RC Model Reviews

The DX-7 replacement XG-7 with the new DMSS is already on it's way....
http://www.infinity-hobby.com/main/news ... esk_id=449

How do we know for sure that this is a true FHSS system? Unless I've completely overlooked or missed something, I'm not convinced that this is a FHSS system. On the Rx and the box of the entire system says it is DMSS with telemetry. So DMSS stands for Dual Modulation Spread Spectrum??? Right??? So how does this differ any from what they are using now other than not calling it DSM2. I guess I'm a little confused by this? Also, is there any speculation or reasoning behind releasing this in Taiwan first and not Japan? Or is the DSMJ too new? I don't know I guess I'll just have to wait and see what happens now. I truthfully would like to see that JR get away from the DSM2/Spektrum technology and get a really strong FHSS system. I really like JR radios and I've been real close to buying a new 11X but now I think I'm going to hold out, especially after that one "techie" wasn't real sure if the new system would be compatible with any of the present systems. I'm even strongly considering a new Hitec Aurora. That seems to be a pretty good buy and a good system. If there was a way to tie the 11X radio with Hitec's AFHSS then we might really have something? Is it possible for the Spectra 2.4 module to work in the 11X??? Anyone know for sure? I'm pretty sure it can't from what I've read so far but wasn't sure if anyone has tried any compatability tests. Well hope to see some feed back from this and I'd like to thank you Bruce for all the great info that you've provided. What you're doing is great. Keep up the great work!!!

FYI, some have said "Futaba has it figured out" with FHSS in their industrial equipment. However, that is not the case. For example, this industrial module is DSSS http://en.futaba.co.jp/industrial/frh_sd07tu/index.html

So to confirm, Futaba uses DSSS for industrial purposes, FHSS for RC.

JR belatedly realized that just selling TX box to Spektrum was not bringing much profit.
JR made a strategic mistake of not producing their own 2.4 radio from the beginning.

Correct me if I am wrong, but DSSS systems select a number of frequencies to work on and then continuously "hop" between those frequencies at a high rate in a fixed sequence, ie when using 3 frequencies, 1-2-3-1-2-3-1-2-3 etc. With FHSS the system "jumps" all over the band, essentially a more complex version of DSSS just with a lot more complex algorithm controling the next channel used in the sequence (right?) Where as most DSSS systems use 2 or 3 channels, FHSS systems might use 20 to 30 and jump around "randomly" (ok, using the complex algorithim, since nothing is actually random for this to work!) in those 20 to 30 channels continuously in the same way as the DSSS system does. SO does the advantage of FHSS just mean that it uses a wider selection of the frequency band..., why not just make DSSS systems that use 10 or more channels instead of 2 or 3, for more robust reception (or is that just FHSS as I have already described?)

Specktrum's Model match system is easy enough to replicate in other systems, when the transmitter sends out its signals there is an encoded "bleep" in there that indicates the start of the sequence, that bleep has the model memory number encoded and must match what is stored in the receiver memory or it won't work. Bruce has already suggested that Telemetry systems could reverse the same idea so that the receiver tells the transmitter what model memory to load. I wonder if we will start to see some systems arriving with very basic telemetry built in such as rx or lipo battery voltage and the ability to do just as Bruce has described in loading up the correct model - really it is the bare minium of useful information that we would need - and it wouldn't be overly hard to incorporate into current technologies, since the model memory bit need only be sent during the initial binding handshake as the systems turn on and begin to communicate.
Even more useful telemetry data might indicate the current draw on the battery including built in warnings if over drawing current etc, temperature alarms for motor and speed controller etc (I dunno about you guys, but Lipos resemble small flying bombs just itching to detonate..! and I'm kind of attached to my models!)

The whole DSSS versus FHSS situation for RC gear is a complex one.

Firstly, none of the FHSS systems currently on the market are true FHSS. They are all constantly agile DSSS systems -- which is good because it's actually better than either the true FHSS or a static DSSS options.

In essence the only real difference between (say) the Corona DSSS and Futaba's FASST is the number of channels being used.

The Corona uses 3 frequencies and alternates between them -- the FASST system uses lots more frequencies and alternates between them (in a pseudo-random order).

The benefits of the 'so called' FHSS systems however, is that they do spread the signal out over a much larger section of the band -- so that if any mall part of the band is affected by interference, the remaining part can still carry enough information to provide perfect control.

The reality is that most of the time DSM2 does the job perfectly adequately by offering two separate frequencies over which the data is sent. However, if those two operating channels happen to be adjacent to each other, it doesn't take nearly as much interference to destroy the link between transmitter and receiver. Even if they are spaced at a reasonable distance, it's still easier to knock out a 2-channel DSSS system than it is to knock out a 3-channel one -- and the 'so called' FHSS systems will tolerate even more noise before losing the link.

Just out of interest, how would you characterise the robustness of DSM2 on two adjacent channels, compared to say old fashioned 35Mhz?

Well, if you're using 35MHz on a band that has been dedicated for RC model use and you have good frequency control at your flying location then you're possibly better off than someone flying DSM2 in a band that is effectively a "free for all" and in which you've got to compete with all manner of other RC and non-RC noise sources.

However, as we know, most MHz bands aren't solely dedicated to RC use so there's always a risk of on-channel interference and most of the time DSM2 will work just fine.

I noticed in the UK announcement that they say it will not be compatible with DSM2 receivers but failed to mention anything about DSMJ compatibility?
One would imagine that JR will anger many thousands of devotees world wide if they bring out a third system over a short period of time, without any compatibility, which could see only JR sponsored pilots and very wealthy people staying with them.

The thing is that sometimes (just as was the case with the shift from long-wire to 2.4), you've just got to leave the past behind and move on if you want to enjoy the benefits of newer technology.

DSM2 is reliant on devices that don't work well at low voltages and have been "repurposed" from their original job of providing very short-range data-links for things like wireless mice, keyboards etc. To maintain backwards compatibility would effectively be like trying to build cars with iron wheels so they could still use the railway tracks as well as the roads. As we can easily see -- doing that would severely compromise their road-handling and effectively negate much of the benefits that were to be gained from the shift away from railway to freeway.

And so it is with newer 2.4GHz technology.

To the best of my knowledge, nobody else is using the Cypress chips that Spektrum/JR have been using -- they're certainly *not* the best tool for the job.

Now, if JR hadn't allowed Horizon to bully them into ditching the RF module concept from the product sold in the USA (which they undoubtedly did to stop people using 3rd-party 2.4 modules) then everyone would be much better off and the transition to a *better* system would be far less painful.

Don't worry about JR losing customers -- brand loyalty (as we've seen time and time again) is a *very* powerful thing.

When it comes to RC however, while the Ford and GM users are bickering away amongst themselves and claiming to each have the best systems, the little Asian Toyotas of this world are stealing their market. One day they'll wake up and realize that instead of trying to lock people into their proprietary systems by ditching modules, creating new unnecessary servo busses etc -- they should have just been delivering good solid products at affordable prices.