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HELP! Spektrum DX7 radio failure?

Old 07-27-2007, 05:09 PM
  #76  
rea59
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Originally Posted by Lieutenant Loughead View Post
I had another thought this morning...

Those of you with a DX7, please look at the "bind button" on the back. Let me know if you think that button could accidentially be pressed when sitting on the ground (or on a harder surface, like the floorboard of your car).

Here's my thought -- what if I'm turning on the transmitter while it's sitting on the ground? If I do that, I'm going to be pushing down on the transmitter a little -- if the "bind button" becomes depressed, it links, and then I immediately fly on it... Well, what would happen then?
You would need to have the bind plug in as well. But if you pressed it while flying it will reduce your transmited signal strength. "ground range checking"
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Old 07-27-2007, 05:10 PM
  #77  
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Based on the above, tip-to-tip orientation is, therefore, a big no-no which could result in a being thrown out of the game and a six game suspension.
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Old 07-27-2007, 05:20 PM
  #78  
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Originally Posted by Prof100 View Post
Based on the above, tip-to-tip orientation is, therefore, a big no-no which could result in a being thrown out of the game and a six game suspension.
Correct! Antenna's need to be oriented parallel with each other in respect to the ground plane. (the spektrum system uses two 90 degrees apart to catch this as the plane moves) The only way you could point directly at the RX is to use a waveguide or a parabolic dish to direct the radiation. (but then you could never point away from it)
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Old 07-27-2007, 06:05 PM
  #79  
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Originally Posted by rea59 View Post
In short (I don't want to get to technical) as we get to using higher and higher frequencies, smaller and smaller objects will cause us more problems. I have a DX7 and Love it, but have to be extra careful about placement.
Very interesting post -- please elaborate on a "small object" which can cause problems in a Spektrum radio system.

Also, please elaborate on how you are "extra careful about placement". It was my understanding that you could more or less just throw the receiver in an airplane and fly. (I did not do this, but I did read about it in the DX6 review on RCGroups -- the guy ran several tests where he just threw the receiver into the airplane, with no problems.)

Originally Posted by rea59 View Post
You would need to have the bind plug in as well. But if you pressed it while flying it will reduce your transmited signal strength. "ground range checking"
Yeah -- I forgot about the bind plug... Duh! :o

Thanks for your input.
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Old 07-27-2007, 06:07 PM
  #80  
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A word of caution.

I know I probably don't need to say this (but for the novices reading this I will).

Please, Please do not attempt to make your own "ground plane" Flat, round, Parabolic, Waveguide or otherwise.

We are talking about microwave radiation here and although the power is low the results could be hazardous.
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Old 07-27-2007, 06:13 PM
  #81  
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After some careful consideration, I think I'm going to purchase a new 72 MHz radio...

It is ironic that in the last two months, I sold my Hitec Optic 6 transmitter and three of my Hitec Electron 6 receivers -- all in favor of "upgrading" to the Spektrum radio system...

Now, I have such little faith in Spektrum, I wish I didn't sell my Optic 6... Not to mention, if I had not sold my Optic 6, I could have flown in the last two weeks (Spektrum DX7 has been at Horizon for almost two weeks now)...

Arrrgggghhhh -- this Spektrum deal is so aggrivating!

So -- the big question... Who has the best deal on a Hitec Optic 6 transmitter? Actually, I don't want to limit myself to an Optic 6 -- if there is a really good deal out there on a computer radio which can handle negative shift receivers...
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Old 07-27-2007, 06:27 PM
  #82  
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Originally Posted by Lieutenant Loughead View Post
Very interesting post -- please elaborate on a "small object" which can cause problems in a Spektrum radio system.
Any object from a landing gear wire to a screw can cause a problem. An Object that is 1/4 wavelength or a multiple of that (even fractional multipliers) will radiate at that frequency. Also the spacing from the antenna to the object has the same considerations (IE; 1/4 wavelength or multiple of it). That said however the odds of accidentally creating an interference is very, very small though.

Originally Posted by Lieutenant Loughead View Post
Also, please elaborate on how you are "extra careful about placement". It was my understanding that you could more or less just throw the receiver in an airplane and fly. (I did not do this, but I did read about it in the DX6 review on RCGroups -- the guy ran several tests where he just threw the receiver into the airplane, with no problems.)
Just the normal. Don't place near large metal objects. Don't run the antenna wires parallel to the servo or battery wires. ETC.

Also I like metal skin for the scale look but you need a (plastic or fiberglass) window for the antenna or hang the antenna outside the skin.
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Old 07-27-2007, 06:29 PM
  #83  
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Originally Posted by Lieutenant Loughead View Post
After some careful consideration, I think I'm going to purchase a new 72 MHz radio...

I keep both. No need to put all my eggs in one basket.......er planes.


Right now I fly with the DX7 and my son uses the 72mhz radio.
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Old 07-27-2007, 06:35 PM
  #84  
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LL,

I understand your concern with the DX7, but its hard to place a validated opinion over this instance. If in fact he purchased a 'lemon' (for a lack of better words ) the chances of getting similiar results can lay within the 72 Mhz radios as well. Alot of people have had problems with 72 Mhz radios, but if you look at numbers sold that worked flawlessly vs numbers sold that were lemons, the ratio would be quite low of 'lemons'. The same holds true for Spektrum's DX7, the ratio is quite low.

I own both 72 Mhz and the DX7. I have never had any problems whatsoever with my DX7 system and I use it to haul up a $1000 electric plane (Aerial Photography).

So think long and hard, put the numbers in front of you and make the decision that you will be happy with...we all need that 'warm & fuzzy' feeling inside us when we fly our planes.
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Old 07-27-2007, 06:36 PM
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Didn't they do a test where the placed the recievers in the worst possible places and nothing happened? I could have sworn I read an article about this.
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Old 07-27-2007, 06:38 PM
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Originally Posted by aviatordave View Post
LL,

I understand your concern with the DX7, but its hard to place a validated opinion over this instance. If in fact he purchased a 'lemon' (for a lack of better words ) the chances of getting similiar results can lay within the 72 Mhz radios as well. Alot of people have had problems with 72 Mhz radios, but if you look at numbers sold that worked flawlessly vs numbers sold that were lemons, the ratio would be quite low of 'lemons'. The same holds true for Spektrum's DX7, the ratio is quite low.

I own both 72 Mhz and the DX7. I have never had any problems whatsoever with my DX7 system and I use it to haul up a $1000 electric plane (Aerial Photography).

So think long and hard, put the numbers in front of you and make the decision that you will be happy with...we all need that 'warm & fuzzy' feeling inside us when we fly our planes.
I would think the Lt. has a cold and clammy feeling inside when he thinks of a DX7. Forget the "lemons" per thousand or million produced. It is 100% of his experience with a DX7.
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Old 07-27-2007, 06:44 PM
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Originally Posted by Mike Freas View Post
Didn't they do a test where the placed the recievers in the worst possible places and nothing happened? I could have sworn I read an article about this.
ask and ye shall recieve !

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Old 07-27-2007, 06:44 PM
  #88  
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Originally Posted by Mike Freas View Post
Didn't they do a test where the placed the recievers in the worst possible places and nothing happened? I could have sworn I read an article about this.
(see Dave's post). As I said earlier the probability of creating an interference is very small.

I tend to think like Dave that this specific problem is a "lemon" Transmitter. Thats the only piece thats been common to all the problems yet no one else has similar problems.

Last edited by rea59; 07-27-2007 at 07:33 PM. Reason: Dave was first.
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Old 07-27-2007, 07:15 PM
  #89  
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I had the same problem with two of my planes, the 1st without a BEC and the 2nd with. The 1st plane when in to level flight the second plane crashed.

Both planes when in line of site, with no trees or structure even in the area


1st plane was at 50ft away, the 2nd was about +250ft.

both times the antenna was pointing at the plane

I sent my Rx6100 for upgrades which was done.


THIS IS THE ANSWER TO MY PROBLEM WITH THE SYSTEM
I don't think it was the upgrade that fixed this problem, my DX7 came with a battery that was self discharging very quickly(bad pack), (which they wouldn't replace)!!! and i don't think it was providing the power the Tx need to keep contact with the little AR6100. Even with the AR6100 at the correct power level, which i checked after each problem.


So with my new working battery the voltage/amps are correct and so far I haven’t had another problem…..

Note the voltage displayed looked okay but the amps the pack was putting out was very low.
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Old 07-27-2007, 07:20 PM
  #90  
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Originally Posted by paranoia View Post
I sent my Rx6100 for upgrades which was done, so far I haven’t had another problem…..
Good Question! Are these 6100's the upgraded version or pre upgrade???
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Old 07-27-2007, 07:32 PM
  #91  
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All his RXs are the 1.2 versions.


LT:

I'm leaning towards one of two possible scenarios.

First, you might just have an intermittent problem with the TX that didn't show on the test bench and that passed QA. It happens. You might want to press for a factory fresh unit and to get your unit "lemoned" out.

Second, over the years you might have some quirk of building, some tiny thing you "always do" that's interfering with 2.4 GHz systems specifically. This seems farfetched but I suppose it's possible.


In all fairness I suppose it's also possible you're a Futaba or XPS shill or something but I don't find that possibility credible. Mention it just to be complete so to speak. Forget I said it.


I love my DX7, and if you're willing to continue to troubleshoot this I will help in any way I can. Except for trading transmitters. Nice try, bucko.
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Old 07-27-2007, 07:36 PM
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Originally Posted by UncleBob View Post
All his RXs are the 1.2 versions.

Thanks! Missed that.
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Old 07-27-2007, 08:04 PM
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oh, by the way my AR7000 never had a problem, i think it was becuase of the 2nd reciever and the fact that it can work with low Tx power
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Old 07-27-2007, 08:09 PM
  #94  
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Maybe, but remember these RXs are really little computers, and the AR6100 had a bug in it's firmware. A firmware bug could take the AR7000 down just as surely. As I understood it, in the case of the AR6100 a properly malformed data packet would cause the CPU to halt in a very specific state where the controls were not in their failsafe locations.

It wasn't a signal loss.
It wasn't a reboot.

It was a software flaw that sounds very similar to a typical security vulnerability, the classic buffer overflow, but that's just a SWAG.
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Old 07-27-2007, 08:14 PM
  #95  
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LOL...SWAG....Haven't heard that in a while.
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Old 07-27-2007, 08:29 PM
  #96  
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Originally Posted by UncleBob View Post
First, you might just have an intermittent problem with the TX that didn't show on the test bench and that passed QA. It happens. You might want to press for a factory fresh unit and to get your unit "lemoned" out.
At this point, I fully agree with this recomendation. At this point, the only way I am going to trust a Spektrum DX7 is if Spektrum sends me a brand new ("factory fresh") unit.

Originally Posted by UncleBob View Post
Second, over the years you might have some quirk of building, some tiny thing you "always do" that's interfering with 2.4 GHz systems specifically. This seems farfetched but I suppose it's possible.
This is possible. If true, I sure wish I knew what it was! :o


Originally Posted by UncleBob View Post
In all fairness I suppose it's also possible you're a Futaba or XPS shill or something but I don't find that possibility credible. Mention it just to be complete so to speak. Forget I said it.
LOL -- I assure you I am no shill. (I don't even know what XPS is!) I've always been a Hitec guy anyway...

Seriously, I have never worked for a radio company, nor have I received any money, product, or any other form of compensation from a radio company.

Originally Posted by UncleBob View Post
I love my DX7, and if you're willing to continue to troubleshoot this I will help in any way I can. Except for trading transmitters. Nice try, bucko.
Awwww come on! It was YOUR idea!
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Old 07-27-2007, 08:30 PM
  #97  
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i really think it "low single strenght"
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Old 07-27-2007, 08:32 PM
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Originally Posted by paranoia View Post
Note the voltage displayed looked okay but the amps the pack was putting out was very low.
Very interesting -- how did you debug this failure mode?



I've been watching the meter on the display -- it's always looked good.
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Old 07-27-2007, 08:36 PM
  #99  
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Originally Posted by paranoia View Post
i really think it "low single strenght"
My understanding was that weak signal or interference would cause data errors. In very rare cases the data would be malformed in a very specific way that would unintentionally "exploit" a flaw in the RX firmware. This exploit would then lock up the RX.

So while poor signal would trigger it the root cause is common to anything with firmware. Did you know that millions of Japanese cellular phones have a vulnerability wherein a properly malformed JPEG can reset the phone? Welcome to the infomation age.
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Old 07-27-2007, 10:31 PM
  #100  
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Originally Posted by Lieutenant Loughead View Post
Very interesting -- how did you debug this failure mode?


I've been watching the meter on the display -- it's always looked good.

i saw that the battery pack was self discharging very quickly, (i understand Nimh battery self discharge but not like this) after two days the pack would go down to 50% or less.

When i did a range check with this pack at full charge (with the Tx button pressed in) it was okay. but when i did a range check with the pack after two+ days the plane would be going in and out of failsafe mode at same distance! Even range checks done later on day one where not get, the voltage would read say 10.1V and be dropping as i was looking at it! even those the voltage was above the min of 9V the range checks where bad. It was like there was a low resistance short in the pack using up the power. Now as I moved the plane closer to the Tx (with the pack at say 10.1) the reception was okay at short distances, and the system would work okay.

So I concluded that the Tx was not pumping out the power needed, even when the display said 10.1

after i changed the pack out, i have had no problems with range, or glitches......

Note: I never had the firmware glitch happen, (horz lock in up position).
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