..awesome service.........