X9D+2019 "Tx antenna problem"

[Allan Bennett]

Hoping to be able to fly at the end of the month, I took my Taranis X9D+2019 out of its carry case, where it's been untouched since we were last allowed to fly, switched on to test one of my models and got an error message "WARNING Tx antenna problem" and a verbal warning "Radio antenna defective".  The battery indicator was showing 4 out of 5 bars, and the RSSI indicator showed 5 bars when I powered up a receiver.  I unscrewed and then reattached the antenna but no change, then took the back off to check its connection to the board, and it looked good.  By then it was too late in the day to phone T9, so I though I'd run it past you guys first.

 

A Google search reveals that there was a problem about six years ago which resulted in this warning, and crashes; but I can't find anything more recent.  It was something to do with an out-of-spec connector for the antenna I think.  Anyone else had this problem with the X9D+2019?  If so, is it known whether it's a hardware or firmware fault?  I'm running v2 ACCST EU LBT firmware and OTX 2.3.11.

[Allan Bennett]

I spoke to Richard at T9 this morning, and he says even the slightest increase in impedence in the aerial and its connection to the board can result in this message.  I did notice a few stray strands of the outer sheath where it connects to the PCB, so maybe that's the problem even though it must have been like that since I bought it.   He's sending me a replacement aerial and cable f.o.c., and we've agreed that I'll install it myself.  If that fails I'll have to send the trannie back to him

[Andy48]

Excellent support from T9. Well done Richard.

[Ron Gray]

Another vote for Richard, he’s a great guy to deal with.

[Dave S.]

Thanks for posting, I have the same tx and will keep an eye on it.

[Geoff S]

I buy all my Frsky stuff from T9 because of the service. I think they may be very slightly more expensive but, if they are, not enough to worry about when you get the back-up to go with it.  My first Neuron 80 amp esc was faulty and was replaced without question. 

 

Geoff

[Allan Bennett]

Here's how the aerial connection looks at the moment.  Even under an illuminated magnifier I can't verify that the outer braid is properly connected to the board.  According to Richard at T9, FrSky just apply a blob of solder around the outer braid, with the attendant risk of melting the insulation to the inner core and/or contaminating the solder joint with melted insulation.  I think the latter is what's happened in my case, and I'm sure I can do a much better solder job than that when the new cable arrives.

.

[Ron Gray]

Got me wondering about mine now ?

[MattyB]

Apologies, double post....

Edited March 26, 2021 by MattyB
Accidental double post

[MattyB]

12 hours ago, Allan Bennett said:

Here's how the aerial connection looks at the moment.  Even under an illuminated magnifier I can't verify that the outer braid is properly connected to the board.  According to Richard at T9, FrSky just apply a blob of solder around the outer braid, with the attendant risk of melting the insulation to the inner core and/or contaminating the solder joint with melted insulation.  I think the latter is what's happened in my case, and I'm sure I can do a much better solder job than that when the new cable arrives.

.

Is that the TX that you lost your Hurricane on Allan? If so I’d say this looks like a pretty likely root cause, that soldering job is.... less than optimal! ?

Edited March 26, 2021 by MattyB

[Allan Bennett]

Yes, it's the same trannie.  It crossed my mind that it might have caused the Hurrican crash, but at the moment it's giving loud verbal warnings about "Radio antenna defective" every time I switch on, and every 5 seconds while powered up, which I'm sure I would have heard if the issue was present back then.  Also, I've used the trannie many times since the crash, without any problems or warnings.

 

When I receive the new antenna I propose to remove the outer insulation and unpick the outer braid for a distance of about 6mm so that I can then twist the braid into a 'pigtail' on one side of the cable.  It seems to me this will allow a much more reliable solder connection to be made to the PCB pad, but does anyone with RF experience know if this has any disadvantage over FrSky's method, which appears to be a big blob of solder over the outer braid?  Presumably keeping the unshielded length of inner to a minimum is desirable.

 

 

[Allan Bennett]

Well, here's the replacement antenna.  No more warnings, and it's been tested with a quad at about 5 metres range.  It'll get a proper range check and test flight when our field opens next week.  Richard of T9 has suggested a blob of hot glue or silicone as support.

 

[Geoff S]

That looks a LOT better than it did before.  A bit of stress relief with either hot glue or silicon won't do any harm either.   What did the old antenna lead look like after you'd removed it?  Was the braid continuous? Was the inner sound?.

[Christopher Wolfe]

With all due respect, the quality of the soldering of the SMD components appears to be a bit dodgy.

The assembly robots require a bit of fine tuning as their solder joints are crap.

Ex HRSI (High Reliability Soldering Instructor) trained to Nasa standards.

[Allan Bennett]

Geoff, the outer braid was sort of crumbly when I de-soldered it.

 

Christopher, I'm not qualified to re-do the SMDs, but I guess you're referring to the quantity of solder deposited around some of them?  The photo's not the best, but at least the solder connections all look shiny.

[Christopher Wolfe]

Not complaining about your repair work Allan, it's a much better looking solder joint than your first photos of the factory job.

 

I was commenting about the soldering of the SMD components photographed below your repair, that looks like poor quality control.

 

Blobby looking cold joints are scary to look at from an electronic reliability point of view.

 

For example, I was taught (many years ago) that if one cannot inspect the solder joint down to the individual wires then the joint was suspect.

 

This was not for moon missions but as it involved my fellow Australian RAAF mates it was vital to get one's soldering skills together.

 

Near enough is not good enough!

[flight1]

looking at the picture the small smt component just below the solder joint looks burnt out , need to find it's value and replace, tiny tip solder iron needed, should solve the problem

[Allan Bennett]

I agree, the SMD just below the antenna connection does look dodgy, and did so in the original photo too.  If it's faulty I don't want to replace it myself because the trannie is still under warranty.  Maybe it's going to have to go back to T9 anyway -- something I was trying to avoid.  I'll try and get a closer look at the SMD to determine whether or not it is dodgy.

[flight1]

As it's under warranty get a new rf board send the picture to t9 and a decision to be made no if and but with new board and easy job.

 

[Mike Blandford]

Looking at a schematic I have, the component is almost certainly an ESD protection device. If it isn't connecting then there should be no adverse effects. Early radios didn't have this component at all.

 

Mike

[Allan Bennett]

Thanks for your contributions guys.  I've had another look at the suspect device and, as far as I can see, it's in good condition.  The blemishes you see, especially when the photo's enlarged, are shadows and reflections.  I've tried, but I can't get a better photo with my phone camera.

 

I've put a blob of hot-melt to give physical support to the connection.

[Allan Bennett]

Having made the repair -- the first I've done on a mission-critical item, though I do have plenty of electonics soldering experience -- I've been a bit wary about using my transmitter with anything 'valuable', so since the repair I've been flying a quad and a hexcopter within the confines of a rugby pitch, i.e. less than 50m away from me, to gain some confidence.

 

Today I flew a 3-channel depron model with an RX6R receiver quite a bit further than my usual circuit so I could log the RSSI.  The resulting log looks pretty good to me, though there is one point where the RSSI graph seems to dip down to 45, though scanning through the numbers I didn't spot anything less than 49, and got no verbal warnings.  Would anyone more experienced than me like to look through the log file for me, and tell me if you think my RSSI is 'normal' for a flight which took the model up to about 500m away from me horizontally, at altitudes up to maybe 100m.

Hurricane-2021-04-19.csv

[Andy48]

That looks absolutely normal to me, no problems. You will always get the odd RSSI downward spike showing below 50 for some reason. It never has any effect, and you still have a good reserve below that.

 

 

Edited April 21, 2021 by Andy48

[Allan Bennett]

Thank you Andy, that's reassuring.  That's given me confidence to start flying less-expendable models with this transmitter.

[Sussex Pete]

On 27/03/2021 at 11:41, Mike Blandford said:

Looking at a schematic I have, the component is almost certainly an ESD protection device. If it isn't connecting then there should be no adverse effects. Early radios didn't have this component at all.

 

Mike

Hi Mike--  Can I ask where you found schematics? 

 

I just had my first TX Antenna Fault on power-up of an 18-month old Taranis X9D+ 2019 running OTX 2.3.11 and ACCESS.  After talking to Richard at T9 (thanks!) I watched the RAS values on the Radio Hardware menu (Relative Antenna Status - was SWR, see user manual p.19, no Rx or telemetry required).  I understand from the user manual RAS>51 is a fault to I'm guessing that's what happened. 

 

Untouched, RAS varied between 0 and 6.  As I moved the antenna by hand, I got it up into the 30s in some holds/positions but it reverted to near zero when I moved my hand away.  This essentially shows the impact of external factors on the antenna impedance at 2.4GHz.  When I got the fault report last weekend, the tx was on damp grass and I was moving the antenna at the same time.  Since then, I have been unable to reproduce the warning.  So my guess is the combination of damp and hand momentarily took RAS over 51, but in normal operation, RAS<10 is fine (as Richard suggested).  

 

I took the back off the tx and checked the original factory-fitted antenna.  Photos below.  It looks like the glue blob is supporting the coax. I cannot actually see all of the solder joints but they look well aligned.  The nearby SMDs look fine. I have to say Allan's before picture made be wonder if his antenna had been (poorly) repaired in the past.  

 

The antenna itself (probably - it's glued in) looks like a standard short FrSky coax antenna stuck into the plastic tube.  The coax probably has the last 30.7mm of outer shield stripped back to make a quarter-wave monopole - just like antennae on receivers (and of course, both ends of a telemetry system are really transceivers so you'd expect some symmetry!).  When you rotate the plastic tube containing the antenna, the coax is inevitably flexed so it's vital that glue and solder carries that load.  

 

That all checked out ok from my standpoint so I'm back to flying after adding "Check and test RAS<10" to my pre-flight procedures.  Unfortunately, RAS is not a value accessible to logical switches to write your own warnings with a special function.  Maybe we should put that in a a GITHUB request?

 

Thanks to all the other contributors to this thread!  Cheers --Pete

 

Edited June 22, 2021 by Sussex Pete
Typos