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macr0t0r · May 25, 2009, 03:30 AM

Finished ATTF #94 - 2.4GHz. Holy Crud, is that a lot of material to cover! Comments!

=== Proprietary 2.4GHz vs Open 72MHz ===
I understand Jamie's wish that all of the companies would just agree on a standard so we could purchase the transmitters and radios that suit us best. However, each company wants to distinguish itself on how it's "better" than the competition, and most companies would demand a licensing fee. Assan seems to be the first to not hold a death-grip on it's standard.

However, proprietary existed in the 72MHz FM days as well. JR and Airtronics were positive-shifted radios, but Futaba decided to introduce a negative-shifted radio, thereby breaking compatibility with JR and Airtronics. Granted, that is an easy thing to work around, so newer receivers can handle both. But, the PCM receivers from all of the RC companies were proprietary and did not work with competitor's transmitters. They were the first of digitally-encoded radio systems, and that philosophy carried into the 2.4GHZ realm.

=== Spektrum DX6 Legacy System ===
Jamie mentioned that the people who bought the Spektrum DX6 got "left behind" when the all of the new receivers required the new radios. I have a DX6, but I don't feel slighted in the least for the following reasons:
1. These things happen to early adopters, but Horizon still sells the AR6000 receiver for us. And, it's a solid little workhorse (especially since it has the dual-receivers versus the single receiver in the AR6100 while being cheaper than the AR6200).
2. All of my purchased AR6000 receivers will still be fully usable with the DX7 and X9303 radios. I'm quite grateful for this.
3. At least it isn't NEARLY as bad as Futaba with their FASST gear! Good grief, what were they thinking?
EDIT: Now that I've had a cup a coffee and dswitkin lent a hand, I decided to tone down the rant. It really wasn't productive anyways.
Futaba has changed their 2.4GHz system a couple times without putting sufficient effort in maintaining backwards or forwards compatibility. This (in my mind) makes purchasing FASST systems a bit of a risk. To show you how bad this has gotten, they had to post a chart to let you know what receiver is compatible with which transmitter (these are all 2.4GHz, mind you):
http://castlehillhobbies.com.au/comp...mart/Itemid,1/

Thankfully, dswitkin has posted an improved chart that is easier to read:
http://www.zerorc.com/futaba-24-ghz-compatibility-chart

By the way, I've heard that the Spektrum DX6i is NOT backwards compatible with the AR6000 DSM receivers and neither are the Spektrum transmitter modules. Of course, the DX6i is not really an "upgrade" from the DX6, so I doubt that will be a major concern to most people.
EDIT: Oops! Jamie corrected me. The DX6i works fine with both DSM and DSM2 systems. It's only the DX5e and the TX Modules that are DSM2-only.
The transmitter module is a bit of an issue considering the cost, though.

In any case, Jamie, I would've kept the DX6. If nothing else, it makes a perfect buddy-box and computer-sim radio.

=== Analog (PPM) versus Digital ===
Chris noticed a major difference in control-lag when he switched from his module-installed 9303 system to the native x9303 Spektrum transmitter. The reason is that Spektrum gear is now all pure digital, but you only feel that speed with a pure-digital setup. Transmitter modules are pretty old technology where they transmit your commands through an analog PPM signal to the module. So, imagine how your commands are translated from your thumb to the receiver:

1: Module System
a. Thumb to digital command.
b. Digital command to PPM analog signal (for module)
c. PPM signal to digital signal (within module)
d. Transmit digital signal to receiver.
2. Native System
a. Thumb to digital command.
b. Transmit digital signal to receiver.

Oh yah...you'll feel the difference if you have good enough servos! I think it's great that Spektrum offers modules, but I'd seriously consider getting a native transmitter. Besides, it's not uncommon to have multiple radios, so you might as well let your 72MHz gear have their own transmitter.

=== One or Two antennas? ===
I believe two heads are better than one. In the Spektrum receivers with two full antennas and receivers, you have a higher chance that at least one receiver will have a decent signal. These include the AR500, AR6000, AR6200, AR7000 and up. The AR6100 and AR6300 look like they have two antennas, but it is actually ONE dipole antenna with a single receiver. Light and cheap, but a higher risk.

=== Computer Radios ===
Woo hoo! My hearty thanks to Lucien for taking me back to the days of popping off the back panel and breaking out the jeweler's screwdriver to flip some dip-switches and adjust pots! Yah, baby! And you know what the BEST part of those radios were?

no model memory!

Let me tell you...when you forget to disable the "elevon" switch prior to taking off your pylon racer...well, flights like those will separate the men from the boys (or at least separate the wing from the fuselage)!

Oh, and make sure you remember to flip that throttle-reverse switch prior to hitting the starter on that motor.

Also, we adjusted the sub-trim by removing the servo-head retaining screw and shoving a jeweler's screwdriver down the shaft. Ah...those were the days...

In any case, we've come a long way. For me, I always loved the JR interface since I got my first JR x347. I also found Airtronics to be very intuitive. Futaba was...well, I talked enough about them. I have to admit, it's been a few years since I handled a Hitec, but the last one I played with was a Flash series, and just figuring out the V-Tail setting was a miserable affair. I'd be interested to see how much they've improved. I always did love their receivers and servos, but I never liked their transmitters.

=== Mode 1 and Mode 3.5 ===
That was an insane story by Lucien! Holy crud, how does that guy see straight? Anyhow, you'll be surprised to know that there are quite a few people in the U.S. that pefer Mode 1 or Mode 3 (throttle on the right). Why? Because they started with console video games!

Go ahead, play a few driving or flying sims on a Playstation or X-Box. Which side has throttle and which side do you turn? That's right! Why the heck don't they sell Mode-2 controllers!?

Anyhow, for those that don't remember what mode is what, this is a nice chart showing the different configurations:
http://www.rc-airplane-world.com/rc-...ter-modes.html

=== Model Match ===
So far, it seems Spektrum DSM2 systems are the only ones with this. While I understand that it is a crutch, I'm in favor of any feature that reduces the odds of me taking off with reversed ailerons.

I should note that you will not have model-match with the AR6000 receivers. It must be a DSM2 transmitter and receiver system.

=== Failure Rates ===
I mentioned this in an ealier post, but there are two reasons why Spektrum gear appears to fail more often.
1. If all radio systems had an equal failure rate, then the radio with the largers population will have the largers number of failures (this was already stated by Lucien).
2. The radio that is most compliant will have the most problems. Why? Because it is the non-compliant radios that will "spray" into channels adjacent to their reserved frequencies and knock out other airplanes. Just like in the old days around 1991. The "Narrow-band" radio systems would get slaughtered by the older wide-band radios.

Well, there's a TON of additional information on this subject, but's half-past midnight already (ugh). Awesome show, guys. Thanks!

- Jim

May 25, 2009, 03:30 AM	#2412
macr0t0r Got more toys than my kid Join Date: Sep 2004 Location: Fremont, CA Posts: 3,390	Finished ATTF #94 - 2.4GHz. Holy Crud, is that a lot of material to cover! Comments! === Proprietary 2.4GHz vs Open 72MHz === I understand Jamie's wish that all of the companies would just agree on a standard so we could purchase the transmitters and radios that suit us best. However, each company wants to distinguish itself on how it's "better" than the competition, and most companies would demand a licensing fee. Assan seems to be the first to not hold a death-grip on it's standard. However, proprietary existed in the 72MHz FM days as well. JR and Airtronics were positive-shifted radios, but Futaba decided to introduce a negative-shifted radio, thereby breaking compatibility with JR and Airtronics. Granted, that is an easy thing to work around, so newer receivers can handle both. But, the PCM receivers from all of the RC companies were proprietary and did not work with competitor's transmitters. They were the first of digitally-encoded radio systems, and that philosophy carried into the 2.4GHZ realm. === Spektrum DX6 Legacy System === Jamie mentioned that the people who bought the Spektrum DX6 got "left behind" when the all of the new receivers required the new radios. I have a DX6, but I don't feel slighted in the least for the following reasons: 1. These things happen to early adopters, but Horizon still sells the AR6000 receiver for us. And, it's a solid little workhorse (especially since it has the dual-receivers versus the single receiver in the AR6100 while being cheaper than the AR6200). 2. All of my purchased AR6000 receivers will still be fully usable with the DX7 and X9303 radios. I'm quite grateful for this. 3. At least it isn't NEARLY as bad as Futaba with their FASST gear! Good grief, what were they thinking? EDIT: Now that I've had a cup a coffee and dswitkin lent a hand, I decided to tone down the rant. It really wasn't productive anyways. Futaba has changed their 2.4GHz system a couple times without putting sufficient effort in maintaining backwards or forwards compatibility. This (in my mind) makes purchasing FASST systems a bit of a risk. To show you how bad this has gotten, they had to post a chart to let you know what receiver is compatible with which transmitter (these are all 2.4GHz, mind you): http://castlehillhobbies.com.au/comp...mart/Itemid,1/ Thankfully, dswitkin has posted an improved chart that is easier to read: http://www.zerorc.com/futaba-24-ghz-compatibility-chart By the way, I've heard that the Spektrum DX6i is NOT backwards compatible with the AR6000 DSM receivers and neither are the Spektrum transmitter modules. Of course, the DX6i is not really an "upgrade" from the DX6, so I doubt that will be a major concern to most people. EDIT: Oops! Jamie corrected me. The DX6i works fine with both DSM and DSM2 systems. It's only the DX5e and the TX Modules that are DSM2-only. The transmitter module is a bit of an issue considering the cost, though. In any case, Jamie, I would've kept the DX6. If nothing else, it makes a perfect buddy-box and computer-sim radio. === Analog (PPM) versus Digital === Chris noticed a major difference in control-lag when he switched from his module-installed 9303 system to the native x9303 Spektrum transmitter. The reason is that Spektrum gear is now all pure digital, but you only feel that speed with a pure-digital setup. Transmitter modules are pretty old technology where they transmit your commands through an analog PPM signal to the module. So, imagine how your commands are translated from your thumb to the receiver: 1: Module System a. Thumb to digital command. b. Digital command to PPM analog signal (for module) c. PPM signal to digital signal (within module) d. Transmit digital signal to receiver. 2. Native System a. Thumb to digital command. b. Transmit digital signal to receiver. Oh yah...you'll feel the difference if you have good enough servos! I think it's great that Spektrum offers modules, but I'd seriously consider getting a native transmitter. Besides, it's not uncommon to have multiple radios, so you might as well let your 72MHz gear have their own transmitter. === One or Two antennas? === I believe two heads are better than one. In the Spektrum receivers with two full antennas and receivers, you have a higher chance that at least one receiver will have a decent signal. These include the AR500, AR6000, AR6200, AR7000 and up. The AR6100 and AR6300 look like they have two antennas, but it is actually ONE dipole antenna with a single receiver. Light and cheap, but a higher risk. === Computer Radios === Woo hoo! My hearty thanks to Lucien for taking me back to the days of popping off the back panel and breaking out the jeweler's screwdriver to flip some dip-switches and adjust pots! Yah, baby! And you know what the BEST part of those radios were? no model memory! Let me tell you...when you forget to disable the "elevon" switch prior to taking off your pylon racer...well, flights like those will separate the men from the boys (or at least separate the wing from the fuselage)! Oh, and make sure you remember to flip that throttle-reverse switch prior to hitting the starter on that motor. Also, we adjusted the sub-trim by removing the servo-head retaining screw and shoving a jeweler's screwdriver down the shaft. Ah...those were the days... In any case, we've come a long way. For me, I always loved the JR interface since I got my first JR x347. I also found Airtronics to be very intuitive. Futaba was...well, I talked enough about them. I have to admit, it's been a few years since I handled a Hitec, but the last one I played with was a Flash series, and just figuring out the V-Tail setting was a miserable affair. I'd be interested to see how much they've improved. I always did love their receivers and servos, but I never liked their transmitters. === Mode 1 and Mode 3.5 === That was an insane story by Lucien! Holy crud, how does that guy see straight? Anyhow, you'll be surprised to know that there are quite a few people in the U.S. that pefer Mode 1 or Mode 3 (throttle on the right). Why? Because they started with console video games! Go ahead, play a few driving or flying sims on a Playstation or X-Box. Which side has throttle and which side do you turn? That's right! Why the heck don't they sell Mode-2 controllers!? Anyhow, for those that don't remember what mode is what, this is a nice chart showing the different configurations: http://www.rc-airplane-world.com/rc-...ter-modes.html === Model Match === So far, it seems Spektrum DSM2 systems are the only ones with this. While I understand that it is a crutch, I'm in favor of any feature that reduces the odds of me taking off with reversed ailerons. I should note that you will not have model-match with the AR6000 receivers. It must be a DSM2 transmitter and receiver system. === Failure Rates === I mentioned this in an ealier post, but there are two reasons why Spektrum gear appears to fail more often. 1. If all radio systems had an equal failure rate, then the radio with the largers population will have the largers number of failures (this was already stated by Lucien). 2. The radio that is most compliant will have the most problems. Why? Because it is the non-compliant radios that will "spray" into channels adjacent to their reserved frequencies and knock out other airplanes. Just like in the old days around 1991. The "Narrow-band" radio systems would get slaughtered by the older wide-band radios. Well, there's a TON of additional information on this subject, but's half-past midnight already (ugh). Awesome show, guys. Thanks! - Jim Last edited by macr0t0r; May 26, 2009 at 01:39 AM.