Messages

61

General Discussion / Re: Where do you mount yours?

« on: September 05, 2015, 01:11:59 pm »

A single antenna is possible, but there are complications.  the signal needs to be split between the TV tuner and the ARF module and duplexed so that the 868MHz transmitter doesn't feed into the TV dongle and cause some de-sensitisation.

That would be the correct technical thing to do anyway... there are other bodge ways of doing it.

62

General Discussion / Re: Where do you mount yours?

« on: September 04, 2015, 11:00:38 pm »

A paper with antenna guidance would be very much appreciated.

I definitely second that.

There are some cheap antennae on eBay which claim to be tuned to 1090. They look similar to the provided DVB-T antenna but with a pigtail coil in the middle. Are they likely to really be optimized for 1090?

I've read several tutorials on building your own 1090 antenna, but they look a bit on the ugly side for placing in an aircraft.

Ok... I'll have a look... I hope you're not in a rush though, it might take me a while to get around to it :-)  Are you guys totally against building your own (if it's an easy wire assembly thing with maybe a touch of soldering)?  I'm not sure what there is 'off the shelf' which would be like a suction cup mounted wire dipole.

63

General Discussion / Re: Where do you mount yours?

« on: September 04, 2015, 02:01:13 pm »

It is very important to take care with flying leads and adding length to USB ports.

What happens is that the digital noise from the RPi may get radiated into the radios.. this can cause de-sensitisation of your receiver and effect detection performance.  Additionally, it could affect the transmitter quality.

If  you have to do this, try to screen the cabling to reduce emissions issues.

An antenna combiner may be possible to integrate the 1090MHz and 868MHz functions (with some considerable care).  I have been thinking about this, but don't have much time to do it at the moment.

Rgds
Andy

64

General Discussion / Re: Only airline traffic in pilotaware

« on: September 04, 2015, 01:50:41 pm »

I think the NATS guys have made a bit of a pigs ear of organising this.  No wonder people don't know what's going on.  I had a similar issue but kept pushing it.. they need volunteers!

There were loads of delays , as there usually are.  As they worked through it and they got clearance with the CAA... then got the LAA/BMAA to sort out the minor mod process, it was pretty much June by then.  I only got mine finally approved at the end of June.

Since then, they have told me they're extending it until August 2016.  So if you still want to do it, I'd suggest you email gps.trial@nats.co.uk and poke them.

If you have a Garmin style GPS these have the RS232 output which interfaces directly to your transponder... maybe time to dust it off :-)  I'm using a GPS 96C.

The way I see it is that if everyone who has mode S is also using ADS-B out (+pilotaware box), while the folks who cannot install a transponder have a pilotaware, then between us we're covered - everyone can track everyone else.

NATS have openly said that they do not use ADSB out for traffic management (at least at GA/sport flying level).. I'm not sure what their longer term view/goal is.. I suspect they don't want to rely on uncertified GPS data for traffic management, so they'd ignore us anyway... this is more for helping out GA/sport flying.

65

General Discussion / Re: Where do you mount yours?

« on: September 03, 2015, 09:19:40 pm »

I have been pondering this.

In a permit aircraft it should be fairly easy to install a decent antenna for 1090MHz and 868MHz (in a similar way to a transponder antenna already installed).  I can foresee some possible issues if not understanding the consequences of poor antenna installation.

It is important to maintain a good antenna performance otherwise detection range will be dramatically affected (which will reduce your early warning time).  I have been thinking of writing a short white paper on this, so folks can get the gist of what is good and what is bad - if that is useful at all?

As you say for non permit aircraft, you need something portable so as not to have to endue the regulation hassle.. How about wire 'dipoles' that stick on the window using suction caps?  It would be quite easy to make one yourself.  Be aware that in the cabin of a typical GA metal bodied type, you will get some considerable antenna shielding out of the back due to the fuselage.

rgds
Andy

66

General Discussion / Re: Only airline traffic in pilotaware

« on: September 03, 2015, 08:59:50 pm »

If you have a mode S transponder and are keen to be spotted by pilotaware and other ADS-B in equipped aircraft, why not join in the NATS ADS-B trial?

They are currently running a trial to see if ADS-B out can be used successfully and safely with uncertified GPSs.  It is currently running probably into the end of next year..  I hope that afterwards there should be enough evidence to suggest we could keep using it (or at least quickly formulate something with the CAA to make it happen).

You need to get a minor mod sign off with the LAA/BMAA but it is a trivial implementation - just the addition of two wires between your GPS and your transponder.

Happy to assist if anyone wants further explanation of what to do.  Mine is running, the www.flightradar24.com network tracks me very accurately when I have my transponder on an transmitting ADSB out (as well as any pilotaware user who can pick up my transmissions).

It can only be a good thing in my view,  the more we assist in helping each other see where we all are, the better for safety and less likely to experience fatal mid air collisions or airprox.

Rgds
Andy

67

General Discussion / Re: Altitude Accuracy

« on: September 03, 2015, 08:33:34 pm »

I have never found GPS GEOID altitude to be hugely different to QNH, it's usually within about 200ft. Although quite rightly altitude isn't something that GPS is good at unless using WAAS/EGNOS correction (DGPS).

I suppose one of the interesting points is that if you are reporting FLs back to SD (as you'd be receiving from ADS-B transponder altitude encoder - pressure referenced to 1013mB), then you need to have a way of correcting it for QNH (just like NATS do with their radar)... because on SD you'd be comparing a FL (not QNH) to a GPS GEOID (a psuedo QNH).. this could introduce considerable error, especially on days with exceptionally low or high pressure.

If ADS-B has Geometric altitude available, this would be the one to take and feed back to the tablet.

Very good point Chris!

although I suppose at the end of it all, pilotaware is there to give a reasonable early warning... you should have either spotted it by eye or with the help of pilotaware by then (otherwise time for a new pair of specs!)

rgds
Andy

68

General Discussion / Re: Power Supply & USB Power Cable

« on: September 02, 2015, 12:01:50 am »

I have had some good success with these, for powering my tablet.  They are based on TI chipset and appear to be designed well..give a good charge rate, so will boost your tablet in no time.  Also I have not experienced any of the horrible noise issues with them (those noise issues that seems to be generated by the car plug adapter type USB chargers).. the output seems to be clean and they perform well.  For extra 'belts and braces' I also fitted an extra smoothing capacitor to avoid noise injection into my radio/intercom.

http://www.ebay.co.uk/itm/5pcs-LM2596S-DC-DC-Buck-Converter-Adjustable-Power-Supply-Step-Down-Module-UK-/141210161794?pt=LH_DefaultDomain_3&hash=item20e0c81282

This would work well with the pilotaware and are really low cost...

in addition, the output voltage is adjustable by the potentiometer (the blue block).. so you can compensate for cable drop/loss by tweaking the output up a little higher than 5V, to say 5.5V (no more).

69

General Discussion / Re: Regulator board & ARF Board

« on: September 01, 2015, 10:55:13 pm »

JCurtis,

Were you planning on placing a screening can over the ARF and regulator board assembly?

It's possible that we may see some self interference effects with digital noise injecting into the radio (with it being so close and not screened at all)..  Tests so far seem to suggest this is ok , but it wouldn't surprise me if at some point some performance degradation is seen due to digital noise coming off the Raspberry PI PCB.

Self interference can sometimes be a bit of a difficult animal to track down (can be intermittent and also vary from unit to unit).  A screening can over the radio would be a good idea.

rgds
Andy

70

General Discussion / Re: Regulator board & ARF Board

« on: September 01, 2015, 12:40:01 pm »

I would like to encourage people who decide to make such adapter boards to make the PCB build files and CAD files available OPEN SOURCED, in the spirit of the way this project is being run.  That way people can also take advantage of it.

The idea of open source is to encourage these such improvements, which overall improves the Pilotaware units making it better for all.

As an RF electronics engineer I'm happy to offer a review of the circuit designs where I can.

Rgds
Andy Fell

Hi All,
I see where Andy is coming from here.
I am a little more sanguine about this to be perfectly honest.
So long as the interfaces remain Free and Open (eg RF),
and there is an Open Reference Hardware Platform to which any further improvement conforms,
eg a shield for an ARF, RPi Compute version, ...
then I have no problem with anybody making developments for commercial gain.

I think anyone spending time, effort and money should have the opportunity to be recompensed for their work.

What I am totally against, are attempts to thwart further efforts of improvement or integration,
through the use of exclusivity & secrecy, eg I would not be in favour of a compatible
version with FLARM, if the method of interaction with the FLARM system were not published
somewhere for all to see.

Remember the mantra : Free Speech not Free Beer 

Thx
Lee
(PS, just so there is no confusion, I will not refuse free beer)

Yep.. fully agree   

71

General Discussion / Re: Regulator board & ARF Board

« on: September 01, 2015, 10:25:47 am »

I would like to encourage people who decide to make such adapter boards to make the PCB build files and CAD files available OPEN SOURCED, in the spirit of the way this project is being run.  That way people can also take advantage of it.

The idea of open source is to encourage these such improvements, which overall improves the Pilotaware units making it better for all.

As an RF electronics engineer I'm happy to offer a review of the circuit designs where I can.

Rgds
Andy Fell

72

General Discussion / Re: No ADS out needed

« on: August 23, 2015, 05:56:57 pm »

Hi,  it's fine to use in France.  The rules are basically the same across Europe. See  ETSI EN300 220. Ero recommendation 70-3.

It's slightly different in the USA, they use 902-928MHz.

Rgds
Andy

73

General Discussion / Re: Enhancement Requests

« on: August 13, 2015, 10:07:26 am »

Agree on the web interface for configuration, makes things much cleaner.

Cheers
Andy

74

General Discussion / Re: Enhancement Requests

« on: August 03, 2015, 10:50:55 pm »

I'm already using a Garmin96C for NMEA data out (RS232 +/-12V format) for the ADS-B ES trial..

A USB<>RS232 adapter thingy could also be wired to this 96C data out to receive NMEA input to the RPi (same data as being sent to my transponder).  http://uk.farnell.com/ftdi/chipi-x10/cable-usb-db9-male-rs232-10cm/dp/2352019

Should be a driver already available for virtual comm port?  then use this stream to send to tablet via flarm intfc?

Cheers
Andy