Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
12-28-2007, 11:44 PM
#26
RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
ORIGINAL: Flying Geezer
I can answer some of your questions.
1. Futaba apparantly believes that switching frequencies 500 times per second doesn't let you stay on a dirty frequency for very long. I believe the other manufacturers switch only when interfered with.
The U.S. military also uses a variation of freq hopping for their communications as it is hard for the enemy to follow and hard to jam. With compressed burst transmissions the entire message can be sent before the enemy can even detect the signal let alone track it's origin.
To the best of my knowledge the Spektrum doesn't change freqs even if jammed. How would the TX know it was blockked and therefore change?
2. I don't know that they do.
Range is slightly better perhaps but more likely just improved components. Also 5.8 GHz is becoming the new optimum phone band.
3. Because they are not limited to just 50 channels where someone can turn-on on your frequency. Also because the ultra-high frequency is almost impervious to things like ignition noise, and because devices operating on these high frequencies also run at low power. Not so on 72 mHz, eliminates distant interference.
All true.
4. Think of the speed of radios like you do the speed of computers. 2.4 gHz is about 33 times faster, if my quick calculation is right. Your receiver get about 2.4 million commands per second.
Nope. First 2.4 GHz is 2,400 million cycles per second which is the operating frequency but not the command repetition rate (much lower). The signal repetition rate is the same a 72MHz radios when modules are used. The Main encoder board inside the TX determines the repetition rate and doesn't change just because you plug in a module.
5. Longer antennae are not possible at 2.4. Antennas are a tuned device, and the proper length of an antenna is inversely proportionnal to frequency. The higher the frequency, the shorter the antenna.
While correct about antennas being inverely proportional to freq you CAN still have a longer antenna but length is more critical in this freq range. Instead of a 1/4 wave antenna you could have a 1/2 wave or other multiple. There is a practical limit of course and for FASST Futaba would also want you to maintain the 90 degree difference.
6. A whip antenna is just too long to work.
Nope. A properly made whip or "spike" andtenna could be used. Difficulty again occurs at higher frequencies where connectors become more critical. If you have ever ran a TDR (Time Domain Reflectometer) on a long length of antenna coax it would show you every little bump(connection) in the line as well as where the coax has been pinched or damaged. Connecting the RX antenna to the whip/spike would be the tough part to do properly.
7. Because there are not channels, they just keep changing frequency anytime they interfere with each other, and they do it so fast, you don't even notice. Most of the non-rc devices switch frequencies too. It's like an insame game of electronic bumper cars.
The FASST systems change freqs constantly without waiting for possible interference. Don't care if there is interference as they are already gone. IMO the Spektrum system is considerably more susceptable to interference but have been doing OK due to dual freqs. Chances of jams on both freqs are minimal.
Not meaning to debate Flying Geezer but his post gave me a chance to present some additional views.
I can answer some of your questions.
1. Futaba apparantly believes that switching frequencies 500 times per second doesn't let you stay on a dirty frequency for very long. I believe the other manufacturers switch only when interfered with.
The U.S. military also uses a variation of freq hopping for their communications as it is hard for the enemy to follow and hard to jam. With compressed burst transmissions the entire message can be sent before the enemy can even detect the signal let alone track it's origin.
To the best of my knowledge the Spektrum doesn't change freqs even if jammed. How would the TX know it was blockked and therefore change?
2. I don't know that they do.
Range is slightly better perhaps but more likely just improved components. Also 5.8 GHz is becoming the new optimum phone band.
3. Because they are not limited to just 50 channels where someone can turn-on on your frequency. Also because the ultra-high frequency is almost impervious to things like ignition noise, and because devices operating on these high frequencies also run at low power. Not so on 72 mHz, eliminates distant interference.
All true.
4. Think of the speed of radios like you do the speed of computers. 2.4 gHz is about 33 times faster, if my quick calculation is right. Your receiver get about 2.4 million commands per second.
Nope. First 2.4 GHz is 2,400 million cycles per second which is the operating frequency but not the command repetition rate (much lower). The signal repetition rate is the same a 72MHz radios when modules are used. The Main encoder board inside the TX determines the repetition rate and doesn't change just because you plug in a module.
5. Longer antennae are not possible at 2.4. Antennas are a tuned device, and the proper length of an antenna is inversely proportionnal to frequency. The higher the frequency, the shorter the antenna.
While correct about antennas being inverely proportional to freq you CAN still have a longer antenna but length is more critical in this freq range. Instead of a 1/4 wave antenna you could have a 1/2 wave or other multiple. There is a practical limit of course and for FASST Futaba would also want you to maintain the 90 degree difference.
6. A whip antenna is just too long to work.
Nope. A properly made whip or "spike" andtenna could be used. Difficulty again occurs at higher frequencies where connectors become more critical. If you have ever ran a TDR (Time Domain Reflectometer) on a long length of antenna coax it would show you every little bump(connection) in the line as well as where the coax has been pinched or damaged. Connecting the RX antenna to the whip/spike would be the tough part to do properly.
7. Because there are not channels, they just keep changing frequency anytime they interfere with each other, and they do it so fast, you don't even notice. Most of the non-rc devices switch frequencies too. It's like an insame game of electronic bumper cars.
The FASST systems change freqs constantly without waiting for possible interference. Don't care if there is interference as they are already gone. IMO the Spektrum system is considerably more susceptable to interference but have been doing OK due to dual freqs. Chances of jams on both freqs are minimal.
Not meaning to debate Flying Geezer but his post gave me a chance to present some additional views.
12-29-2007, 12:00 AM
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
Thanks for the additional info Bruce. I was trying to keep it fairly simple.
When I said they change freq. when they hit interference, I was referring to all but FAAST.
Your point on antenna length is correct, but impractical and unnecessary.
But overall, I think JC down in Texas should have the basic concepts worked out in his mind. And maybe a few others.
I haven't really studied the systems in any detail. My RF experience is mostly from years as a broadcast engineer. Sounds like you've put some time into it.
When I said they change freq. when they hit interference, I was referring to all but FAAST.
Your point on antenna length is correct, but impractical and unnecessary.
But overall, I think JC down in Texas should have the basic concepts worked out in his mind. And maybe a few others.
I haven't really studied the systems in any detail. My RF experience is mostly from years as a broadcast engineer. Sounds like you've put some time into it.
12-29-2007, 12:07 AM
#28
RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
ORIGINAL: Flying Geezer
Thanks for the additional info Bruce. I was trying to keep it fairly simple.
When I said they change freq. when they hit interference, I was referring to all but FAAST.
Your point on antenna length is correct, but impractical and unnecessary.
But overall, I think JC down in Texas should have the basic concepts worked out in his mind. And maybe a few others.
I haven't really studied the systems in any detail. My RF experience is mostly from years as a broadcast engineer. Sounds like you've put some time into it.
Thanks for the additional info Bruce. I was trying to keep it fairly simple.
When I said they change freq. when they hit interference, I was referring to all but FAAST.
Your point on antenna length is correct, but impractical and unnecessary.
But overall, I think JC down in Texas should have the basic concepts worked out in his mind. And maybe a few others.
I haven't really studied the systems in any detail. My RF experience is mostly from years as a broadcast engineer. Sounds like you've put some time into it.
General Radio Telephone (ex-first class). Sorry, no broadcast endorsement.
12-29-2007, 09:02 AM
#29
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
I had the "first class" for many years, left broadcasting but kept it renewed. When they issued me a "general" for life I was glad I didn't have to keep up with renewals anymore.
I think they have quit requiring it for broadcasting. The equipment is so expensive now, I guess they figure management won't hire an incompetant.
Young engineers come to see me sometime for help with some of the old tube type transmitters.
I think they have quit requiring it for broadcasting. The equipment is so expensive now, I guess they figure management won't hire an incompetant.
Young engineers come to see me sometime for help with some of the old tube type transmitters.
12-29-2007, 09:26 AM
#30
Senior Member
RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
Thank you for the info Bruce and Geezer,
I had a 20 year career in radio and TV broadcasting and used to have the 3rd Class FCC License, but that was just so I could "read the meters" and make the required entries in the transmitter logs. I was an on-air announcer (DJ, news reporter, and finally TV weatherman). So I didn't do any hands-on technical stuff.
Yesterday I did a little Googling on "Digital Spread Spectrum" and found answers to most of my questions. This link was informative: http://www.howstuffworks.com/question326.htm It's interesting that Tesla invented "Spread Spectrum". He invented the first radio-controlled machines, a submarine and a boat and demonstrated them in 1898. So here we are the beneficiaries more than one hundred years later and the technology has been greatly developed and refined. We owe those early electrical pioneers a huge "THANK YOU". Just think, if it hadn't have been for Thomas Edison, we would all be watching TV by candlelight.
Regards
JC
I had a 20 year career in radio and TV broadcasting and used to have the 3rd Class FCC License, but that was just so I could "read the meters" and make the required entries in the transmitter logs. I was an on-air announcer (DJ, news reporter, and finally TV weatherman). So I didn't do any hands-on technical stuff.
Yesterday I did a little Googling on "Digital Spread Spectrum" and found answers to most of my questions. This link was informative: http://www.howstuffworks.com/question326.htm It's interesting that Tesla invented "Spread Spectrum". He invented the first radio-controlled machines, a submarine and a boat and demonstrated them in 1898. So here we are the beneficiaries more than one hundred years later and the technology has been greatly developed and refined. We owe those early electrical pioneers a huge "THANK YOU". Just think, if it hadn't have been for Thomas Edison, we would all be watching TV by candlelight.
Regards
JC
12-29-2007, 09:39 AM
#31
RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
http://en.wikipedia.org/wiki/Hedy_Lamarr
The inventor of SS Frequency Hopping technology.
The inventor of SS Frequency Hopping technology.
12-29-2007, 02:11 PM
#34
Senior Member
RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
The FASST spread spectrum was doing it's thing perfectly this morning.
I got to the flying field at 9 am. No wind...temp 56 degrees and lots of sunshine.
The kind of morning you hope for.
Engine runs better and prop bite better in colder air.
It warmed up to 67 and I flew until the world looked level.
Over the years, I've golfed, I've fished, I've played tennis, I've rode motorcycles.
For me, nothing is as much enjoyment as a good day flying RC.
Regards to all my fellow RC pilots everywhere.
JC
I got to the flying field at 9 am. No wind...temp 56 degrees and lots of sunshine.
The kind of morning you hope for.
Engine runs better and prop bite better in colder air.
It warmed up to 67 and I flew until the world looked level.
Over the years, I've golfed, I've fished, I've played tennis, I've rode motorcycles.
For me, nothing is as much enjoyment as a good day flying RC.
Regards to all my fellow RC pilots everywhere.
JC
12-30-2007, 08:23 PM
#35
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
JR/Spektrum has the edge with support. I asked a question in the futaba forum and it got deleted. In effect my question was answered, JR here I come.
01-02-2008, 06:49 PM
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
yakman
what was the question to Futaba that was not answered, i am looking towards the FASST system myself??
thanks
bill
what was the question to Futaba that was not answered, i am looking towards the FASST system myself??
thanks
bill
01-03-2008, 07:32 AM
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
I asked if the 14MZ was going to have the 2.4 module integral or if it was just the FM set with a 2.4 module in the back. I would like to know because if they are just a plug in module I will buy one now and the module later. My radio is really outdated( original multiplex cockpit, no ccpm and no dual elevator servos) and I am dying for a new set.
01-03-2008, 09:36 AM
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
The 14MZ, 12FG and 12Z all use the same TM-14 module. The 2.4 version of the 12FG radios are all identical with the FM version - just swap out the modules. They are not selling a 14MZ 2.4 version yet but when/if they do it most likely will be the 14MZ radio with a 2.4 module which is what they are doing with the 12FG.
01-03-2008, 07:51 PM
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RE: Spektrum 2.4Ghz DSM2 VS Futaba 2.4Ghz FAST
ORIGINAL: shakes268
The 14MZ, 12FG and 12Z all use the same TM-14 module. The 2.4 version of the 12FG radios are all identical with the FM version - just swap out the modules. They are not selling a 14MZ 2.4 version yet but when/if they do it most likely will be the 14MZ radio with a 2.4 module which is what they are doing with the 12FG.
The 14MZ, 12FG and 12Z all use the same TM-14 module. The 2.4 version of the 12FG radios are all identical with the FM version - just swap out the modules. They are not selling a 14MZ 2.4 version yet but when/if they do it most likely will be the 14MZ radio with a 2.4 module which is what they are doing with the 12FG.
Thanks Shakes. I have just spent an hour going through the futaba support form and saw the question asked many times, maybe thats why they deleted it. Would have been nice to know before.
Now i am stuck, I want 2.4, a radio that will service me for a long time, but i dont want no $3000+ radio with a flimsy looking appendage and useless stub on top.
