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Apr 11, 2007, 06:01 PM
NY Slope Dog
Wind Junkie's Avatar
Thread OP
Discussion

Spektrum RX range tests (6000, 6100, 7000)


I haven't seen any of this info posted, so I ran my own experiment today:

I wanted to find out what the relative ranges of the AR6000, AR6100 and AR7000 were -- especially when used INSIDE a carbon sailplane fuselage.

Here's the equipment I used:

Spektrum DX7 TX
Spektrum AR7000
Spektrum AR6100
Spektrum AR6000

JR 4 cell Nicad pack

Hitec HS 85 MG servo

Cappuccino 2.6M Carbon fuselage:

http://www.soaringusa.com/products/p...ategory_id=291


I mounted the servo with a highly visible long "servo arm" made from yellow corplast so I could see it easily as I paced off the distance. The servo wire was fished through a wing root hole so I could leave the servo mounted outside the fuse for the tests that were "out" vs "in" concerning the fuselage.

The 3 receivers were bound to 3 different models in the TX, and I taped them to the box "test stand" as shown. They're off the ground about 1 foot which is typical for a Gas/glo fuel installation when doing range checks. This may differ from the "typical" sailplane range check, but all RX's were at the same height for the checks.

When determining the acceptable range, the TX "bind" button was pressed and held in during the entire range check. To verify control integrity, I oriented the TX antenna in various positions when testing "good" vs "no good", and always declared "good" when ALL TX antenna orientations were acceptable. I found that 2 paces was often the repeatable resolution in distance to re-acqure a control integrity condition once lost (ie: "no good", step 2 paces closer, declare "good", then back up 2 paces again to verify "no good").

Here are my results:

..............Outside Fuselage........Inside Fuselage
AR7000.........80 paces..................26 paces
AR6000.........55 paces..................19 paces
AR6100.........30 paces..................12 paces


Note the AR6000 displays a superior range check than the AR6100 in all cases. My guess this is due to the longer antenna wires of the AR6000.

You can see there =IS= a drastic attenuation due to the carbon fuselage. I consider the Cappuccino to be a typical carbon layup. The moral of the story is to be sure to range check your own installation. The accepted wisdom seems to be "30 paces is acceptable" and that is almost within spec for the AR7000 inside a carbon fuselage. It would be nice if the folks at Spektrum offered a remote antenna option on a new sailplane receiver. I didn't see this offered on the new AR9000.

I hypothesize that one may poke 2 holes in a carbon fuse to route the (longer) AR6000 antennae outside the fuselage, and obtain a superior range check than a fully enclosed AR7000. I did not verify this (yet). I consider the AR7000 antenna too short to attempt this.

Does anyone know if it would be possible to lengthen the antennae of ANY of these receivers to acquire better range -- especially for sailplane use?
Last edited by Wind Junkie; Apr 11, 2007 at 06:24 PM.
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Apr 11, 2007, 06:44 PM
Registered User
Good testing. Did you take a note of how much impact antenna orientation had with the three configurations?

It looks like the 6100 was vertical and having a single antenna would be most sensitive to rotating the transmitter - probably giving the best results with the transmitter vertical too.

I haven't done the carbon test but have checked every installation I have very carefully. All have gone well beyond the 30 paces and I am not seeing the same amount of variation between the three. Of course, my street is probably a different environment to yours etc.

Jim Davey
Apr 11, 2007, 07:46 PM
iWeasel
jludwick's Avatar
Also, for baseline data, how does a standard 72mzh system perform both inside and outside. If the loss in signal strength is still superior (ie. less than) than the "old" system, we're still ahead, right?

Thanks for testing this, I've had the same concerns.

BTW, I would add "carbon fuse" to your thread title to clarify.
Apr 11, 2007, 07:54 PM
Inciting Riots
village_idiot's Avatar
Please explain the "normal" testing procedure that yields the 30 pace rule you mentioned. Is this with a 72Mhz system with the antenna only partly extended, or with the antenna fully extended?
Apr 11, 2007, 09:17 PM
NY Slope Dog
Wind Junkie's Avatar
Thread OP
I didn't put a 72 mhz system in the plane, but that's a good idea. I suspect less attenuation due to a longer antenna, and the Capp is still a good candidate because I believe it has carbon all down the tail.

Note, I didn't want to limit my audience to sailplane guys only. The data is good for relative ranges of the 3 receivers outside carbon fuselage, which is another motivation. I want people to see that the 6000 is a superior receiver (range wise) compared to the 6100. I'd have no problem putting the 6000 into a 40 size glo fuel powered plane, but I'd think twice about the 6100 based on my data. My local hobby shop had silently resolved to discontinue stocking of the 6000 until I said I wanted more of them, suspecting the 6100 would have less range.

I didn't see any TX/RX antena orientation issues that didn't solve themselves when I stepped 2 paces closer. That's why I noted my criteria for total acceptance. I didn't address is the RX antenna orientation in reference to the ground, which I believe could influence the data, but it was too cold for me to spend any more time outside today fiddling.

Anyone can easily repeat my experiments with any one of the receivers to test the effect of differeng RX antenna/ground orientations on range without needing to take a RX out of an airplane. I suspect a variance of less than 5 paces, but that's just a hunch.

The 30 pace rule I was quoting came from the manual. You can see a sample DX 6 manual here from the spektrum web site which specfically spells out 30 paces or 90 feet:

http://www.spektrumrc.com/Content/PD...al-english.pdf

HOW TO RANGE TEST THE SYSTEM
1. With the model resting on the ground, stand 30 paces (approx. 90 feet) away from the model.
2. Face the model with the transmitter in your normal flying position and depress and hold the bind button on
the back of the transmitter. This causes reduced power output from the transmitter.
3. You should have total control of the model with the button depressed at 30 paces.
4. If control issues exist call the Spektrumô service center at 1-877-504-0233.
Apr 11, 2007, 09:50 PM
Inciting Riots
village_idiot's Avatar
Ok, I thought you were comparing results from previous 72Mhz systems. Because the Spektrum has the special power reduction button, it isn't really possible to compare apples to apples with 72Mhz. The onlt way would be to do a full power range test and see how far you could get without trouble.
Apr 12, 2007, 12:33 AM
Memb DEAF R/C
RonR214's Avatar
Quote:
Originally Posted by village_idiot
Ok, I thought you were comparing results from previous 72Mhz systems. Because the Spektrum has the special power reduction button, it isn't really possible to compare apples to apples with 72Mhz. The onlt way would be to do a full power range test and see how far you could get without trouble.
What is wrong with the old antenna down range test for 72??????

Ron
Apr 12, 2007, 08:51 AM
Inciting Riots
village_idiot's Avatar
Antenna down might harm some radios, antenna part way up seems to be the suggested method, but how far up? How much gain reduction does that condition represent? How much gain reduction is the Spektrum using for its check? That was my whole point in asking, I wanted to see if it was apples to apples, or apples to oranges, or just one apple. It was just one apple.
Apr 12, 2007, 09:55 AM
Vitruvian JART
Reed's Avatar
Thanks for going to the trouble to check this so carefully, Joe. Very informative.
Apr 12, 2007, 05:24 PM
Proud member of LISF and ESL
Wind Junkie, this is a great post. I literally was looking for info like this today.


I wonder how it would be with a carbon/kevlar fuse?
Apr 12, 2007, 05:53 PM
Registered User
Daemon's Avatar
Nice test, good information.

I'm thinking the next test would be to try this
https://www.rcgroups.com/forums/showthread.php?t=657685
He cut longer lengths of wire in multiples of 31mm in length
shrink wrapped one end of the wire to the original Rx antenna with
31mm overlap (didn't join them), and then stuck the other end about 31mm
outside the fuse.

ian
Apr 12, 2007, 07:01 PM
Registered User
Wind Junkie, here's the post where Paul Beard talks about antenna lengthening. Can't get better info than that!

Antenna lengthening
https://www.rcgroups.com/forums/show...50#post6665450

RX differences - read back to post 23 for more info
https://www.rcgroups.com/forums/show...81#post6870181

Operating voltage
https://www.rcgroups.com/forums/show...22#post6684022

Good tests you're running, very useful.

LH
Apr 12, 2007, 07:08 PM
Ascended Master
Sparky Paul's Avatar
Inflight, the "range" button appears to cause the AR6000 to go into fail-safe when the plane is about 250-300 feet up.
The plane remains in range until it flies out of sight with the button released.
I don't have any composite fuselages to test the Spektrum with.
Apr 12, 2007, 10:05 PM
Registered User
I'm the one who's been playing with the Carbon MiniBlade. I actually asked Paul about the antenna lengths, and an RF engineer friend about the splicing together trick. It works, but has a problem: slope landings aren't friendly to antennas sticking out of the fuse, even on top. Those wires on my miniblade would have to be replaced every half dozen flights or so, which isn't good.

So, I'm working on a flush external antenna solution for carbon fuses. I may be able to try it this weekend, as I almost have the airframe fixed (the crash WAS NOT radio related, a control link failed in flight... completely my fault).

The flush antenna will simply be some brass shim shapes soldered to those wires and stuck to the fuselage; I'll probably test it by just sticking it down with tape, but eventually we'll be able to cast these into fuselages. The thing to figure out is the precise dimensions of the shape, which I don't have quite yet.
Apr 13, 2007, 08:49 AM
Inciting Riots
village_idiot's Avatar
I mentioned something like that antenna in the XPS thread. Some kind of surface mounted antenna made of metal foil bonded to thin plastic sheet. Maybe even a phased array. Unfortunately the design of this antenna is far beyond my skills. The only other advice I might offer is that it might work better if it was 1 wavelength away from the carbon fiber fuse. Since we are talking about such a small distance, a plastic standoff that is aerodynamic shouldn't be too hard to construct and attach.


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