Memory corruption or SDR aerial fault?

[ridders]

Hi
I’ve noticed that glider reception was pretty non existent since I upgraded the OGN at EGKL. PAW does however work.

We had a period of outage as the network link was down to the site and now that’s all up and I upgraded to the latest OGN code, (changed from Deanland to EGKL as should have been originally) and it’s been running, but a bit deaf on Flarm.

I’m pretty sure I noticed some results on the Flarm SDR and aerial test when I put the upgrade in a few weeks back.......but maybe I didn’t....

Today running the calibration .sh as I had some spare time I noticed the following - not enough data collected, and sometimes I am getting odd memory errors during the test:



What’s the opinion of the gurus on here - the SDR is on ID0, detected (it’s on a USB extension cable to the SDR thats up on the mast, just under the colinear) and plugged into top left USB alongside the RJ45.

My thoughts are the colinear has karked it....as the SDR is being seen.  But what are these memory corruption statements when it does the test?
Advice appreciated.

[Ben Smith]

Have you killed the OGN service first, the gsm scan won’t run if the OGN service is still active.

sudo service rtlsdr-ogn stop
cd rtlsdr-ogn
./gsm_scan --ppm 0 --gain 20

(Assuming you are using a decent TCXO dongle, if it’s one of the older crystal controlled ones then set ppm to 50)

Ben.

[Admin]

It looks like the sdr is faulty
Can you plug another into the same slot to see if those errors disappear
Thx
Lee

[ridders]

Ok, if it is, that’s a right pain as it’s right at the top of a mast.

I’ve got one of these jokers, which I think is an SDR,  I can shove it in the usb slot tomorrow and see what happens

[Admin]

Yep that will be a good test
Thx
Lee

[ridders]

And... the little SDR worked. It’s the Flarm one up the mast 

What model is the recommended/preferred/must be used these days?

[Admin]

And... the little SDR worked. It’s the Flarm one up the mast 
What model is the recommended/preferred/must be used these days?

Damn, thats a pain
I will defer to Keith, but pretty certain we are using the low power sdrs now, and running coax, rather than putting the dongle up the antenna
Thx
Lee

[exfirepro]

Riddlers,

That depends on the length of the coax run and the quality of the coax. I am still using my NooElec NESDRSmart up the mast for the 868MHz side at East Fortune, with a 5m USB down to the Pi, but I understand others are getting good results using standard PilotAware Low-Power SDRs.

If you are putting an SDR up the mast it’s essential to keep the rain out. They don’t like getting wet.

Regards

Peter

[Keithvinning]

Ridders I will send you a PM to fix

Keith

[ridders]

Thanks Keith, awaiting 

[Winged_Jaguar]

Hi Ridders,

I have an standard OGN-R aerial supplied by Keith (which is very good) but a 10+ metre cable-run to where the Pi and NooElec Smart SDR have to be (indoors). It is connected to the aerial with good quality thick coax (11mm) and n-type connectors to a 1 metre pigtail. The outer range for gliders that OGN-R has  logged  is >70kms and that is from only 68m agl. I have located my SDR inside in the dry as Lee suggested. You could reuse whatever cable you are using and see what results you get with the SDR inside. It is a right royal pain getting to the aerial - I had to hire a long ladder and use my kind neighbours drive :-( - however well worth it!!!. I live in an area where there are several OGN-R receivers within 30kms, I have noticed that OGN-R appears selective about what aircraft it wants a station to report on. On busy days it seems to request reports primarily from the most local ones (within 10-30kms) when I have seen more than a dozen simultaneously being reported by my station, as seen on ognrange.onglide.com - with occasional random links to ones much further out. Not sure what criteria OGN-R uses to select who sends in reports on what or whether it moves the SDR gain about to limit the range. Hopefully you will get very good results with the shorter cable run and an indoor setup. Very timely as the gliding and competitions are just getting going - lets hope for some decent weather!

KRs
Chris

[ridders]

Thanks. I built the system a couple of years ago. Our mast is shared with WiFi routers, cameras and lights, It’s located in the middle of the airfield in a shed with the mast some 6-8m above it. Here’s an old picture, since then I’ve installed airfields WiFi long range extenders and new camera up there.


Back then the sdr was up the mast via a usb extension, I was meticulous with weather protection and amalgamating tape wasn’t spared.  I’m a licensed radio amateur of many years and have operated from HF up to 23cm having built aerials and transmitters for the 1.3GHz band.  So I’m very familiar with low loss coax and connector loss and such like.

I was really impressed with the colinear and the Flarm range we got until recently, the unit could occasionally see high gliders right up into the midlands, as well as a lot of local stuff such as parham, ridge soaring and cross channel stuff.

I’m pretty sure the SDR unit up the mast in the tube has died, getting to it and having something to replace it with,  is the challenge for me at the moment.

I’ve left it running with no Flarm receive because I wasn’t sure if the new code would be operational with mode S MLAT transmission on the PAW aerial, although I don’t have the ADSB receive sdr attached.  Main issue is I am a bit tight on money currently, so blowing a load of cash on new aerials and such like, isn’t going to happen immediately, I’ve a few other things I need to sort before this.

[exfirepro]

Hi Ridders,

It’s obviously beneficial to add your own locally received 1090 data into Phil Lee’s 360Radar network and all users are encouraged to do so, but MLAT rebroadcast isn’t conditional on running a 1090MHz Receiver.

For the original trials each station had to have the 360Radar data ‘switched on’ by Phil, but I presume this has now been done automatically via an OGN-R software update, so should run provided you are running the latest software. You can easily check by logging into your OGN-R unit’s Status Page via its IP address or via ‘ognpaw.local’. The Status Page will show data being handled and if a PAW is running locally, will confirm which data is being uplinked to that PAW.

Regards

Peter

[Moffrestorer]

Hi WJ,

I assume that the OGN network selects the strongest signal from the multiple receiving stations. This can be a function of the efficiency of the aircraft antenna positioning as well as the groundstation characteristics and topography. It is very noticeable when gliders turn in a thermal that they sometimes progressively link to different groundstations possibly due to antenna masking/bias.

[ridders]

Just an update from yesterday as I was up the mast.
I took the SDR tube off and removed the contents - it was all totally dry inside, no signs of damage to the amalg tape I had put on it a few years ago, all the connectors were pristine as I had amalged everything thoroughly.

I got the lot home and ripped the SDR apart. There was no signs of any moisture or wet inside although I observed strangely some oily type of residue substance where the PCB met the case.  The blue squishy thermal foam was dry.  The heatsink thats stuck to the bottom of the pcb and mates with the case was not fully stuck, but it looked to me like the glue used on its sticky pad was the source of this substance. 
It certainly was not water as I gave it a blast with the soldering iron inside the metal case and nothing evaporated with considerable heating of the case.

The residue, seen along a line where the PCB met the case sides:


The Squishy blue stickon thermal foam removed from the component side and here the underside, where the heatsink was stuck on - identical residue where the pad was "stuck"


The heatsink sticky pad


Im confident there was no water ingress and the residue I am seeing is from the glue thats used on the pad to stick the heatsink on.

Anyway.....
I cleaned it up, replaced everything as should be inside the case and ran it up on a spare Pi with a little aerial attached.  it worked fine.

So - conclusion is that it was the USB extender that had karked it, up the mast. I can not test that as I cut it off to save me time on site.

Ive spoken to keith and I have some cable, adapters and SDRs on the way to get the unit back up and running. I think having the SDR inside rather than up a mast is the best way to go.