Horizon relases DSMX -- it hops!

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Re: Horizon relases DSMX -- it hops!

Postby RCModelReviews » Sun Feb 06, 2011 9:17 pm

VideoKing wrote:I’m still looking at exactly how this DSMX system works, because the worrying aspect for me is that they are staying with wide band sequencing. This could possible mean that every hop of their system, can blank out 3 or 4 of the competitions narrow band signals.

The beauty of spread-spectrum is that you can have multiple signals co-existing in the same part of the band without any significant interference. This is because of temporal dilution -- the fact that a transmitter can only send on exactly one frequency at any given instant in time.

So, the more of the band that a signal uses, the less chance there is that it will actually be sending any exact frequency at any given time.

This is how "spreading" (or PN) codes work with spread spectrum. They are a bit like "microhopping" within the channel that the system is currently using.

Perhaps I should do a video to show exactly how that works and therefore, how many SS systems can use what appears to be exactly the same range of frequencies at the same time without interfering with each other.

Any votes for that vid?
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Re: Horizon relases DSMX -- it hops!

Postby Allan Warner » Sun Feb 06, 2011 9:45 pm

Could be instructive to many.
If you also demonstrated the effect of using a 2.4gHz video Tx on the RC and conversly the effect of the 2.4gHz RC on the video it would fit in nicely with your FPV project. I get the impression, from reading the forums, that some people believe that it is possible to mix the two, which I believe is in error. A mention of the increased problem of mixing video and DSSS (Spektrum) RC would also be useful. If the DSSS system is switched on first and selects two channels that are covered by the video transmission then when the video is switched on - ''SPLAT-PLANE CRASH!!''
IMO the problem is not limited to flying from the same site. A lone FPV'er flying an airborne 2.4gHz 1000mW VTx close(towards) to a club site may cause the same result.
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Re: Horizon relases DSMX -- it hops!

Postby RCModelReviews » Sun Feb 06, 2011 10:22 pm

Yes, I've already demonstrated that if DSM2 chooses two adjacent channels (which it does on occasion) then a video transmitter on 2.4GHz can completely kill the RC link. I tested it with a 600mW 2.4GHz video sender but someone else repeated my experiments with a 50mW video and found exactly the same thing.

In my case, the video transmitter only had to be the same distance or closer to the receiver than the DSM2 transmitter for the lock-out to occur.

For this reason (and others) I don't recommend you use a 2.4GHz video signal with *any* 2.4GHz RC system.
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Re: Horizon relases DSMX -- it hops!

Postby toolman79 » Mon Feb 07, 2011 1:11 am

RCModelReviews wrote:
VideoKing wrote:I’m still looking at exactly how this DSMX system works, because the worrying aspect for me is that they are staying with wide band sequencing. This could possible mean that every hop of their system, can blank out 3 or 4 of the competitions narrow band signals.

The beauty of spread-spectrum is that you can have multiple signals co-existing in the same part of the band without any significant interference. This is because of temporal dilution -- the fact that a transmitter can only send on exactly one frequency at any given instant in time.

So, the more of the band that a signal uses, the less chance there is that it will actually be sending any exact frequency at any given time.

This is how "spreading" (or PN) codes work with spread spectrum. They are a bit like "microhopping" within the channel that the system is currently using.

Perhaps I should do a video to show exactly how that works and therefore, how many SS systems can use what appears to be exactly the same range of frequencies at the same time without interfering with each other.

Any votes for that vid?


1 vote here, I'd be very interested in seeing how that works
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Re: Horizon relases DSMX -- it hops!

Postby raptor22 » Mon Feb 07, 2011 6:07 am

Bruce I'd be dead keen on seeing such a vid reach fruition.

Just a thought, if you're finding it difficult to get radios for review is there no way that you could apeal to the New Zealand Advertising Standards Authority for funding to verify claims made by vendors in New Zealand.
I have some experience of how tough and exacting they can be. All it takes is a complaint where you or someone else feels that they are being mislead by the adverts.
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Re: Horizon relases DSMX -- it hops!

Postby RCModelReviews » Mon Feb 07, 2011 7:48 pm

Vid is filmed, just editing it up now.
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Re: Horizon relases DSMX -- it hops!

Postby RyanNX211 » Tue Feb 08, 2011 11:22 pm

Will Spektrum users now be permitted to operate in Europe and Japan :?:
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Re: Horizon relases DSMX -- it hops!

Postby RCModelReviews » Tue Feb 08, 2011 11:52 pm

I would say they will. From what I've read, DSM2 system was too powerful for a non-agile system but now that it "hops" it'll fall into the same category as FASST. Hopefully they've added a setting for France, where not all the band can be used.
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Re: Horizon relases DSMX -- it hops!

Postby Buzzkill » Wed Feb 09, 2011 6:05 am

How can average people (like me) get something to test our own 2.4 equipment like you (Bruce) do without going to the poor house? I'd love to be able to llook at the 2.4 in action like Bruce does on his monitor. I linked to this site on RCG without getting banned (yet) lol!
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Re: Horizon relases DSMX -- it hops!

Postby RCModelReviews » Wed Feb 09, 2011 6:26 am

You can use the same system I do -- I reviewed it here
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