Topic: Is 2.4 all its cracked up to be (again)

I only posted this question to get your reactions to this site I recived in an email this morning.

It has  made me stop and consider my actions as I have committed myself to do a complete change to jeti 2.4 in the new year.

I know this has been disscused ad nauseim but this is on a eshop front page, I would like to hear the reactions of knowledgeable forunites as I am not a techie and the reference material quoted is over my head in places

http://www.pyramidmodels.com/shop/article.php/20/2_4ghz_maybe_not_as_good_as_it_is_cracked_up_to_be_by_dave_horvath


Regards

Who ever claimed that 2.4Ghz was 100% reliable 

My personal experiance tells me that while not perfect it does have advantages over 35mhz however it relies on better installations in the model and use of adequate power supplies 

Who ever claimed that 2.4Ghz was 100% reliable 

My personal experiance tells me that while not perfect it does have advantages over 35mhz however it relies on better installations in the model and use of adequate power supplies 

While he is right in some respects, things like latency he has completely misunderstood. It's nothing to do with the time of flight of the signal, it's the time to go from the sticks, be interpreted by the tx CPU, be formed into radio packets, transmitted, decoded, error checked and finally reformed into a pulse to drive the servos that matters. And there's a lot of room for software improvements in transmitters and receivers to improve the overall latency.

Yes it would be nicer to have a clear dedicated bit of spectrum but it isn't going to happen. Radio spectrum is very expensive due to rarity, especially if you try to get the same bit all over the world.

Terrific info - I now know how to pronounce "fresnel" 

I mostly agree with the article, but it contains nothing new, there are no revelations there. Fresnel zones have been explained here and on GC, as has diversity (which he doesnt even mention) and the effect of packet collisions on latency.  He's slightly oversimplified the effects on range - in fact the problems listed impact 'effective range' where the number of packets received successfully will drop such that latency hits the 'failsafe' boundary. This happens well above zero packets so strictly we're still 'in range'.
I agree with his perception of latency - few can feel the 20ms difference
between a 50fps ppm driven module and a native driven module*, but Yoyo is right, processing overhead does vary between mfrs in both the tx and the rx.
It seems that the only people who think 2.4 is 'solid', 'interference free' or 'immune to EMI' are either people with little or no RF knowledge, or 2.4g equipment manufacturers 
Cheers
Phil

* although 3D heli pilots might 

It seems that the only people who think 2.4 is 'solid', 'interference free' or 'immune to EMI' are either people with little or no RF knowledge, or 2.4g equipment manufacturers 
Cheers
Phil

* although 3D heli pilots might 

I think that in the same way camera gear is sold on how many megapixels a digital camera can render, and it implied it's the be all and end all (and Joe and Josephine public accept it as fact-when it's anything but); the 2.4 Ghz was marketed in exactly the same way; imply, and don't correct misinformation put out that suggested it's use would mean never having another problem caused by interference. I don't know (which is why I'm asking) but how many 2.4 radio sets are sold that give clear and comprehensive guidance on how and how not to install rx, when engines, carbon fibre, metal plates etc are installed in the airframe?

Or are people just expected to muddle along and learn by hit and miss experience? Granted it would likely involve the destruction of several models before realising that A shouldn't have been placed near B, and C should be tilted at X angle...

Well the real test is out on the field and since day 1 my system has worked flawlessley, much the same as 35MHz Futaba system did before it.

J

Well the real test is out on the field and since day 1 my system has worked flawlessley, much the same as 35MHz Futaba system did before it.

J

exactly- so the one and only advantage of 2.4 is the fact you dont need a peg? And the one and only disadvantage of 35 is that you have to have a pegboard discipline? Anyone get the feeling of being manipulated? 

Well the real test is out on the field and since day 1 my system has worked flawlessley, much the same as 35MHz Futaba system did before it.

J

Agreed. Both have worked well for me. I still favour 2.4 Ghz as I did notice an improved feel from what can only be described as a more precise input using exactly the same models that were on 35mhz previously. I have also had zero glitches with my electric models which is not something I can claim on 35mhz. I also feel safer flying my larger models knowing that I can't be shot down by a fellow modellers mistake of switching on while I'm flying.

I do however know that I can still loose any model to some form of radio failure but if your not prepared to loose it then don't fly it.

Anyone get the feeling of being manipulated? 

Not really, with 2.4 we have had

Improved resolutions
Reduced response times
Model match
Can't get shot down by someone elses mistake
A system that is happier working in electric and petrol models
Telemetry - Not tried it myself
Shorter aerials, very helpful on small models

Anything else?

Not really, with 2.4 we have had

Improved resolutions
Reduced response times
Model match
Can't get shot down by someone elses mistake
A system that is happier working in electric and petrol models
Telemetry - Not tried it myself
Shorter aerials, very helpful on small models

Anything else?

Hmm- improved resolutions? Not noticed that.
Reduced response times? Gimme a break, most of the time I am a few seconds behind the model anyway!
Model Match? My 35 Tx has the model names on- not senile yet thanks.
I have never been shot down in 25 years, not shot down anyone else, either.
How do you know its happy? As for telemetry, why?
Only thing I notice about aerials is that my Tx now seems unbalanced.
Anything else?
I know we are going swiftly down the 2.4 route, and it may be a 'Good Thing' TM, but I still feel that there must be a great advantage to the manufacturers, or am I being cynical? (again)

Anyone get the feeling of being manipulated? 

Not really -
1. I no longer have to worry about being shot down by fequency clashes (once nearly shot myself down  )
2. I switched to 2.4 after losing a nice little model - which had constantly glitched on 35 - to a BIG glitch. Other small 35 models which have been changed to 2.4 have become glitch free (TBF - l only had the glitches with small electrics)
3. Model match - once almost gave up R/C and returned to F/F and C/L after letting a model go with the wrong memory selected on the Tx - only by luck did I not cause harm or injury - OK operator plonker-up, but it's good to get a greater level of idiot-proofness
4. No more hanging around whilst a glider flier breaks the two hour mark on the same frequency as myself

Mike

Hmm- improved resolutions? Not noticed that.
Reduced response times? Gimme a break, most of the time I am a few seconds behind the model anyway!

Definately noticed it here but I would guess its very dependent on the type of model you fly. I fly models with huge surfaces yet I still want to do precision aerobatics. I was really shocked when I changed from my 9 Zap to my DSX 9, the difference was quite noticable on all my models. The heli flyers in my club also seemed to notice the improvement.

How do you know its happy?

I have yet to witness a 2.4 electric or petrol model glitch like I have had myself on 35mhz. They are just more robust against that type of interferance  Just not all types though 

Not really -

4. No more hanging around whilst a glider flier breaks the two hour mark on the same frequency as myself

Mike

At last- a good reason! 

Not really, with 2.4 we have had

Improved resolutions
Reduced response times
Model match
Can't get shot down by someone elses mistake
A system that is happier working in electric and petrol models
Telemetry - Not tried it myself
Shorter aerials, very helpful on small models

Anything else?

All of the above plus:
Nobody hogging "my frequency", fly virtually when I want.
Don't have to buy expensive & fragile crystals
Receiver installation is simplified because you don't have to make provision to change crystals
Less damage/disruption to model wiring through having to change crystals
Not having to have multiple crystals to suit different makes of receiver (Maybe I have a thing about crystals!  )
Not having a model smash into my legs due to a shoot down through someone elses stupidity.....
Not shooting down another model through my own stupidity.... 
More lower cost receivers with built in fail safe
Eflite/Parkzone BNF indoor/parkfly models! 

Any more for any more?

2.4 Is great, if in doubt try flying a decent size electric heli on 35.  Then trust me you'll know just what a glitch means.  But just like 35Mhz its still possible to mess up an installation, and have equipment failures. 

2.4 perfect, NO.
2.4 bullet proof, NO
2.4 an improvement on 35Mhz ABSOLUTELY

Cheers
Ian

exactly- so the one and only advantage of 2.4 is the fact you dont need a peg? And the one and only disadvantage of 35 is that you have to have a pegboard discipline? Anyone get the feeling of being manipulated? 

I suspect that matters more to us free-range gliderists than to people who like to cluster round old caravans and drink tea in small groups while flying occasionally for a few minutes.

When another pilot could be anywhere at all, not having to have channel agreements in place with all the locals and fingers crossed about visitors is a great boon.

exactly- so the one and only advantage of 2.4 is the fact you dont need a peg?

Oh dear Bob, stop being a caveman...... in most places I have flown a peg is still needed anyway.

And the one and only disadvantage of 35 is that you have to have a pegboard discipline?

No matter how you argue this, you can take utmost care and it makes not one jot of difference, it's the prat that switches on that causes the problem.
Further to that, the radio link is more secure, Tx batteries last a lot longer, no chrome wire stuck out the front to prod people in the eye with and the list goes on.

Anyone get the feeling of being manipulated? 

Nope, just some people getting left behind that try to preach to the converted 

J

So really, gl*d*rists and electric heli flyers = 2.4 is great. To power flyers who take a bit of care with frequency control, there are very few advantages. By the way, I cant understand anyone changing crystals- once a model is set up, thats it for me!
John- how long will it be before that little piece of excess baggage is done away with? Look, 2.4 is good, no doubt. Holy Grail? Nope. Talk about deja vue, this reminds me of the 35 vs 27meg arguments 25 years ago, and I never had a glitch on 27!  Pretty new to 2.4, I still feel safer with my Futaba 35meg PCM gear. I will get more confident in it, but not JUST yet....

So really, gl*d*rists and electric heli flyers = 2.4 is great. To power flyers who take a bit of care with frequency control, there are very few advantages. By the way, I cant understand anyone changing crystals- once a model is set up, thats it for me!
John- how long will it be before that little piece of excess baggage is done away with? Look, 2.4 is good, no doubt. Holy Grail? Nope. Talk about deja vue, this reminds me of the 35 vs 27meg arguments 25 years ago, and I never had a glitch on 27!  Pretty new to 2.4, I still feel safer with my Futaba 35meg PCM gear. I will get more confident in it, but not JUST yet....

There's only two things I don't like about 35mhz:

- relying on other peoples frequency discipline

- fishpoo aerials

Oh dear Bob, stop being a caveman......

Cavemanist ridicule is shortly to become a criminal matter under new discromination legislation - careful!

Further to that, the radio link is more secure, Tx batteries last a lot longer, no chrome wire stuck out the front to prod people in the eye with and the list goes on.

I wouldn't argue with any of that *except*  the bit about it being a more secure radio link. It *could* be, if a proper bi-directional link was used, but in most cases (once bound) the link itself is essentially the same as a 35MHz PCM link.

PDR

I still feel safer with my Futaba 35meg PCM gear.

That might be misplaced confidence Bob. PCM is the worst offender for sweeping problems under the carpet.  A commonly used phrase is "It works right up to the point where it doesnt".  At least with plain old PPM (AM or FM) you get to know when the receiver is struggling, at which point you can make an attempt to save it -  either by bringing it in quickly, or raising the tx above your head etc.  PCM gives you no clues until it fails.

...more secure radio link. It *could* be, if a proper bi-directional link was used,

Wot, like XPS?

Cheers
Phil

There's only two things I don't like about 35mhz:

- relying on other peoples frequency discipline

- fishpoo aerials

as I said, I have never been shot down in 25 years.
And has there not been a whole thread on the right (and wrong) way to point a 2.4 aerial?

Phil- that was the same argument I used to use before I went on to PCM....

sent from my cave with a stone hammer and flint chisel..

John- how long will it be before that little piece of excess baggage is done away with? Look, 2.4 is good, no doubt. Holy Grail? Nope. Talk about deja vue, this reminds me of the 35 vs 27meg arguments 25 years ago, and I never had a glitch on 27!  Pretty new to 2.4, I still feel safer with my Futaba 35meg PCM gear. I will get more confident in it, but not JUST yet....

No rush Bob, take your time, just don't be quite so quick to knock it 

J

I have a DSX9 (Spekkie DSM2) and a PCM9XII (35MHz, mostly PCM), basically the same radio except for the RF section. It is possible to transfer model settings from one to the other via a cable. I can't detect any difference in how a model flies with the DSX9 to how it flies with the PCM9XII, but I am sure that I have a more robust radio link with DSM2 than I have with 35MHz PCM. There isn't much in it with glow or petrol engines, but it's definitely noticeable with electrics.

At least with plain old PPM (AM or FM) you get to know when the receiver is struggling, at which point you can make an attempt to save it -  either by bringing it in quickly, or raising the tx above your head etc.  PCM gives you no clues until it fails.

This is not my experience. Give me digital protocols every time.

Steve

At least with plain old PPM (AM or FM) you get to know when the receiver is struggling, at which point you can make an attempt to save it -  either by bringing it in quickly, or raising the tx above your head etc.  PCM gives you no clues until it fails.

Whereas with a decent 2-way 2.4 system you get signal strength feedback starting well before there are any control problems at all, because the packet radio format, the much higher bandwidth which allows significant redundancy, and digital error correction/detection mean that it can warn you a long time before the massive safety margin gets near to running out.

No rush Bob, take your time, just don't be quite so quick to knock it 

J

Nope, not knocked anything, just asked questions. So, back to the opening post.........

The original post asked what did we make of the linked article.  I think Dave Horvath made a reasonable attempt to explain why 2.4g is not perfect, though he's clearly sacrified 100% technical accuracy for a readable and digestable story, and omitted a lot for brevity. 
I think he did ok. 
Cheers
Phil

I go to quite a number of fly-ins during the course of the year, and 2.4 GHz has had a HUGE impact there!

At the Charmouth heli fly-in, it wasn't unusual to have to wait half-an-hour or more for your frequency to become available, once you'd decided to fly. Now you can fly as soon as there is a space on the flight-line!

And whilst frequency discipline may be good at many clubs, its always a source of concern at big events. Think of all those uncontrolled transmitters being sold from the trade stands at the Nats, for instance!

So, for a well controlled club environment, where you would probably be hard pressed to find enough active members to use all of the 35 MHz allocated channels, there is little if any advantage. However, if you fly competitively, or attend fly-ins, there most certainly is!

I'd readily agree 2.4ghz has made a big impact.

Thinking laterally, it's probably fair to say that some brands of 2.4ghz have made more of an impact than others.........

 If nothing else it has taken the worry of forgettingto put your antenna up before taking off!!!

I'd readily agree 2.4ghz has made a big impact.

Thinking laterally, it's probably fair to say that some brands of 2.4ghz have made more of an impact than others.........

ouch!

For me, at the moment, 2.4 has had little impact EXCEPT that as I mostly fly in a public space and about 2 miles from where others occasionally fly gliders it  has taken away all the worry and uncertainty and of course, significantly reduced the risks which has to be a good thing.

At the Nat's this year only 14 pilots registered on 35MHz and I believe the majority of those were in F4C.  I'm not certain how many pilots were registered overall but across all of the RC disciplines it has to be a couple of hundred I would have thought, if not more.

At the Nat's this year only 14 pilots registered on 35MHz and I believe the majority of those were in F4C.

I find that very interesting, since in many ways F4c models represent the greatest investment of all the classes, perhaps not in purely monetary terms but certainly in the hundreds of hours it takes to create these models.

I find that very interesting, since in many ways F4c models represent the greatest investment of all the classes, perhaps not in purely monetary terms but certainly in the hundreds of hours it takes to create these models.

Might be because some of those models have been around for a few years so were originally fittted out with 35 and the fliers have seen no reason to change?
Mike

Might be because some of those models have been around for a few years so were originally fittted out with 35 and the fliers have seen no reason to change?
Mike

My point exactly, Mike.

I have used Futaba 35Mhz on PCM for many years, and it has been superb.
The only problem I ever encountered was being shot down a couple of times by old duffers who couldn’t summon enough intelligence to use a peg board. 

I migrated to 2.4Ghz a couple of years ago and have had no issues with it.
One very noticeable fact of life is that 2.4Ghz receivers are cheap, and even the £5 ones seem to work equally as well as the most expensive PCM receivers.

I still have a few models on 35Mhz but my migration to 2.4Ghz is still continuing.

35Mhz PCM works very well, but for peace of mind from being shot down you can’t beat 2.4Ghz systems.

B.C.

Just a question: Does ANY carbon installation in an airframe cause 2.4Ghz Rx to have a sulk unless the antenna are outside of the airframe? I'm still on 35mhz (and expect to be so for some considerable time to come), and in my builds I use different materials including CF, steel, ali,, and other than not interfering with control rods and servos, make no allowance at all for the proximity  of the aerial to materials down the fuselage., That being the case, would I have to have a total rethink if I was on 2.4? 

Just a question: Does ANY carbon installation in an airframe cause 2.4Ghz Rx to have a sulk unless the antenna are outside of the airframe? I'm still on 35mhz (and expect to be so for some considerable time to come), and in my builds I use different materials including CF, steel, ali,, and other than not interfering with control rods and servos, make no allowance at all for the proximity  of the aerial to materials down the fuselage., That being the case, would I have to have a total rethink if I was on 2.4? 

Ive flown 4 gliders on 2.4 that had a small amount of carbon, ie wing spars, control rods, etc with no issues at all after well over 200hours flying, i am careful to follow the manufacturers recommendations for installation though, however when I tried fitting 2.4 in my Caldera (with the aerials outside) I couldn't find a position for them that ensured a signal in all axis, so I fitted my 35MHz and have had no problems what so ever. The manufacturers instructions are quite specific about installation and it has meant a certain amount of adjustment to gear positioning, basically I'm only fitting 2.4 to new models where the installation is easy otherwise I'm happy to fit 35mhz

Just a question: Does ANY carbon installation in an airframe cause 2.4Ghz Rx to have a sulk unless the antenna are outside of the airframe? I'm still on 35mhz (and expect to be so for some considerable time to come), and in my builds I use different materials including CF, steel, ali,, and other than not interfering with control rods and servos, make no allowance at all for the proximity  of the aerial to materials down the fuselage., That being the case, would I have to have a total rethink if I was on 2.4? 

My 50cc MX2 has a carbon main spar, carbon tail spar, carbon u/c and carbon stringers in the wing and fuselage. The rest of the model is mainly built from ply and balsa. I have never had a single issue using a JR 921 (DSM2) but it does have 2 satellites as well as the RX itself being 2 RX's   

Just a question: Does ANY carbon installation in an airframe cause 2.4Ghz Rx to have a sulk unless the antenna are outside of the airframe? I'm still on 35mhz (and expect to be so for some considerable time to come), and in my builds I use different materials including CF, steel, ali,, and other than not interfering with control rods and servos, make no allowance at all for the proximity  of the aerial to materials down the fuselage., That being the case, would I have to have a total rethink if I was on 2.4? 

2 metre span electric glider with carbon spars and carbon cloth covered wings, squarish kevlar fuselage with a carbon tow in each corner running full length of fuselage, large motor and battery completely filling the front part of the fuselage - both (2.4 GHz) Rx aerials insided the fuselage and no problems in 2 years of flying.

Dick