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HELP! Spektrum DX7 radio failure?

Old 07-18-2007, 05:34 AM
  #26  
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Originally Posted by Rabbitcreekok View Post
Now if you make a hat out of tinfoil, preferable heavy duty Reynolds Wrap, the radio waves will bounce off the hat and be directed to the receiver in your airplane and reception will be improved. Also your status at the flying field will definitely change.
Now that has got to be the best advice in this thread so far.
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Old 07-18-2007, 06:08 AM
  #27  
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Having read this thread and its reiteration of the need to point the antenna in a correct orientation leads me to believe the design is inherently flawed because with one and only one transmitter antenna the possibility exists that it will fail to send a signal that the plane can receive. Therefore, the design needs to be revised to provide two antennas oriented 90 degrees from one another. With two antennas it should cover a broad spectrum of transmission that will not be missed by the airplane receiver.

Just my two cents. I sure wouldn't by one of these radios if the antenna position / orientation is that critical. The failure mode effects are extremely expensive!!!
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Old 07-18-2007, 03:21 PM
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Originally Posted by Rabbitcreekok View Post
Now if you make a hat out of tinfoil, preferable heavy duty Reynolds Wrap, the radio waves will bounce off the hat and be directed to the receiver in your airplane and reception will be improved. Also your status at the flying field will definitely change.
LOL -- okay... I'm going to do this, and take a picture, and post it here!

I looked through my Spektrum DX7 instruction manual, and DID manage to find a statement about not pointing the antenna directly at your aircraft. It's on one of the last few pages of the manual... Again, it IS possible this was my problem... When I regained control of the P-51 (about 100 yards away, 10 feet off the ground, on the other side of the parking lot), I had lost sight of the airplane and thought I crashed it -- I hung my head low, and dropped the transmitter (the lanyard held it to my neck) -- THAT's when I saw the P-51, tried again, and saw that I had control of the aircraft!

Also, I'm wondering something -- does any RF radiate from the BASE of the antenna? What I mean to say is this -- if you bend the antenna 90 degrees, is your Spektrum radio effectively transmitting on two different antennas (90 degrees to eachother)?
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Old 07-18-2007, 03:27 PM
  #29  
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A few pictures of the carnage...

Here's the information I included with the Spektrum DX7 I shipped back for repair:

Rest In Pieces!!!

Spektrum DX7 radio lockout on July 16, 2007. First flight was at 7:10, with a duration of 15.6 minutes no problems. Second flight (with fresh battery) was at 7:30, with a duration of 2.1 minutes radio lockout for 10 seconds. Airplane nosed over from approximately 100 feet, and hit ground so hard it BOUNCED five to six feet in the air. After flight battery voltage was 16.52 volts. Battery was a CommonSenseRC 4s 3150 mAh LiPo. Speed controls were twin Castle Creations Phoenix 25s. This airplane used a Dimension Engineering SmartBEC.
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Old 07-18-2007, 03:40 PM
  #30  
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Originally Posted by Prof100 View Post
Having read this thread and its reiteration of the need to point the antenna in a correct orientation leads me to believe the design is inherently flawed because with one and only one transmitter antenna the possibility exists that it will fail to send a signal that the plane can receive. Therefore, the design needs to be revised to provide two antennas oriented 90 degrees from one another. With two antennas it should cover a broad spectrum of transmission that will not be missed by the airplane receiver.

Just my two cents. I sure wouldn't by one of these radios if the antenna position / orientation is that critical. The failure mode effects are extremely expensive!!!
By this logic you shouldnt be flying ANY rc aircraft. The same rules apply to 27, 72, and 2.4 ghz radio waves. So be careful where you point your Tx no matter what the frequency. Just thought I would let you know
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Old 07-18-2007, 06:54 PM
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Originally Posted by Lip84 View Post
By this logic you shouldnt be flying ANY rc aircraft. The same rules apply to 27, 72, and 2.4 ghz radio waves. So be careful where you point your Tx no matter what the frequency. Just thought I would let you know
From what I am reading the Spektrum 2.4 ghz is much more sensitive to antenna orientation. If it is not, then I am wrong and better fly control line.
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Old 07-18-2007, 07:20 PM
  #32  
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Haha, yea...control line FTW

Do you have a link to a source on that Prof? I dont doubt you but am curious since I have not seen this and have been doing research on the DX7 system recently.

lip84
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Old 07-18-2007, 07:48 PM
  #33  
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Originally Posted by Lip84 View Post
Haha, yea...control line FTW

Do you have a link to a source on that Prof? I dont doubt you but am curious since I have not seen this and have been doing research on the DX7 system recently.

lip84
lip84,

I don't have an annotated bibliography of my conclusions since I feel like I am being cross-examined in a product liability case by the defendant, Spektrum radios. Seriously, I just recall in several reviews I have read the authors dwelled on the importance of proper antenna orientation. Even Horizon's (they market them) writeup devotes 5 paragraphs to signal fade and how the "dual link" featue counters any fade (a euphemism for losing contact) problems. See below:

http://www.horizonhobby.com/Articles...ID=1535&Page=2

My thoughts are the addition of the dual link feature is a counter measure for potential or probable signal losses.
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Old 07-18-2007, 07:49 PM
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Originally Posted by Prof100 View Post
Having read this thread and its reiteration of the need to point the antenna in a correct orientation leads me to believe the design is inherently flawed because with one and only one transmitter antenna the possibility exists that it will fail to send a signal that the plane can receive. Therefore, the design needs to be revised to provide two antennas oriented 90 degrees from one another. With two antennas it should cover a broad spectrum of transmission that will not be missed by the airplane receiver.

Just my two cents. I sure wouldn't by one of these radios if the antenna position / orientation is that critical. The failure mode effects are extremely expensive!!!
I agree with Lip; your logic is flawed. It's simple; do NOT point the tip of the antenna at your rx. But then, you shouldn't do that with ANY transmitter like these.
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Old 07-18-2007, 08:23 PM
  #35  
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Prof,
I meant no disrespect and did not want to make you feel like you were being cross examined in a court case. You simply made me aware of information that I had not been aware of prior to your input and wanted to see it first hand. that is all. I am sorry if you felt that I was attacking you, that was not my intent at all.

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Old 07-18-2007, 08:25 PM
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Originally Posted by Prof100 View Post
lip84,

I don't have an annotated bibliography of my conclusions since I feel like I am being cross-examined in a product liability case by the defendant, Spektrum radios. Seriously, I just recall in several reviews I have read the authors dwelled on the importance of proper antenna orientation. Even Horizon's (they market them) writeup devotes 5 paragraphs to signal fade and how the "dual link" featue counters any fade (a euphemism for losing contact) problems. See below:

http://www.horizonhobby.com/Articles...ID=1535&Page=2

My thoughts are the addition of the dual link feature is a counter measure for potential or probable signal losses.
And when I read those statements, I took them to mean the Dual Link feature is not to overcome a TX shortcoming, but the possibility of the rx antenna being shielded by an engine or motor in the aircraft.
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Old 07-18-2007, 08:46 PM
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Originally Posted by Lip84 View Post
Prof,
I meant no disrespect and did not want to make you feel like you were being cross examined in a court case. You simply made me aware of information that I had not been aware of prior to your input and wanted to see it first hand. that is all. I am sorry if you felt that I was attacking you, that was not my intent at all.

Lip84

lip84,

I never felt disrespected nor did I feel I was being attacked. My response was simply a poor attempt at humor.

I would like to have a radio system that doesn't require crystal changes, is bullet proof in terms of interference, and does not fade or lose communication with a plane. The new Spektrum radio systems are extremely appealing because they appear to meet those needs.

However, my experience taught me (albeit scattered over 25 years of RC in both surface and air) was alarmed by the amount of information provided about the veracity of the new Spektrum systems in terms of fade or communication loss. I am always suspicious when I hear a sales pitch that stresses features to counter problems you might have with the product you are considering buying.
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Old 07-18-2007, 08:55 PM
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Originally Posted by gfdengine204 View Post
And when I read those statements, I took them to mean the Dual Link feature is not to overcome a TX shortcoming, but the possibility of the rx antenna being shielded by an engine or motor in the aircraft.
I would think the Dual Link feature is to overcome a shortcoming of the radio system, with system being a key word.
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Old 07-18-2007, 09:02 PM
  #39  
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Originally Posted by Prof100 View Post
lip84,

I never felt disrespected nor did I feel I was being attacked. My response was simply a poor attempt at humor.

I would like to have a radio system that doesn't require crystal changes, is bullet proof in terms of interference, and does not fade or lose communication with a plane. The new Spektrum radio systems are extremely appealing because they appear to meet those needs.

However, my experience taught me (albeit scattered over 25 years of RC in both surface and air) was alarmed by the amount of information provided about the veracity of the new Spektrum systems in terms of fade or communication loss. I am always suspicious when I hear a sales pitch that stresses features to counter problems you might have with the product you are considering buying.

With our our old systems, we has a long antenna trailing behind our models as they flew. Or the antenna was hidden inside the fuselage or wing, but it was long.

The 2.4 Ghz systems use short, 2" or so, antennas, due to the higher frequency. Because these antennas could be blanked out by a large lump of metal in the front, read engine, they use 2 separate links and antennas. This is to assure that they can always receive a signal. Folks are flying 200mph turbine powered jets with the 2.4 Ghz systems.

With anything new there are going to be lots of rumors about the systems, as well as some problems. These problems will be reported with enthusiasm, as they should. The old systems have problems but they aren't reported on forums since it is not news.

I like my DX systems and have had no problems. But then, I did not have problems with the 72 Mhz systems.
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Old 07-18-2007, 09:19 PM
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Originally Posted by Rabbitcreekok View Post
With our our old systems, we has a long antenna trailing behind our models as they flew. Or the antenna was hidden inside the fuselage or wing, but it was long.

The 2.4 Ghz systems use short, 2" or so, antennas, due to the higher frequency. Because these antennas could be blanked out by a large lump of metal in the front, read engine, they use 2 separate links and antennas. This is to assure that they can always receive a signal. Folks are flying 200mph turbine powered jets with the 2.4 Ghz systems.

With anything new there are going to be lots of rumors about the systems, as well as some problems. These problems will be reported with enthusiasm, as they should. The old systems have problems but they aren't reported on forums since it is not news.

I like my DX systems and have had no problems. But then, I did not have problems with the 72 Mhz systems.

Jim,

Great comments, thanks. I, too, have never had any problems with 72 mhz radios.
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Old 07-18-2007, 09:22 PM
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Me either!
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Old 07-18-2007, 10:37 PM
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Originally Posted by Prof100 View Post
Having read this thread and its reiteration of the need to point the antenna in a correct orientation leads me to believe the design is inherently flawed because with one and only one transmitter antenna the possibility exists that it will fail to send a signal that the plane can receive. Therefore, the design needs to be revised to provide two antennas oriented 90 degrees from one another. With two antennas it should cover a broad spectrum of transmission that will not be missed by the airplane receiver.

Just my two cents. I sure wouldn't by one of these radios if the antenna position / orientation is that critical. The failure mode effects are extremely expensive!!!
Is this what you are talking about? This would work on smaller electrics with the safety of two antennas (its new):

http://www.horizonhobby.com/Products...odID=SPMAR6200

I have the DX7 and I have been using the AR7000 rx on my electrics (24 oz on up) and not even used the AR6100 unless its on my 3D foamy which flys right in front of me. The 6100 is noted for radio blocked signals if it gets in the way of a Battery or such.
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Old 07-18-2007, 11:00 PM
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Originally Posted by aviatordave View Post
The 6100 is noted for radio blocked signals if it gets in the way of a Battery or such.
I find this statement VERY interesting -- please tell me more!
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Old 07-18-2007, 11:04 PM
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Well, being that the AR6100 has 2 very small antennas, were one to place it in a plane with a large engine or motor (made of metal), and the engine/motor were directly in the path of the radio signal, the rx could be shielded and not receive the signal. That would cause the RX to use the failsafe positions programmed in at binding, until it can re-acquire the signal.

The AR6200 has a remote rx like the AR7000, which eliminates this problem.
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Old 07-18-2007, 11:13 PM
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I'll try to find the threads on that interference later tonight....its Miller time 4 me!
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Old 07-19-2007, 03:25 PM
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Hmmmm -- thinking back to my radio failures...

1) The flat foamie was in a 3-D "hovering" attitude when it failed. The only thing between the receiver and the transmitter was a small piece of 6mm Depron, and about 20 feet of wide open air.

2) This GWS P-51 was traveling towards me -- about 50 feet up, and about 50 feet west. The receiver is in the bottom of the aircraft (cut into the wing, where the landing gear servo used to go). In this case, there is some 6mm Depron, some beaded styrofoam, some fiberglass, some MicroLite covering, and the possibility of the stock GWS wing mount screw between the transmitter and receiver.

3) This was an interesting one, because the receiver was "rebooting" for about 25 seconds; during that time, the airplane traveled approximately 200 yards, in a gentle left turn, and showed it's bottom/nose, bottom/starboard side, and tail (but never it's top or port side) to the transmitter. The airplane was in a similar attitude as #2 (above), but was at about 100 feet of altitude, and 100 feet west when the loss of signal occurred. Signal was regained at 10 FEET of altitude, and 100 YARDS away. Since the receiver is at the bottom of the wing, you would think that the weak signal would occur when it was closest to the ground (and farthest away)... This airplane actually glided (unpowered and in free-flight mode), directly over my head at about 75 feet of altitude -- at that point, the only thing between the receiver and transmitter was a piece of 6mm Depron, some fiberglass, and some MicroLite covering.

4) This P-38 was at about 100 feet up and about 75 yards south-east. It was making a gentle bank to port when the glitch happened. The receiver is in the bottom of the gondola (center pod). This is the ONLY case where the motor, gearbox, and/or ESC could have been between the receiver and transmitter. This airplane was also fiberglassed -- I wonder if the fiberglass could be the problem?! ??

Last night, I was thinking more about this, and it sounds to me like Spektrum has a design flaw... First, a 10 to 25 second reboot time is unacceptable. Second, steps should have been taken to keep a momentary low-voltage dip from having such catastrophic results. A simple Resistor/Capacitor network on the receiver's power input would alieviate this issue!!!

Sorry to vent. :o
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Old 07-19-2007, 03:47 PM
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Oh -- one more thing I wanted to make perfectly clear to everyone...

Please note how, in each case, my DX7 seems to fail 2 minutes into the second flight of the day. It's always the same story:
1) I fly airplane "A" with excellent results (15 to 20 minute flight, with no glitches).

2) Then, I fly airplane "A" with a different battery pack, and I get a receiver reboot about 2 minutes into the flight.
All three airplanes crashed with different batteries (so it's not the battery). :o (3s 800 mAh LiPo, 3s 2220 mAh LiPo, 4s 3150 mAh LiPo.)
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Old 07-19-2007, 04:05 PM
  #48  
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could it be the TX batt? Maybe there is a short that is draining the tx battery faster tha normal. Or perhaps the Tx battery was a dud or it is faulty (ie not taking a full charge).

Just wanted to venture a spur of the moment guess
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Old 07-19-2007, 04:37 PM
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I really don't think it is a design flaw because it would be showing up in other systems. I have never had a minutes problem with my DX-6 or DX-7 and I have never heard of anyone else with this problem.

It sounds more like there is a problem with your transmitter. I think you said you sent it back to Horizon. Please let us know what they say.
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Old 07-19-2007, 05:15 PM
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I agree with Jim; a "design flaw" would be showing up in multiple units. This is the first time I have ever heard of your particular complaint.

Please let us know what HH has to say about it. I would venture to guess it is either a bad TX battery or, like previously suggested, a short or something draining the battery quickly.
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