2.4 Glitches - It Does Happen!
06-10-2010, 06:41 PM
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RE: 2.4 Glitches - It Does Happen!
dbcisco,
Dirtybird is right. I think you'll find that it's much harder to jam a signal than you think. But okay, I'll play along, and I have a 2.4G spectrum analyzer.
Assuming I've attached the images correctly (this is the first time I've posted images on this forum), there should be three images attached. The first image is simply the local 2.4G traffic in my neighborhood. I let it run for about 10 minutes. My router is clearly seen on wifi channel 2, and a neighbors router can be seen on channel 6. It also looks like there are some frequency hopping signals, but I don't know what those are (phones, baby monitors, who knows). The frequency hopping traffic peaks around -65 dBm, but the two router signals average somewhere around -85.
The second image is the same as the first, but I let it run an addtional 10 minutes. At around 12 minutes into the analysis, I turned on my microwave oven for two minutes. You can clearly see the trash that is being generated by it. Most of it is evident between wifi channel 6 thru 12, but you also see a strong concentration at both edges of the 2.4 band. The noise ranges anywhere from -80 to -30 dBm.
On the third image I restarted the test. I let the analyzer log for about 1 minute to record the background traffic. At around minute 1, I start the microwave oven and let it run for 3 minutes. Again you can clearly see the trash it is creating. About a minute or so into the oven cycle, I turn on my JR transmitter and receiver. I did this in my kitchen and I could only get the plane (receiver) about four feet from the microwave oven. The transmitter was located near the 2.4g analyzer, and they were both about six feet from the microwave oven and plane (receiver). Anyway, you can clearly see the two distinct channels the JR transmitter locked on by the red vertical bands in the upper graph. One is about 2.453 GHz, and the other is 2.468. They are about 15 MHZ apart. It's interesting that one of the two channels the JR transmitter picked was in the middle of the dirtiest part of the spectrum. The plane responded fine. The peak signal of my radio was around -10 dBm (this was when it was less than a foot from the analyzer)). I moved the transmitter around my kitchen & living room and I never noticed any interference. I moved the transmitter up to twenty plus feet away during this time. Once the microwave shut-off, I placed the transmitter less than six inches away from the analyzer. You can see the strong darker red band on the upper graph. I moved the transmitter around the room again just to illustrate the reduction in signal. You can clearly see the red band starting to lighten at the bottom of the upper graph.
Off course this doesn't really prove anything absolute, but it does illustrate how spread spectrum can continue to operate fine even in a dirty environment.
06-10-2010, 06:53 PM
#152
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RE: 2.4 Glitches - It Does Happen!
ORIGINAL: Nitro-Tom
I have worked extensively in RF, years ago....Motorola, Harris Corp, etc…We were doing high speed synthesizers and frequency hoping for military and commercial customers …..In the 1980’s[X(]
Now I have been out of the RF game for years and years (as I can’t make a living in that field where I live any longer) and now I do computers and LAN engineering….and I agree totally with dbcisco…..Knowing basics on both sides here (Computers and RF) one could shoot down ANY 2.4 with equipment I can purchase locally…..granted it would be an illegal setup…..but it could also simulate a failure from a “Legal†system…..spray enough poop on the band and you are done.
It would not even be difficult at all……to totally hose Futaba, JR/Spektrum, and or Hitec here……the linear amps, 802.11 (Computer wireless) devices available (routers, bluetooth devices, antennas)….. These are all readily available and would be all the equipment needed to do the job…
Heck, you want to “interfereâ€â€¦.. just use a spark plug, an oscillator and pulse into an ignition coil with the right setup reflecting the emissions like a satellite antenna (directional)……the broad band emissions coming from there will interfere with anything. (As evidenced by the original post)
I guess my point here is we take for granted how good the equipment we use really is…..and expect it to be 100% when it really is not…..it can’t be due to part 15 of the FCC rules…and I do not think Futaba / Hitec frequency hopping is any more “Immune†to real inference that my JR/Spektrum stuff. (My opinion)
You could be on my channel, but my Rx will not listen due to the GUID not being there…..so you would have to “Saturate†my Rx, which “Binds†on a different channel every time I boot up..(Tx on first, Rx on last)….and is “Flying†around at 60 MPH…..not easy to do unless it is intentional…
My 2 cents (the above is opinion and not fact)(in most cases)
ORIGINAL: dirtybird
I suggest you try what you are advocating. Then report your findings. I suspect you will find it is harder to jam a system than you think it is.
ORIGINAL: dbcisco
Well, each WIFI device acts (and competes for frequencies) just like a channel hopping 2.4Ghz RC TX/RX. The more you have the less effective the area will be. We are not talking interference here, it is competion for bandwidth. Identical to adding users on a computer hub with everyone trying to constantly download files. There comes a point where a 100/10Mhz hubbed LAN becomes as slow as a 56k modem. Surely in this day and age everyone can relate to that. At least you must have noticed that your broadband internet slowed down as more people in you area got it. Mine went from 10Mb/s to under 2Mb/s in a year.
Again, without a spektrum analyzer you have no idea what is going on. How could you tell that your radio is skipping 10% of the channels?
Get 20 planes, a WIFI routers and a dozen laptops surfing the web (streaming Netflix would be a real killer) and you will start to notice that things aren't quite right.
Of course I could bring over my router and knock out the entire field except FM. [>:] No I wouldn't do that. However I easily could. Boost the output to 2Watts and trim the input to the amp to insure severe clipping and I could jam the entire 2.4Ghz spektrum within at least a 1/2 mile radius. That of course is illegal to do on purpose, I am sure nobody ever tried boosting their routers output (and some routers will then clip the carrier wave as well).
Well, each WIFI device acts (and competes for frequencies) just like a channel hopping 2.4Ghz RC TX/RX. The more you have the less effective the area will be. We are not talking interference here, it is competion for bandwidth. Identical to adding users on a computer hub with everyone trying to constantly download files. There comes a point where a 100/10Mhz hubbed LAN becomes as slow as a 56k modem. Surely in this day and age everyone can relate to that. At least you must have noticed that your broadband internet slowed down as more people in you area got it. Mine went from 10Mb/s to under 2Mb/s in a year.
Again, without a spektrum analyzer you have no idea what is going on. How could you tell that your radio is skipping 10% of the channels?
Get 20 planes, a WIFI routers and a dozen laptops surfing the web (streaming Netflix would be a real killer) and you will start to notice that things aren't quite right.
Of course I could bring over my router and knock out the entire field except FM. [>:] No I wouldn't do that. However I easily could. Boost the output to 2Watts and trim the input to the amp to insure severe clipping and I could jam the entire 2.4Ghz spektrum within at least a 1/2 mile radius. That of course is illegal to do on purpose, I am sure nobody ever tried boosting their routers output (and some routers will then clip the carrier wave as well).
Now I have been out of the RF game for years and years (as I can’t make a living in that field where I live any longer) and now I do computers and LAN engineering….and I agree totally with dbcisco…..Knowing basics on both sides here (Computers and RF) one could shoot down ANY 2.4 with equipment I can purchase locally…..granted it would be an illegal setup…..but it could also simulate a failure from a “Legal†system…..spray enough poop on the band and you are done.
It would not even be difficult at all……to totally hose Futaba, JR/Spektrum, and or Hitec here……the linear amps, 802.11 (Computer wireless) devices available (routers, bluetooth devices, antennas)….. These are all readily available and would be all the equipment needed to do the job…
Heck, you want to “interfereâ€â€¦.. just use a spark plug, an oscillator and pulse into an ignition coil with the right setup reflecting the emissions like a satellite antenna (directional)……the broad band emissions coming from there will interfere with anything. (As evidenced by the original post)
I guess my point here is we take for granted how good the equipment we use really is…..and expect it to be 100% when it really is not…..it can’t be due to part 15 of the FCC rules…and I do not think Futaba / Hitec frequency hopping is any more “Immune†to real inference that my JR/Spektrum stuff. (My opinion)
You could be on my channel, but my Rx will not listen due to the GUID not being there…..so you would have to “Saturate†my Rx, which “Binds†on a different channel every time I boot up..(Tx on first, Rx on last)….and is “Flying†around at 60 MPH…..not easy to do unless it is intentional…
My 2 cents (the above is opinion and not fact)(in most cases)
06-10-2010, 07:31 PM
#153
RE: 2.4 Glitches - It Does Happen!
ORIGINAL: dbcisco
How would you know? Unless you have a 2.4Ghz spektrum analyzer you will not what is going on.
You're sharing 80 frquencies with all the devices near you. Wireless routers use frequency hopping so if you or your next door neighbor has a wireless router or cordless phone you are sharing and competing for the 80 frequencies, that is fully within FCC rules.
That is not truly interference, it is much like the cable/FIOS company adding internet users until people start complaining about how slow their connection is, then they add another line and router to provide a seperate path. It is also like an ethernet hub; add users until it gets so bad that you have to buy a switch (anyone using a hub today needs a shrink).
Interference is another matter. If any nearby device goes on the fritz it can stop everything (esp. a bad amp circuit clipping the carrier wave). I had an access point start transmitting on every channel at once (instead of hopping) and took out the entire school's WIFI. Generators and faulty car iginition systems (esp. older ones) can generate a noise spektrum that can be anything and everything RFI/EMI short of Xrays. Again without the proper electronics equipment you will have no idea what is going on.
Now, who has a 3Ghz oscilloscope at their clubhouse? I won't even ask about the 2-3Ghz spektrum analyzer
ORIGINAL: nonstoprc
I did not see another 2.4G source of increased power can interfere with our equipment, unless the device does not obey the FCC rule for operating in the 2.4G frequency band. I check my 2.4g radio at home all the time where signals from multiple wireless networks exist.
I did not see another 2.4G source of increased power can interfere with our equipment, unless the device does not obey the FCC rule for operating in the 2.4G frequency band. I check my 2.4g radio at home all the time where signals from multiple wireless networks exist.
You're sharing 80 frquencies with all the devices near you. Wireless routers use frequency hopping so if you or your next door neighbor has a wireless router or cordless phone you are sharing and competing for the 80 frequencies, that is fully within FCC rules.
That is not truly interference, it is much like the cable/FIOS company adding internet users until people start complaining about how slow their connection is, then they add another line and router to provide a seperate path. It is also like an ethernet hub; add users until it gets so bad that you have to buy a switch (anyone using a hub today needs a shrink).
Interference is another matter. If any nearby device goes on the fritz it can stop everything (esp. a bad amp circuit clipping the carrier wave). I had an access point start transmitting on every channel at once (instead of hopping) and took out the entire school's WIFI. Generators and faulty car iginition systems (esp. older ones) can generate a noise spektrum that can be anything and everything RFI/EMI short of Xrays. Again without the proper electronics equipment you will have no idea what is going on.
Now, who has a 3Ghz oscilloscope at their clubhouse? I won't even ask about the 2-3Ghz spektrum analyzer
1. Frequency hopping works by jumping to different channels at different time. It is not static like the 2-channel scheme.
2. Fancy error-correction logic is in place to filtered out bad data packets from these "noise" sources.
3. The amount of data needed to operate our RC planes is not that great. Most of time just some deltas to a reference frame (see Fufata's encoding scheme). So the RC control response delay as you described similar to cable companies adding users is difficult to detect (or become a problem). The new 2.4G equipment uses faster chips which help improve the response even more.
The bottom line is that RC equipment is unique.
06-10-2010, 08:54 PM
#154
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RE: 2.4 Glitches - It Does Happen!
DBSPL,
You are terrific! So glad you provided some real evidence!
I am now convinced that nosie is not a problem with JR/Spektrum (at the least).
Forget all theories of mine (and others), they are rubish.
Proof trumps any theory.
I thank you for the experiment and proving me wrong!
You are terrific! So glad you provided some real evidence!
I am now convinced that nosie is not a problem with JR/Spektrum (at the least).
Forget all theories of mine (and others), they are rubish.
Proof trumps any theory.
I thank you for the experiment and proving me wrong!
06-10-2010, 11:48 PM
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RE: 2.4 Glitches - It Does Happen!
For those that like to worry,here is something to chew on for next year.
http://www.insidegnss.com/node/114
http://www.insidegnss.com/node/114
06-11-2010, 10:17 AM
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RE: 2.4 Glitches - It Does Happen!
DBCISCO,
Are you using the $99 WY SPY module for the spectrum monitor? If so, how do you like it? I'm on the verge of buying one for club use at our local field.
Jim
Are you using the $99 WY SPY module for the spectrum monitor? If so, how do you like it? I'm on the verge of buying one for club use at our local field.
Jim
06-11-2010, 10:35 AM
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RE: 2.4 Glitches - It Does Happen!
Its an obsolete (way before 802.11) network card but it doubles as a spektrum analyser with included program.
I should have a new antenna for it next week.
To bad modern cards doen't have this feature since it is built into the chips they use.
There is a hack for some of them to access the function, but I can't recall the link to it.
The WySpy and others are pretty much the same thing. At least they are affordable. Not as exact as a $5000 one but we don't really need a certified unit do we?
I should have a new antenna for it next week.
To bad modern cards doen't have this feature since it is built into the chips they use.
There is a hack for some of them to access the function, but I can't recall the link to it.
The WySpy and others are pretty much the same thing. At least they are affordable. Not as exact as a $5000 one but we don't really need a certified unit do we?
06-12-2010, 11:24 PM
#158
RE: 2.4 Glitches - It Does Happen!
Things I have learned here:
1. 2.4Ghz can get shot down.
Duh! its electronics there are always limitations.
2. Faast is less likely to get shot down.
Are you willing to pay more for a little more piece of mind?
3. In general 2.4Ghz is more reliable than 72Mhz.
Does 72Mhz still work for you?
4. In every argument you reach a point of diminishing returns.
I think it has been surpassed
What I still haven't learned is did the new plug work?
1. 2.4Ghz can get shot down.
Duh! its electronics there are always limitations.
2. Faast is less likely to get shot down.
Are you willing to pay more for a little more piece of mind?
3. In general 2.4Ghz is more reliable than 72Mhz.
Does 72Mhz still work for you?
4. In every argument you reach a point of diminishing returns.
I think it has been surpassed
What I still haven't learned is did the new plug work?
06-13-2010, 12:51 AM
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RE: 2.4 Glitches - It Does Happen!
ORIGINAL: cfircav8r
....Does 72Mhz still work for you?
....did the new plug work?
....Does 72Mhz still work for you?
....did the new plug work?
His last post began "I got my hands on a replacement plug and will try it in just a few minutes"
Haven't heard from him since.
Either the plug worked or he stayed with the working FM setup. In either case I am assuming he has been out flying while we .... debated.
06-13-2010, 08:33 AM
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RE: 2.4 Glitches - It Does Happen!
Yes I have a job. I have the next two months off so don't get me going.
To show FASST would need a video rather than still shots form the analyzer.
To show FASST would need a video rather than still shots form the analyzer.
06-13-2010, 11:34 AM
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RE: 2.4 Glitches - It Does Happen!
I don't have a job. I just play with my airplanes all day long.
That is when I am not playing on the internet.
BTW I paid $100 for a thing called AirSleuth. I didn't get much out of it.
That is when I am not playing on the internet.
BTW I paid $100 for a thing called AirSleuth. I didn't get much out of it.
06-13-2010, 11:53 AM
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RE: 2.4 Glitches - It Does Happen!
Well the NZ guy is showing video.
For some reason Futaba FASST is afraid to send a system for test. Why don't you write Futaba and tell them to send one. Or better yet send one to the guy on loan for test.
For some reason Futaba FASST is afraid to send a system for test. Why don't you write Futaba and tell them to send one. Or better yet send one to the guy on loan for test.
06-13-2010, 12:31 PM
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RE: 2.4 Glitches - It Does Happen!
Futaba is not afraid of NZ guy. They just they just think if he wants to test it he should buy it. Thats what most testers do.
06-13-2010, 06:03 PM
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RE: 2.4 Glitches - It Does Happen!
Sounds lame to me. Have you spoke to Futaba about this?
If they are so sure of the superior approach they should be willing to provide a unit for eval.
If they are so sure of the superior approach they should be willing to provide a unit for eval.
06-13-2010, 06:45 PM
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RE: 2.4 Glitches - It Does Happen!
If NZ guy is big enough companies will donate products for review.
Forums (like RCU), websites and magazines are always given products for free to review.
Many times the reviewer gets to keep the product as "thanks" for reviewing their product and publishing the results.
I can get lots of products for review in my field of expertise, sadly it has nothing to do with RC.
Forums (like RCU), websites and magazines are always given products for free to review.
Many times the reviewer gets to keep the product as "thanks" for reviewing their product and publishing the results.
I can get lots of products for review in my field of expertise, sadly it has nothing to do with RC.
06-13-2010, 07:10 PM
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RE: 2.4 Glitches - It Does Happen!
ORIGINAL: JIMF14D
Sounds lame to me. Have you spoke to Futaba about this?
If they are so sure of the superior approach they should be willing to provide a unit for eval.
Sounds lame to me. Have you spoke to Futaba about this?
If they are so sure of the superior approach they should be willing to provide a unit for eval.
John also borrowed systems to do his test: http://rc.runryder.com/helicopter/t172571p1/
Do you really think that JR/Spektrum sent him a system to test?
Doug.
06-14-2010, 11:42 AM
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RE: 2.4 Glitches - It Does Happen!
Well there is an old saying "Never ask a question if you cannot afford the answer". Maybe at Futaba prices they cannot afford an independant test answer.
06-14-2010, 11:44 AM
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RE: 2.4 Glitches - It Does Happen!
Then why do they? Several magavines and websites get given Futaba stuff for review?
Do you think the magazines buy the stuff? Nope!
Do you think the magazines buy the stuff? Nope!
06-14-2010, 11:52 AM
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RE: 2.4 Glitches - It Does Happen!
I don't mean a fly around and play with the knobs beauty contest test. Imean an RF interference and response evaluation type thing so we can see some science and data on a spectrum analyzer.
You could buy one and run the test and then sell it on Ebay. Maybe loose $50 bucks but be an RCUniverse Technical Hero!
You could buy one and run the test and then sell it on Ebay. Maybe loose $50 bucks but be an RCUniverse Technical Hero!
06-14-2010, 12:13 PM
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RE: 2.4 Glitches - It Does Happen!
ORIGINAL: dbcisco
Then why do they? Several magavines and websites get given Futaba stuff for review?
Do you think the magazines buy the stuff? Nope!
Then why do they? Several magavines and websites get given Futaba stuff for review?
Do you think the magazines buy the stuff? Nope!
I did some reviews for RCU who paid for the items.
06-17-2010, 11:59 AM
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RE: 2.4 Glitches - It Does Happen!
ORIGINAL: dirtybird
All of the mags I know of bought their own review items.
I did some reviews for RCU who paid for the items.
All of the mags I know of bought their own review items.
I did some reviews for RCU who paid for the items.
What magazines did you do work for?
I know other RC websites (with forums) get the products for free and have an intensive interview process for reviewers to detrmine the products they might review. The reviewers must have their own digital (still and video) cameras, code in html and java script, pass a writing test, follow all standards for publication etc.
Reviewers get to keep what they review. The website gets the products from the companies for free (possibly even pay to get the review on the site).
I doubt that magazine are any less rigorous or pay for products. Maybe buy a "hot item" occasionaly but I doubt much more.