43 replies to this topic

[Elena P.]

Anybody has any experience will they interfere each other - in terms of range or video problems as they are on the same frequency?

[Terry]

From what I hear the Spektrum will interfere with the video.

Terry

[wilson]

Anybody has any experience will they interfere each other - in terms of range or video problems as they are on the same frequency?

Hello Elena,
I did not hear anything official about it yet, but theoricaly yes, it might interfere, because both are using the same 2.4ghz.
I was thinking two months ago in buying a SPEKTRUM DX7, it's awesome, diversity receiver, actualy dual receiver for safe and better reception, but the 2.4Ghz pushed away in case of FPV flight.
Like I said, nothing official, but I think they interfere on each other.

Edited by wilson, 14 January 2007 - 11:06 PM.

[Kilrah]

There's someone here awaiting to receive a DX6 and DX7 to run tests:
http://www.rcgroups....t=590190&page=7

No doubt he'll post the results

[Mark Harris]

If i remember i'll take my video stuff into the shop this saturday and see what its like with the DX6, DX7 and the Blade CX radio's

[Elena P.]

If i remember i'll take my video stuff into the shop this saturday and see what its like with the DX6, DX7 and the Blade CX radio's

I just called Spektrum and they said should not be any issues. But all over the internet thet post it will cause interference. My DX7 will come next week, we'll see.
Elena
http://beauty.beads.googlepages.com

Edited by Elena P., 16 January 2007 - 08:03 AM.

[Mark Harris]

Ok, well i guess i wont worry about taking stuff in at this stage

[Terry]

What are the exact frequencies the Spektrum uses ?

Terry

[Kilrah]

The problem is that they use spread spectrum... so that means they use pretty much all of them, simply not continuously but changing from one to another. I had problems with spread spectrum data modems and video, because the 70 different channels will all use the same range but simply in different orders or with an offset. So with any channel it would sometimes pass on the video's one or close enough to it to create ugly lines every second.

[Mr.RC-Cam]

It's designed to operate in the unlicensed ISM band 2.400-2.483Ghz (basically 2.412 2.462Ghz in the USA). It ping-pong broadcasts on two frequencies during operation. The frequencies are chosen during a short RF monitoring/sampling phase (the transmitter is also a receiver) during initialization. The transmit frequencies occupy almost 1Mhz bandwidth each, so they are spaced 1Mhz apart. It is not a frequency hopping system, but is a spreaded code modulation.

Very good details can be found on the data sheet at the Cypress web site. Just look for the CYWUSB6935.

[Terry]

Thanks, so it jumps right on the video channels. It maybe time to start thinking about using another band/frequency for video, its getting very busy here !

Terry

[Mr.RC-Cam]

... so it jumps right on the video channels.

In a perfect world, if the 2.4Ghz video system was transmitting before the Spektrum Tx was turned on, the Spektrum system would choose alternate frequencies to avoid an RF conflict. From what I have read on the various forums, it seems to work for most users, but not all (but it is hard to say given the fuzzy posted info). Also, a couple users have reported a reduction in range from their Spektrum Rx when the nearby mounted video Tx was turned on.

Long story short, each installation will probably experience one of those YMMV situations. I haven't bothered to do any tests to see what I come up with (just not that interested at this point). But, it does make sense that in some situations the two might not play well together.

It maybe time to start thinking about using another band/frequency for video, its getting very busy here !

Sounds good to me. But, going higher in frequency causes performance issues for us; it would be best to go lower. That leaves us with the 900Mhz RF band. But some users reported bad experiences with them (and claimed that the 2.4Ghz worked much better after they switch to them). I suspect it is because most of the 900Mhz video system designs are a few years old. I expect that they would earn a boost in performance if they used more modern RF designs. But, the 900Mhz market has been effectively killed by the introduction of the 2.4Ghz and 5.8Ghz bands (which offer reduced performance, mW for mW). So, there is not much attention to 900Mhz video and all the innovation is occuring on the higher RF band based designs.

[Wavess]

From what I have read on the various forums, it seems to work for most users, but not all (but it is hard to say given the fuzzy posted info). Also, a couple users have reported a reduction in range from their Spektrum Rx when the nearby mounted video Tx was turned on.

Which forums have your read about it. I´d like to read more about two systems coexisting.

Sounds good to me. But, going higher in frequency causes performance issues for us; it would be best to go lower. That leaves us with the 900Mhz RF band. But some users reported bad experiences with them (and claimed that the 2.4Ghz worked much better after they switch to them). I suspect it is because most of the 900Mhz video system designs are a few years old.

I´ve read the oposite thing, 900 mhz seems to behave better with long distance flights and obstacles than 2.4 Ghz for example this guy:

http://www.rcdon.com...am_project.html

Edited by Wavess, 21 January 2007 - 03:26 PM.

[Mr.RC-Cam]

Which forums have your read about it. I´d like to read more about two systems coexisting.

I have not kept track. Check rcgroups, rcuniverse, and rcapa. I'm not sure you will find many folks that have claimed good success, but there appear to be some. Remember, this is a YMMV thing.

I´ve read the oposite thing, 900 mhz seems to behave better with long distance flights and obstacles than 2.4 Ghz for example this guy:

Yes, the 900Mhz band is more effective when it comes to effective range and multipath reduction. That is why I suggest it as the better place to go (rather than a higher RF band). I used an expensive 900Mhz system and was very pleased with it.

But over the years I've come across a variety of users that felt they got better operation after they replaced their rig to one of the popular 2.4Ghz systems. The only explanation I can offer is that some of the 900Mhz stuff is based on older designs that were often copied or morphed by the various off shore mfgs. For sure, I'm not saying that all 900Mhz systems are bad (I was careful to say "some" users reported that), or that all 2.4Ghz systems are good. The trick is to identify a video system that works well in the specific application.

Edit: If I had my wish, I would ask for a latest generation 900Mhz video system, in a tiny form factor, that had stereo audio (one channel with built-in mic), tolerated typical R/C vibration, and operated on 5VDC. Low cost would be nice too.

Edited by Mr.RC-Cam, 21 January 2007 - 04:36 PM.

[Terry]

It's not just the Spektrum that bothers me, it's just one more source of interference. Some will know I have been suffering increasing problems with wireless broardband and now this. In the past I was more than happy to fly most of my flights with 10mW but now I find 100mW has to be used and I am assuming I will need 500mW for flights over a mile.
Flying at my club site is out of the question, a 100mW Spectrum next to my video receiver would not be good.

I think mobile phones are on 900Mhz in the UK so I may have to think about 1.2Ghz. I'm not sure, I will see what I can find out.

Terry

[Terry]

I have had a look at 2.3Ghz and 2.5Ghz as I think it may be an easy way to go but 2.5Ghz is going to be used for my old friend brordband in the UK. It's going to be like living in a microwave oven soon, they don't call them 'hot spots' for nothing !

Terry

[Mr.RC-Cam]

Some will know I have been suffering increasing problems with wireless broadband and now this.

Me too. One of the places I fly my small electrics is outlined by homes. 2.4Ghz wireless video is impossible there now.

[JetPilot]

Do NOT expect the specktrum and 2.4 GHZ video to work together. Even though the Specktrum channel hops, it is not an issue of just going to a different channel. The specktrum is not designed and can not reject a 2.4 GHZ signal from a video transmitter on the same plane ( or within a few feet of the receiver ). Even though the specktrum receiver hops to a different frequency, the interference from the video TX will be so strong, that ALL the frequencies are blocked to the specktrum recever.

Operating on different channels works fine when the TX is at a distance from the plane, but it has its limitations and will not work with a video TX transmitting on the plane with a frequency close to what the receiver uses.

JettPilot

[Elena P.]

So, I've got DX7 and tested it.

Range test - no problem, nice feature - both receivers have LEDs and they started to blink when signal is weak.
They can not acquire the signal when they 1 inch or close to the camera's anthenna. But move them away 3 inches - and no problem.

But. When I checked the picture quality - I have clear picture only when plane is nearby. As soos as I put the plane 5-10 meters away, I was getting horizontal lines on the screen.

So, tomorrow I'll take DX7 back to the shop. What a pity - I love that radio already.

Good luck,
Elena.

[Mr.RC-Cam]

As soon as I put the plane 5-10 meters away, I was getting horizontal lines on the screen.

I recall someone else that mentioned that. But they said if the Spektrum TX was moved further away from the wireless video Rx, it went away. Do you see any improvement as the two are separated by a good distance?