FLYING BALONEY
11-11-2011, 08:39 AM
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FLYING BALONEY
There seems to be a lot of misinformation being tossed adound on another site regarding two major spread spectrum radios on the market. The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop. Frequency hopping is indirect spread spectrum, not direct spread and operates in a completely different way than direct spread. In the direct spread spectrum system a P/N code is mixed with the data stream in a phase shift modulator (sine of X/X). The resulting envelope is a carrier suppressed double sideband spread signal. When the P/N sequence is re-inserted in the de-spread correlator (an Exclusive Or) in the receiver the embedded P/N in the signal and the added P/N cancel and only the data is left. The signal de-spreads or, vector sums to one while signals that do not correlate are spread into the noise. That is what makes direct spread far less prone to jamming and data loss.
So I wish the numbskulls who clearly have no understanding of the process yet are tossing BS around about how they work would just be quiet. They are not educating anyone and are putting out false information.
John.
So I wish the numbskulls who clearly have no understanding of the process yet are tossing BS around about how they work would just be quiet. They are not educating anyone and are putting out false information.
John.
11-11-2011, 11:39 AM
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RE: FLYING BALONEY
Ha! I was thinking this was going to be a thread about a tube (that looks like and is labled up like balogna) with stubby wings and a ducted fan or something....
Oh well....I'll keep dreaming about it then...[&:]
Oh well....I'll keep dreaming about it then...[&:]
11-11-2011, 12:20 PM
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RE: FLYING BALONEY
ORIGINAL: tommygun32
Ha! I was thinking this was going to be a thread about a tube (that looks like and is labled up like balogna) with stubby wings and a ducted fan or something....
Oh well....I'll keep dreaming about it then...[&:]
Ha! I was thinking this was going to be a thread about a tube (that looks like and is labled up like balogna) with stubby wings and a ducted fan or something....
Oh well....I'll keep dreaming about it then...[&:]
11-11-2011, 12:39 PM
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RE: FLYING BALONEY
Here's what Futaba has to say: http://www.futaba-rc.com/technology/fasst.html
If "continuous channel shifting" isn't frequency hopping (just another name for changing channels), then what is it? I think the OP has an error in their posting.
If "continuous channel shifting" isn't frequency hopping (just another name for changing channels), then what is it? I think the OP has an error in their posting.
11-14-2011, 07:08 AM
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RE: FLYING BALONEY
ORIGINAL: tommygun32
Ha! I was thinking this was going to be a thread about a tube (that looks like and is labled up like balogna) with stubby wings and a ducted fan or something....
Oh well....I'll keep dreaming about it then...[&:]
Ha! I was thinking this was going to be a thread about a tube (that looks like and is labled up like balogna) with stubby wings and a ducted fan or something....
Oh well....I'll keep dreaming about it then...[&:]
11-14-2011, 08:15 AM
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RE: FLYING BALONEY
The Spektrum system which is what they were attempting to rag on uses direct P/N sequence spread spectrum. It occupies a bandwidth that is determined by the P/N rate. Fewer bits equals less bandwidth, more bits equals more bandwidth. The FASST system uses an indirect spread spectrum system and does frequency hop so it's instantaneous signal bandwith remains the same but the average bandwidth is again determined by the P/N (Chip) rate so yes, it does hop. These are two ways to accomplish the same thing but the modulation and demodulation technique and the signal output is very different. The indirect spread system hops randomly within a preset bandwidth so that statistically there is a lower probability that interference will be on every frequency. The output looks like a standard FM PCM signal that jumps around.
The direct spread system spreads the signal over a bandwidth determined by the data rate so that the data is in many places at once and looks like a very wide suppressed carrier double sideband signal. The data in each sideband (either side of the carrier null) is identical and thus the probability of interference is greatly reduced. Because each tranmitter generates a unique code it allows a great many systems to occupy the same bandwidth at once without interference. This is exactly the same system used by cell phones where each phone has a unique P/N enabling Code Division Multiplex (putting many phones in the same radio spectrum) such that you only hear the signal that corellates to your unique ID (P/N code).
The direct spread system spreads the signal over a bandwidth determined by the data rate so that the data is in many places at once and looks like a very wide suppressed carrier double sideband signal. The data in each sideband (either side of the carrier null) is identical and thus the probability of interference is greatly reduced. Because each tranmitter generates a unique code it allows a great many systems to occupy the same bandwidth at once without interference. This is exactly the same system used by cell phones where each phone has a unique P/N enabling Code Division Multiplex (putting many phones in the same radio spectrum) such that you only hear the signal that corellates to your unique ID (P/N code).
11-15-2011, 08:48 AM
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RE: FLYING BALONEY
ORIGINAL: topspin
There seems to be a lot of misinformation being tossed adound on another site regarding two major spread spectrum radios on the market. The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop. Frequency hopping is indirect spread spectrum, not direct spread and operates in a completely different way than direct spread. In the direct spread spectrum system a P/N code is mixed with the data stream in a phase shift modulator (sine of X/X). The resulting envelope is a carrier suppressed double sideband spread signal. When the P/N sequence is re-inserted in the de-spread correlator (an Exclusive Or) in the receiver the embedded P/N in the signal and the added P/N cancel and only the data is left. The signal de-spreads or, vector sums to one while signals that do not correlate are spread into the noise. That is what makes direct spread far less prone to jamming and data loss.
So I wish the numbskulls who clearly have no understanding of the process yet are tossing BS around about how they work would just be quiet. They are not educating anyone and are putting out false information.
John.
There seems to be a lot of misinformation being tossed adound on another site regarding two major spread spectrum radios on the market. The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop. Frequency hopping is indirect spread spectrum, not direct spread and operates in a completely different way than direct spread. In the direct spread spectrum system a P/N code is mixed with the data stream in a phase shift modulator (sine of X/X). The resulting envelope is a carrier suppressed double sideband spread signal. When the P/N sequence is re-inserted in the de-spread correlator (an Exclusive Or) in the receiver the embedded P/N in the signal and the added P/N cancel and only the data is left. The signal de-spreads or, vector sums to one while signals that do not correlate are spread into the noise. That is what makes direct spread far less prone to jamming and data loss.
So I wish the numbskulls who clearly have no understanding of the process yet are tossing BS around about how they work would just be quiet. They are not educating anyone and are putting out false information.
John.
ORIGINAL: topspin
The Spektrum system which is what they were attempting to rag on uses direct P/N sequence spread spectrum. It occupies a bandwidth that is determined by the P/N rate. Fewer bits equals less bandwidth, more bits equals more bandwidth. The FASST system uses an indirect spread spectrum system and does frequency hop so it's instantaneous signal bandwith remains the same but the average bandwidth is again determined by the P/N (Chip) rate so yes, it does hop. These are two ways to accomplish the same thing but the modulation and demodulation technique and the signal output is very different. The indirect spread system hops randomly within a preset bandwidth so that statistically there is a lower probability that interference will be on every frequency. The output looks like a standard FM PCM signal that jumps around.
The direct spread system spreads the signal over a bandwidth determined by the data rate so that the data is in many places at once and looks like a very wide suppressed carrier double sideband signal. The data in each sideband (either side of the carrier null) is identical and thus the probability of interference is greatly reduced. Because each tranmitter generates a unique code it allows a great many systems to occupy the same bandwidth at once without interference. This is exactly the same system used by cell phones where each phone has a unique P/N enabling Code Division Multiplex (putting many phones in the same radio spectrum) such that you only hear the signal that corellates to your unique ID (P/N code).
The Spektrum system which is what they were attempting to rag on uses direct P/N sequence spread spectrum. It occupies a bandwidth that is determined by the P/N rate. Fewer bits equals less bandwidth, more bits equals more bandwidth. The FASST system uses an indirect spread spectrum system and does frequency hop so it's instantaneous signal bandwith remains the same but the average bandwidth is again determined by the P/N (Chip) rate so yes, it does hop. These are two ways to accomplish the same thing but the modulation and demodulation technique and the signal output is very different. The indirect spread system hops randomly within a preset bandwidth so that statistically there is a lower probability that interference will be on every frequency. The output looks like a standard FM PCM signal that jumps around.
The direct spread system spreads the signal over a bandwidth determined by the data rate so that the data is in many places at once and looks like a very wide suppressed carrier double sideband signal. The data in each sideband (either side of the carrier null) is identical and thus the probability of interference is greatly reduced. Because each tranmitter generates a unique code it allows a great many systems to occupy the same bandwidth at once without interference. This is exactly the same system used by cell phones where each phone has a unique P/N enabling Code Division Multiplex (putting many phones in the same radio spectrum) such that you only hear the signal that corellates to your unique ID (P/N code).
See the bolded portions of each post. Let us know when you decide which you really mean...
11-15-2011, 09:43 AM
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RE: FLYING BALONEY
ORIGINAL: CashD
See the bolded portions of each post. Let us know when you decide which you really mean...
ORIGINAL: topspin
There seems to be a lot of misinformation being tossed adound on another site regarding two major spread spectrum radios on the market. The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop. Frequency hopping is indirect spread spectrum, not direct spread and operates in a completely different way than direct spread. In the direct spread spectrum system a P/N code is mixed with the data stream in a phase shift modulator (sine of X/X). The resulting envelope is a carrier suppressed double sideband spread signal. When the P/N sequence is re-inserted in the de-spread correlator (an Exclusive Or) in the receiver the embedded P/N in the signal and the added P/N cancel and only the data is left. The signal de-spreads or, vector sums to one while signals that do not correlate are spread into the noise. That is what makes direct spread far less prone to jamming and data loss.
So I wish the numbskulls who clearly have no understanding of the process yet are tossing BS around about how they work would just be quiet. They are not educating anyone and are putting out false information.
John.
There seems to be a lot of misinformation being tossed adound on another site regarding two major spread spectrum radios on the market. The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop. Frequency hopping is indirect spread spectrum, not direct spread and operates in a completely different way than direct spread. In the direct spread spectrum system a P/N code is mixed with the data stream in a phase shift modulator (sine of X/X). The resulting envelope is a carrier suppressed double sideband spread signal. When the P/N sequence is re-inserted in the de-spread correlator (an Exclusive Or) in the receiver the embedded P/N in the signal and the added P/N cancel and only the data is left. The signal de-spreads or, vector sums to one while signals that do not correlate are spread into the noise. That is what makes direct spread far less prone to jamming and data loss.
So I wish the numbskulls who clearly have no understanding of the process yet are tossing BS around about how they work would just be quiet. They are not educating anyone and are putting out false information.
John.
ORIGINAL: topspin
The Spektrum system which is what they were attempting to rag on uses direct P/N sequence spread spectrum. It occupies a bandwidth that is determined by the P/N rate. Fewer bits equals less bandwidth, more bits equals more bandwidth. The FASST system uses an indirect spread spectrum system and does frequency hop so it's instantaneous signal bandwith remains the same but the average bandwidth is again determined by the P/N (Chip) rate so yes, it does hop. These are two ways to accomplish the same thing but the modulation and demodulation technique and the signal output is very different. The indirect spread system hops randomly within a preset bandwidth so that statistically there is a lower probability that interference will be on every frequency. The output looks like a standard FM PCM signal that jumps around.
The direct spread system spreads the signal over a bandwidth determined by the data rate so that the data is in many places at once and looks like a very wide suppressed carrier double sideband signal. The data in each sideband (either side of the carrier null) is identical and thus the probability of interference is greatly reduced. Because each tranmitter generates a unique code it allows a great many systems to occupy the same bandwidth at once without interference. This is exactly the same system used by cell phones where each phone has a unique P/N enabling Code Division Multiplex (putting many phones in the same radio spectrum) such that you only hear the signal that corellates to your unique ID (P/N code).
The Spektrum system which is what they were attempting to rag on uses direct P/N sequence spread spectrum. It occupies a bandwidth that is determined by the P/N rate. Fewer bits equals less bandwidth, more bits equals more bandwidth. The FASST system uses an indirect spread spectrum system and does frequency hop so it's instantaneous signal bandwith remains the same but the average bandwidth is again determined by the P/N (Chip) rate so yes, it does hop. These are two ways to accomplish the same thing but the modulation and demodulation technique and the signal output is very different. The indirect spread system hops randomly within a preset bandwidth so that statistically there is a lower probability that interference will be on every frequency. The output looks like a standard FM PCM signal that jumps around.
The direct spread system spreads the signal over a bandwidth determined by the data rate so that the data is in many places at once and looks like a very wide suppressed carrier double sideband signal. The data in each sideband (either side of the carrier null) is identical and thus the probability of interference is greatly reduced. Because each tranmitter generates a unique code it allows a great many systems to occupy the same bandwidth at once without interference. This is exactly the same system used by cell phones where each phone has a unique P/N enabling Code Division Multiplex (putting many phones in the same radio spectrum) such that you only hear the signal that corellates to your unique ID (P/N code).
See the bolded portions of each post. Let us know when you decide which you really mean...
FWIW, I was involved in the development of Spread Spectrum technology when I worked at the Harris Corp. in Florida. We developed both indirect and frequency hopping systems for the military back in the early to mid 1980s. When properly implemented direct sequence SS is a much better system than frequency hopping for several reasons especially immunity to inerference. That and the ability to implement CDMA is why the cell carriers all use it.
But yes, the Futaba does frequency hop. You happy now?
11-15-2011, 10:13 AM
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RE: FLYING BALONEY
ORIGINAL: topspin
There seems to be a lot of misinformation being tossed adound
The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop.
There seems to be a lot of misinformation being tossed adound
The Futaba and Spektrum systems use direct spread modulation schemes and don't frequency hop.
Yep...there sure is
