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Old Jul 07, 2012, 04:58 PM
Stop scaring my donkey!
JohnathanSwift's Avatar
Greenland
Joined Mar 2012
8,215 Posts
Very likely a batch of bad displays, eh?

I'll bet a Chinese subcontractor is on the hook.
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Old Jul 08, 2012, 05:18 AM
flitelab's Avatar
Canada, NS, Halifax
Joined Feb 2010
7,044 Posts
So is the only known issue with DX18 thus far the LCD screen glitching?

Looking at this radio but concerned it will be another round like the DX8 with issues still showing long after the fact like on my DX8. At $800 I'd like something that works fine out of the box.

Also I assume probably not but can the DX8 model files be used on the DX18 or any way to import them to move between radios?
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Old Jul 08, 2012, 05:23 AM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
23,888 Posts
The DX8 SPM file do NOT work in the DX18.
The screen issue appears to be with a few radios, I believe the majority do not have this issue, I know I don't.
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Old Jul 08, 2012, 12:40 PM
Certified Propellerhead
Copenhagen, Denmark
Joined Mar 2001
315 Posts
Quote:
Originally Posted by Mikael Pedersen View Post
I've just checked my own DX18, and it only show infrequent horizontal shifts on the monitor screen. Nowhere as bad as yours.
Now I've been out all day flying with my new DX18. A beautiful, sunny day, with almost no wind. Everything (including the radio) got quite warm. However, that didn't seem to affect my display in either direction. I still had the occasional glitch, just as back home in normal indoor temperature.

But I have noticed a completely different issue with my radio. The RF doesn't seem to perform anywhere nearly as good as my old DX8. Read on:

My main mission today was to maiden a new airplane I've just assembled (FMS BF-109). I've equipped it with an AR7610 with satellite, running DSMX. Range test went without any problems. I took it up in the air, trimmed it, and had a blast from there on. A nice, well behaved airplane.
Back on the ground, I plugged in my SPM9540 (Flight Log reader), as I usually do after flying a new airplane, and I was chocked. One antenna have had about 250 fades, and the other 999+ (maxed out the display). All this on a 7 minute flight. There was a handful of frame losses, and luckily no holds.
Granted, it was a new plane, and it could just be poor placement of receivers. But it made me look closer at my other planes.

Two other planes (old and reliable), both equipped with AR600 receivers, has just been rebound to the DX18 instead of my old DX8. Nothing else has been touched in the planes. Both displayed several hundred antenna fades, and one even exceeded 100 frame losses on one flight. Still no holds at all.
They have never been anywhere near these numbers on my DX8. And as the only thing that has changed is the transmitter, I am inclined to blame the DX18.

Has anyone else made any RF link comparison between the DX18 and any older DSMX transmitter? I would very much like to find out if this is to be expected from the new diversity antenna construction, or if there is an issue with my radio.
BTW, I have an european version, as I am supposed to over here, and no I haven't accidentally set it up for the restricted french frequency band.
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Old Jul 08, 2012, 01:06 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,481 Posts
From AR7610 manual:

"Antenna fades—represents the loss of a bit of information on that specific antenna.
Typically it’s normal to have as many as 50 to 100 antenna fades during a flight. If any single antenna experiences over 500 fades in a single flight, the antenna should be repositioned in the aircraft to optimize the RF link.
Frame loss—represents simultaneous antenna fades on all attached receivers. If the RF link is performing optimally, frame losses per flight should be less than 20. A hold occurs when 45 consecutive frame losses occur. This takes about one second. If a hold occurs during a flight, it’s important to evaluate the system, moving the antennas to different locations and/or checking to be sure the transmitter and receivers are all working correctly."

From AR9020 manual:

"Note that DSMX hops through the band while DSM2 finds two quiet channels and
remains on those channels. Consequently because DSMX operates on quiet and
noisy channels, it’s common to have more Antenna Fades than when using DSM2,
when used in busy 2.4GHz environments. When taking flight log data readings, the
Frames and Hold Data are important and should be used a reference while Fades
are insignificant due to the nature of frequency hopping. A 10-minute flight will
typically result in less than 50 Frame Losses and no Holds."

I would maybe think about repositioning one of the antennas based on your description, but wouldn't get too bent out of shape about it.

Yes, Yes, Yes. Not exactly the same Rx's you are talking about, just noting the nature of DSMX would not give me any pause for concern.
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Old Jul 08, 2012, 01:07 PM
flitelab's Avatar
Canada, NS, Halifax
Joined Feb 2010
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I would have thought there would be less of these with the DX18 having dual antennas though not more. Perhaps I'll wait on the DX18 a bit more before jumping in.
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Old Jul 08, 2012, 02:04 PM
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Thomas B's Avatar
United States, TX, Fort Worth
Joined Jun 2000
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Quote:
Originally Posted by flitelab View Post
I would have thought there would be less of these with the DX18 having dual antennas though not more. Perhaps I'll wait on the DX18 a bit more before jumping in.
The manual explanation mentioned previously cites the new DSMX protocol as having the potiential for more fades as it shares other 2.4 channels instead of parking on the two quiet ones at start up as DSM2 did. Has nothing to do with the DX18, IMO.

The case with the DX18 in Denmark is interesting, though. I would like to know if it is indeed an issue with his particular radio.

I have tested two models for frame losses and fades that were on the DX8 a while back and are now on the DX18.
In each case I had a few fades and one-two frame losses, with no change from the 8 to the 18. (USA version)
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Old Jul 08, 2012, 02:15 PM
Canada, BC, Burnaby
Joined Sep 2010
40 Posts
The european DX18s send out only 100mW instead of 200 for ours, could that be a factor ?
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Old Jul 08, 2012, 02:20 PM
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Rhode Island USA
Joined Aug 2010
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Quote:
Originally Posted by Fricotin View Post
The european DX18s send out only 100mW instead of 200 for ours, could that be a factor ?
His DX8 must be 100mW also, I can see his concern that the DX18 has significantly more losses than his DX8.

VP
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Old Jul 08, 2012, 02:24 PM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
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The 999+ value was most likely a bogus number recorded.
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Old Jul 08, 2012, 02:30 PM
flitelab's Avatar
Canada, NS, Halifax
Joined Feb 2010
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Quote:
Originally Posted by Thomas B View Post
The manual explanation mentioned previously cites the new DSMX protocol as having the potiential for more fades as it shares other 2.4 channels instead of parking on the two quiet ones at start up as DSM2 did. Has nothing to do with the DX18, IMO.

The case with the DX18 in Denmark is interesting, though. I would like to know if it is indeed an issue with his particular radio.

I have tested two models for frame losses and fades that were on the DX8 a while back and are now on the DX18.
In each case I had a few fades and one-two frame losses, with no change from the 8 to the 18. (USA version)
And I'm still suprised the DX18 would be no better, is that not the point of its diversity antennas? Seems then it offers no advantage to the DX8 if fades are the same?
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Old Jul 08, 2012, 02:32 PM
Suspended Account
Rhode Island USA
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Quote:
Originally Posted by freechip View Post
The 999+ value was most likely a bogus number recorded.
What is this response based on?

VP
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Old Jul 08, 2012, 02:36 PM
Certified Propellerhead
Copenhagen, Denmark
Joined Mar 2001
315 Posts
I am not too concerned with the issue.... yet.
But when two different airplanes both experience substantial raises in both fades and frame losses going from DX8 to DX18, without rearranging anything electric in the planes at all, that does get me thinking. I almost never got two-digit frame losses with DX8, but with DX18 I got a flight exceeding 100 on the first day out.

No, the 100 mW in Europe isn't a factor, as my old DX8 is european too.

I think I need to make some more controlled tests. I have a large 3D airplane with telemetry, where I have plenty of experience with where the numbers should be, because I don't need to plug in the logger after each flight. Next time the weather permit (on a weekend), I will move this plane to my DX18.
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Old Jul 08, 2012, 02:56 PM
Certified Propellerhead
Copenhagen, Denmark
Joined Mar 2001
315 Posts
Quote:
Originally Posted by flitelab View Post
And I'm still suprised the DX18 would be no better, is that not the point of its diversity antennas?
I thought the diversity antennas was mainly to improve telemetry reception, which some have reported wasn't all that good at a distance on older radios.

If the RF signal from the transmitter is sent out on both antennas, they could potentially (in certain geometric constellations) cancel each other out, causing more fades. But I haven't taken my DX18 apart to take a peek, nor have I tried to measure any antenna radiation to see if this is indeed the case or not. This is purely speculations on my part, not even hearsay from anywhere else.
(Being an electrical engineer working with satellite communication for a living, will do that to your thought patterns)

I do believe the 999 reading is correct. It was a new plane, quite crammed for space and that space is packed with Y-wire harnesses and extension cables for 10 servos as well as lighting. It is very likely that the receiver just need repositioning, if at all possible. And being new, I don't have any numbers for that plane on the DX8. It is the other planes I am a little concerned about.
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Old Jul 08, 2012, 02:56 PM
Registered User
Vienna, Austria
Joined Oct 2010
2,548 Posts
As far as I understand the diversity function in the DX18, there are 2 antennas, between them the TX switches permanently. One frame this antenna, the next frame the other. Since they are positioned differently, more fades can happen. When I opened the TX I saw the TX module, and between the two antenna connectors there is a diversity switch.

I also have more fades than before, but nothing which makes me worry.

Maybe you want to use a telemetry module so you can see the fades in real time ?
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