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May 21, 2008, 04:43 AM
Oopss. Oh well.
borneobear's Avatar
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Question

Only now Applying for FCC frequency Hopping?


I refer Jims comment here:

https://www.rcgroups.com/forums/show...1&postcount=21

Quote:
Originally Posted by JimDrew
We expect a mid-June release of the new software and firmware, providing we get a favorable response from the FCC concerning frequency hopping issues.
Jim, are you saying that you are only now applying for your product to hop???

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May 21, 2008, 10:48 AM
Dick Corby
altacom's Avatar
Quote:
Originally Posted by borneobear
I refer Jims comment here:

https://www.rcgroups.com/forums/show...1&postcount=21



Jim, are you saying that you are only now applying for your product to hop???

I as well caught that! Interesting to me as I thought that when I bought into it that it was FCC approved.
May 21, 2008, 10:59 AM
User
This was mentioned several times in the "hopping video" thread:
https://www.rcgroups.com/forums/show...6&postcount=39

Quote:
Originally Posted by JimDrew
...How this all came about is I was very curious how Spektrum can legally hop between two channels using a device that was certified for transmitting on a single channel. Every 22ms, their system changes frequencies, and it is not a pseudo-random hopping sequence that is required along with no fewer than 15 channels. So, I contacted the FCC about this, SAR testing, and some other things. I got conflicting responses in regards to the channel hopping. Hybrid rules are a bit sketchy. Our current hopping code uses a minimum switch time of 450ms at the recommendation of the FCC 2+ years ago. Since that time, there has been several changes to the rules, which is why I believe their has been some confusion in responses from the FCC.

I look forward to the response from the FCC about this matter. As soon as we have a definitive answer, we can proceed forward with foiling the bench testers.
May 21, 2008, 12:07 PM
We are not applying for anything. We were looking for clarification from the FCC concerning the definition of a Hybrid device in regards to the difference between true FHSS and DSSS.

We just received more information from the FCC and have one clarification pending. We just want to make sure that we don't violate any rules by adding the change on saturation hop.
May 21, 2008, 07:05 PM
Registered User
so hopefully after this we can send our old stuff in for an upgrade so it will hop?
May 22, 2008, 10:06 AM
The upgrade would add a hop on saturation event to the existing hopping code. This is only going to foil the bench testers as this type of thing does not occur in the real world.
May 22, 2008, 11:02 AM
Registered User
jellyfish's Avatar
Quote:
Originally Posted by JimDrew
The upgrade would add a hop on saturation event to the existing hopping code. This is only going to foil the bench testers as this type of thing does not occur in the real world.
OMG, Another case of Forward-looking statement
May 22, 2008, 01:46 PM
Registered User
Just to be clear - When you say "hop" you do not mean the boot-up channel selection, right?

What kind of noise does the system need to see to initiate a hop as it is now without the update? How can this noise be reproduced on the bench so that these "bench testers" can test that part of the system? Why write the extra code, go through all the individual component updates if it's not really needed?

I don't think anyone is asking for the top secret software code, just a way to reproduce the magical hop-inducing noise for the system as it is right now.
May 22, 2008, 02:08 PM
Proud to eat Kraut ;-)
Julez's Avatar
Quote:
Originally Posted by JimDrew
The upgrade would add a hop on saturation event to the existing hopping code. This is only going to foil the bench testers as this type of thing does not occur in the real world.
The thing is, the bench testers did not saturate the band
Last edited by JimDrew; May 22, 2008 at 02:54 PM.
May 22, 2008, 02:11 PM
Inciting Riots
village_idiot's Avatar
He is making it so that if the signal gets whacked by a video system, as soon as it can communicate with the TX module again they will decide what channel to go to and move away from the video signal (or other disruptive signal). And apparently he is being cautious about the amount of time and number of jumps that are allowed by the current FCC rules, so until the FCC clarifies everything it is pointless to finalize the code for the XPS system. Jumping too often might require that the system be labeled as an FHSS system, and would need to comply with those rules, so it is wise to wait until the FCC sets things "in stone" before finalizing the changes.
May 22, 2008, 02:47 PM
Registered User
'as soon as it can communicate with the TX module again they will decide what channel to go to and move away from the video signal "

And if they can communicate why move? Adaptive hopping (that actually works) usually applies to frequency hopping system that identifies certain channels are "bad" and modifies its sequence (in some way) to avoid them.
May 22, 2008, 03:12 PM
People do not fly with Wifi device attached to their aircraft (especially one that is not even FCC certified, like the Air Horn used in the bench test video). Bench testing does not represent real world results. A report made to the AMA frequency committee, stated that the Futaba FASST system slows down after 30 DX7 systems are turned on and it would not be advisable to fly with more DX7's turned on. The XPS and Spektrum module systems experienced no issues with any number of DX7's turned on. However, the SEFF event where XPS, Spektrum, and FASST systems (59 total in use simultaneously) were being used, clearly showed that there were no slow downs or lockouts in a REAL WORLD condition.

The system does not need to wait to communicate for switching frequencies. That would be too late. While not transmitting data, the frequencies are always scanned and compared. That is how the current hopping code works. What I would like to add are several instant backup channels, where we can transmit on multiple frequencies in a row to re-arbitrate the connection. Instead of "locking on" to two channels like Spektrum does, we could "lock on" to all of the channels, and release the channels we don't need until finally only one is being used. The FCC has cleared us for this type of communication, but there is a question in regards to timing considerations. This type of hopping ability would foil the bench testers and would actually allow multiple video cameras to be used on board at the same time.
May 22, 2008, 03:43 PM
Inciting Riots
village_idiot's Avatar
How much battery power is going to be consumed when all the channels are locked (even though it may be for a very short time)?
Last edited by JimDrew; May 22, 2008 at 06:35 PM. Reason: oops!
May 22, 2008, 03:52 PM
Inciting Riots
village_idiot's Avatar
Quote:
Originally Posted by teamdavey
And if they can communicate why move? Adaptive hopping (that actually works) usually applies to frequency hopping system that identifies certain channels are "bad" and modifies its sequence (in some way) to avoid them.

That's great if you can see the noise coming, and I would hope that the adaptive is part of the change. But what if you don't see it coming? If you can get out enough data to say "change to channel 4" and get a reply back through the noise that the other end said "OK I'll be waiting on channel 4" then you would be covered for sudden sustained problems too.

Now if it is scanning all the time, and it sees a small amount of garbage on channel 3 and 4 while using 3, it might be wise to jump up to another free channel before the jerk with the 2.4Ghz 50 watt video system flys up close to you. ( I say jerk because a lot of people buy highly over powered devices illegally without even knowing that they are illegal to use in their location)
May 22, 2008, 04:38 PM
Registered User
Big if - adaptive system configurations are very hard to get right.


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