Originally Posted by JetPlaneFlyer

Yeah, the problem comes when there are so many transmitters operating that the Tx cant find a free frequency and so ends up being forced to take one that's already occupied. This could only occur if there are very many transmitters operating simultaneously, like some of the biggest flying meetings.

If you just fly alone, with a few friends or at regular club fields then it's a non-issue.

I fully agree with your first point. The vast majority of so called interference is user error either in poor set up or most likely dumb thumb error. The fact that the 'interference' can hardly ever be reproduced after the crash speaks volumes.

The other potential fault with dsm2 is the system will sometimes (admittedly rarely) grab two channels right next to each other with the result that if there is some interference in that region of the spectrum it is very likely you'll get knocked out. FAAST and now dsmx along with FHSS and the other iteration of frequency hopping systems are far superior. Personally I use Futaba with FRsky modules and receivers, there is pretty much nothing the big players offer that frsky don't.

Hate to sound like an Old Phart, but in the '80's, we had 6 frequencies (there were a couple
reserved for licensed Ham radio guys), lots of interferance, and only 2 or 3 folks (depending on frequency) could fly at one time (cross-channel interferance).

We have come a long way and AMA deserves a lot of credit for getting us the 72 band and lately the 2.4 frequencies. Whatever the problems in the current situation, it's not as bad as it was, and IT IS UP TO US to live with the situation. AMA is making sure we aren't screwed or forgotten in the RPV field.

I think my point is that we owe AMA a lot and this is a reminder of just how much.

howell

50 bucks will get a cool little USB spectrum analyzer, well worth it if you are concerned, and also good for tracking down the interference (if you can cobble something to make it somewhat directional).

Originally Posted by CNY_Dave

... (if you can cobble something to make it somewhat directional).

You mean, like the side of your truck?

Andy

A jug of water

Wait, I know - my body! It's big as a truck and full of water!

Andy

Originally Posted by luke352

.. FAAST and now dsmx along with FHSS and the other iteration of frequency hopping systems are far superior. Personally I use Futaba with FRsky modules and receivers, there is pretty much nothing the big players offer that frsky don't.

Wow. Since I have had precisely zero radio problems due to anything to do with DSM and DSM2 after thousands of Spektrum flights since 2006 including flights at events with up to 275 flyers, I wonder how much better performance I will see with DSMX...

Nothing wrong at all with DSM or DSM2, except in the very rare circumstances of a fly in like Joe Nall when there are hundreds of 2.4 radios turned on and scattered around a number of flying sites in close proximity.

wile 2.4Ghz IS gettnig crowed Spektrum could easily move to 5.8Ghz

Andy have you guys thought at all about using 5.8Ghz down the road? DSMX2 maybe?

oh and there are 78? i think channels in the 2.4Ghz band for use in the US
each is 1Mhz wide

now IF they are all in use even with older DSM2 you should be ok as DSM2/X has one last trick
each TX has a GUID when you bind the RX to the TX the RX learns the GUID of the TX and ill ONLY listen to data from that TX
i think they even use a new GUID per model which is how "Model Match" works
now you will get some lag but you can still fly
kinda like a networking MAC address
DSM/2/X is pretty bullet proof when used right

Originally Posted by CNY_Dave

50 bucks will get a cool little USB spectrum analyzer, well worth it if you are concerned, and also good for tracking down the interference (if you can cobble something to make it somewhat directional).

When I was in California we had a problem where all planes would lose link at the same time. A pilot brought his Spectrum analyser, and a directional antenna to the field. Tracked it to comunications between a top secret facilitiy locally called the Blue Cube, and a government contractor. We left a letter with the security guard, with suggestions on how they could reduce the problem. They actually responded, with sorry but they would not change what they do, and would do it at anytime.

Originally Posted by Roto Rob

When I was in California we had a problem where all planes would lose link at the same time. A pilot brought his Spectrum analyser, and a directional antenna to the field. Tracked it to comunications between a top secret facilitiy locally called the Blue Cube, and a government contractor. We left a letter with the security guard, with suggestions on how they could reduce the problem. They actually responded, with sorry but they would not change what they do, and would do it at anytime.

Would have been legal for you to interfere with their signal, too. Or offer to record it with a waveform analyzer and post the data to any interested parties on the internet.

With spread spectrum technology, multiple signals can be carried on the same frequency.

Originally Posted by jasmine2501

With spread spectrum technology, multiple signals can be carried on the same frequency.

Spread Spektrum spreads it's transmission across many frequencies, that's what spread Spektrum means. No two Tx's should transmit on the same frequency at the same time except for occasional instances where the random frequently hopping causes a momentary (as in milliseconds) convergence, as it's so brief and overlap this would cause no loss of control.

Originally Posted by JetPlaneFlyer

Spread Spektrum spreads it's transmission across many frequencies, that's what spread Spektrum means. No two Tx's should transmit on the same frequency at the same time except for occasional instances where the random frequently hopping causes a momentary (as in milliseconds) convergence, as it's so brief and overlap this would cause no loss of control.

NO... I was waiting for someone to say that actually.

Spread spectrum (with a 'c') is a set of different technologies, which spread the signal out to occupy more bandwidth. Frequency hopping is only one method of doing that. Spektrum's DSM2 used a different spreading method (DSSS, see below), and it is actually better than frequency hopping, if you're only going to use one method at a time. Futaba took Spektrum's signal and hopped it around, now DSMX does the same thing.

However, with the old DSM2 system, my radio and your radio can pick the exact same two frequencies, and they will still work together. If you don't know why that is true, you should probably avoid saying any strong opinions you might have about this subject. Two signals mixed together can be separated by the receiver using the spreading code. That is the whole frikkin point!

http://en.wikipedia.org/wiki/Direct-...pread_spectrum

If an undesired transmitter transmits on the same channel but with a different PN sequence (or no sequence at all), the de-spreading process results in no processing gain for that signal. This effect is the basis for the code division multiple access (CDMA) property of DSSS, which allows multiple transmitters to share the same channel within the limits of the cross-correlation properties of their PN sequences.

Simply put - your signal looks like noise to someone using a different spreading code, and their signal looks like noise to you.

Originally Posted by Elios000

wile 2.4Ghz IS gettnig crowed Spektrum could easily move to 5.8Ghz

Andy have you guys thought at all about using 5.8Ghz down the road? DSMX2 maybe?

I suspect that is highly unlikely as 5.8 has only half the penetration of 2.4, so range will be reduced and it will be even more important to do a very careful install without masking the aerials. Not a receipe for a successful consumer product!

Originally Posted by MattyB

I suspect that is highly unlikely as 5.8 has only half the penetration of 2.4, so range will be reduced and it will be even more important to do a very careful install without masking the aerials. Not a receipe for a successful consumer product!

wi-fi is moving to it