SKyecho imperfections

[kgwilson]

The battery life is supposed to be 12 hours per charge. I waited for the battery light to go yellow which is 66% of charge before I recharged the first time. I can't remember now how many flights/hours I did but it seemed a long time. Now I just charge it up about once a month as recommended & the charge has never got to 66% since. You can check the state of charge by connecting your phone via wifi & enter 192.168.4.1/stats in your browser.

 

For a club aircraft it will run all day without a problem so just stick it on charge every night like most people do with their phones. You can probably charge the batteries at least 1000 times. My LG G6 phone was new in 2018 & still holds charge for a day & it is charged every night. The SE2 has LG batteries.

[RFguy]

AGreed. I have recommended the simple thing is just to charge at night and leave on all day. 

[RFguy]

Today I was messing around with multiple GPS antennas on active repeaters. they're really all active because most GPS antennas have amplifiers in them to cope with the lossy long thin cable.

had couple of antennas on the roof, fed with a power injector, and a few different rerad antennas.

I also updated the SW in my SE2 to 2.41

Started working with some ublox receivers I have with the very fancy U-center program that tells you all the backroom GPS data.  then I moved to using the SE2.

 

It's clear why the SE2 will report some very poor position fixes.  It's bar is very low.  With NIC (Navigation integrity category)  =0 and NACp (Navigation uncertainty category) = 6

(on the wifi GUI)   the box shows GPS green.

If we ignore NIC of 0  means containment radius integrity  is unknown. IE NFI !

The NACp  of six means better than 566 m in horizontal and worse than 45m in vertical. (95% confidence) 

So what I see (transmission of poor fixes) makes sense.

WHen life is good, I see up to NIC=6 and NACp = 8.

Now, this is much better - NACp of 8 implies better than 93m in H, but STILL > 45m in V .  (95% confidence) 

and containment radius better than 926m. The SIL for a SE2 is 1, which means likeihood of being beyond the containment radius  is < 1 in 1000.

I've seen a NACp of 9, which implies  better than 30m H and better then 45m in V

Now, what is accepted by receivers and processors and displayed online like flight aware and flight radar might be very different to what is displayed by ATC

IE ATC are unlikely to display poor NIC and NACp numbers (or shouldnt) . I wonder what SE2 pass to the EFB. 

NACp is transmitted in ADSB message type 31 in V2. so the nav performance is transmitted.

 

So, of all this I think it is very practical to be able to provide a supplemental GPS antenna to a skyecho, so that the SE2 can be on some inside back window, and also have an aux GPS antenna on the window on the other wise of the aircraft. 

I started with a log periodic wideband antenna and then made a little dipole antenna to gauge polarization matching sensitivity, and there is that to it. The antenna in the GPS receiver should be a circularly polarized type, but its a very very simple little thing and seems to be rather random but with a preference of paralell to the board axis.

 

Pictures to come

 

Edited July 8, 2023 by RFguy

[RFguy]

Ublox receiver sitting on log. There is a PATCH antenna on the bottom of that receiver , so it is just sitting on it,

 
SE2 with log periodic

 

this  is good and about the best reliable distance . works up to about 65mm

 

my GPS antenna power injector (since the roof top antennas need power on the cable) 

checking polarization dependence this iis cross pol (poor)

 

Edited July 8, 2023 by RFguy

[Old Koreelah]

Glen is this poor reception in your Jab?
Just wondering if SE “sees” more easily through fibreglass and plywood aeroplanes than metal ones.

[kgwilson]

What I didn't understand about that explanation of GPS antennas was, well, all of it.

[RFguy]

My experiences are in the PA28 with SE2 on the 2nd pax row seats window behind me. (It's currently up on the instrument panel deck until the GPS-35 antenna is fitted for the xponder). OK I think the GPS wont see well through the wet wings, but through the body would be ok  otherwise.  To recap- we need satellites from around the whole sky to get a good fix. So SE2 position matters if it is blocked in directions.

 

KG : Those experiments were to determine the practical sensitivity  to using an 'outside' antenna, a length of cable, and an inside antenna that is close enough to re-radiate the signal to the SE2 on the bench, inside of my shielded box electronics workshop.   AND, performance with multiple antennas to a combiner and then to a re-radiating "coupling" antenna near the SE2.

 

The results are good. I think that it might be possible to get good fixes with just a single 2nd antenna on the other window with a coupling antenna near the SE2.  and much better with a third antenna on the nose / instrument panel. 

 

The receiver is measuring time delay between sats in order to determine position . To get a accurate GPS fix the receiver needs to be able to see  SVs (space vehicles ) around the sky so that it gets diversity .  IE if all the sats are around the horizon, the vertical accuracy of the fix will be poor without a satellite overhead .  In practice  we are not after mm of precision, so we dont need much.. Remember the trig tables, and the relationship with small angles .

 

 

[Thruster88]

Glen, I just checked about 15 approaches to the farm in the RV on fr24. My driveway is on the map, it seems like accuracy of SkyEcho2 is better than 10-20 metres coming over the tree line at the house.

 

Is the altitude transmitted taken from the barometric or gps source? 

[RFguy]

Both GNSS altitude and barometric are available and are transmitted. 

In the RV, your SE2 has an excellent all round view of the sky.

[RFguy]

and baro from the SE2 would have a high uncertainty because it's position could be the subject of variations from atmo pressure.

[rhtrudder]

On 31/5/2023 at 12:25 PM, RFguy said:

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.

 

 

 

Dumb question, but how do you access the track logs from the skyecho 

[RFguy]

SkyEcho generates position data on the wifi interface. then you must have a program that takes the GDL90 info and puts it onto a display or record.  Or, Skyecho transmits its (approximate) position to an ADSB base sation which then receives the data  and displays it somewhere.

[Old Koreelah]

Glen you might be able to advise me; I’m at the airport getting my plane ready to fly  for the first time in a year. Instead of just tossing my SE2 into the pouch under the window, I’m about to mount it properly. After removing the suction cup, there’s a neat plastic bayonet base, ready to screw or rivet in place.

I have only two viable locations, neither near my compass, which swings 10 degrees when the SE2 is near (I guess that’s the metal mounting bolt).

 

The first above my right forearm just under the window, where it can “see” half the sky, but forward view is through my plywood instrument panel.

 

The second site is under my canopy, with a wide view of the sky; trouble is, view forward and up is covered by a 30 mm wide aluminium strip. Is it likely that the internal aerial can see either side of this metal barrier?

 

[Kiwi]

On 03/06/2023 at 9:37 AM, RFguy said:

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.

Do you get feedback through your headsets from the skyecko?

I'm getting a lovely ticking noise through mine.

Does not seem to make a difference where I mount mine. I have tried two different Skyecko units and they both do it.

(PA-28 140)

 

[kgwilson]

There is no interference from mine which is stuck on the side of my bubble canopy approximately in line with the panel.

[RFguy]

It's the battery that causes the compass swing.... I have mine a few inches away.

 

So the ticking- that is the device sending ADSB bursts.

If it is giving you a ticking in your audio, you are probably missing an earth or a shield on your microphone/headset/speaker/ intercom wiring. 

The other possibilities is, could be getting into fancy NC headphones if that's what you are using. 

[Kiwi]

On 02/08/2023 at 12:03 PM, RFguy said:

could be getting into fancy NC headphones if that's what you are using. 

I'll try a old set, thanks for the reply.

[Old Koreelah]

The best location I’ve found in my tiny cockpit is just above my right shoulder; that’s a bit close to my head.

 

The SE2 transmits at 20watts, compared to our mobile phones’ 1.5w, so I’d prefer to keep it further away from my already frazzled brain.

 

[RFguy]

HI OK, but the pulses are extremely narrow- IE the energy per second is miniscule.

At 1m away, the SE2 will produce a peak level of about  1.6W/sqM, and a time averaged value of no more than 2.4mW/sqM

For the record- let's look up the peak level for 1090 MHz in the latest ARPANSA STD Rev 1 Page 6 section 2.3  

Table 5 Peak spatial 24W/sqM.  We have peak of 1.6W/sqM .

General public : Local Head and Torso - 2 W/kg. averaged over 6 minutes.  Peak level cannot exceed 0.72kJ/kg

Another way -  Table 6 : 8.5kJ/m2 . The peak spatial is 1.6W/m2 (150uS)  = 240uJ , a long way below the 8.5kJ

Suggestion - keep it > 30cm away  anyway- why -  any less and your presence be affecting its performance.  The head will soak it up.

Permitted peak level will be exceeded at about 20cm.

Levels fall with square of distance, so at 1m, there isnt much left.

 

Edited August 9, 2023 by RFguy

[Old Koreelah]

Thanks Glen. To keep it away from my head it will have to be mounted to one side of my panel. That’s also away from the compass, but it will restrict forward visibility a little. 

 

 My efforts will be wasted unless other aviators do likewise. Hope that happens.  I’ve been working at our airport this week and most of the traffic did not appear on either OzRunways or FlightRadar 24. 

 

[RFguy]

Do you have a local receiver for ADSB ?

[Old Koreelah]

Nope. Just the SE2 talking to my iPad via WiFi.

[kgwilson]

You may need to set up your SE2 as an ADSB device in FR24 and then there must be a ground station somewhere receiving the transmission from the SE2 which passes it to FR24 through the internet. You can set one up very cheaply with a Raspberry Pi connected through your home network but there may be some in your area already. Somewhere in FR24 there is a huge list of all the ground stations registered with FR24.

[Old Koreelah]

6 hours ago, RFguy said:

Do you have a local receiver for ADSB ?

If I added an external aerial to my SE2, I could position it inside the top of the windscreen, then mount the white box down out of the way.

[kgwilson]

10 hours ago, kgwilson said:

You may need to set up your SE2 as an ADSB device in FR24 and then there must be a ground station somewhere receiving the transmission from the SE2 which passes it to FR24 through the internet. You can set one up very cheaply with a Raspberry Pi connected through your home network but there may be some in your area already. Somewhere in FR24 there is a huge list of all the ground stations registered with FR24.

https://www.flightradar24.com/add-coverage