Kiwi's XPS test results are up.

[bobzilla]

Nice post XJet...spot on everything!

[Julez]

	Quote:
	and I've not seen any 2.4Ghz system work with 100% carbon planes without serious modifications (either to the plane or warranty voiding mods to the Rx antennas)

I have:

http://christian-hanke.blogspot.com/...g-post_25.html

[Wojcigitty]

	Quote: Originally Posted by XJet
	Or you could wait -- I'm aware that there's yet another 2.4GHz system coming onto the market later this year from a very reputable European manufacturer who's already selling into the giant scale and turbine markets. They've offered to send me a sample unit and I'll test it as soon as it arrives. It might be great, it might not but it is another option.

Oh boy! I wonder if this is the same one Kiwi mentioned earlier...

If both of you are talking about the next iteration of SpectraLink... :24:

I'm glad I'm still on 72 for now. I believe that 2.4 is the better option once the bugs are discovered and worked out, and I don't have the money to be an involuntary beta tester.

[BZFrank]

There is more coming...

ACT is about to release their dual FHSS system (it uses two redundant transmitters and receivers, has telemetry build in and more):

http://www.acteurope.de/html/s3d-2_4ghz.html

And Weatronic will soon present their FHSS system, from what I heard it is also dual FHSS based.

http://www.weatronic.com/cms/index.php?lang=en

(nothing yet on their web site, but they gave a sneak peek at the trade show in Sinsheim, Germany)

Frank

[Flyfast1]

	Quote: Originally Posted by Julez
	I have: http://christian-hanke.blogspot.com/...g-post_25.html

Julez,

I am glad it worked well with a carbon fiber fuselage. Was he able to do it without any modification to the receiver? In the pictures of the plane the antennas look spread apart relative to their native position on the receiver, but I can't tell from the photographs.

-Ed B.

[cptsnoopy]

Nice post Xjet.

Julez, that method has been used in full carbon fuse by me for at least a year now. I have posted about it quite awhile ago.

It is simple, if the fuse is small enough at some point you route the antenna outside and there are no problems. I am using the AR6000 in a DLG (full carbon fuse) and an Omega1.8 (carbon/Kevlar fuse). The most difficult thing with something like the F5D is what to do about the antenna to prevent it from whipping about and breaking off? If you tape them to the fuse the angle is not correct and there may be some problem with being that close to the carbon. I have considered using small fins on the fuse or maybe just small hollow coffee stirring straws to hold the antenna straight while in the slipstream. I also put the receiver in so that the antenna point rearward at a 45 degree angle to keep the 90 degree angle between them.

[BZFrank]

	Quote: Originally Posted by Flyfast1
	In the pictures of the plane the antennas look spread apart relative to their native position on the receiver, but I can't tell from the photographs.

There is no 'native' position. FASST antennas are flexible wires and only the last outermost inch of the wire is the antenna. You can run the cables as you like, as long as the antennas have the correct orientation.

Frank

[Julez]

What he said.^^

No modifications needed, just make sure that the last 30mm of the 100mm long antenna, which are the actual sensitive part, are routed away from problematic environments (cables, metal, etc), or are routed outside CF fuselages.
This antenna approach is the most comfortable, and is used by Futaba, Airtronics, and Assan (Don't know exactly about corona).

[Daemon]

Strangely the Batleth fuse doesn't look like full carbon


Maybe it's just heavily painted, or perhaps they changed the layup more recently.
What about the wings? I ask, because carbon wings can cast a big shadow
which is why when I say 100% carbon plane I don't mean a carbon fuse with a bagged
glass/kevlar + carbon reinforced D-box wing (DLG), or carbon/kevlar weave fuse
with a glass and balsa wing (Omega 1.8)

These are the type of 100% carbon planes I'm talking about.

2-3 layers of carbon in the fuse, and at least that in the wings.

Anyway, with regard to the dual antennas on long wires.
My Airtronics FHSS Rx has a similar dual antenna setup (in the photo above). I think
this configuration has the best chance, because you can route the antennas
some distance away from the wing. But these planes are designed for DSing at 200-300mph
(not an exaggeration. My PB is 283mph. The WR is 307mph), so the antennas will need
some reenforcement to keep em from folding down flat. Some stiff plastic tubes might do it,
but they become a vulnerable draggy bit, which we are trying to avoid at these speeds. I
might try the FHSS setup on that plane on the right in the photo, as it's my 200mph capable
beater, and has already lived 8 of its 9 lives.

ian

[Daemon]

	Quote: Originally Posted by XJet
	And this is where I think some people have a real beef with XPS and JD. He's grossly oversold the capabilities of the system. ... XPS is a fine 2.4GHz system when people are made fully aware of its limitations and it is used appropriately (with these limitations in mind) -- unfortunately the company persists in over-hyping its technology and capabilities. The result is the utter fiasco that has pretty much exploded in recent months as the facts are revealed, XPS raises its shields to deflect all criticism, and customers are denied any proof that they've actually got the features they've paid for.

I agree on both points. JD has over-hyped it ridiculously, and instead of focusing
on what the system does well (it does have a few good points), he's hyped features that it
doesn't do well, or at all. Imagine if JD had ever bothered to follow through on his promise of
a telemetry module. Could monitor signal strength at both Tx and Rx, re-transmit counters,
battery voltage, reboots, current channel #, etc.. all realtime. You'd know if your plane was at
risk as soon as you turned it on. You'd know a lot about your Rf environment when
the plane was in the air, and you'd be able to see if shadowing was a problem, as the
orientation changed and so forth. You'd know if you had a power supply problem
at any time during the flight. All things the system is capable of right now.
XBee modules are designed to send *data*. Oh well.

BTW, the upcoming 900Mhz FHSS version looks like it'll be a power pig, according
to the specsheet's info on the 900Mhz Xbee module.

ian

[Julez]

	Quote:
	Strangely the Batleth fuse doesn't look like full carbon

The Bathlet is not a kit, it is a project from the Akamodell München:
http://www.akamodell.vo.tum.de/projekte/pylon/am9.htm
I think one can lend the positive models for molds from them, to make a mold by oneself.
http://www.speed-mania.de/batleth.html
Then it is up to the individual opinion, how one wants to build the model.
Eike seems to have built the fuselage from kevlar, but surely there are other possibilitys.

These guys made a range test with 3800m with one reciever in a CF fuselage:
http://www.mfv-marbach.ch/Berichte/r...test_fasst.htm

Cheers,

Julez

[Garland]

Hey thanks to everyone for giving me a no BS assessment on my XPS gear....

I dont mind a dumb thumbs incident on my large performance/scale helis. Its not so much the $$ in repairs....Its the time and bench setup on each model is the most expensive part.

Hell I am building a trainer LT-40 from a kit not a ARF, and already have many, many hours on the wing alone. It will be my 1st non Heli aircraft ever to fly.

Helis are almost the same time consuming bench repairs after a crash.

I cant risk my fleet to XPS at this time. I wont sell my XPS as it should be great for my indoor helis and a RC truck.

thanks FG.com! ya'll just saved me a TON of time and $$ and I know exactly where I stand.

Im only into XPS for about 250$, so even though its way overhyped as a rc system
I'll get my $$ out of it in non risky areas.

[JimDrew]

	Quote: Originally Posted by Daemon
	Short answer, using the current 2.4Ghz XBee modules. No. Because it is two way, the satellite receivers are at best, dumb, and at worst a liability. They can't transmit ACKs without interfering with the main Rx's ACKs (you'd actually be creating multipath interference at the source) so if the main Rx antenna is blocked, and the satellite receiver antennas are not, the Tx will still think it has lost the link, even though the Rx is still getting signals from its satellites. That'd be ok, if it was meant to always be a one way system, but it's not.

People forget that we use only the XBEE hardware. The firmware is our own, and if you look at the chipset used with the XBEE, you can clearly see that multiple receivers can be used and the ACKs will not collide.

	Quote: Originally Posted by Daemon
	As for hopping, it can be done, but it's always going to be *slow*, again because the two way nature gets in the way and it's tough for both ends of a two way link to know for sure if the link is 100% broken or only 50% broken, and you risk more by hopping when it's 50% broken than you would by staying put.

That is completely wrong. We can support 5ms frames, complete with ACKs and change frequencies every single frame. Frames are typically every 22ms. Think that is slow, well I have some news for you. Spektrum frequency hops every frame between two frequencies. They don't "lock on" to two channels as they claim. Every 22ms, the data is transmitted to the other frequency. Interesting too, since their FCC ID clearly shows their system to be a DSSS configuration. Part 15.247 clearly states that any device changing frequencies faster than once every 400ms/dwell is required to occupy no fewer than 15 channels. Hopping every frame is not legal by these rules. When I added the "hop on saturate to foil the bench testers code", I asked for clarification from the FCC on the hopping speed and we either have to transmit with a psuedo-random 15 frequency algorithm, or we can not hop faster than roughly once every 300ms, which is actually faster than the 450ms spacing we had in the original hopping code. So, it was a benefit to look into this.

[KrisW]

	Quote: Originally Posted by JimDrew
	People forget that we use only the XBEE hardware. The firmware is our own, and if you look at the chipset used with the XBEE, you can clearly see that multiple receivers can be used and the ACKs will not collide. That is completely wrong. We can support 5ms frames, complete with ACKs and change frequencies every single frame. Frames are typically every 22ms. Think that is slow, well I have some news for you. Spektrum frequency hops every frame between two frequencies. They don't "lock on" to two channels as they claim. Every 22ms, the data is transmitted to the other frequency. Interesting too, since their FCC ID clearly shows their system to be a DSSS configuration. Part 15.247 clearly states that any device changing frequencies faster than once every 400ms/dwell is required to occupy no fewer than 15 channels. Hopping every frame is not legal by these rules. When I added the "hop on saturate to foil the bench testers code", I asked for clarification from the FCC on the hopping speed and we either have to transmit with a psuedo-random 15 frequency algorithm, or we can not hop faster than roughly once every 300ms, which is actually faster than the 450ms spacing we had in the original hopping code. So, it was a benefit to look into this.

Is it possible that Spektrum has two transmitter sections in each module, retransmitting the same data and encoding, but on two different frequencies? Seems like every Spektrum receiver I've ever seen has two antennae. . possibly two receiver sections per unit??

hmmmmm. . something to think about, eh? Not that I know. . just that the possibility seems plausible if there are laws and such against single transmitters doing certain things.

After all this time, I'd expect JD to have something better to throw our way than "but. . but. . but SPEKTRUM. . .etc etc etc. . . ."

so, the question then remains, IF XPS is so. . . agile. . .WHY doesn't it ever hop??? AndIF you coulduse multiple receivers. . WHY don't you do it?

Anyone ever seen a video proving that it can, or does? I certainly haven't.

[aviti]

	Quote: Originally Posted by JimDrew
	People forget that we use only the XBEE hardware. The firmware is our own, and if you look at the chipset used with the XBEE, you can clearly see that multiple receivers can be used and the ACKs will not collide. That is completely wrong. We can support 5ms frames, complete with ACKs and change frequencies every single frame. Frames are typically every 22ms. Think that is slow, well I have some news for you. Spektrum frequency hops every frame between two frequencies. They don't "lock on" to two channels as they claim. Every 22ms, the data is transmitted to the other frequency. Interesting too, since their FCC ID clearly shows their system to be a DSSS configuration. Part 15.247 clearly states that any device changing frequencies faster than once every 400ms/dwell is required to occupy no fewer than 15 channels. Hopping every frame is not legal by these rules. When I added the "hop on saturate to foil the bench testers code", I asked for clarification from the FCC on the hopping speed and we either have to transmit with a psuedo-random 15 frequency algorithm, or we can not hop faster than roughly once every 300ms, which is actually faster than the 450ms spacing we had in the original hopping code. So, it was a benefit to look into this.

If you can't dazzle them with brilliance, baffle them with BS. Thanks for clearing all this up Jim. I'll put my Spektrum gear up for sale and convert to XPS immediately if not sooner.