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Mar 16, 2007, 03:12 AM
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Thread OP
Mini-HowTo

Make a Spektrum RX range check in an all-carbon fuselage


Recently I bought an X-Models Mini-Blade, and once I had it assembled, I found that this airframe is one of those that Spektrum systems have trouble with. It wouldn't range check even at 5 meters, and would cease responding at about 30 meters even without the check button depressed. Obviously it's not flyable like that.

So, I consulted a few people, including a radio engineer friend of mine and Paul Beard, and came up with a solution.

So, the things to know are:

1) Almost any fuselage is too small for 2.4GHz microwaves to propogate down it. So the signal strength will fall off extremely rapidly with distance inside the fuselage.

2) Wire will conduct 2.4GHz microwaves through a space like that.

3) Lengths of wire that are multiples of 31mm resonate at 2.4Ghz. This is why all Spektrum DSM2 antennas are a multiple of this length (the AR6000 is a bit different, but that's off topic). The 31m is fairly critical, so try to get it as close as you can.

4) At 2.4GHz, you don't need contact or solder to get a signal from one bit of wire to another, and in fact it often works best if you don't try to do that. Just laying the wires alongside each other for 31mm (magic number), and taping or heatshrinking them together will do it. This time the 31mm isn't very critical.

So, I made a length of wire 186mm long (since the next shortest length, 155mm, wasn't quite long enough) and ran it to a hole drilled in the top of the fuselage. The last section of the wire was laid parallel to the antenna of the AR6100 receiver and taped on. Note that on an AR6100 the antenna is on the left with the RX pins facing you and the logo rightside up... the right hand wire is the ground. See the attached picture for reference. On mine the ground wire fell off, and I would have sent it back except that there were other modifications to try.

This setup range checked at 30m with the transmitter antenna parallel to the receiver antenna, but not with the antennas perpendicular, nor with the model inverted or tail-on. So, an improvement, but still not right.

I added another two lengths of wire, 124mm this time, taped each alongside a section of the first wire and ran them out holes in the sides of the fuselage. Now it range checks in every orientation I have tried, at about 50m range with the check button pressed.

The proof will be when I fly it of course, which is waiting for the weather and will have to be after I come back from a trip for work, but the results so far are encouraging.

Edit: Yes, it's the first of April, but this is no joke: it flew today, and how. Fabulous model, and the radio system was flawless. On-site range check was solid out to 65 meters, so I went ahead and launched it. It hasn't specked out yet, but it worked great out to about 350m or so.
Last edited by Andrew McGregor; Apr 01, 2007 at 12:52 AM.
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Mar 16, 2007, 08:44 AM
Chuck it and see!
Wing-span's Avatar
I think a lot of the gliding community that reviews this web site will be interested to hear the results of your flight tests. I think what you have done is exactly what will be needed to install the system in larger TD, F3J and F3B moulded gliders.

The RX has 2 boxes does'nt it? where is the second part?

Good work!
Mar 16, 2007, 01:31 PM
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R.M. Gellart's Avatar
Not the 6100 Wingspan, it is a self contained unit compared to the 7 and 9 channel units.

Marc
Mar 16, 2007, 03:39 PM
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Exactly. I have AR7000s as well, and it is simply impossible to get one into this airframe, there is nowhere it will fit.
Mar 16, 2007, 04:36 PM
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treehog's Avatar

Not sure if I got the idea the right way


@Andrew McGregor

well done hope I got the idea correct

are you using the DX6 reciever which has only two antenna and one single box or are you using the DX7 with 4 antenna
but seem to me its the DX6

I have done a diagram

i understand you to say make as many of these 31 mm wire as you want

as per the diagram you can make them divide and go for any lenth what you want and also any direction
A exagerated gap in between but I presume 1mm gap is better

If that is the case I placed a similar set up in a model as per digram if this is the idea

If not enlighten me

If it is this this will mean the Dx6 will work on every size plane as you can eliminate shadow issues

keep up the good work keep us posted

Ralf
Last edited by treehog; Mar 16, 2007 at 04:41 PM.
Mar 16, 2007, 07:51 PM
Registered User
Quote:
Originally Posted by treehog
@Andrew McGregor

well done hope I got the idea correct

are you using the DX6 reciever which has only two antenna and one single box or are you using the DX7 with 4 antenna
but seem to me its the DX6

I have done a diagram

i understand you to say make as many of these 31 mm wire as you want

as per the diagram you can make them divide and go for any lenth what you want and also any direction
A exagerated gap in between but I presume 1mm gap is better

If that is the case I placed a similar set up in a model as per digram if this is the idea

If not enlighten me

If it is this this will mean the Dx6 will work on every size plane as you can eliminate shadow issues

keep up the good work keep us posted

Ralf
The 6100 is a DSM 2 receiver, for the DX7 Transmitter, not the Dx6
It is the two antenna park flyer receiver.

I may have to try this in my Ava with the AR7000, which I have had horrible Range checks with.
Mar 16, 2007, 08:21 PM
AZ Outback
Robert Burson's Avatar
Quote:
The 6100 is a DSM 2 receiver, for the DX7 Transmitter, not the Dx6
It is the two antenna park flyer receiver.

I may have to try this in my Ava with the AR7000, which I have had horrible Range checks with.
Chip the AVA has a lot of room in the open bay and center section of the center wing panel. Have you thought about moving the receiver to this location. It would probably require opening up the center ribs, but I think you could make two different aerial arrangements.

The Best
Robert
Mar 16, 2007, 08:27 PM
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Thread OP
Treehog, you do pretty much have the idea. Don't make unnecessary breaks though; if you can have a continuous bit of wire, do it.

However, it's not necessary to go to that extent. The most you should need is four, the three I have and one pointing down, and if you can do without the downward one that's good. Having more is not a good thing, because it is possible for two parallel antennas to interfere with each other as seen from the receiver, unless they're on opposite sides of a shadowing object, like my two horizontal antennas.

Also, of course, each bit of wire sticking out in the airflow is a bit more drag.

This should all work with an AR6000. Since that is two receivers in one box, you should put the vertical antennas on one and the horizontals on the other.

If you're doing it with an AR7000, it may take some experimenting to find which two of the four antennas are the live ones and which the grounds. In that case you might possibly need eight external antennas, but I expect dividing at most four between the two receivers would do it; verticals on one, horizontals on the other.
Mar 17, 2007, 12:01 AM
Registered User
Quote:
Originally Posted by Robert Burson
Chip the AVA has a lot of room in the open bay and center section of the center wing panel. Have you thought about moving the receiver to this location. It would probably require opening up the center ribs, but I think you could make two different aerial arrangements.

The Best
Robert
Robert, I havent thought of that. Maybe what I will do is put the satelite receiver up there, and make it disconnectable on an extention.

I think I will try the wire part too.

I want to find good ways to use these things once the Module comes out for my 9303, and then my unlimited planes. Right now, putting the Ava on the DX7 will be cool.

It is so nice to be at the field and not worry about conflicts in freqs.
Mar 17, 2007, 05:45 AM
UN Earth peoples true enemy
treehog's Avatar

Thanks for info about reciever


I have the DX6 and dont want to go DX7 in this time
this solution should allow me to go for bigger planes and even some all carbon types

When I start to get into more serious speed DS probably look to get DX7 or similar 1024 for faster reaction speeds

Ralf
Mar 17, 2007, 08:41 AM
Registered User
RTHawk's Avatar
I have been wanting to use the DX6/AR6000 in a couple of my sailplanes. No carbon fiber just foam and Fiberglass. Has any body been using this system and any problems? When in thermals altitudes of 1000+ are always possable, some times greater depending how good your eyes are. When asked Spektrum seems to stick to the ParkFlyer recomendation no matter what. Saying it is the receiver that has the limitation, the only full range receiver they recomend is the AR7000 which is a little large for most sailplanes.

RT
Mar 18, 2007, 04:45 AM
Registered User
I have been using a AR6000 which comes standard in the DX6 in a CAT (aka hl's tiger)with both ant INSIDE the tail bloom without any problem, 36steps in all direciton OK.
Similar set up with the after bought AR6000 AND use of DX7 in another CAT ok too.
I firstly have the ants. in right angle thro 2 holes but I once took out the AR 6000 in the field for checking batt, and in hurry to just stuffed it back to the bloom with NO WAY TO re-extent the ants. and such accidental incidence discover the above set up ok. I have tried them by 3 burst of motor of 5 secs each, should took it VERY HIGH about some 1200ft+. (assume 100ft+/ sec burst) , it was almost out of my sight distinct the head or tail direction. the response is excellent at that height by checking with rocking the aileron stick. no slow or any sign of out of range.
I think I would try the 7CH rx comes with dx7 in a FULL CARBON version of RW2. which has a bloom with full of carbon. Let's see what it will do.

David
Mar 18, 2007, 07:37 AM
Fly long and land softly
Jim_Marconnet's Avatar
Quote:
Originally Posted by RTHawk
I have been wanting to use the DX6/AR6000 in a couple of my sailplanes. No carbon fiber just foam and Fiberglass. Has any body been using this system and any problems? When in thermals altitudes of 1000+ are always possable, some times greater depending how good your eyes are. When asked Spektrum seems to stick to the ParkFlyer recomendation no matter what. Saying it is the receiver that has the limitation, the only full range receiver they recomend is the AR7000 which is a little large for most sailplanes.

RT
Simple answer, the DX6 works without practical range limitations in foam and fibreglass airplanes. This has been shown repeatedly by ground and air tests.

I've been a little frustrated by Spektrum about their whole "ParkFlyer" explanation. But I think they have finally gotten it understandable.

My personal DX6 experience is that (unless there is some large metal object in the plane - which none of mine have had) range is simply not an issue.

In their FAQ http://www.spektrumrc.com/DSM/FAQ.aspx
they say:

What is the range of my DX6?

When used in intended parkflyer models, the range is farther than you can see the model to control it. We don't give a specific range because many issues such as signal attenuation due to metallic conductive material in the aircraft has an effect on the overall range. In fact, that is the main reason why the DX6 is limited to parkflyers only.

and then further down in the FAQ:

The DX6 is limited to parkflyers only. Is this because it has limited range?

Testing the range of the DX6 transmitter and AR6000 receiver in open space generally results in total control beyond the point at which you can see the model. The issue arises when a significant volume of conductive material is located near the receiver. Since park flyers and mini helicopters have limited conductive materials, these issues don't occur and they fly perfectly with 2.4GHz DSM technology.

So my take and personal experience in this is that as long as you are not dealing with a carbon plane or something with huge motor, gas tank, etc., that even the lowly DX6 simply gets the job done.
Mar 18, 2007, 01:36 PM
Registered User
Well,
I managed to get about 220 meters with the test button pressed while using a 11.1v lipo as the radio battery. (opened up a can of worms on that one)

Ben
Mar 18, 2007, 02:37 PM
Registered User
RTHawk's Avatar
I had one reply from Spektrum and they quoted the Parkflyer limitaion and added that as long as the aricraft uses submicro servos thier should be no problems. I guess small servos mean smaller aircraft, and smaller and less signal blocking metal and other material. They also said that the new AR6100 micro recevier used with the DX7 is subject to the same limitations as the AR6000, and the limitation is not the transmitter but the recevier. I can understand they have to set some guidlines.

When flying at higher altitudes with FM the chances of interference from another radio just a few blocks away can be a problem. My electric powered sailplanes do not have any larger motors than the Parkflyers I have and use submicro servos, so I will give it a try. When I graduate up to carbon fiber aircraft I will have to aproach it differantly.

Thanks for the info and its reasuring that others are having good success with the DX6 in their sailplanes.
RT


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