Jester241

I'm new and looking to upgrade from my futaba 4exa to a 6+ channel model. I hear alot of stuff about 2.4Ghz radios. What is the difference(in newbie terms) between my current 4exa and a 2.4Ghz model? And do I need one? While your at it,if someone could explain what the deal is with "duel conversion" recievers,that would be much apprieciated too! Thanks...

vertigo72480

Where to start? No you don't have to have 2.4 gHz, but, it seems that 2.4 gHz is going to stay.

What you have is a new type of control transmission that uses 2.4 gHz instead of 72mHz. 2.4 gHz is higher in frequency and theoretically can transmit more information faster. What the down side is, is that it can take a lot of energy to get any kind of range. This has been compensated for, by both manufacturers, by the use of dual antennas that are opposite to, or at 90 degree angles to each other to make sure that the receiver can hold a "lock" on the transmitter.

I still fly with 72mHz, but at some point I will probably switch to 2.4 gHz, mainly because the 2.h gig radios use dual channel technology that prevent s the possibility of turning on a radio and someone else being on the same frequency. Futaba's system, I believe can actually change channels during operation if one channel gets noisy.

I'm not a 2.4 gig pro, but have a little radio experience being a HAM radio operator and all. So, if someone has more information, or I'm wrong somewhere, let me know.

Welcome to R/C, lotsa fun here!!!

DadsToysBG

My Feedback: (35)

What it boils down to is safety. with the new 2.4 no one can turn on a radio and shoot you down. At the last heli meet they had 720 pilots and only 138 of them had the old 72 radio's. At some point the radio companies will only make 2.4 gig radio's and the old 72 will not get any service. Since you are so new and don't have alot invested yet, this is a good time for you to make the move to 2.4. I did with my 40%'ers and never looked back. Dennis

Redback

Jester,

There's a heap of stuff about 2.4GHz and spread spectrum (another bit of jargon!) in the radios forum. You could also try googling SPEKTRUM (one of the manufacturers) and read up what they have to say.

One of the main advantages of 2.4GHz Spread Spectrum technology is that it doesn't work on a specified frequency, so you don't need crystals and don't have to wait until your frequency is free to be able to fly.

I have put my money where my mouth is by buying a Spektrum set and a 2.4GHz module for my trusty old JR388.

Regards


Terry

heli_Rod

There is no doubt that 2.4 gHz spread spectrum is here to stay. I'm starting to switch over myself, having just bought a new Spektrum DX7 and the new JR 9303 2.4 radios. From my limited experience with 2.4 gHz., I'd have to say hands down that now would be a good time for you to switch over. The 72 mHz equipment will start de-valuating as more 2.4 stuff becomes available. Even the AMA is requiring 2.4 radios for some of the racing classes.

There are still some doubts about the spread spectrun technoligies, but they are quickly being put to rest. The Spektrum radios are somewhat voltage sensitive, meaning they can reset in flight if the battery pack drops below a certain voltage. The easy fix is don't run them low!

I have to admit to being one of the sceptics and have done a lot of reading, but overall the spread spectrum systems perform very well. There are some conversion systems available for some radios, if they have plug in transmitter frequency modules.

If you are planning on purchasing new equipment or upgrading, I wouldn't hesitate to go with the 2.4 gHz. radios. Life will be a lot easier for everyone with the new systems.

Just my opinion.

Rod

Jester241

Does the 2.4 stuff have the same or better range in the air as the 72? And just HOW bad are they on batteries? I wouldnt want the thing going out of range due to the tx dying unexpectedly mid-flight. Right now I quick charge my radio and rx's about every 2 or 3 flights just to make sure. Sry for all the dumb questions.

heli_Rod

The only dumb question is the one that's never asked! It's the receiver battery that causes the reset. If you watch the voltage with a loaded voltmeter, you shouldn't have a problem. The use of common sense goes a long ways here...LOL...just don't push them to the edge of their duration.

The Spektrum radios come in two styles...a park flyer version, which uses the AR6000 receiver. The AR6000 has only 2 antenna wires and is designed for short range park flying type models. It has a range of maybe 1000 feet. The DX7 Spektrum comes with the AR7000 receiver. It's actually 2 seperate receivers, each with their own antennas. They are mounted about 3" apart and at 90 degrees antenna polarity apart. People use these in 40% size, Jets or about anything you can think of. There range is probably around 1 mile, which is further than you can see a model.

Futaba, JR and Spektrum make great systems. Airtronics are lagging behind badly with technoligy.

At the 2007 IRCHA Jamboree At the AMA national flying site in Muncie, In., of the 718 registered pilots, 650 showed up anf flew with spread spectrum radios. None of these radios were impounded during the event and there was 17 pilot stations from which to fly. Not one problem was encountered during the evet with these radios. It was enough to convience me to Spend $730 on a new JR XP9303 2.4 radio!

Don't be afraid of them. These are really greaty systems.

Rod

Redback

Can't comment on range as I haven't used mine at the field yet.

As far as power is concerned I am doing a few simple tests of my own. Indications so far are:-

1. The Spektrum receiver draws a higher steady state (no servos) current than one of my JR 36MHz receivers (as used in Oz).

2. The digital servos that come with the Spektrum set seem to take less current than comparable standard servos. I do need to do more work on this test, I have been using a rig with elastic bands to apply progressive resistance to the servo.

The higher receiver current is unlikely to have a significant impact on battery duration as most of the power goes into the servos.

Regards

Terry

khodges

My Feedback: (1)

More comment on the two types of transmission on the 2.4 GHz band:

Spectrum's system, when turned on, scans the bandwidth and locks on to two separate frequencies and transmits to the Rx solely on these two frequencies as a redundant system; part of the theory is that whatever interference that might affect one won't affect the other. When a second or subsequent Tx on this system is turned on, it will read the frequencies in use and pass them over to find a pair of unused freq's. This insures that no one radio can interfere with another. The Tx WILL NOT emit a signal to the Rx before it has scanned the entire 2.4 band.

Futaba's system, uses a constant scan. It only stays on a particular frequency for a couple of milliseconds at a time, and will bypass any that it detects in use, so it is completely compatible with Spectrum's system (meaning that you can use both at the same field on different planes and they won't interfere with each other). Futaba's method of frequency hopping is much older than Spectrum's system; Futaba has used this in industrial radio control applications for years.

Both systems utilize a "Binding" of the Rx to the Tx. Before you use them, the Rx must be "bound" to its Tx; this means that the Rx will only recognize a signal from the Tx it is bound to, so that one person's Tx will only control his plane and not another one. The two systems are not compatible with each other, meaning you can't mix and match Futaba Rx with Spectrum Tx and vice versa.

I bought a DX-7 about 6 months ago, and love it. One big difference in 2.4GHz compared to 72 MHz is what's called "latency". This is the time factor between an input to the Tx (stick movement) and the resulting control surface movement. 2.4 is way faster, and the feel it gives is like the difference in a digital vs. an analog servo, or like flying a plane with a lot of expo and then flying the same plane with the expo taken out. It's kind of hard to describe, but the first time you fly on 2.4, right after flying on 72, you'll immediately feel the difference. Response time is incredibly fast, and it takes a bit to get used to it.

One thing to watch out for in 2.4MHz is someone using a video system on their plane that transmits the signal to a ground receiver. If you turn on the Tx, and it "selects" its frequencies, and then someone turns on a camera system (they also transmit in the 2.4 band), then there is a potential for interference. If the video is turned on first, then the Tx will pick up the signal when it scans and avoid the freq it is operating on. So I've been told.

heli_Rod

Nice explanation, khodges! You are correct about the 2.4 gHz video systems. As an amatuer radio operator, I can utilize a 1 watt (1000 milliwatt) 2.4gHz airborne video transmitter. It will saturate a 2.4 gHz radio system and render it useless. That's why I'm keeping one 72 mHz radio...just for aerial video work. I also have to take precautions against interfering with other radios nearby.

Rod

jetmech05

try a Futaba 9 CAP
There is an external module that takes 60 seconds to change. Buy a 2.4 GIG module and receivers and start changing over to 2.4 GIG a little at a time. Change the module back and you're still on 72MHZ. The best of both worlds....
Oh you have to unscrew the exsisting antenna when you change the module. The 2.4 GIG module has an antenna on it

Redback

Bit more on comparative current figures:-

1. Receiver current, no servos connected
JR RS10DS 23mA
AR7000 54.8mA

Servo figures with JR Receiver
No Load Load Applied
JR507 38.8mA 170mA
JR539 55mA 140mA
DS821 31.5mA 40mA

Servos with AR7000
No Load Load Applied
JR507 69.9mA 180mA
JR539 60.5mA 170mA
DS821 63.5mA 80mA

The load figures were steady state values after the servo had come to rest against an applied load. Unfortunately I don't have any effective way of measuring the transient current when the servo is moving.

I used the 507 and 539 servos as they are the ones that used to come as part of JR sets (similar to the Spektrum DS821s). The 539s look extenally similar to the DS821s (same as the case of the DX7 and my JR6210!).

Tried hard to keep conditions the same for each servo and the results were repeatable.

Conclusions based on the above are that the AR7000 takes a bit more current but the servos take less. Make of it what you will!!!


Terry

jzinckgra

My Feedback: (11)

Are you sure about this? I wasn't aware the 9C radio's module could be switched to a 2.4 mod. I have a 9C and you can change the 72mhz freq module in the back to another channel, but I don't know about putting a 2.4 in there. anyone?

sharpshooter223

theres also the cost issue, if you only have about 300 bucks for a beginning plane, you will want to get an fm cause they cost less, if you have the money though, go for it. right now cost is the only thing keeping me with fm. yes im very cheap

khodges

My Feedback: (1)

Sure, all the mfg's (well, JR and Futaba, anyway) are making 2.4 modules to retrofit 72 MHz transmitters. They just replace the output module on back, and have a short cable that attaches to a "stubby" type antenna that replaces the original. The modules are almost as expensive as buying a new Tx, but allow you to use one radio for everything. I have a 9C, but plan to just keep it on 72 MHz for all the planes that are on it now; As I replace Rx's or get new planes, I'll eventually just buy a new Tx. I already have a DX-7 and I'm in a quandary as to stay with Spectrum technology or switch to the FAAST system Futaba uses. I just couldn't wait and bought the DX-7 about 2 months before Futaba came out with theirs; I'm just a Futaba fan.

jetmech05

the guy at my field that showed me his 2.4 module said the cost was 130 if I remember correctly. Yea I'm sure I've seen it in action lol

Rodney

heli Rod, have you tried to operate your vidio with the Futaba FASST system, I think you may find that it is not effected adversly as the Spectrum is. I am also a HAM and a retired EE and have choosen the Futaba FASST system over the others as, from my past experience in electonics, instrumentation and RF testing, the Futaba system is theretical superior to the other two systems now in use. Only time will tell for sur but, we have two of the Futaba FASST systems and about 11 of the Spectum. So far we have had 5 problems with the Spectrum (two lost lock in flight, one on the bench) and one was so effected by the ignition system on the plane it was unflyable until equipment was moved around and even then was very glitchy at all times. The fifth failure cause was not reliably determined due the the severity of the resulting crash but probably not a radio problem, more likely a loss of battery capacity. I'm sure we would all like to know if your vidio system system upset the Futaba FASST.

heli_Rod

I haven't tried it with the FAAST system, as I'm not a Futaba person. I don't think I've even seen the Futaba 2.4 yet. I wouldn't try it in an expensive plane, or my case in a helicopter. I can't help but believe that 1 watt of video output woudn't cause a problem when placed in close proximity to a reciever. To me it's not worth the risk of equipment. I'll let someone else do the experimenting.

At this stage, I'm happy using the 72 mHz band for my airbore video platforms. I need to ask Steve Molmer his opinions on this. He is probably the foremost authority with video system in R/C aircraft. There might also be some forums already on the subject in: Aerial Photography and Video.

Rod

Bax

My Feedback: (11)

Futaba has modules available and more coming for all of their module systems. Just plug in the transmitter module, install the receiver and you will be operating with Futaba's FASST spread-spectrum technology!

http://2.4gigahertz.com/modules/modules-receivers.html

You don't have to remove the transmitter antenna, or anything. Just leave it collapsed. The transmitter module has its own antenna.

RCKen

My Feedback: (9)

Bax,
Any idea when teh module will be available for the 9C???

Ken