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[TimCo]

A rather poor video ( https://www.youtube.com/watch?v=UP7CVkgybyA ),  but an attempt to illustrate the susceptibility of a RadioLink T4EU Tx and R7EH Rx to interference from a Fly Sky FS-T4B / FS-R6B system by way of the following steps:
1. Servos on the RadioLink system glitching when both RadioLink and Fly Sky Transmitters are operating.
2. Fly Sky Tx turned off. Servos fall silent.
3. RadioLink joysticks operated: servos move as expected.
4. Fly Sky Tx turned on again. RadioLink joysticks operated: servos move in jerks.

In the video, the transmitters are very close. I have retested outdoors. The same thing happens when the two transmitters are 1m, 5m, or 10m apart and the receiver up to 50m away. With an ESC the interference is dramatic: the motor speed fluctuates wildly, then the motor stops and must be restarted by zeroing the stick.

The Fly Sky system has performed reliably for me for the last six months, as well as throughout this test. The RadioLink system, with two Rx's which both perform (or fail) in the same way, is a recent purchase intended to allow two of my 2.4GHz models to operate at the same time. Clearly, it fails in this. Perhaps I have received a faulty set. I write this as a warning to other owners of these low-price  (or other) systems and to ask whether anyone else has seen the same problem.

[barriew]

Have you tested against any other make of 2.4Ghz? I use my Radiolink without problems surrounded by Planet 5 and Spektrum sets.

Barrie

[Netleyned]

My grandson uses a Radiolink stood right next to me with a Spektrum DX6i and within 5 metres there are usually
two or three Planets, a Futaba, a couple of Radiolinks and at least one Flysky and no-one has any problems.
Is there anyone at the sailing area with a Radiolink experiencing the same problems when you switch on?

Ned

[dodgy geezer]

Perhaps I have received a faulty set. I write this as a warning to other owners of these low-price  (or other) systems and to ask whether anyone else has seen the same problem.

With all cheap chinese I would always suggest checking them over before using. I can well imagine a poor aerial connection getting through what passes for 'quality check' on any system...

How did you discover this? I note that in your video the Radiolink T4U Tx aerial seems to be pointing to the top right of the screen, while the Rx aerial is pointing towards bottom left - precisely the worst direction for a good connection. And your FlySky Tx seems to have its aerial almost touching the Radiolink Rx aerial - in the best position to cause interference. Is there a computer Wi-Fi transmitter close by as well?  The illustration would be a much better one if it were filmed outdoors with the Txs a couple of yards apart and the Rx about 20 yds away (which I note you say causes similar interference).

I have certainly found that an ESC can suffer badly from wire-born interference from a motor, which is nothing to do with the radio connection. Did you have inductors in the power line when you tested the ESC?

I suggest that you make either Phil_G on the Giant Cod forum (or, of course, any of the Giant Cod team) aware of this concern. They ship both FlySky and Radiolink, and would be in an ideal position to do a simple test, and then tell you if you have a dodgy unit or not....

[TimCo]

Thanks for these responses. To answer some of the questions, roughly in order:

1. I have not tested against any other 2.4GHz yet, but Giant Cod say they will do this. I would be amazed if I was the only person who had received two sets that interfered so obviously. I did, however do a  range-check, albeit in a residential area, with only one R/C system running at a time. With the transmitter in my back garden, I walked out of the driveway with a small model boat, with ESC/motor running at "idle", and continued along the road until the motor stopped and the ESC bleeped to indicate loss of signal. With the Fly Sky, this was achieved without glitch or spurious motor response. The RadioLink, installed identically, gave a similar ultimate range, but for the last 20% of this, the servos glitched wildly and the motor revved and stopped, indicating susceptibility to some other source of interference, perhaps a neighbour's WiFi.

2. I have not yet met any other RadioLink owners.

3. I discovered this interference issue within 1 hour of receipt of the RadioLink Gear! I probably should have bought a second Fly Sky Tx/Rx but chose the RadioLink only so as to have two different-looking Tx's to avoid confusion. While checking for the unlikely bonus that one brand might bind with the other (they won't), I noticed the RadioLink performing erratically....

4. The "rather poor" video was only submitted to illustrate the frequency of glitches. Testing-wise, it is the tip of the iceberg, because I was motivated to find some way that these two sets could be operated together: after many permutations of Tx-Tx and Tx-Rx distances, up to 50m, so far, my conclusion is that they can't.

5. When the Fly Sky is seen to cause the RadioLink to glitch, pressing its "range-check" button, to reduce its RF power, makes no difference to the glitching.

6. The ESC/motor combinations (one brushed, one brushless) that I have tried have previously been shown to work fine with 27MHz, 35MHz FM (not for boats, I know) and 2.4GHz radio sets, until combined with the RadioLink, and then only under 2.4GHz interference conditions.

7. I made Giant Cod, who sold me the RadioLink, aware of my problem on the day of receipt (13 March 2012). Unfortunately, although they have RadioLink T4EU and R7EH in stock, they do not have any Fly Sky FS-T4B with which to reproduce my exact conditions. I hope we will be able to arrive at a good solution that I can tell to the forum.

[Netleyned]

If it were mine I would be looking for a dry joint where the aerial lead is connected to the pcb.

Ned

[dodgy geezer]

Thanks for these responses. To answer some of the questions, roughly in order:

1. I have not tested against any other 2.4GHz yet, but Giant Cod say they will do this. I would be amazed if I was the only person who had received two sets that interfered so obviously. I did, however do a  range-check, albeit in a residential area, with only one R/C system running at a time. With the transmitter in my back garden, I walked out of the driveway with a small model boat, with ESC/motor running at "idle", and continued along the road until the motor stopped and the ESC bleeped to indicate loss of signal. With the Fly Sky, this was achieved without glitch or spurious motor response. The RadioLink, installed identically, gave a similar ultimate range, but for the last 20% of this, the servos glitched wildly and the motor revved and stopped, indicating susceptibility to some other source of interference, perhaps a neighbour's WiFi.

Now that's interesting. My comments on rangechecking a T4U are here: http://www.modelboatmayhem.co.uk/forum/index.php?topic=35862.0

In my case I was walking across fields to retain a direct line-of-sight. The T4U maintained a reliable glitch-free ground link up to about 2200ft, actually well past a line-of-sight. That's quite a distance - how far did you have to walk down the road?

My test protocol was to walk for a few hundred feet with the system off - then sit down, turn the system on and call the remote radio operator on a walkie-talkie to operate the sticks. That meant that I didn't cover a point where control was lost - I just had one point where control was fine, and then another a few hundred feet further on where there was no control. But I got no glitching at all over the last 20% of the range...

Of course, this was in a field where spurious radiation was likely to be low. I wanted no other sources, as I was testing against motor interference and comparing with a 27Mhz set.

I will separately see if I can test the T4U with any other interfering 2.4Ghz radiation. Your report is obviously a matter of concern. But at the moment I would not rule out the possibility of a dodgy T4U set. Or poor Tx/Rx batteries? Or some odd local interference...

[Netleyned]

If it were mine I would be looking for a dry joint where the aerial lead is connected to the pcb.

Ned

On the receiver I mean

Ned

[TheLongBuild]

Interesting This, At the Ellesmere port show my boat started to go into reverse/forward, I'm was Using a Radio Link, there was no one within 15 ft of me..


Back at our pond I have had no repeat of the problem. ?.

[dodgy geezer]

and were you close to a lot of other txs?

[TimCo]

Thank you for these comments.

The range check was actually done in response to a comment made by Giant Cod: that I might have received a faulty Tx that was down on power, or that the Fly Sky was putting out more than the allowed 100mW. I therefore did a comparative range check that, although it couldn't definitely prove either of these cases, one might at least infer that something was wrong if the ranges were dramatically different. As it happened, both systems managed only around 80-100m, because, by this point, there were 2 or 3 houses in-between. The surprising result was the glitching of the RadioLink gear that was completely absent from the Fly Sky's test, and the nature of the glitching, which was just as in the indoor video, but now not caused by the Fly Sky Tx.

I am not suspecting poor soldering at the moment, (a) because I received two R7EH Rx's and they both behave the same way, and (b) because of the similar range results, above.

[Netleyned]

First time two
rxs mentioned
Changes things a bit

Ned

[dodgy geezer]

As it happened, both systems managed only around 80-100m, because, by this point, there were 2 or 3 houses in-between. The surprising result was the glitching of the RadioLink gear that was completely absent from the Fly Sky's test, and the nature of the glitching, which was just as in the indoor video, but now not caused by the Fly Sky Tx.

I've just set up a simple range check system similar to yours. Photo of the kit I used is below. Batteries are new.



I took it up and down my street, and then checked the range against Googlemaps, while the Tx sat vertical on a front windowsill. The street is a fairly straight one, but the houses are set forwards and back, so you soon have at least one house in the way.

One way was across a railway line with electric overhead lines, via an enclosed metal gantry bridge. I got to 475ft (which was beyond the railway line) before the motor died. There was no servo glitch. I turned around, so that my body was not shielding the aerial, and got a signal back. Walking backwards, I could then go out to 560ft before the motor died. At this point I could not regain a signal, and had to walk back to about  520ft before getting it back. I found that I could make the signal die and return by shielding the aerial with my body, or pointing the Rx aerial directly away from theTx. Again, there were no servo glitches.

I then walked the other way down the street - this was a fairly straight open road, though not line-of-sight because of the houses (most of which were probably putting out Wi-Fi). Here I could go to 700ft before the motor died, with my body in the way. Walking backwards, I managed 850ft. At this point the motor was running, then stopping, then running again, depending on where my hands were. I found that if I held the Rx set as far away from my body as possible, I could get a good signal. Again, at no point did the servo glitch.

So, what can we say? It looks as if big masses of metal in the way cut the range by about a third. It looks as if having a human body in the way of a Rx can cut the range by about a fifth. At the limits of range, swinging the aerial or moving within about 6 ft of the Rx can have an effect. Perhaps putting a human body BEHIND a Rx might increase signal range?

Do you think you might have been shielding the Rx aerial with your body? That might make the system look as if it were glitching. However, the servo shouldn't have moved. Did you use the same servo and esc for the FlySky test? It's possible that it's the servo or esc that's faulty.Your range seems a bit low, but that might be street furniture and houses in the way.  

[TheLongBuild]

and were you close to a lot of other txs?

No, only about 2/3 were in use and I think 1 of them was a 40, we have more than that at the pond and no issues..

[dodgy geezer]

No, only about 2/3 were in use and I think 1 of them was a 40, we have more than that at the pond and no issues..

I don't think it's interference - at least not directly. I think there's something below spec somewhere in that system. But it needs to be isolated and repeatable before sorting it out...

[TimCo]

Thanks, dodgy geezer, for the range-test details. I am reasonably aware of these influences on microwave range, so was only interested in the comparative ranges of the two systems, when tested with the same orientation, height, route, etc., and the glitch behaviour, after the Giant Cod suggestion, above.

I complained to Giant Cod, UK vendors of RadioLink, on the day of receipt (13 March 2012), ending with the query, "Could you look into interference between Fly Sky and RadioLink gear? Do you think mine might have a fault, or is there a mistake in the design?", and have copied them with my subsequent tests, as described in the above posts.

Guess what? Today they have replied with the suggestion that I return the Tx and two Rx's to them so that they can have them tested because the Tx might be low on output: if deemed not faulty, I have to pay 30% of the original purchase price for the testing, plus postage!

Outrageous! Their only hope should be that my Tx IS faulty. If it isn't, we should consider that the RadioLink design of FHSS system is not fit for purpose.

[davem99]

Hi Timco
Having read your posts it seem fairly obvious to me that your Radio Link equipment is faulty. Your range check with just the Radio Link on gave you interference before the signal was lost indicating a system malfunction. I also note that you attempted to bind your receiver(s) to the other system, I hope you rebound to the correct system with the other transmitter switched off. I agree Giant Cod should not expect you to pay for any testing, postage well maybe but not really good customer relationship building. Hope you get to the source of the problem.
Dave 

[dodgy geezer]

Guess what? Today they have replied with the suggestion that I return the Tx and two Rx's to them so that they can have them tested because the Tx might be low on output: if deemed not faulty, I have to pay 30% of the original purchase price for the testing, plus postage!

Outrageous! Their only hope should be that my Tx IS faulty. If it isn't, we should consider that the RadioLink design of FHSS system is not fit for purpose.

Umm... given that other people haven't reported this problem, I can't see that the RadioLink design has been shown to be faulty at this point...

And Giant Cod do provide quite a lot of warnings about their approach to customer service. They claim (and I paraphrase) that they expect to be fair, but that they have cut prices to the bone, and have no budget for general customer support over and above their legal obligations. So if a product is faulty they will of course replace it for free, but if they think that the problem is a customer error they will not - though many other companies (who charge higher prices) will do this to maintain goodwill.  They use an independent test centre to determine technical issues, who (I believe) are paid by Giant Cod if the fault is theirs, and by the customer if it is not.

That was why I suggested that you try to confirm that the problem is indeed in the RadioLink Tx/Rx, and is reliable and repeatable and well-described before sending it back, rather than a battery problem or an issue with the servo or esc. I have heard of glitchy servos or connectors causing all sorts of obscure problems on other occasions .....     

[TimCo]

With all the above considered, I have done three further tests today:

1. A comparative range-check, as before but in a flat, rural location. No houses for at least half a mile. One RC system at a time. With the transmitter on the ground, and walking away with the model. Tx and Rx antennas vertical. The Fly Sky system gave 300m before the ESC bleeped "no signal", and the servos did not glitch. The RadioLink achieved around 350m, but the last 50 were accompanied by glitching and erratic ESC.

2. Range checks as above, but when the Fly Sky system was tested, the RadioLink Tx was switched on, and carried along in my other hand, i.e. 0.5m from the model, and vice versa for the RadioLink system. Result for the Fly Sky was exactly the same: at 300m, no glitches, ESC started to bleep. For the RadioLink, as expected, the servos glitched from zero distance and worsened as  both model and Fly Sky tx were moved away. The ESC became erratic at 10m and stopped the motor, and the test abandoned at 50m.

3. Back indoors, a bluetooth-equipped phone was set to "search for new devices", near to the model, with the Tx at a 5m distance. With the Fly Sky system it was impossible to disturb servos or ESC this way, even with the phone touching the Rx antenna. With the RadioLink, the servos and ESC were affected as per my original video, when the phone was searching, but the phone had to be within 300mm of the Rx.

I would also like to reiterate that the troublesome system comprises RadioLink T4EU Tx and R7EH Rx. I believe the majority of sets sold are with a different, 6-channel, Rx.

[dodgy geezer]

I think that the other receiver - the R6EH - only varies in the direction of the socket (straight out of the end rather than upwards). Both receivers have the same number of output pins - 6, and an extra one marked 7/B. So I suspect that they have the same electronics.

I have just tried doing some wi-fi file transfers next to an operating Radiolink with an R6EH.  Even touching the antennae together there was no glitching.

I presume that you were using the same esc and servo for both tests? And have you swapped batteries between the Txs to eliminate them as a problem? If so, I think you have a pretty clear problem with the Radiolink, probably the Tx. Can anyone else think of any other check that needs to be done?

[barriew]

Obviously the best test would be with another Radolink Tx to confirm the strong suspicion of a faulty Tx. I assume TimCo doesn't know anyone with such a Tx. If we knew his location maybe there is another Mayhemer near who could help.

Barrie

[dodgy geezer]

Yes, that would be ideal - but probably only possible if Timco is somewhere convenient....

[TimCo]

Sunny Stoke-on-Trent!

I have another test to report: on a very brief check, today, a Spektrum DX6i did not interfere with my RadioLink system.

[dodgy geezer]

No mayhem members near Stoke-on-Trent able to help Timco yet?

It's a bit odd about the Spectrum.  Where is the nearest R/C club - flying or boats? I would guess that turning up there on a club night would get you some Radiolinks to compare directly with yours...

[davem99]

Hi TimCo
I'm pretty sure we have some members with Radio Link Tx's at Crewe Model Boat Club. I will check next Sunday and let you know. As you are in Stoke the Potteries MBC is probably nearest and I suspect they may also have some users - they sail at Westport lake on Wednesday pm and Sunday mornings but check their web site as I may have the wrong times.