Kiwi's XPS test results are up.

[littlephoenix]

looks like Graupners is going out of business, or is that a roomer?

[Julez]

Not likely.

But they switched to Weatronic now as their "primary" 2.4 system.

http://www.graupner.de/filerootdir/d...nic_screen.pdf

[aramsdell]

Seems that all 2.4 products have had their growing pains. Most of them are really attributable to low Rx voltage and locouts during re-boots.
I have flown the XPS V1 internal module in my Royal Evo 9 ch for a couple years now. I fly it confidently in a $2000 + heli-cam. I fly this system in low and high noise background scenarios. If anyone has been to the NEAT Fair in NY USA then you know how many radios are on at one time. I even have the ut-most faith in the 6 ch 'Park' receivers. I flew 3 of those there this year. They don't even have external antennas yet have 1000 foot range(while still haveing bidirectional comm.) I know I was close to that 1000 foot mark a lot this year with those receivers.
I still think people can't admit they had electronic/voltage problems causing loss of planes.
Frankly I could care less if my XPS hops if it continues to work as it has.

[Julez]

	Quote: Originally Posted by aramsdell
	Seems that all 2.4 products have had their growing pains. Most of them are really attributable to low Rx voltage and locouts during re-boots. [] I still think people can't admit they had electronic/voltage problems causing loss of planes. []

Well, this is the mantra that two 2.4GHz manufacturers keep repeating over and over again.
The only problem: It is an incorrect generalisation.

It is a myth that all 2.4GHz systems all need more juice than MHz systems.
This has only been claimed by two manufacturers, whose systems really need more juice than the rest.

Spektrum, for example, does not only have little headroom concerning low voltage reboots, but it also synchronizes the servo outputs.
This means, that all servos begin to move at exactly the same time.
http://homepages.paradise.net.nz/bhabbott/Servo.html
This way, the current demand peaks of all servos are also synchronized. The resulting large current surge contributes to the problem.
Almost all other systems sequence the servo outputs, and spread the load over a time, insted of concentrating it.
The only other system despite Spektrum synchronizing the servo output is XPS V3.
And, you might have guessed it, per default the manufacturer blames every malfunction on a "bad" RX battery, even when the very same setup has worked just fine before.
See a pattern here?

I for one consider it a valuable feature that my system of choice does not need a better power supply than usual.
First with Fasst, and now with Jeti, I can fly the RX packs I have used before, as they do not reboot above 2.9V.
In fact, I have even switched to using single LiIon cells on some light planes, and it works out great so far.

[Woketman]

Yeah, its amazing! Everytime a consumer has issues with XPS it is the consumer that is at fault. Jim Drew would never admit a problem!!!!

[cptsnoopy]

Have not heard too much chatter about the XPS 8 channel end pin rx for carbon fuselages. Anyone know of any issues?

Charlie

[JimDrew]

Actualy, the "myth" here is that simultaneous or grouped servo outputs cause a severe increase in current over sequential outputs. Do a test like what Julez linked to with all channels simultaneously (8 channel scope w/current sensors) and you can clearly see that there is no significant difference in current draw. Even if there were an increase in current draw, the benefits of simultanoues servo outputs are well worth it. Ask any of the heli guys how they like flying with absolutely no swash plate interaction due to the simultaneous outputs.

Another "myth" is that 2.4GHz receivers use less power than MHz receivers. Typical current requirements for 2.4GHz receivers (even Futaba's) are 3 times of what a MHz receiver requires. However, since we are talking less than 60ma of current, it really doesn't matter in the grand scheme of things.

The REAL difference between 2.4GHz and MHz receivers is their ability to cope with low voltage situations. MHz receivers typically use shift registers, running on just fractions of a volt. 2.4GHz receivers use computers and require power full time or they will reboot. Since we added our low voltage warning to our receiver firmware we have seen that 8 out of 10 customers were using systems where the voltage dropped below 4.4v. Our system works down to 3.2v with the original hardware (2.9v with the current hardware, and 1.8v with the latest hardware being released next month). Our reboot/reconnect speed is the fastest of all 2.4GHz systems, at 80ms-300ms.

Keep in mind that we have sold over 100,000 plug-n-play systems for setups that are generally quite old. A lot of people still try to use their original 600mAh Nicad receiver battery pack with their 10 year old switch, and modern servos. It just doesn't work with 2.4GHz, and technically it doesn't work with MHz systems either - you just get away with it because there is no reboot occurring.


Our 8 channel receiver for gliders is so popular that we are sold out and won't have stock for another 2 weeks. People are using this receivers in all type of airplanes, helicopters, cars, and boats.

[cptsnoopy]

	Quote: Originally Posted by JimDrew
	Our 8 channel receiver for gliders is so popular that we are sold out and won't have stock for another 2 weeks. People are using this receivers in all type of airplanes, helicopters, cars, and boats.

Glad for you Jim. I was happy to see you add an antenna that can be placed outside the fuse but until you have at least two antenna I will not be able to use them. I cannot understand why you did not do that in the first place as it is obvious that two antenna is the absolute minimum to keep at least one in view of the Tx at all times. Is there a physical or technical reason why you cannot do that or is it simply because you do not feel it is needed?

I sold off all of my old receivers but I am hanging onto my tx module. Two of the last three issues we had with your system installed turned out to be servos going South. The third I cannot say for sure what it was. That was the reason for letting go of all the receivers. Once we found the two bad servos we are now more interested in trying the newer receviers. Once I see that there are some available that will fit in limited space with at least two antenna, I will give them a try. I do not currently need any receivers for my larger stuff that might be able to fit satilite receivers.

Charlie

[flarssen]

	Quote: Originally Posted by JimDrew
	Do a test like what Julez linked to with all channels simultaneously (8 channel scope w/current sensors) and you can clearly see that there is no significant difference in current draw.

Why make things so complicated?? A sensor between battery and Rx is all that's needed. No need for a XPS Rx, just connect servos to the same Rx port using Y-cables.

Fred

[Julez]

	Quote:
	I cannot understand why you did not do that in the first place as it is obvious that two antenna is the absolute minimum to keep at least one in view of the Tx at all times. Is there a physical or technical reason why you cannot do that or is it simply because you do not feel it is needed?

It is a technical reason. Have a look at the XBee modules in use.
They only have one antenna.
http://images.google.de/images?q=xbe...N&hl=de&tab=wi

Jim has claimed that his "spherical antenna" makes diversity obsolete.
Recently, there were claims about this techology being "patented".
But until a patent number is provided, I do not believe a word.

[JimDrew]

"Jim" claims what the manufacturer of the RF module claims.

The new hardware that I have designed does have two antennas because we don't want to pay royalties for Digi's antenna patent. Our new receiver sensitivity and selectivity is actually much improved over the XBEE solution, thanks to 18 months worth of develoment with a new chipset, along with PCB layout experimentation and testing .

[AWorrest]

	Quote: Originally Posted by Julez
	. . . Spektrum, for example, does not only have little headroom concerning low voltage reboots, but it also synchronizes the servo outputs. This means, that all servos begin to move at exactly the same time. . .

Not exactly corrrect. Spektrum synchronizes the outputs of the servos within a group. For example if using flaperons and dual-matched elevator servos, the left and right aileron servos will be updated simultaneously but there will be a slight delay before the left and right elevator servos are simultaneously updated.

Allan

[Julez]

	Quote:
	"Jim" claims what the manufacturer of the RF module claims.

How come that noone has ever seen any claims of a special antenne patent by the manufacturer of the Xbee modules?
How come, that the representatives say that the modules only use standard groundplane monopole antennas when asked?
How come, that in the FCC certificate, which has to list all antenna types the Xbee modules are approved for, nothing but standard antennas are mentioned?

Result:
Until a patent number is provided, I do not believe a word.

[dick hanson]

I think Jules may be part CZECH---
" If I can not find it in print-
It does not exist".
My good friend Ed Skorepa lives by this code

[Woketman]

Great post Julez.