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Sep 19, 2016, 03:35 PM
Registered User
Thread OP
Question

interference with two frequency hopping 2.4 Ghz radios next to each other?


hi

I currently own a Spektrum SPM6630 DX6i 6-channel DSMX® Zender met AR610 receier, Mode 2 . (2.4 Ghz)

I know it does this frequency hopping thing. Can I use another cheap 2.4 GHz transmitter next to this one (to control other stuff)? Or will it interfere?
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Sep 19, 2016, 04:10 PM
S.A.D. member
ivanc's Avatar
We do it all the time when flying 2 or more models at the field. Have not had any issues coming out of this.

Ivan
Sep 19, 2016, 04:13 PM
Registered User
Thread OP
Ok, thx!
Sep 19, 2016, 05:02 PM
Sagitta Fanboy
Depends on how close they are. There is a reduction in receiver sensitivity if there is another transmitter in close proximity that is not synchronized with the receiver. At the power levels we use, close proximity is under a half meter or so.

Remember, the receivers also transmit in certain circumstance (telemetry and on bind).

The other caveat is you want the other device to be of similar tech. Something like a video transmitter can swamp large chunks of the 2.4GHz band and cause major issues.
Sep 20, 2016, 03:58 AM
Registered User
Thread OP
My video is on 5.8 Ghz. Well, in my case, I would have to receivers within 10 cm of each other on the same quad, and two radios next to each other on the ground. I guess I better go for a different frequency I guess.
Sep 20, 2016, 06:18 AM
Perpetual Noob
BoxCar31's Avatar
There is enough frequency separation between 5.8 and 2.4 that you shouldn't run into any issues with the video transmitter and your control receiver separated by 10 cm. We also have to assume your platform has a carbon fiber frame and that does require some additional planning. Carbon fiber absorbs RF signals effectively blocking the exchange of data between your transmitter and receivers so antennas need to be away from any carbon frames.
Sep 20, 2016, 11:15 AM
Registered User
Quote:
Originally Posted by ivanc
We do it all the time when flying 2 or more models at the field. Have not had any issues coming out of this.

Ivan
Not it's not the same. There is swamping then there is regular on channel interference when both are away from each other and on the same channel. interference is Un-noticeable but may make your connection lag, either way it's still there.
Sep 20, 2016, 02:42 PM
Registered User
Thread OP
I wasn't very clear, let me clarify:

My video is on 5.8 Ghz
my radio is on 2.4 Ghz.

but now I wanna add channels to my radio control, and the cheapest way is to add an extra receiver on 2.4 Ghz and an extra radio. Both receivers and radios/transmitters would be very close to each other. I could just buy a 9 channel radio or so, but this would be more expensive if I want a good one. But I guess I could just buy a 73 Mhz/900 Mhz radio system, as I understand from thermal hobby interference will be there. However, e.g. on hobbyking, I don't seem to find many 73/900 Mhz systems... .
Sep 20, 2016, 03:35 PM
S.A.D. member
ivanc's Avatar
Quote:
Originally Posted by Thermal Hobby
Not it's not the same. There is swamping then there is regular on channel interference when both are away from each other and on the same channel. interference is Un-noticeable but may make your connection lag, either way it's still there.
Sorry, but I don't understand what you are saying. What same channel? 2.4GHz Spread Spectrum is a broadband system where the useful signal is below the noise floor. All devices can communicate in this environment due to the methods used to spread the data over the radio band being used. Even if two transmitters happen to be on exactly the same channel at exactly the same time (chances are really slim though) the receivers may still be able to pick their data based on the spreading code they use.

I've flown with other pilots in very close proximity, I've used two 2.4GHz modules attached to the same module transmitting at the same time and have never noticed any delay if there was any. So from theoretical and practical point of view there's no interference, or at least no noticeable difference.

Now, the 2.4GHz video transmitters do not play by those rules and yes, they will shoot you down. But anything which does not play by the rules is illegal to use anyways.

Ivan
Sep 22, 2016, 02:48 PM
Registered User
Thread OP
It seems that e.g. at hobbyking, only 2.4 Ghz radios are sold? Are radios in other frequency spectra still available?
Sep 22, 2016, 03:18 PM
AndyKunz's Avatar
You can probably find a 27MHz or 49MHz in some toys, but in general the model market has moved to 2.4gHz. There are a few 900MHz and 1200MHz systems out there for specialty sub-markets in the modeling hobby field, but very few.

Andy
Sep 23, 2016, 05:22 AM
Registered User
Thread OP
Ok, but then I guess the only option is to add another 2.4 ghz radio and receiver on the quad, which should work according to Ivanc. (Or buy a 9 channel radio)
Sep 23, 2016, 08:26 AM
Perpetual Noob
BoxCar31's Avatar
The DX8 G2 is sold at the same price point the now discontinued DX7 G2 was. It essentially is a DX9 in a DX6 case with some functions and the 9th channel not available.


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