Messages

421

General Discussion / Re: Long Marston Test 17 October

« on: October 20, 2015, 05:18:30 pm »

Hi Jeremy,

Thanks for the explanation. I took the web-site description to indicate an XRF at both ends of the ARF! I now realise they meant an ARF at both ends of the radio link.

Whilst I was a Satcomms engineer in years gone by, I'm now extremely rusty..

Nowhere in WT web-description does it seem to quote an output power for the ARF. Is there any mileage in my suggestion that the transmit and receive side could be separated out and an external RF power amp be used to boost the eirp?

Regards,

Chris

I remember calculating geostationary satellite wobble for a tracking project, a good few years ago now, to always keep a dish pointed correctly.  That was fun...

The recommended power from an ARF is +18dB according to TI who make the chipset, it's pushed to +20dB which is the maximum recommended limit for the chipset.  The CC1190 is a combined TX and RX booster, so it also lifts the RX sensitivity too - it's controlled via a signal line from the CC1110 to flip states.

There is no way to split them out, the ARF is an integrated package based on the TI reference design. 

You could get WT to design a new ARF, based on a similar chipset that has a potential higher power.  TI state it would need shielding to prevent harmonics leaking out everywhere and would need some work to get right and stay within the legal limits.

For more power it's either a WT redesign, with some assurances over the limits and getting things measured and profiled (i.e. legal in terms of transmission, harmonics etc.), that has the benefit of being backwards compatible. 

The other option is use a replacement, fully certified, module from one of the big players, downside doesn't talk to the ARF.  Price wise there would probably be about a £10 to £15 hike in the price of the packet radio element of PAW to get to 500mW with support and backup from the manufacturer.

422

General Discussion / Re: ADS-B tranmitted via a Mode S TX for the NATS Trial

« on: October 20, 2015, 03:01:31 pm »

Hi J

Yes P version only as this gives one an easier connector wiring option. The Funke TRT800 has the option to set the baud rate input level which I believe generally in GPS world is 4800 and so this is the only rate the P puts out.

Totally agree on ensuring RS232 used and not TTL - I gather I can measure that output in V on the respective pins with a multimeter?

For now I am not overly concerned about chipset no longer in production providing the unit works and does so accurately enough - or do I miss understand this and that actually it could be a dodgy GPS source 

You could use a DMM to measure the RS232 vs TTL Serial - I would expect to see bigger numbers on the RS232.  If it has a max hold that may help too. 

My only concern with these things is they say they are using a GPS receiver that is out of production, yet they still keep selling them, which could mean it's using some generic cheap GPS and they are using the U-Blox name as a reputable brand to sell them.  It will no doubt work, and be accurate enough, but long term reliability could be an issue - how will you know if it stops or throws out some odd data?

For such a "fit and forget" type of installation I would err on the side of caution and see what was available from an EU/US source with a manual not riddled with typos.

423

General Discussion / Re: Long Marston Test 17 October

« on: October 20, 2015, 01:50:47 pm »

Hi Jeremy,

Just quickly looked at ARF web page. Apparently it can be used with the XRF (as a preamp?). It states that using XRF at each end a range of 10s of km is possible. The bonus is that the units talk to each other.

Regards,

Chris

There are two modules from WirelessThings, the XRF and ARF.  If you look at the XRF it has a small daughter board on it - that they call the SRF module.

The SRF module is a Ti packet radio chip with an embedded micro controller, that WirelessThings have written software for to give it an easy to use AT command based serial interface. 

The XRF is this SRF module mounted onto carrier to give it the XBee form factor you see.
The ARF is the same SRF radio module combined with a Ti PowerAmp to boost the radio signal (and also increase the sensitivity for reception) again presented in the XBee form factor.  The ARF is the highest power radio WirelessThings currently make.

You might be able to get 10k+ with directional high gain antenna on a point to point link, with all the power going to where you need it.  You can go a long way with a directional antenna with very little power, I've seen Bluetooth run nearly a mile using, in effect, a glorified Pringles tube.
What we need good omnidirectional broadcast transmission.

So, yes, the ARF could loosely be described as an XRF with an amplifier on it.

Edit: Reading the description on the website, "When used with an XRF the gain overall is around 10db" I think this means the ARF has a signal strength of +10dB over that of the ARF, as it continues to say "using an ARF at both ends will give the greatest range (expected to be 10's Km's)".  That 10's of KM's I would expect to see with directional antenna.

424

General Discussion / Re: Long Marston Test 17 October

« on: October 20, 2015, 12:57:47 pm »

Very interesting observations Dave regarding absorption or fades caused by human body. Could explain why the results appear to depend on direction flown etc. It sounds as though to achieve more power a simple power amplifier might be needed on the P3i ARF transmit side to more closely achieve the 500mw into the antenna. I don't know if anything is likely to be available off the shelf or whether the ARF can be modified easily to connect the output through such an amp set-up. I assume with greater power output from the PAW, there shouldn't be any need to modify the ARF Rx side.

The ARF is a packet radio IC and a signal booster as a package, no margin there to boost it again without a redesign and a move to a different IC. Alternatives modules exist, with 500mW power and fully certified from other suppliers. Downside is they won't talk to the existing ARFs.

425

General Discussion / Re: ADS-B tranmitted via a Mode S TX for the NATS Trial

« on: October 20, 2015, 10:50:58 am »

You would need the 'P' variant.

Don't get the TTL serial and RS232 levels mixed up, the former will be 0v-5v (or 3.3v) but the latter can be +24v to -24v (normally +/- 12v) for the signals.  Depending on the serial input of the transponder that could cause permanent damage.  Double check everything before plugging in.

If your transponder is expecting 4800 (or can bet set to 4800) then also check if it is the normal 8 bits, No parity, 0 Stop bits (8,N,0) too.  If they match then in theory it should work at the physical layer.

I guess it boils down to how comfortable you are using a unit based on a chipset no longer in production, so of potential dubious origin, to feed your transponder?

426

General Discussion / Re: ADS-B tranmitted via a Mode S TX for the NATS Trial

« on: October 20, 2015, 10:01:09 am »

Found this Specification sheet.

http://www.wintec-gps.de/download/wintec_wgm-302_manual.pdf

Usb which through a USB/PS2 connector provides RS232, see end of above.

Not sure that it is a reliable source for the transponder as Im not sure of the workings of the USB/PS2 connector - thought they were just straight wired through of the USB in/out pins but could be wrong.

My TT21 I drive with a standard RS232 input from an AVMap V panel mounted which has the capability.

Another option would be the Garmin series, 795, 695 196 etc. Not sure the Aero can drive anything though not familiar enough for this to be definite.

So it looks like the USB version creates a virtual com port, which is the norm really.  As it requires a driver then it *may* not be plug and play on the Pi, depends on how they create the VCP.  I'd forget the PS/2 version, as you would need to inject 5v power into the signal path between the GPS and Transponder if you wanted to plug it into the DB9 port on a transponder.

There are two different versions, WGM-302 U for USB and WGM-302P for the PS/2 version.

U-Blox5 started in 2008 and doesn't appear to be around any more?

Anything like this, the devil is in the detail.

427

General Discussion / Re: Regulator board & ARF Board

« on: October 19, 2015, 11:24:13 pm »

I see WirelessThings are out of stock of the ARF again.

I have put the ARF modules that I have up on the Charge4 website, for those who might be looking for a standalone module.

428

General Discussion / Re: Long Marston Test 17 October

« on: October 19, 2015, 08:38:54 pm »

I'll pop it onto a power meter if you would like, but I suspect it will be the same ~90dBm as the rest.

1 megawatt seems a bit excessive 90 mW?

Yep, should be ~90mW, spent to much time flipping between units today.  I'll nip back and edit that!

429

General Discussion / Re: Long Marston Test 17 October

« on: October 19, 2015, 08:12:41 pm »

Sorry - please don't interpret that post as being rude about your soldering am sure it's better than mine by far!

No problem there , a connector issue won't resolve the problems with the ARF.

430

General Discussion / Re: Enhancement Requests

« on: October 19, 2015, 07:20:41 pm »

Hi  Lee,

I'm still testing on the ground. Currently, the HDMI output blanks after a few minutes, so I can't see logging to the attached screen anymore. Only way to get the screen back is to hit a key on the keyboard *if* one is attached. I usually don't. Would you please disable the screen timeout so it keeps displaying data?

Thanks!
Rob

I have no idea how to do that, do you know a way ?
Also, you know you can get the log output through the web interface ?
Thlee

From my "handy commands" text file of all sorts of odd things you can try....

Code: [Select]

Edit /etc/kbd/config
sudo pico /etc/kbd/config

Change the settings;

BLANK_TIME to 0
POWERDOWN_TIME to 0
As you don't use X that should stop the screen blanking.  Or it did at the time when I put it onto my tips file, be a while ago now though.

431

General Discussion / Re: Long Marston Test 17 October

« on: October 19, 2015, 05:54:37 pm »

Two of them used the JCurtis module, including mine which didn't appear to transmit much at all. I can't comment on the quality of the soldering!

Well, it was soldered with additional flux to ensure good wetting on the joints.  The Rx would't have got through if it was too bad, the signal would have been very low at 5nm and a bad joint would have made that much worse.  I'll pop it onto a power meter if you would like, but I suspect it will be the same ~90mW as the rest.


Edit: Correct units from dB to mW...

432

General Discussion / Re: Regulator board & ARF Board

« on: October 19, 2015, 03:10:10 pm »

Quick question on the ARF board. I ordered mine with the SMA connector installed. Can I still use the pigtail that came with the board or will the unused SMA connector mess up the RF? If so, do I need to terminate the SMA connector (50 Ohm dummy or so)?

You get the kit from WirelessThings, so you can use the pigtail if you want.

Leaving the SMA open won't be a problem, don't put a 50 Ohm load on it, you could put an SMA dust cap on that will shield the end of the SMA, but as the whole board is unshielded it won't really do anything.


edit: Correct typo

433

General Discussion / Re: Long Marston Test 17 October

« on: October 19, 2015, 11:02:16 am »

Don't know if JCurtis has any sort of scheme to send these things back?

I have contacted those who have already placed orders for ARFs to be absolutely sure they want to continue with their order.  I'm not taking any more orders for the ARF modules.

If the ARF heartbeat is flashing then the module is up and active, bar plugging one into an RF Power meter there is little you can do to test them.  The PAW box doesn't start to transmit on the ARF until it gets a GPS fix, so when testing after a power up always ensure you either have a GPS unit attached or CollisionAware active.

The shield is still available, as it gives the Barometric sensor for those who want an easy option to fit one of those.

Anyway, if these things are only outputting 80-90mW even when they're working as suggested in another post, we might be able to do better.

Doing better is an option as 500mW rated, fully certified, packet radio modules are available for a very similar price point and physical size, downside is they won't talk to the existing ARFs.

434

General Discussion / Re: Setting up the software

« on: October 15, 2015, 11:08:42 pm »

The settings are now on the web interface, so if you open your browser on the iPad and go to 192.168.1.1 you can enter the configure details there.

435

General Discussion / Re: Regulator board & ARF Board

« on: October 15, 2015, 10:25:12 am »

Following on from the forum announcement posted today http://forum.pilotaware.com/index.php/topic,150.0.html ...

Anyone who has an order that has yet to ship, which will be orders number RC18333048 or above, and would like to amend their order to exclude the ARF board please let me know by the end of the weekend.  I will hold all shipping until the after weekend to allow people to amend orders as required.

I will e-mail those who have placed orders too...