Futaba Receivers - any alternatives ?

[The Wright Stuff]

Amongst the confusion, I think we totally agree, Rich.

Moving on, obviously applying the logic of evaluating for oneself the likely comparative reliability of different receivers (or transmitters come to think of it) does require a certain amount of understanding. A range check is obviously a big part of that.

One thing I've never fully understood, is why some receivers have two aerials, but others (e.g. the R3106GF mentioned above) only have one, but still claim to be full range. Digital protocol shouldn't really be a factor - a 2.4 GHz carrier wave is a 2.4 GHz carrier wave, as far as the diffractive and transmission properties of the radiation are concerned. Any thoughts? The cheap Corona version has two aerials, as do the original Futaba S-SHSS versions...

[Biggles' Elder Brother - Moderator]

Guys can we cool down a little bit here please? It seems to me (as a spectator to this debate and someone who uses FrSky and their Rx are a good price so I can afford brand name!) that you are getting yourselves very hot under the collar over what often seems to be (on both sides) generalisations and misunderstandings.

I think we can all agree two things:

The law is primary and the law requires that you have a "reason to believe the flight can be completed safety". And that holds whatever the make or cost of the Rx - it's as true for a £10 clone as it is for a multi-hundred pount set up with £100 Rx's and loads of redundancy built in. If your experience is that the £10 Rx is fully reliable in your application then you are justified in your actions to fly the model. If you have doubt, you should not fly it, no matter how expensive and sophisticated it is.

But this is matter of personal judgement - which we have to remember that under some circumstances we may be called on to explain and defend. But that's easy with any receiver, whatever the cost, if you have had 200 sucessful flights with it and no recorded issues. But,...we also need to remember that simply spending more money is not an automatic indicator that you can have greater confidence - and I believe it could be dangerous to take such a view. Each Rx should be assessed in the context of its application and its passed performance - those are the only justifiable rational criteria. Note, when I say "context" I am not refering to how expensive the model is - instead I am referring to issues such as; is there any carbon fibre about that might impeded reception, how far away are you planning to fly this model, is there sufficient room for a high quality, robust, installation etc.

The second thing I believe we could agree on is that no system, no matter how sophisticated and expensive (or low cost and simple) is 100% "safe". We use the word "safe" in everyday language as a sort of shorthand I believe. When we aeromodellers say "this is safe" what we really mean is something like "I have taken all reasonable precautions to ensure this system is as safe as I can reasonably make it. I have selected suitable components, I have installed them carefully, tested them and my data on previous use tells me they are reliable". But that's a bit of a gob full isn't it! So we just say "its safe" for short - but we know all that other qualifying stuff too and respect it. Or at least we should do!

So, let's chill on this. The fact is different folks have slightly different views, experiences and contexts. All you can say really is "This is what I do and I'm happy with it" - the problems come when we change that slightly to "This is what I do and if you don't do the same you're wrong"! Because responsibility is an invidual thing - its not up to any of us to dictate the other guy's position - as long as he is happy he can defend it that should be enough for us!

Let's all be friends then, and respect each others position. Here endeth the sermon!

BEB

Edited By Biggles' Elder Brother - Moderator on 05/10/2018 10:18:41

[The Wright Stuff]

the problems come when we change that slightly to "This is what I do and if you don't do the same you're wrong"!

Let's all be friends then, and respect each others position.

At the risk of sounding slightly flippant, BEB, what if the other's position is "This is what I do and if you don't do the same you're wrong"? Do we respect it or not?

Catch 22...

[Biggles' Elder Brother - Moderator]

Well, personally, I just listen to their viewof course (never too proud to listen to someone elses experience) but if I don't agree I just shrug my shoulders, walk away and do my own thing. No one can tell me what equipment to use in my model - as I say it's my responsibility not theirs. If they pressure me to adopt their way and it fails - are they are going to take the consequences? No, the buck stops with me, I'm the pilot in charge - so, if I have the buck I get to make the decison too!

But you know looking at this from the outside of the debate I don't think any of you guys are doing that - I think you all basically agree but frankly are splitting hairs on exact definitions of technical terms compared to everyday colloquial usage. So it's a academic really.

BEB

[Nigel R]

"Any thoughts?"

Does this RX have an internal stub aerial?

e.g. the AR400/AR610 have one short stub and a long trailing aerial.

The soon to be released AR620 has two (I believe) internal stubs.

 

Edited By Nigel R on 05/10/2018 11:55:14

[Peter Christy]

Posted by The Wright Stuff on 05/10/2018 10:06:59:

Amongst the confusion, I think we totally agree, Rich.

Moving on, obviously applying the logic of evaluating for oneself the likely comparative reliability of different receivers (or transmitters come to think of it) does require a certain amount of understanding. A range check is obviously a big part of that.

One thing I've never fully understood, is why some receivers have two aerials, but others (e.g. the R3106GF mentioned above) only have one, but still claim to be full range. Digital protocol shouldn't really be a factor - a 2.4 GHz carrier wave is a 2.4 GHz carrier wave, as far as the diffractive and transmission properties of the radiation are concerned. Any thoughts? The cheap Corona version has two aerials, as do the original Futaba S-SHSS versions...

As you go up the frequency range, the aerials become smaller and are more likely to be the correct resonant length. A half-wave aerial on 35 MHz would be around 5 meters long! Not very practical, so we made them shorter and tuned them electronically, with a consequential loss of efficiency!

However, the aerials we use at 2.4 GHz are much more sensitive to orientation. In addition to the "dead spot" off the tip of the Tx aerial, there is also a "weak spot" when the Tx and Rx aerials are at 90 degrees to each other. Having two aerials at 90 degrees minimises this effect, as at least one should be partly broadside on to the the Tx at all times..

In days of yore, we always used to recommend having a 90 degree bend in a 27 or 35 MHz receiver aerial, for the same reason. Most of the "old hands" traditionally ran the aerial out to the tip of the tailplane, then up to the top of the fin for this very reason, although in view of the much longer wavelength, these systems were generally less susceptible to this effect.

On 459MHz, it is quite pronounced, and it is really only the superior noise immunity of a spread spectrum signal that allows us to get away with 2.4 GHz operations.

For short range operations, a single aerial on 2.4 GHz is probably fine, but I, personally, would be wary of using such a receiver in a model of any size and at any distance. But that's just me being cautious!

--

Pete

[Rich too]

I don't think we are splitting hairs, the OP was asking about an alternative RX because Futaba are pricey - the whole point of the thread was the cost. I merely pointed out that with larger models the overall investment can be much higher so I tend to stick with Futaba.

John's logic suggests to me that the LMA's advice to use two RX's in 20kg models should be used in smaller models because obviously we don't trust one RX!!

And BEB, your comment about no equipment being 100% reliable - that's exactly right!! Thank you!

 

Edited By Rich too on 05/10/2018 12:24:44

[PatMc]

Posted by Rich too on 05/10/2018 06:37:31:

The LMA recommend specific RC layout/systems for larger aircraft, why doesn't that apply to smaller aircraft?

Because it has no more weight than an opinion of one organisation.

[Rich too]

I'm done with the thread!

[The Wright Stuff]

Rich, I understood your point, I understood the implications of your analogy, and I 100% agree.

[john stones 1 - Moderator]

Still going then

Nowhere have I said anything is 100%, I did say safe, you can nitpick over that if you like

I would put my cheap Frsky rx's in any model I own, would even use two, if I flew models where it was needed.

I have NOT said anyone's wrong to use cheaper rx's in any model, quite the opposite.

I question why you use rx's you consider safe (there's that word again) in one model but consider not fit for the next model, purely because that model cost more ? It makes no sense.

When you post such comments it implies you don't really trust these rx's, and as a consequence others may get the opinion there's something wrong, also I may take offence because I feel yer having a pop at my gear.

So to answer the O.P. Yes there are alternatives, I use Frsky myself, I am 100% as confident in these, as I was when using my £100 pukka JR rx's. You get what you pay for ? sometimes is misleading, because it cost less don't always mean it is less reliable.

I'm calm BEB, and apologies for annoying you lads.

[Paul Marsh]

I see it, the model is only worth at it's weakest link, so if you put a 50p switch you've bought from a swap meet, then the model is worth 50p, and if you suspect that switch, you should not use it anyway.

As for receivers, I see the receiver as another weak link - I have some FASST orange receivers (keeping with the subject of Futaba receivers), which it works on, but although these have been totally solid, would I put them in a 50cc aerobat? no.

It's not about being "safe", it's fit for purpose, even a genuine Futaba receiver may be not fit for purpose, for example you put a Futaba 617 FASST receiver into a 400cc large model (say Paul Carr's 400cc models), with the servos using the bus on the receiver, and the servos burning the board out, as there should've been a Powerbox system, feeding power to the servos. Although the receiver is more than capable of receiving the signals and transmitting it to the servos, the installation wasn't suitable for flight...

I would put a Frysky/Orange FASST rx in this:

but not in this (A Futaba 617 rx in this-which is has)...

[john stones 1 - Moderator]

Modern science, much debate and almost all evidence, points to the object holding the tx as the weakest link.

[The Wright Stuff]

Posted by john stones 1 on 05/10/2018 14:01:35:

Nowhere have I said anything is 100%, I did say safe, you can nitpick over that if you like

I question why you use rx's you consider safe (there's that word again) in one model but consider not fit for the next model, purely because that model cost more ? It makes no sense.

John, I think we have to nitpick over the word 'safe' in order to resolve this apparent misunderstanding.

Let me calmly try to put across my point of view one last time. I am a very numerical person, I'm afraid. Numbers mean far more to me than words, so bear with me.

It all hinges on what we define to be 'reasonably confident that a successful flight can be made'. There is a difference between 'safe' and 'probability of a failure', and the magnitude of that difference depends upon the model. Not purely the cost, but the cost is a reasonable indicator of size, required range, and the value to the owner.

Let's say (just for sake of argument) that the probability of a successful flight using genuine Futaba part is 99.99% that is, we expect one crash due to receiver malfunction per 10,000 flights.

Let's just say also (for example) that the Corona receiver is twice as unreliable as the Futaba one. That is one crash due to receiver malfunction per 5,000 flights.

The question is, is this 'safe' enough to commit to the flight?

I would strongly argue (indeed have been arguing) that it is a function of the model.

For a £30 foamie from Hobbyking that weighs 300 g. I would say, yes, the Corona receiver is sufficiently safe.

For a £10,000 turbine quarter scale jet, over 30 kg, is it still considered sufficiently safe. Well, that's down to personal interpretation, but not necessarily. The 'safety' aspect is not just probability of a failure, it is also multiplied by the consequences of such a failure.

I am just illustrating the point, so please don't quibble over exact numbers.

[Paul Marsh]

So for the £10k jet, using a non-Futaba rx will be ok on the first 4999 flights, and fail on the 5000th flight. Don't fly the model on the 5000th flight!!!

oh, oh, numbers...

[The Wright Stuff]

Paul, by the same principle, it's extremely unwise to declare 'just one more flight' at the field. Always go for 'a couple more' but then pack up after one more...

[john stones 1 - Moderator]

There is no resolving this misunderstanding.

Now you've brought another red herring into it, 30kg turbine, I would have NO problem fitting the appropriate Frsky rx to one, would have major problems affording one.

You are not going to twist my words by bringing complexity of model into it, the second it's stated " i use X brand of rx, but wouldn't use one in my good stuff" you've implied you lack trust in them, any lawyer would rip you a new one in a court of law, should you state that after an incident.

This time I am done, over to you.

[The Wright Stuff]

I lack trust in all receivers, John, as do you, having previously stated that you agree that nothing is 100% reliable.

We're both aeromodellers, and I'm sure that there are many aspects of model flying upon which we would agree.

It seems this isn't one of them!

[Biggles' Elder Brother - Moderator]

This is becoming circular and incredibly tedious.
You're getting no where, basically you have the same position but can't (or won't) see it

Time to draw a line under this.

BEB