2.4 Glitches - It Does Happen!
 

Well,
I installed a Spektrum 2.4 AR6000 receiver in my Balsa USA Fokker whicch is powered by a converted Homelite 25cc weedwhacker engine. When I turned everything on and started the motor I noticed glitching in all control surfaces. At first, I suspected loose wires but there were none. Then I shielded the spark plug cable and made sure there were no loose wires on the kill switch. The distance from the engine to the receiver was 19 inches and the receivers antennas were positioned perpendicular to each other. The receiver battery was a 3300mah 4.8volt pack (freshly made). The static voltage tested out at 5.59 volts. I also pulled the AR6000 and installed an AR7000 with the same results. As a last resort I fell back to my trusty JR PCM receiver and all the glitching stopped. So, I am left with the fact that 2.4 is not as rock solid as many people think and does not perfrom well under certain RF environments.

Happy Flying!

Loopman :eek:

RE: 2.4 Glitches - It Does Happen!
 

Well the 6000 is shown at the Spektrum site as a park flyer Rx. It should never be used in a large model of anykind as far as Iknow. Ithink the range is suggested to be 600 feet.

To use it in a large gas model where the possibility of electrical noise is high is really asking for trouble. Not only for the loss of your plane but for people on the ground.

Ihave used 2.4ghz stuff for about a year now and it is rock solid out to the range of my eyeballs.

Get a real Rx! It is only $20 more.

Jim D

RE: 2.4 Glitches - It Does Happen!
 

Oops my mistake! It was an AR6200 not a 6000. But regardless, I also tried an AR7000 with the same results! SO that still means that 2.4 is not solid in every environment. Of course, neither is PCM but I'm still gonna fly both!

Happy Flying!

Loopman

RE: 2.4 Glitches - It Does Happen!
 

I wish I had access to your plane for a couple of hours to work out what is really going on.

RE: 2.4 Glitches - It Does Happen!
 

Well,
I had several IMAC guys at the field do that very thing with no solution. It has to be interference from the Homelite. I guess the next bit of advice though will be for me to get a real engine! (ha ha). I also fly a Wildhare Extra with a TGY 50HP and I use 2.4 with no issues - it's rock solid!

Happy Flying!

Loopman

RE: 2.4 Glitches - It Does Happen!
 

Why not stick with the FM if it works?
Most people seem to have switched to 2.4Ghz just to have the newest stuff and they bought Spektrum and Futaba to have the most expensive gear to show off and brag about. A few had real reasons but not the majority. I know lots of people are still flying AM gear with no problems!
If it works, why "fix" it?

RE: 2.4 Glitches - It Does Happen!
 

DBCisco,
You are so right! I have switched out the 2.4 rx for one of my R790 scan select rx's and I will not be switching back. However, I will continue to fly 2,4 in some of my other planes.

Happy Flying!

Loopman ;)

RE: 2.4 Glitches - It Does Happen!
 

Beside the obvious advantage of not being shot down by other systems here are some other reasons for switching to 2.4GHZ.
1. The receiver is all solid state components. There are no fragile components like IF cans to be subject to vibration failure.
2. The SS receiver has a sensitivity of about 6db better than the superhetrodyne receiver used on 72mhz. A 6db increase in receiver sensitivity is the same as increasing the transmitter power 4 times.
3. The receiver is smaller and cheaper than the 72 mhz receiver. The Chinese are selling them for $15-$20 these days. They will soon have receivers compatible with both Spectrum and Futaba.

BTW all of the SS systems I know of use PCM.

RE: 2.4 Glitches - It Does Happen!
 

Is your last statement really true. I just installed a FrSky 2.4 module in my JR xp9303 and the instuctions call for setting the Tx to the PPM mode. All I know is I flew a half dozen glitch free flights saturday with the Tx in the PPM mode with the 2.4 module and Rx.
........RJ

RE: 2.4 Glitches - It Does Happen!
 

I know for a fact that you have to set your transmitter to PPM when you convert, at least that's how it works with JR.

Happy Flying!

Loopman ;)

RE: 2.4 Glitches - It Does Happen!
 

PCM is a proprietary protocol to each manufacturer, PPM encodes the stick position in a way any module can understand, the link between the module and the receiver is pcm transmitted on 2.4 gig with additions to the protocol to ensure the the reciever only listens to packets from the transmiter that it's bound to.

RE: 2.4 Glitches - It Does Happen!
 

In other words the PPM pulse train is applied to the RF module where it is converted to PCM and transmitted via 2.4GHZ to the receiver where it is converted back to the pulse train that the servos can understand.
On the 72mhz transmitter in PCM mode the PPM train is converted to PCM in the transmitter and transmitted to the receiver via 72MHZ FM.
So the transmitter must be in PPM mode to get the proper pulse train to the module. But the transmission mode is PCM on 2.4

RE: 2.4 Glitches - It Does Happen!
 

One other advantage. You get more flights in per hour since you don't have to wait for that other guy to get off channel 38 etc etc.

RE: 2.4 Glitches - It Does Happen!
 

So you are saying that there is an analog to digital conversion in the Tx module and then a digital to analog conversion in that little tiny Rx. How in the world are they doing that and still coming up with the latency figures I read. I know that some of the PCM Tx and RX are among the worst when it comes to speed what with all the time required for the conversions. Just curious.............RJ

RE: 2.4 Glitches - It Does Happen!
 

At Spektrum prices it would cost me over a thousand dollars to convert all my planes. I seriously doubt that FM which has worked fine so far will ever cause me a $1000 crash. Now I do have a HK Spektrum compatible RX on order and if it works in my foamies with an eflite TX then I will start installing them in my builds as they are cheaper ($15) than used FM RXes. Dang if I didn't open another can of worms.

RE: 2.4 Glitches - It Does Happen!
 

do not want to start a brand war. Maybe try a different brand of 2.4 equipment? 2.4G RC gears really are not created equal.

Frequency hopping is the key characteristic of 2.4G that offers the best capability to counter interference.

RE: 2.4 Glitches - It Does Happen!
 

The problem on 72mhz is all that conversions and pcm transmissions must be done in a 10kc bandwidth. To get 10 bit resolution you have to spread it over two frames.That causes the latecy problems- not the a/d & d/a conversions
That's another advantage of 2.4GHZ, you have all kinds of bandwidth to play with. They really have not done too much with that yet. XPS claims 16 bit resolution.

RE: 2.4 Glitches - It Does Happen!
 

In my opinion frequency hopping is overkill. DSSS has all the interference protection you need.

RE: 2.4 Glitches - It Does Happen!
 

Spectrum does not have a patent on SS technology. That was patented by Hedy Lamar in 1939.
The best Spectrum can do is claim copyright infringement.
The Chinese receiver should be just as good as the Spectrum unit. The Chinese have the latest SMT machines we have.The Spectrum unit itself is probably made in China as well.

RE: 2.4 Glitches - It Does Happen!
 

Correct. Spektrum's patent is mostly based on using two frequencies simultaneously. IMHO a patent that has no real standing if it came push to shove. The patent office will grant anyone a patent on anything as long as they get their fees. They might as well have a patent on the wheel. Probably why the only thing Spektrum is pursuing with their lawyers are the trademark infringement counterfeits. It is their trade secrets that are open to reverse engineering and, as I predicted last year, only a matter of time before compatibles came out. Same thing happened in computers in 1981 when Phoenix and AMI reverse engineered IBM's PC BIOS. Then everyone came out with IBM clones and MS-DOS compatibility. If it wasn't for them you would have a 640K memory biege PC on your desk running PC-DOS on your desk right now.

RE: 2.4 Glitches - It Does Happen!
 

first of all, flying IMAC does not make one an expert. It is just another event. Also, the advantages of 2.4 are so vast it is ludicrous to even argue about it at this point. Many sport flyers may not have a reason to switch, but when flying very large scale aircraft or anything else with value, 2.4 is the only way to go. Also events with hundreds of pilots are a pain waiting for frequency.

Back to the original post, I would follow the old rules of figuring out what is causing the glitching. use an FM RX and make adjustments until it all goes away. The problem still exists whether you can mask it with PCM or 2.4. There are many things to cause glitching. I had a serious problem with a G38 on magneto until I put on a high quality plug cap.

Good luck, you will find it.

RE: 2.4 Glitches - It Does Happen!
 

Okay,
I mentioned the IMAC guys at my club because they all fly 2.4 with very demanding requirements. So while IMAC is "just an event" those that are in it are very, very knowledgeable. Now, I have exhausted all possible causes for the glitches that I am having and I will emphatically re-state that after finding no other gremlins, the RF noise coming from the engine has to be the problem. I am going to try one last thing in that I am going to change the spark plug from a Champion to an NGK and see what happens.

Happy Flying!

Loopman ;)

RE: 2.4 Glitches - It Does Happen!
 

I wonder if these HK 2.4ghz Rxs will have the Model Match function capability? This is patented by Spektrum and one of the few advantages Spektrum offers in terms of functionality.

By they way if you read the testing that this guy has done, Spektrum DSM2 is not that great.


http://www.rcmodelreviews.com/2.4ghzshootout.shtml

Oh and for you 72mhz guys, don't forget to put the antenna up each flight!


Jim D

RE: 2.4 Glitches - It Does Happen!
 

Change the spark plug in your Homelite engine, put a resistor plug in and see what happens. I have a Homlelite engine with a Spectrum 7000 Rx, and that fixed my problem.

RE: 2.4 Glitches - It Does Happen!
 

I changed to 2.4 ghz so I wouldn't have to remember to pull my antenna out :) no other reason