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Old May 18, 2012, 03:44 AM
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karoliinasalmin's Avatar
Finland, Espoo
Joined Jan 2012
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Broken DX7? Super poor range with Spektrum DX7

Hi,

There are maybe someone experienced with Spektrum radios and possibly could advise (like why this could have happened, etc.). And to be sincere I would like to get confidence back with Spektrum in general as I would not like to switch to other brand due to the receivers we already own:

We have one Spektrum DX7 (couple of years old, European crippled down model with European restricted output power as it is purchased from Europe). When we were total newbies in piloting RC aircraft, we thought it was lack of piloting skill why planes sometimes dropped from the sky. Now when we are more experienced and don't crash that often due to insufficient piloting skills, it turns out that it was and is the Spektrum why planes are coming down strangely. It may lose control in a relatively short distance (when floating a 450 class helicopter), 25 meter may be enough distance to make the DX7 to glitch and the copter to come down in pieces - the output power somehow seems comparable to what it is supposed to be in range test mode than what it should be. We have tried different receivers (original Spektrum, original Spektrum with satellites and different types of Oranges from HK and have experimented with placing the satellite far away with extension), but it seems that the receiver is not the problem and neither is diversity the problem. The antenna was recently replaced in the DX7, but seems that it did not fix the problem, the problem still exists. Comparing to other radios like a DX6i and Flysky and some cheap noname 2.4 GHz (which cost a fraction of the price of the Spektrum), none of them have had this severe problems than the Spektrum has (apparently) always had, all the way from when it was brand new.

Already hopefully solved the problem by ordering a Spektrum DX8 (I am afraid to fly with that too, will try at first with something inexpensive), but would be nice if there would be some way to fix/repair the DX7 too (and I really do hope that the DX8 will work and will have much greater range than the DX7 has had and this glitching / lack of range is not a feature).

Could it be that the radio transmitter of our DX7 is broken/deficient? If I do not put the range check mode on, and simply start walking with the receiver away from the DX7 transmitter, it starts glitching about in the middle of the field always and sometimes sooner and at 180 m point it can lose the signal completely. The field is 180 meters long. In other words it has "good range" of up to 90 meters (in a foamie without any radio restricting barriers) and sometimes working range up to 180 meters, and with a copter that has some carbon structures on it, it can lose connection already in bare 25 meters and if there is someone standing between the model and the pilot, the connection can be lost even earlier.

Our models are (e.g. EDF jets) becoming such big that it is very expensive and very dangerous (not only for model, but also for both people and property) if the radio glitches all of the time (or any of the time). At one point I was thinking that I must be a really poor pilot when I crashed a Easyglider from straight cruise down now and then sometime in 2010, but looking back it must have been the Spektrum DX7 as well all along - Indeed I have not crashed from controlled straight level flight ever the models which have used different (e.g. those el-cheapo) radios. But day before yesterday one plane (Multiplex Blizzard) nosed down to field uncontrollably and a 450 helicopter broke almost all its parts by "dropping" uncontrollably to ground (that was also day before yesterday). Two weeks ago Multiplex Xeno came down and went into pieces due to failure with the DX7. Also the Multiplex Blizzard came the first time down due to DX7 radio failure. And there was also one almost crash with 600 class copter, blades touched ground. And Multiplex Cularis ... it crashed, split into two parts and there was battery fire.

The DX7 has costed us already a lot for glue and replacement airframes and copter parts. Fortunately the destroyed hardware has been inexpensive foamies and 450-550 class copters (so far) and no damage to external parties. But still kinda much more expensive than the original purchase price of the DX7 was.

So what should I do with this DX7? Get it repaired (by who/where at what cost?) or throw it away (kinda expensive to just throw away)? Any advises/experiences with similar issues? It has no longer warranty because it is couple of years old (about as old as our RC flying hobby) (purchased sometime in 2008 I think from a Finnish Spektrum reseller). Or maybe LRS system - can a LRS radio be connected to DX7 (so that the DX7 possibly broken/deficient radio is not used at all)?

As I mentioned; we are equipped with great amount of Spektrum receivers (all our systems are based on Spektrum because we thought it works before finding out that it doesn't) and switching to e.g. Futaba, Multiplex, Graupner or whatever (maybe LRS system?) would mean buying again also all the receivers (for dozen(s) models) and that does not look so great as I would like that money to spent otherwise.

Best Regards,
Karoliina
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Old May 18, 2012, 06:49 AM
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richard hanson's Avatar
United States, UT, Salt Lake City
Joined Oct 2007
6,883 Posts
Why not have your equipment thoroughly checked by Spektrum .
Apparantly you have:
A . bad results
B. don't know why
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Old May 18, 2012, 07:56 AM
AndyKunz's Avatar
Illinois
Joined Sep 2001
23,500 Posts
I don't know if Finland is covered by the UK or DE office. Try the one your local dealer suggests.

www.horizonhobby.co.uk
www.horizonhobby.de

Andy
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Old May 18, 2012, 08:08 AM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
23,843 Posts
Quote:
Originally Posted by karoliinasalmin View Post
... Already hopefully solved the problem by ordering a Spektrum DX8 (I am afraid to fly with that too, will try at first with something inexpensive), ... Best Regards, Karoliina
There are hundreds and thousands of satisfied DX8 owners and they don't all use it on inexpensive models.

When you get your DX8 send the DX7 for service and then when you get it back keep it for buddy box / trainer system with the DX8. Enjoy your new purchase.
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Old May 18, 2012, 09:30 AM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,306 Posts
There is obviously a problem with your transmitter. The DX7 is an excellent system which gives full range when working correctly.

About the only thing likely to produce short range that you might be able to diagnose would be a bad antenna connection or broken cable to the antenna. I would take a close look at the connector to make sure it's firmly in place and also see if the cable has been obviously damaged.

Apart from those checks, the only real choice you have is to send to Spektrum Service. I don't have any information on how to do that in your part of the world.

Good luck.
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Old May 18, 2012, 10:19 AM
AndyKunz's Avatar
Illinois
Joined Sep 2001
23,500 Posts
If the cable or connector are damaged, that can cause damage to the RF power amp. That would require replacing the RF deck - something that can only be done by a service center.

Andy
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Old May 27, 2012, 01:57 PM
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karoliinasalmin's Avatar
Finland, Espoo
Joined Jan 2012
88 Posts
Hi,

We were testing the brand new DX8. Looks and feels much better than DX7. However, here is the result (see attached picture). In addition to the plane being in pieces also a farmer's barn has a Xeno shape dent in its roof. Plane is still about repairable with lots of epoxy and some micro slurry, but it will be rather ugly after repairs as it has some pieces missing. Not sure about the barn roof :/. I was not piloting but I can confirm that the plane lost radio contact since the throttle went to zero and there was no control in the elevons at all (was wathing behind the pilot). The transmitter antenna was bent upwards as it should.

Specs: Spektrum DX8 (just taken from package), new AR6200 + new satellite receiver. Satellite receiver was placed outside of the canopy area of the Multiplex Xeno foamie and the satellite was in 90 degrees with the main receiver. We tested that both were bound ok.

This same plane flies perfect the same distance (about 250 meters away and maybe ~100 meters high (around 1/3 of the altitude where I fly the X8), it was at the edge of our field and at quite high altitude) glitch free with Hobbyking cheap Orange receiver without a satellite with the same BEC (I don't think brown out can be the cause, especially because Xeno needs very little power for the controls as it has only two mini-servos), HK receiver placed poorly next to battery (the el-cheapo-version or the Orange and not even the long antenna version), if the radio transmitter is my DX6i which has US-version transmit power. In comparison the both DX7 and DX8 are purchased from EU and have the reduced transmit power. The DX8 appears to glitch at about the same distance than the DX7 used to (starts glitching at around 150 meters and loses control at ~200 meters at the latest). The US transmit power DX6i commands my Skywalker X8 to as far as I can see it without a single glitch. The EU power version (DX7 or now proven with DX8 that it is no different than the DX7) will bring it down in pieces.

So is the DX8 also broken or is there some difference/way to get better diversity with additional satellites and/or does AR8000 have better range? The DX7 had the original AR7000 + satellite in when it brought down and totalled my Easyglider last year, so at least AR7000 was not behaving better than the cheap Orange.

Now I will go to range test the DX8 again. So what could be the reason now? And what would be the cure? Get cheapest plane tickets and fly to USA to buy a transmitter since EU models do not seem have sufficient range for even small foamies for our use (based on two samples we have now experience on) or is there a less expensive way to fix it? Especially if I wanted to fly my X8 with the DX8, I would need at least 500...700 meter radius of range. Question is that is there any way to get that kind of range from a ridiculously regulatory power limited EU-Spektrum [any model with any receiver combination]?

Best Regards,
Karoliina
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Old May 27, 2012, 02:50 PM
Canada, BC, Burnaby
Joined Sep 2010
40 Posts
Thousands of people all over Europe are using the same power output as you do and seem to be doing fine. It is strange...
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Old May 27, 2012, 03:03 PM
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karoliinasalmin's Avatar
Finland, Espoo
Joined Jan 2012
88 Posts
Very strange indeed.

Here is a map of the flight (clip from Google maps) (see attachment):

It flew only 1/2 circle before it crashed.
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Old May 29, 2012, 10:41 AM
throw new IOPilotException();
IceWind's Avatar
Ireland, County Dublin, Dublin
Joined Feb 2005
2,650 Posts
Open the radio, remove the antenna connector from the filter and plug it directly into the TX module and done! You now have more power.
It will not be the same as the US (i read somewhere that there is also some software imposed limits) but it will be better. I did that to my DX7.
So far I only lost radio link twice,first while doing FPV with my tricopter and while using a Orange 6ch RX that is a parkflyer version.
Second when antenna wires in a original Spektrum AR6200 RX fell off and I didn't noticed. (pretty crappy RX design btw...)
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Old May 29, 2012, 11:38 AM
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Dallas, TX
Joined Jan 2010
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Does anyone else fly from your field?

If so, what equipment do they use?

Just wondering if you have some local problems as you must realize that if this was just EU vs USA signal strength then most of Europe would be crashing planes every day, which they obviously aren't ...
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Old May 29, 2012, 02:33 PM
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karoliinasalmin's Avatar
Finland, Espoo
Joined Jan 2012
88 Posts
Nobody else than me and my partner fly on that field because it is farmer's field, not rc field (there are almost zero dedicated rc fields in Finland (there is one I have heard about but never been there), people either fly on farmers fields or go to uncontrolled airfield). I am flying frequently there with dx6i that has usa power, my partner has the dx7 and d8 and these are causing crashes. I have Never had problems with it (us configured dx6i), not even with the 6 ch parkfly Oranges. Same field, same time, same distance, same planes, same rx, the dx6i just works every time and dx7 crashes every time, and dx8 caused crash on first attempt. Main receiver was not optimally placed, could be blanketed with battery, but on the other hand, with the dx6i that placement never was a problem, and the satellite was placed as far the wire let it to have diversity and to have unrestricted signal into it. There should not be radio interference anywhere nearby as it is farmers field and very little houses/population nearby. Even cell phone has weak signal on that field indicating that there is not base station nearby interfering with dx7 or dx8. And it would not explain why Usa model dx6i is completely glitch free always in the very same place.

sorry for typos - sent from ipad (ipad virtual keyboard loses key presses sometimes)
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Old May 30, 2012, 06:49 AM
throw new IOPilotException();
IceWind's Avatar
Ireland, County Dublin, Dublin
Joined Feb 2005
2,650 Posts
Well losing signal at around 180mts seems like antenna issues.
I just had that on my FrSky gear and turned out to be the TX module antenna that was damaged.

Replaced it and after +300mts with both radio and rx with the ground it still had signal.
(and I had the FPV gear working that cause interference)

If it's still under warranty send it to be checked, if not get a replacement antenna and try.
Well you could even use the one on the DX6i to test, despite of course it will make you open both radios.
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Old May 30, 2012, 05:39 PM
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karoliinasalmin's Avatar
Finland, Espoo
Joined Jan 2012
88 Posts
Actually the antenna of DX7 was just replaced. Did not help. And the DX6i antenna is broken and is fixed with duct tape. Still works awesomely better. On the other hand isnt 10 mW compared to 100 mW actually equaling 10 decibels? That sounds significant to me.
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Old May 30, 2012, 05:42 PM
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karoliinasalmin's Avatar
Finland, Espoo
Joined Jan 2012
88 Posts
Forgot to mention, my Nokia N9 cell phone has been riding on my X8 wing and with DX6i no problem despite it was directly next to receiver and had all radios on and data transmission on.
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