Dick,
Obviously I disagree.

The park flyers wind up on our frequencies and unless someone has taken an extraordinary effort to hunt them down and educate them, they could care less if they happen to get some glitching while flying near the dump where there is little housing. The problem was that on the top of the hill overlooking the dump, I was flying my 33% Lazer on the same frequency. Once it got below the crest of the hill, I regained control but it was way too late to prevent impact. I managed to save the engine.

We clearly need a different, improved technology that serves all.

a failsafe to motor dead, probably wouldna/didna help too much in that one either.

Well for all the nay sayers Digital Spread Spectrum is now available and its not from a small outfit either [link]http://www.horizonhobby.com/Explore/Article.aspx?ArticleID=1389&Page=1[/link]

Check out Horizon's web page they now have it available for ground use currently and its a replacement module for the existing transmitter module with a new receiver.

Great price also:
3-Channel Surface System (include transmitter module & receiver) - $159.99
Additional 3-Channel receivers - $79.99

All I say is bring it on for the Aircraft,

The system I was referring to is the one now being sold by Horizon. He had an idea (for a very short time) to use it on helicopters....he dropped that idea.


BTW I looked through the thread, not sure where the "naysayers" are in this thread? I am working on it all the time.

Mark
This is Dave Jones from AUAV.net, thank for the link to the Horizon site.
I went to the site clicked on DSM 3 Channel Surface System: FUT/HRC it looks as if it is for a Futaba transmitter, got my visa card out to order one and then in BIG RED letters says Not Yet Available. It is not unusual to see products advertise long before they are ready.
As soon as they are available I will have one for evaluation and comparison to our system.
Thanks for posting the information

Dave,

Do you think your system is going to work on planes with one antenna?

Matt
It's working on planes and helis with only one antenna.
We have logged 4.5 hours in 27-10 minute flights on one of our early versions installed in a single boom pusher.
1.666 hours in 10-10 minute flights on helis (see the short video on our web site) http://www.auav.net/videos.htm.
1.166 hours in 4-10 minute flights test flights and two 15 minute autonomous test flights in a Sig. LT 40 with the DSS RC and the Ezi-Nav. systems installed.
Plus 2.0 hours in 12-10 minute flights on our latest version.
Every time we make a version change we start the clock over.
As of date we have a total of 9.332 hours of combined flight time logged on our systems.
Wile 9.332 hours may not sound like much flight time it averages out to 56-10 minute flights.
As I have stated many in the past the system that we have developed was not designed for use by the R.C. hobbyist it was and is intended for use with UAVs for the takeoffs and landings.
If you or any one would like to see the system work just give us a call and we will set up a demo flight.
Dave Jones
AUAV.net

I guess I did not ask the question the right way....let me try again.

Do you believe the RF link performance of your existing design (particularly as determined by utilizing one antenna on the handheld and in the aircraft) will ever work for high performance RC aircraft.

Matt
If I under stand your question correctly you are asking: Do I believe our system will work in high performance RC aircraft such as jets.
I have to say yes that I believe that our system as it is now will work in jets.
I have been told that this system won't work in a 200 mph jet because it would would suffer from doppler Shift causing the 2.4 GHz frequency to shift up as the jet was flying toward the transmitter and shift down in frequency as it was flying away from the transmitter.
In the atmosphere RF travels very close to the speed light 186,000 mph.
I really don't think that the small doppler shift from of a 200 mph jet will have much of an effect at 2.4 GHz.
Check out this site on doppler shift it is one of the best that I have found for the calculations of doppler effect.
https://ewhdbks.mugu.navy.mil/doppler.htm
We have never tested it in a jet but if you have one that you are willing to risk we are willing to give it a try.

Dave Jones
AUAV.net

The Doppler shift at 200 MPH is going to be around 700 Hz. That should be OK since a model jet won't be able to change it's velocity (in the vector sense) relative to the transmitter faster than the carrier recovery loop can respond.

Phase changes due to rapid manoeuvre-induced changes in the antenna orientation may be a problem.

Rapid fading due to multi-path reception would also be something to consider, I suspect.

First let's thank the inventor of Spread Spectum - Actress Heddy Lamar in the 40's. She came up with the original concept of Frequency Hopping. Then let's add the guys that came up with the psuedo-code systems.

For a system to work properly, there ARE a number of technical issues, but electronics has also covered a large distance since I last worked on one of these systems. You will still have problems with phase jitter in the oscillators (on both ends) and differential group delay in filters. But after that, the signals can be processed with DSP technology. And that is an area where costs are down and processing power is beyond belief.

A SS system would really add to safety and be a welcomed addition to events like pylon racing and large contests. The pin system depends on humans to work, and that is it's problem. I have been sent to the line to race three others, and once one of the other guys was on the same frequency. I took off and was getting glitches in the air, while his airplane nosed over. (It's good to have a strong signal). Human error on the part of the contest. And this was a very well run contest with many years of experience. The only frequency error that had been made in over 15 years, yet it could have killed somebody. 180+ MPH airplanes have enormous kinetic energy, more than "dirty Harry" had in his hand

Phil
One of the thing that I have found with DSS is that multi-path is not as big of a problem as it is with constant carrier.
With constant carrier if the directly transmitted signal arrives at the receiver and there is no multi-path every thing is fine however if there is multi-path due to buildings or something for the signal to reflect off of and the reflected signal arrives at the receiver out of phase with the directly transmitted signal then you can have all kinds of problems.
With DSS by the time the reflected signal arrives at the receiver the transmitter and receiver have hopped to a new frequency and the receiver will not see the reflected signal.
This is all depend on how fast the hopping sequence is and how long it takes for the the reflected multi-path signal to arrive at the receiver.

Dave Jones
AUAV.net

I suspect that is strictly a function of frequency band. IOW, at 900 MHz it would be more significant as the hop time is longer. Wonder how much faster (cleaner) 5.8GHz would be...

Bingo.

Dave, this is the issue, not the doppler shift. If the antennas are not oriented correctly you will have massive signal fade, almost infinite, but for sure -20 to -40 dB.

If you fly around level, or close to it, and hold the handhelds antenna correctly, you might get by. So the maneuvers are the thing, not the speed.

Comments?

Mr. Matt
Check this out http://linuxdevices.com/articles/AT9733962835.html
Dave Jones
AUAV

That's really cool.

Can you answer my original question?

The AMA cannot lobby because they will lose their tax exempt status. OK. So, they should encourage a new volunteer organization to take contributions (on which taxes will have to be paid, I guess) and lobby. Such an organization can lobby without risking the AMA's tax exempt status.

EJ

The AMA should be concerned about SAFETY. Are they? Based on the comments presented here the concerns are questionable. A few have been forward thinking but many are in love with yesterday’s technology.

There is a very big difference between jawboning/encouragement and lobbying.

Bill

Dave,

I would like to vote for transmitter programming since the methodology is closer to current and more likely to be accepted by the naysayer. Commercial acceptance will be important.

Sure it’s dangerous and recommended only under very controlled circumstances. It might not be as dangerous as flying while ‘battery reckless’ is in the air.

That’s self explanatory but somewhat ambiguous. How many bytes? Memory is cheap.

The Radio manufacturers appear to have their thinking so far up their behinds that they will never recognize the need, short of a catastrophic event that threatens to shut down their business. Of course they will claim the idea was invented in house.

My apologies for the delay in responding but a high level of frustration with the “It’s good now crowd.” stopped my reading here for a few days.

Thanks.

Bill

Never mind the legal issues. Does anyone know anyone who may have used the above Spread Spectrum equipment in an aircraft?

Bill