2.4gHz

surf1845

Hi all.

I was wondering if anyone is using 2.4gHz and if so what are your opinions. It sounds wonderful but I've read a couple of articles which say that the range is not as good as 35mHz and that it's prone to interference. I also heard that it may be banned in Europe in the near future. Any input would be appreciated. I want to get a good radio from the outset but obviously want to know the facts before I buy.

coolwings

I don't know about the articles you referred to. Some of the points you mention seem to be inaccurate given my understanding of the situation, and the technology.
The 2.4GHz band is used by many users, mainly as a wireless band for computer networks.
It is intended as an indoor (mainly) band, as it does not go through solid objects, and therefore an indoors transmission is "contained". This makes it perfect for multiple RC modellers operating indoors in close proximity to each other.
It also does not reflect. So the direct line of sight need is introduced with this technology that was not previously necessary.
Lower frequencies (35FM, 40FM, 27AM, 800Mhz) reflect off the ground, the sky, distant buildings, and their signal can arrive at the model from many directions.

Used outdoors 2.4GHz works, and does what it says on the box. JR 2.4GHz has been tested at very long range, excess 2000 metres, but not all 2.4GHz systems are adequate to long range.
The existing 35FM works well at extreme range, a person I know tested a JR MX-12 on 35FM at 5000 metres recently. It uses a greater power level of transmission, but there are rules of physics that ensure that lower frequencies travel farther than higher frequencies.
So 35FM is physically suited BETTER for long range reception than an uiltra high frequency like eg 2.4GHz. (By the way that is why the cheap 27AM radios can be very low power, and still transmit over great distance.)
But this is not saying 2.4GHz does not work, it works very well.

I personally have not bought into the 2.4GHz system because firstly my 35FM gear works perfectly, and secondly my existing receivers would become redundant (an extra significant cost to be added to "costs of upgrading"), and thirdly 2.4GHz is direct line of sight transmission only, no penetration of solid objects, like flying behind a tree. This also means that a carbon fibre model itself can "mask it's own receiving antenna", or antennas, and antennas are at 90 degrees to the circuit board which is cumbersome. They are nice and short - but they stick up.

So (speaking for myself) I'm just not buying into 2.4GHz technology, not when 800MHz RC technology is already being tested, and due out in about 12 months, and it has the ability to penetrate solid objects and carbon fibre, and 800MHz reflects, so can "can go around" a masking object between the modeller and the model.
Therefore 800MHz will contain the advantages of both 35FM and 2.4GHZ, but the disadvantages of neither.

But that is my humble view. The users of 2.4GHz will say it works fine, and interference is negligible, and I would not argue with that at all, since it is also true. It has the feature that if some twit switches on without checking first, the signal will not affect models already flying.

Of course 35FM band B was legalised recently in Ireland, and those channels are sitting there mainly unused. I use a 35FM synthesised system ,(no crystals) and using those channels is simply a matter of typing the 35B channel number into the transmitter (a JR MC-22S) and pressing "enter". The synthesized receiver locks on with a touch of a button. And all previously bought crystal receivers work (when I select the frequency of the rx crystal) and do not have to be replaced.

So there are many issues, and personal choices to make, and what you already have, affects your decision.

As you would expect, the high end radios work best, and the low end radios work, and the budget radios work just about. And this will always be the case, whatever the waveband the radio transmits on.

T-Maxx

+1 on what Dr Coolwings said.:D

The 2.4GHz systems are pretty much the talk of the town at the moment. You got to ask yourself what your immediate and foreseable requirements are in terms of number of models, type and cost of models, your level of skill, etc. And also how deep your pockets are.

For my ground models I use the cheap-and-nasty 27kHz AM radio that comes with the model. They work for my application and I don't mind handing it over to my kids (I got a drawer full of spare antennas;))

surf1845

Hi guys.

Thanks for the replies. Coolwings, the articles I referred to about range and interference were on various forums (damned if I can remember which ones) and I also read about the ban on a forum too. Here is one such item.
http://www.rcgroups.com/forums/showthread.php?t=722815

I realise that everyone will have their own opinion and will favour whatever they use themselves. I started with a basic Futaba set back in the 80's and it served me quite well, but at the time there wasn't a huge choice. I'm a bit bamboozled at the moment and conflicts of opinion are rife on almost every forum. For instance I just read that synthesised transmitters can be affected by mobile phones!

SYNTHESISED TRANSMITTERS AND MOBILE TELEPHONES. BMFA BULLETIN.

Following the crash of an expensive gas turbine model helicopter, the investigation into the cause revealed that the synthesised transmitter being used to control the helicopter was interfered with by a nearby mobile telephone. In this case it was a Multiplex transmitter but it is possible the same could occur with other synthesised transmitters.

The transmitter manufacturer’s instructions were scrutinised and found to contain a warning that mobile telephones were not to be used within the direct vicinity of the transmitter and subsequent trials revealed that the incident was repeatable with that transmitter. The UKRCC will be carrying out further investigations to determine the extent of the problem and will be advising in the future.

The BMFA already recommends that mobile telephones are not taken into the pits or flying area for other reasons but be aware that mobile telephones could interfere with synthesised transmitters.

Reading articles like this only adds to my confusion. Maybe I should stop reading and go flying again!:)

Seriously though it is difficult to make a choice when there are so many systems out there. I don't know at this stage how far I want to go with the hobby. I would probably like to get into bigger scale models eventually so reliability would be a big factor as well as value for money. However I think I'll avoid 2.4gHz for now. I didn't realise that it was intended for indoor use, nor did I know about the line of sight issue.

coolwings

surf1845 wrote: »

... For instance I just read that synthesised transmitters can be affected by mobile phones! ...

I was advised by a Multiplex employee that the incident referred to occurred as a result of the operating instructions not having been followed. Unfortunately for them, it was by a demo flier in front of a large audience.
The BMFA safety note is a conservatively worded "cover all possible similar future problems" type analysis of the accident.

surf1845 wrote: »

... Maybe I should stop reading and go flying again!:)

Always a good idea!

surf1845 wrote: »

... avoid 2.4gHz for now. I didn't realise that it was intended for indoor use, nor did I know about the line of sight issue...

It is not just for indoor use. The more powerful sets are designed for outdoors. And the wattage they output or radiate into the air, is sufficient to pass through some semi porous items like certain trees, but I have concerns about "all trees" if you see my meaning.

I think Syl77 on this forum has a heli flying on 2.4 with good results. he will likely chip in soon and give his experiences.

syl77

The range for 2.4ghz is usually farther than you can see the model to control it. However some 2.4ghz technology like spektrums DMS is only used for surface models as there can be signal attenuation caused by metallic conductive material in aircrafts which can effect overall range. Spektrums DMS2 over comes this with the use of two Receivers placed at right angles to each other and can be used with all models that have carbon or G-10 frames. Even more powerful radios like the JR9303 2.4ghz radio will even improve on the range, however this radio is still illegal to use in Europe because of its power and will most likely have to drop its power output before it is allowed on the European flying sites in the form of the DX9.

There have been some issues with Futaba's 2.4Ghz technology FASST. They have recalled some of their futaba 6channel radios, some were found to ZERO under certain circumstances (ZERO is when the radio loses its link with the Rx and starts to search for the next available powered on Rx to link with), this meant it could interfere with another 2.4ghz radio system. They have recalled the suspect radios, but rumours are out that it’s affecting the FASST Technology as a whole. I probably would avoid Futaba until they sort it out.

As for your original Question, like T-max said, ask yourself what you need the radio for, many 3d heli pilots use the 2.4ghz system because they like the speed it transmits which means that the heli responds faster to input, fly’s more like a sim. Spektrum 2.4Ghz has been very successful in 3d helis, I’m sure the same could be true with scale, the DX7 would be the recommended as it uses DMS2 ....