Two dodgy FrSky XM+ receivers in a row - the hunt for answers

CurryKitten · May 15, 2018, 11:48:57 AM

Hmmm, well the mind boggles. Another update from me on my original receivers. As I mentioned earlier, one of the dodgy receivers, I tried winding the firmware version back to the previous level (i.e the 2nd newest version from the FrSky site) an it magically fixed the problem.

Although I know that the latest international firmware is fine in general (as I'm using it on a bunch of other XM+s) I figured that the right set of circumstances/slight differences in hardware or tolerances and it could cause an issue.

I set out to demonstrate this so started to make a video. I figured I would reflash the latest version and demonstrate how bad the range is, and then reflash the previous version and show the difference. I reflash the latest level..... and it's fine, absolutely normal range. I took it out and flew it and at 300m away at around 6ft off the floor, the RSSI is reading 80%+

Confusing !

I really don't get it. Flashing firmware is a binary event which either works/doesn't work. There's the flashing, checksum verification etc - I don't really see how I could flash something successfully and have it work differently on two occasions. I'd actually reflashed the "dodgy" receiver multiple times with different versions of the firmware to see what difference it would make (rssi on ch 8 and 16 for example) so I'm a bit flummoxed about this. On the plus side though, I have 2 receivers that work again.

So anyone suffering the same problem can at least retry the flashing.... I just can't tell you why that might sometimes fix it

BigT · May 16, 2018, 09:24:29 AM

80% at 300 ft!! I don't get 80% @ 20 ft......in fact I only get 90% in the same room. So the dilemma is either change the tx or change the backboard. FrSky don't make any differential in range between LBC and International formats do they?

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CurryKitten · May 16, 2018, 10:49:51 AM

Quote from: BigT on May 16, 2018, 09:24:29 AM
80% at 300 ft!! I don't get 80% @ 20 ft......in fact I only get 90% in the same room. So the dilemma is either change the tx or change the backboard. FrSky don't make any differential in range between LBC and International formats do they?

No difference that I'm aware of. Somethings definitely amiss in your setup, and if it's all rx's that have the problem, I'd certainly think about the radio being at fault. Usually, the Taranis can detect an antenna fault and tells you about it. You could check the connection of the antenna onto the rf board, or potentially solder on a new one to see if that helps

BigT · May 17, 2018, 09:21:52 AM

When I see something like this video it really does make me GWE (green with envy)
https://youtu.be/0XMiutcFVfQ

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BigT · May 17, 2018, 09:30:53 AM

Quote from: CurryKitten on May 16, 2018, 10:49:51 AM
No difference that I'm aware of. Somethings definitely amiss in your setup, and if it's all rx's that have the problem, I'd certainly think about the radio being at fault. Usually, the Taranis can detect an antenna fault and tells you about it. You could check the connection of the antenna onto the rf board, or potentially solder on a new one to see if that helps

The tx is a 2015 model with a few hours on it, would you A) replace the backboard in the hope it cures the range issue, cost is about £65, leaves me with old everything else, gimbals, switches etc. Or B) Buy new TX from T9 and sell old tx on eBay for Parts Not Working etc net cost to me about £100 (£162 for new tx less approx £60 or more for old tx).

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Loopdreams · May 17, 2018, 09:38:18 AM

You can actually get an X9D Plus from HobbyKing UK at the moment for about £115 delivered. Use Hobbyking10 to get 10% off. I know because a friend just bought one.

CurryKitten · May 17, 2018, 09:38:37 AM

Quote from: BigT on May 17, 2018, 09:30:53 AM
The tx is a 2015 model with a few hours on it, would you A) replace the backboard in the hope it cures the range issue, cost is about £65, leaves me with old everything else, gimbals, switches etc. Or B) Buy new TX from T9 and sell old tx on eBay for Parts Not Working etc net cost to me about £100 (£162 for new tx less approx £60 or more for old tx).

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Depending on what I was flying - I might get a Q7 (I have actually already have one - just speaking hypothetically) Unless you need those extra 3 position switches and the sliders, they are great radios (cheaper) and the wheel is a massive improvement over the cursor buttons on the x9d

BigT · May 17, 2018, 09:58:11 AM

Quote from: Loopdreams on May 17, 2018, 09:38:18 AM
You can actually get an X9D Plus from HobbyKing UK at the moment for about £115 delivered. Use Hobbyking10 to get 10% off. I know because a friend just bought one.

Amazing, makes me wonder if it is due for the chop. Certainly not worth replacing the board for that money.

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BigT · May 17, 2018, 10:33:17 AM

Quote from: Loopdreams on May 17, 2018, 09:38:18 AM
You can actually get an X9D Plus from HobbyKing UK at the moment for about £115 delivered. Use Hobbyking10 to get 10% off. I know because a friend just bought one.

Must have been a limited offer, out of stock now in UK and EU.

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English Turbines · May 19, 2018, 09:15:21 AM

Quote from: BigT on May 16, 2018, 09:24:29 AM
80% at 300 ft!! I don't get 80% @ 20 ft......in fact I only get 90% in the same room. So the dilemma is either change the tx or change the backboard. FrSky don't make any differential in range between LBC and International formats do they?

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Hi Big T,
I would measure the power output from the "Tee Board"....This is the board which drops main Lipo voltage down to 5 volts I suspect. They have been known to fail reducing RF output.

Question: What model of receiver has the crappy RSSI.?

Procedure...:

1) Power up and measure Input and output voltages..

2) Leave powered up and measure output at 5 minute intervals to check it is stable.

Im not sure, but I thought the LBT Firmware reduced TX RF output compared to the FCC Firmware...? Should be in the specs provided FrSky were allowed / wanted it to be common knowledge.

:vulture:

FPVSteve · May 19, 2018, 11:36:07 AM

Quote from: BigT on May 17, 2018, 09:21:52 AM
When I see something like this video it really does make me GWE (green with envy)
https://youtu.be/0XMiutcFVfQ

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That's a cool video - do you think the signal bouncing off the trees helped? I mean he's got to be 1km out and only 3 feet off the deck.

English Turbines · May 19, 2018, 08:56:48 PM

Quote from: Steve W on May 19, 2018, 11:36:07 AM
That's a cool video - do you think the signal bouncing off the trees helped? I mean he's got to be 1km out and only 3 feet off the deck.

Hi Steve,
Remember, you can use a 2.4G directional Patch on a Taranis which will give this sort of range easily when pointed down this long straight road. He's actually using a 5DBI antenna on his Q7 Transmitter.
I dont think he gets more than 1 km distant either because he flies past himself in the video, maybe 700 metres or so.

:vulture: