JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
12-12-2009, 08:19 PM
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JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
Hi,
Getting back into RC and just bought a Specktrum DX-7. Recently I've been told that this line of radios is not up to the current technology of Futaba and others. Apparently the JR/Spektrum line of radios are good but more prone to interference than other radios. I've been told that their radios in Japan are different (better) than ours here. Please comment on to what I've been told.
Thanks, Jerry
Getting back into RC and just bought a Specktrum DX-7. Recently I've been told that this line of radios is not up to the current technology of Futaba and others. Apparently the JR/Spektrum line of radios are good but more prone to interference than other radios. I've been told that their radios in Japan are different (better) than ours here. Please comment on to what I've been told.
Thanks, Jerry
12-12-2009, 08:55 PM
#2
My Feedback: (2)
RE: JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
I have a JR XP9303 with a Spektrum Module and numerous Spektrum Rx's. Most of our 121 RC Club members have Spektrum. We have had very little if any issues with Spektrum. There seems to be a Brand war out there and people line up to take sides and fight about which is better. There are many more players now then a couple of years ago.
See how the Tx looks and feels and what kind if programming is available. Look at the availability of Rx's and related hardware.
I do not really believe that there are enough significant differences in the way each manufacturer implements the 2.4 technology and the percentage of Link failures, to discount any manufacturer's 2.4 product.
The one truth is that what ever manufacturer you go with, when you buy their Tx, you have to use their Rx's. There are no 3rd party 2.4 Rx's.
Service and Warranty are also important.
Pick a brand and go have fun.
See how the Tx looks and feels and what kind if programming is available. Look at the availability of Rx's and related hardware.
I do not really believe that there are enough significant differences in the way each manufacturer implements the 2.4 technology and the percentage of Link failures, to discount any manufacturer's 2.4 product.
The one truth is that what ever manufacturer you go with, when you buy their Tx, you have to use their Rx's. There are no 3rd party 2.4 Rx's.
Service and Warranty are also important.
Pick a brand and go have fun.
12-13-2009, 06:23 AM
#3
Senior Member
RE: JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
Chevy? Ford? Chrysler? or Futaba? Spektrum? Nothing ever really changes much..
People defend their choice by knocking the other choice(s). Bah humbug. Don't pay any attention to them. rich
People defend their choice by knocking the other choice(s). Bah humbug. Don't pay any attention to them. rich
12-13-2009, 08:17 AM
#4
Senior Member
RE: JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
ORIGINAL: richg99
Chevy? Ford? Chrysler? or Futaba? Spektrum? Nothing ever really changes much..
People defend their choice by knocking the other choice(s). Bah humbug. Don't pay any attention to them. rich
Chevy? Ford? Chrysler? or Futaba? Spektrum? Nothing ever really changes much..
People defend their choice by knocking the other choice(s). Bah humbug. Don't pay any attention to them. rich
Extreme Link is the only brand that seems to have had some significant issues. We have JR/Spektrum, Futaba and Airtronics 2.4Ghz systems at our club. No problems
12-13-2009, 08:55 AM
#5
Member
RE: JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
I returned to this hobby after a very long absence. As a matter of fact I still have one of my "rubber power" escapement models ... Kraft was the big name then ... so I have a very large gap in my RC time as well as any modelling time. I have looked and listen to all about the pro's and con's of the various RC systems ... to me I found the modelers to be very proud of the system they used and noticed how hard they defended the Brand they had ... it looked to me as thought all these system were darn good! But I decided to go with a 2.4 as I believe this to be the coming technology in this sport. Was I wrong ... I think not ... the brand was I thought, a leader in this technology, so I based my choice of brand on that ... again I don't think I was wrong nor do I think that brand will continue the "lead" as this technology moves forward but I do think they will be at the front of the pact ... but that is just what I see ... the bottom line is, in my opinion, as long as you go with a recognized brand that has proven to be dependable, you will be making the right choice. Yes, I chose Spektrum!
12-13-2009, 10:25 AM
#6
My Feedback: (61)
RE: JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
Face it - neither frequency hopping (FASST) or DSM spread spectrum type radios are "new".. FHSS was used successfully in WWII with torpedos, DSS is what all the GPS satellites use, among other users, too. All the GPS satellites transmit on the same frequency, (the civilian accessible stuff, at least) and use different pseudo-random codes to allow the receivers to track multiple satellites at the same time. The use of them for model airplane / car control is fairly new, but the basic systems have been around a while.
From Wikipedia..
Frequency hopping
The concept of frequency hopping was first alluded to in the 1903 U.S. Patent 723,188 and U.S. Patent 725,605 filed by Nikola Tesla in July 1900. Tesla came up with the idea after demonstrating the world's first radio-controlled submersible boat in 1898, when it became apparent the wireless signals controlling the boat needed to be secure from "being disturbed, intercepted, or interfered with in any way." His patents covered two fundamentally different techniques for achieving immunity to interference, both of which functioned by altering the carrier frequency or other exclusive characteristic. The first had a transmitter that worked simultaneously at two or more separate frequencies and a receiver in which each of the individual transmitted frequencies had to be tuned in, in order for the control circuitry to respond. The second technique used a variable-frequency transmitter controlled by an encoding wheel that altered the transmitted frequency in a predetermined manner. These patents describe the basic principles of frequency hopping and frequency-division multiplexing, and also the electronic AND-gate logic circuit.
Frequency hopping is also mentioned in radio pioneer Johannes Zenneck's book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck himself states that Telefunken had already tried it several years earlier. Zenneck's book was a leading text of the time, and it is likely that many later engineers were aware of it. A Polish engineer, Leonard Danilewicz, came up with the idea in 1929.[1] Several other patents were taken out in the 1930s, including one by Willem Broertjes (Germany 1929, U.S. Patent 1,869,695, 1932). During World War II, the US Army Signal Corps was inventing a communication system called SIGSALY for communication between Roosevelt and Churchill, which incorporated spread spectrum, but due to its top secret nature, SIGSALY's existence did not become known until the 1980s.
The most celebrated invention of frequency hopping was that of actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their "Secret Communications System". Lamarr had learned about the problem at defense meetings she had attended with her former husband Friedrich Mandl, who was an Austrian arms manufacturer. The Antheil-Lamarr version of frequency hopping used a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam. The patent came to light during patent searches in the 1950s when ITT Corporation and other private firms began to develop Code Division Multiple Access (CDMA), a civilian form of spread spectrum, though the Lamarr patent had no direct impact on subsequent technology. It was in fact ongoing military research at MIT Lincoln Laboratory, Magnavox Government & Industrial Electronics Corporation, ITT and Sylvania Electronic Systems that led to early spread-spectrum technology in the 1950s. Parallel research on radar systems and a technologically similar concept called "phase coding" also had an impact on spread-spectrum development.
Direct Sequence Spread Spectrum:
In telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated. The name 'spread spectrum' comes from the fact that the carrier signals occur over the full bandwidth (spectrum) of a device's transmitting frequency.
Contents
[hide]
* 1 Features
* 2 Transmission method
* 3 Benefits
* 4 Uses
* 5 References
* 6 See also
* 7 External links
[edit] Features
1. It phase-modulates a sine wave pseudorandomly with a continuous string of pseudonoise (PN) code symbols called "chips", each of which has a much shorter duration than an information bit. That is, each information bit is modulated by a sequence of much faster chips. Therefore, the chip rate is much higher than the information signal bit rate.
2. It uses a signal structure in which the sequence of chips produced by the transmitter is known a priori by the receiver. The receiver can then use the same PN sequence to counteract the effect of the PN sequence on the received signal in order to reconstruct the information signal.
[edit] Transmission method
Direct-sequence spread-spectrum transmissions multiply the data being transmitted by a "noise" signal. This noise signal is a pseudorandom sequence of 1 and −1 values, at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band.
The resulting signal resembles white noise, like an audio recording of "static". However, this noise-like signal can be used to exactly reconstruct the original data at the receiving end, by multiplying it by the same pseudorandom sequence (because 1 × 1 = 1, and −1 × −1 = 1). This process, known as "de-spreading", mathematically constitutes a correlation of the transmitted PN sequence with the PN sequence that the receiver believes the transmitter is using.
For de-spreading to work correctly, the transmit and receive sequences must be synchronized. This requires the receiver to synchronize its sequence with the transmitter's sequence via some sort of timing search process. However, this apparent drawback can be a significant benefit: if the sequences of multiple transmitters are synchronized with each other, the relative synchronizations the receiver must make between them can be used to determine relative timing, which, in turn, can be used to calculate the receiver's position if the transmitters' positions are known. This is the basis for many satellite navigation systems.
The resulting effect of enhancing signal to noise ratio on the channel is called process gain. This effect can be made larger by employing a longer PN sequence and more chips per bit, but physical devices used to generate the PN sequence impose practical limits on attainable processing gain.
If an undesired transmitter transmits on the same channel but with a different PN sequence (or no sequence at all), the de-spreading process results in no processing gain for that signal. This effect is the basis for the code division multiple access (CDMA) property of DSSS, which allows multiple transmitters to share the same channel within the limits of the cross-correlation properties of their PN sequences.
As this description suggests, a plot of the transmitted waveform has a roughly bell-shaped envelope centered on the carrier frequency, just like a normal AM transmission, except that the added noise causes the distribution to be much wider than that of an AM transmission.
In contrast, frequency-hopping spread spectrum pseudo-randomly re-tunes the carrier, instead of adding pseudo-random noise to the data, which results in a uniform frequency distribution whose width is determined by the output range of the pseudo-random number generator.
[edit] Benefits
* Resistance to intended or unintended jamming
* Sharing of a single channel among multiple users
* Reduced signal/background-noise level hampers interception (stealth)
* Determination of relative timing between transmitter and receiver
[edit] Uses
* The United States GPS and European Galileo satellite navigation systems
* DS-CDMA (Direct-Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes. It is the most widely used type of CDMA.
* Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands
* IEEE 802.11b 2.4 GHz Wi-Fi, and its predecessor 802.11-1999. (Their successor 802.11g uses OFDM instead)
* Automatic meter reading
* IEEE 802.15.4 (PHY and MAC layer for ZigBee)
From Wikipedia..
Frequency hopping
The concept of frequency hopping was first alluded to in the 1903 U.S. Patent 723,188 and U.S. Patent 725,605 filed by Nikola Tesla in July 1900. Tesla came up with the idea after demonstrating the world's first radio-controlled submersible boat in 1898, when it became apparent the wireless signals controlling the boat needed to be secure from "being disturbed, intercepted, or interfered with in any way." His patents covered two fundamentally different techniques for achieving immunity to interference, both of which functioned by altering the carrier frequency or other exclusive characteristic. The first had a transmitter that worked simultaneously at two or more separate frequencies and a receiver in which each of the individual transmitted frequencies had to be tuned in, in order for the control circuitry to respond. The second technique used a variable-frequency transmitter controlled by an encoding wheel that altered the transmitted frequency in a predetermined manner. These patents describe the basic principles of frequency hopping and frequency-division multiplexing, and also the electronic AND-gate logic circuit.
Frequency hopping is also mentioned in radio pioneer Johannes Zenneck's book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck himself states that Telefunken had already tried it several years earlier. Zenneck's book was a leading text of the time, and it is likely that many later engineers were aware of it. A Polish engineer, Leonard Danilewicz, came up with the idea in 1929.[1] Several other patents were taken out in the 1930s, including one by Willem Broertjes (Germany 1929, U.S. Patent 1,869,695, 1932). During World War II, the US Army Signal Corps was inventing a communication system called SIGSALY for communication between Roosevelt and Churchill, which incorporated spread spectrum, but due to its top secret nature, SIGSALY's existence did not become known until the 1980s.
The most celebrated invention of frequency hopping was that of actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their "Secret Communications System". Lamarr had learned about the problem at defense meetings she had attended with her former husband Friedrich Mandl, who was an Austrian arms manufacturer. The Antheil-Lamarr version of frequency hopping used a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam. The patent came to light during patent searches in the 1950s when ITT Corporation and other private firms began to develop Code Division Multiple Access (CDMA), a civilian form of spread spectrum, though the Lamarr patent had no direct impact on subsequent technology. It was in fact ongoing military research at MIT Lincoln Laboratory, Magnavox Government & Industrial Electronics Corporation, ITT and Sylvania Electronic Systems that led to early spread-spectrum technology in the 1950s. Parallel research on radar systems and a technologically similar concept called "phase coding" also had an impact on spread-spectrum development.
Direct Sequence Spread Spectrum:
In telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated. The name 'spread spectrum' comes from the fact that the carrier signals occur over the full bandwidth (spectrum) of a device's transmitting frequency.
Contents
[hide]
* 1 Features
* 2 Transmission method
* 3 Benefits
* 4 Uses
* 5 References
* 6 See also
* 7 External links
[edit] Features
1. It phase-modulates a sine wave pseudorandomly with a continuous string of pseudonoise (PN) code symbols called "chips", each of which has a much shorter duration than an information bit. That is, each information bit is modulated by a sequence of much faster chips. Therefore, the chip rate is much higher than the information signal bit rate.
2. It uses a signal structure in which the sequence of chips produced by the transmitter is known a priori by the receiver. The receiver can then use the same PN sequence to counteract the effect of the PN sequence on the received signal in order to reconstruct the information signal.
[edit] Transmission method
Direct-sequence spread-spectrum transmissions multiply the data being transmitted by a "noise" signal. This noise signal is a pseudorandom sequence of 1 and −1 values, at a frequency much higher than that of the original signal, thereby spreading the energy of the original signal into a much wider band.
The resulting signal resembles white noise, like an audio recording of "static". However, this noise-like signal can be used to exactly reconstruct the original data at the receiving end, by multiplying it by the same pseudorandom sequence (because 1 × 1 = 1, and −1 × −1 = 1). This process, known as "de-spreading", mathematically constitutes a correlation of the transmitted PN sequence with the PN sequence that the receiver believes the transmitter is using.
For de-spreading to work correctly, the transmit and receive sequences must be synchronized. This requires the receiver to synchronize its sequence with the transmitter's sequence via some sort of timing search process. However, this apparent drawback can be a significant benefit: if the sequences of multiple transmitters are synchronized with each other, the relative synchronizations the receiver must make between them can be used to determine relative timing, which, in turn, can be used to calculate the receiver's position if the transmitters' positions are known. This is the basis for many satellite navigation systems.
The resulting effect of enhancing signal to noise ratio on the channel is called process gain. This effect can be made larger by employing a longer PN sequence and more chips per bit, but physical devices used to generate the PN sequence impose practical limits on attainable processing gain.
If an undesired transmitter transmits on the same channel but with a different PN sequence (or no sequence at all), the de-spreading process results in no processing gain for that signal. This effect is the basis for the code division multiple access (CDMA) property of DSSS, which allows multiple transmitters to share the same channel within the limits of the cross-correlation properties of their PN sequences.
As this description suggests, a plot of the transmitted waveform has a roughly bell-shaped envelope centered on the carrier frequency, just like a normal AM transmission, except that the added noise causes the distribution to be much wider than that of an AM transmission.
In contrast, frequency-hopping spread spectrum pseudo-randomly re-tunes the carrier, instead of adding pseudo-random noise to the data, which results in a uniform frequency distribution whose width is determined by the output range of the pseudo-random number generator.
[edit] Benefits
* Resistance to intended or unintended jamming
* Sharing of a single channel among multiple users
* Reduced signal/background-noise level hampers interception (stealth)
* Determination of relative timing between transmitter and receiver
[edit] Uses
* The United States GPS and European Galileo satellite navigation systems
* DS-CDMA (Direct-Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes. It is the most widely used type of CDMA.
* Cordless phones operating in the 900 MHz, 2.4 GHz and 5.8 GHz bands
* IEEE 802.11b 2.4 GHz Wi-Fi, and its predecessor 802.11-1999. (Their successor 802.11g uses OFDM instead)
* Automatic meter reading
* IEEE 802.15.4 (PHY and MAC layer for ZigBee)
12-13-2009, 06:19 PM
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RE: JR/SPEKTRUM NOT TO LATESTTECHNOLOGY??
ORIGINAL: jerryantczak
Apparently the JR/Spektrum line of radios are good but more prone to interference than other radios.
Apparently the JR/Spektrum line of radios are good but more prone to interference than other radios.
2.4 Ghz technology does not have a problem with interference. Some may experience difficulties with "brown-outs" or "signal loss". But, those are caused by other symptoms, such as, receiver or satellite installation, or diminished battery power.
It would be to your advantage to learn the correct terminology for a given problem. Especially, as you're a new technology newbie, so to speak. Too often someone will use the wrong term, in explaining the cause of their mishap, and they'll get the wrong corrective action in return.
Lots of help available on RCU, from lots of experienced users. Be sure to ask away, (or search, first) and you can avoid some of the common errors.
Have fun, and HTH,
EJ
