SKyecho imperfections

[RFguy]

SKyecho might have a high grade GPS, but a low grade antenna AND on the window of an aircraft leads to some very large transmitted GPS errors.

I see this from time to time (see below) note track errors. I have checked the received GPS stamps in the  logs from  the skyecho, it appears to be sending position data when the GPS fix is very poor- It should not do that, I am going to write to Uavionix.
  I am going to move it from a back window to just ahead of the compass on the panel, where it has a better view of the sky.

So, with respect to separation - always consider that an airplane with a skyecho might be a few hundred meters out !!! And vertical performance might be even worse.

There is a reason that TSO GPS ships require a GPS in an optimal spot - external along  the roof line.  I do not see such gross errors in aircraft flying with TSO GPS+antenna.

 

 

 

[RFguy]

Best option is a UHF grade solder joint for the ADSB RF. But that isnt anywhere near as critical as the GPS

BUT that doesnt fix the GPS ! GPS really needs external antenna OR needs to be mounted where it has a good view of the sky. (front of instrument panel under windshield etc) 
'Glass or fabric planes are probably OK , but metal plane is not.

 

I am currently doing a little PCB to turn on the skyecho when USB power is applied, and turn off the skyecho with USB power is removed.

This way aircraft supplying their skyecho with ship power get auto on and off and charge...

-glen

Edited June 1, 2023 by RFguy

[Neil_S]

I would also caution against using just the suction cup mount if your cockpit lexan/perspex has any curvature at all. I had my plane out of the hangar warming up one cold morning with the suction cup facing towards the sun. As I began taxiing the mount and Skyecho unit fell onto the cockpit floor and refused to turn back on. I assume the combination of vibration and maybe the sun heating and expanding a bit of air behind the suction cup caused the suction to fail.

I thought the unit was broken, but when I got back home I searched the web and found someone else had had the same issue. But he found that when he plugged the charging cable back in the unit restarted. I did the same and mine started again too, so apparently this is the way to reset it. This is not documented anywhere in the manual.

He also found a dumpfile had been produced in the unit, so I looked in mine and found the same, but when I tried downloading it just hung for about 10 minutes and I gave up.

I will probably just delete the file as my unit has been working fine since.

So then I put some velcro on the suction cup and on some tubing in my cockpit, with a couple of zip ties as well to hold the mount in place. That baby ain't going anywhere now.

It seems to work fine as the unit still has a good view of the sky.

Others I have spoken to have found similar issues with the suction cup - so best to explore a few other options IMO.

 

Cheers,

Neil

[kgwilson]

I have a bubble canopy so the GPS reception is good but have had the unit fall off a couple of times when I put it on a place with a bit much curve. None of the bubble is perfectly flat but it will deal with a slight curve. In NZ the CAA won't allow them to be mounted with a suction cup. It is important to keep the cup clean & dust free and also the place you choose to put it. Don't moisten it or it won't hold.

[RFguy]

This morning's circuits. ALOT better sitting in front of the compass with a OK view of the sky... (cant see behind airplane too well) 
but not perfect. Had a cloth over it (like Hillary and the emails) to avoid marking the wind shield.

Edited June 2, 2023 by RFguy

[Garfly]

Yeah, not only does the device need to see the sky but you also need to see it's face to check for 'three greens' before trusting it.

The BAT/ADS-B/GPS all need to give the green light.  If GPS reception/transmission gets dodgy it will turn orange and finally red.

 

 

 

 

 

 

Edited June 3, 2023 by Garfly

[Old Koreelah]

On 3/6/2023 at 9:37 AM, RFguy said:

ALOT better sitting in front of the compass with a OK view of the sky...

Glen do the SE’s electrical innards affect the compass?

[RFguy]

No. I moved it around the compass,  in various orientations rotating in A B and C axis. No...
I did remove the metal locking prong  on the rear, though. (hex key) Wasnt sure at the time if it was ferrous. non ferrous. 

[RFguy]

On 04/06/2023 at 7:47 AM, Garfly said:

Yeah, not only does the device need to see the sky but you also need to see it's face to check for 'three greens' before trusting it.

The BAT/ADS-B/GPS all need to give the green light.  If GPS reception/transmission gets dodgy it will turn orange and finally red.

 

 

 

 

 

 

Even if it shows three greens it can still have poor GPS fix and be transmitting bogus data...

[danny_galaga]

Um, don't they say to mount it forward with clear view? Mounting it in the back is not the same thing.

[Markdun]

I think my SE2 has the GPS accuracy indication correct. When it’s first turned on its one green and two reds on the LEDs and once it’s going ‘properly’ its 2 greens and a blank for the GPS led.

[RFguy]

yeah Mark but you have a fibreglass airplane.. It can likely see OK through the skins, (not carbon fibre though)   but not through the wing structure...  and of your OTHER airplanes, they all are low/mid wing and have a canopy, so good !

 

so for a J2XX  on the fore end of the passenger window would be acceptable. J170 , J160 etc would really need to be on the instrument panel . Metal planes are a different beast. 

I have seen my SE2 generate bogus data with greens showing.
 

Edited June 7, 2023 by RFguy

[Blueadventures]

13 hours ago, Markdun said:

I think my SE2 has the GPS accuracy indication correct. When it’s first turned on its one green and two reds on the LEDs and once it’s going ‘properly’ its 2 greens and a blank for the GPS led.

Mine when working has middle blinking green and the ones either side lit green.

[Markdun]

I shouldn’t be so obtuse.  The SE2 is well known for failing LEDs.  I’ve had one replaced on warranty.  This one I know of the GPS LED is blank, that’s equivalent to green.

 Any thoughts on an inductive passive GPS antenna for it, say built into a mount?

[RFguy]

" inductive passive GPS antenna "?
what ?

you mean coupled to the internal antenna without galvanic connection?


 

Edited June 8, 2023 by RFguy

[RFguy]

Skyecho has a very small and fairly compromised GPS antenna.
However, up in the sky there are no trees.  so as long as there isnt sheet of metal or inch thick fibreglass in the way , or any carbon fibre, should be fine.

However, Mark I will give some thought to your suggestion of a coupled antenna, (even if technicially inept in your description).
Amplified coupled antennas need to be considered and engineered very carefully to avoid accidently jamming the GPS for miles around (feedback) 
mmmmm

for the moment, Just get it in the clear as best you can. But I would be sure the device's compromised antenna is one of the problems I am seeing. 
 

Edited June 8, 2023 by RFguy

[Markdun]

Thanks Glen.  When I’m next asked for any medical conditions I suffer from I’ll add ‘inept’ along with ‘intolerance’. -:)

[RFguy]

Today, with SE2 sitting on the instrument panel, over in the middle of the  PAX view (no pax) , facing FORWARDS (LEDs facing forward), performance seemed to be a little better in circuit- got better GPS fixes. smooth  But I'd need to do a view times to get arguable data, today  I also improved the ADSB receiver by reducing the gain a little more, - preventing receiver overload with planes outside the window. not so much cellular traffic now on the 3G (upload to flightaware) , sees up to 40nm on 200W Xponder (reduced)).  But few other aircraft today- maybe half a dozen  whole day!!!??. SE2 can take 10 minutes to show all greens after start. (hence aireborne when first fixes came in) .  One NORMAL approach (15) and TWO glide (15,33).

 

 

 

Edited June 11, 2023 by RFguy

[kgwilson]

I am surprised that it can take 10 minutes to get a GPS fix on your SE2. It took quite a while to get a fix the first time I used mine after configuration as the setup instructions stated but since then no more that about 3 minutes even after it has not been used for more than a week

[RFguy]

Yeah,  it depends if the system maintains some memory and can execute a 'warm start' of the GPS without having to download the GPS info to start 3D fixing.

 

Circuit for auto on and off from ship (charge) power : 

 

So, I made a circuit on Friday to turn on the SE2 on charge power applied (equivalent to 3 second press to alleviate any power application bounce) , and then on charge power remove (ship power off) , generates another 3 second push (which is  power off).  (1 x 74HC4538 + 2 x 1N914 diodes), and it is aware if it is on and off.
 

Simple enough. On discussion with an esteemed colleague (Shane) He suggested on power removed, suggest run on time in case of emergency ops. So I will do something a little more elaborate and have power OFF occur 15 minutes AFTER charge power is removed. (comments pls?) 

 

Fortunately, the wire connections for this mod are really easy because it connects to the power end and the solder points to connect to are wide spaced and certainly not small.   Ground, Battery, charge in, pushbutton sense. I will make kits.

 

[kgwilson]

Some sort of auto power off sounds like a good option. My Spot tracker has this. If it detects no GPS activity in 1 hour it automatically switches off to conserve battery life. I forgot to turn it off once and it tracked me all the way home in the car even though it was in the centre console with the lid shut so it must have been getting enough GPS signal diagonally through the windscreen plus the salellites were in good positions that day..

[danny_galaga]

Is there any circumstances where the auto power off will shut it down mid flight? That wouldn't be handy...

[RFguy]

no, not unless you remove the power supply to the unit, then you have 15 minutes

OTHERWISE the tiny PCB now gets bigger and needs some sort of flying sensor.  Probably another wire off the board to a GPS data line.  But now, the mods are increasing.

 

Could put a chip accelerometer on the PCB I guess (3 x 3 mm) , and detect flight.....

 

 

REMEMBER the SE2 is a poor man's transponder/ and conspicuity device. If you want the world, go buy a proper ADSB transponder.

 

[danny_galaga]

I agree, which is why I'm wondering what the point of an auto off is. If you have trouble with your USB port, you'll have to unplug it, and then 15 minutes later it shuts down. Or can you disable that? I'm not going to bother running mine on a charger, but a better aerial sounds useful 

[RFguy]

but then it runs flat. The idea came from the need to have it in the club plane  and it turn on and off, without adding to the checklist to turn it on and off  . That aint usual checklist fodder.  ALSO Very useful for instructors to look at the data of their solo pilots.  (in addition to being visible in a busy environment)