RTL-2832 and Raspberry Pi for ARPT and FUNcube

RTL-2832 and Raspberry Pi for ARPT and FUNcube

Last year I was playing with a cheap USB dongle for weather satellite reception. Eventually though I gave up on it, as although I could receive reasonable pictures with it, the device kept causing my machine to freeze.

Anyway, I recently dropped a raspberry Pi in the shack to act as a router between my shack and my wireless network. It got me wondering as to the possibilities of running the dongle via it. Turns out, it was as easy as… pi! (Sorry… 🙂 )

It really only takes a few simple steps:

  1. Download the rtl tools source code via git from OsmoSDR
  2. Build up the tools (make sure you’ve installed the build-tools package on your pi)
  3. Make sure you unload an DVB kernel modules with rmmod (after checking with lsmod)
  4. Run rtl-tcp on the raspberry pi
  5. And then connect via TCP from something like SDRSharp

Doing this I’ve had no problems with anything freezing, and have captured images with as much ease as I did before – although I have a dodgy coax cable I need to fix.

Further, I’ve gone on to receive beacons (6m, 2m and 70cm) as well as the FUNcube telemetry. Actually, to my surprise I’m the only VK7 to have recorded reception of any telemetry (according to the FUNcube Upload Ranking page).

To finish, here’s a couple of images received via this setup (one from NOAA-15 and one from NOAA-19). And the title picture of New Zealand is from NOAA-19.

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Improved NOAA-19 Reception

Improved NOAA-19 Reception

This week, my ebay ordered RTL2832U based USB digital TV receiver dongle arrived! I’ve been working through a bit of a cold, but that wasn’t going to stop me going down to the garage and having a play. I was too excited at the possibilities!

With no time at all I had my RTL-SDR solution up and running with SDR#. All that was needed was a custom driver install and then a couple of very minor mods to SDR# and all was working. Other than that, I connected the antenna socket out via my access panel to the Diamond X-50 on the roof. Before I knew I had local WFM radio stations playing on my computer.

The main purpose though for even trying all this, was the hope that it’d improve on my weather satellite reception as per my previous attempt. My thinking was that the main limiting factor was the narrow bandwidth of my receiver.

With using an SDR setup, I should be able to have as wide a bandwidth as needed (and more if wanted). However it required one extra bit of software, and that was a virtual audio cable to route the audio out of the SDR software into the audio in of WxtoImg. For this I chose VB-Audio Virtual Cable. It’s free and couldn’t be easier to use.

NOAA-19 @ 0446 UTC - Both Channels

NOAA-19 @ 0446 UTC – Both Channels

After getting past some recurring computer freezes (think I need to rebuild my PC) I was able to play with an initial pass to play with some settings. But before even changing anything things were looking drastically different. Then on turning the gain in SDR# up full and increasing the AF Level slightly things were looking (to my eye) perfect!

So with all trimmed and ready to go, I  keenly awaited 0446UTC for the next NOAA-19 pass. The results were amazing – the best by a long shot that I’ve every received. These can be seen in the first NOAA-19 image with both channels,  and you’ll notice only a few spots of noise which I believe was mainly due to physical obstruction.

To consider this was achieved with essentially a $25 receiver and some free software is amazing. Considering further I’m still just using the Diamond X-50 and haven’t even bothered to consider the circular polarisation. And further, this was from the West were I do have far less of a view – South/East is the preferred approach.

With that success, what now? Well, I’ll keep trying some more receives (hopefully my PC will stop freezing) and I might try some of the other SDR# features/plugins so that I can attempt to switch frequency for each of the three active NOAA satellites. That way I can aim for a full set of images!

Further, I’m also interested to see how some of the other SDR software offerings go and then I can also start to look at all the other possible items to receive out there – considering this dongle (with the FC0013 chip) covers from just below 30MHz to just up over 1Ghz. So many options! Oh, and then there’s the idea of an upconverter for all the offerings below 30MHz!

NOAA-19 Received

As mentioned in my previous post, now that I’ve got my 2m/70cm setup in place, I thought I’d try some Weather Satellite reception again. Sure the antenna is not ideal (it’s neither tuned for that band – 137MHz – nor is it circular polarised) and sure the radio is not ideal (recommended IF is 30kHz to accomodate doppler shift etc.) but you’ve got to try.

My previous attempts were in Canberra with more or less the same gear – albeit a different computer which only had a standard AC’97 inbuilt (current computer has an Audigy 4). But that location was with a temporary low install of the antenna that had many blocking objects. So I was hoping the new location with far greater access to the sky would see better results.

NOAA-19 0404UTC

NOAA-19 0404UTC

Last night I quickly downloaded WxToImg onto the machine and went about dialing it all in – making sure the audio was all correct as I’d have to leave it to run over night while I slept. I settled on NOAA-19 as it looked to have the best passes over the coming period.

Checking the images this morning, there was nothing too spectacular, however there was a good predicted pass for this afternoon just after 2pm (local time). So I waited the day with keen anticipation to see what would occur.

Checking the image just after 2pm, I was amazed with what I could see. The resultant image even as a thumbnail was far better than anything I’d ever achieved in Canberra – and that is what you see in the first image. I didn’t expect anything with such detail and colour unless I got a better receiver (and most likely a proper antenna).

But it was a good pass, and indeed with such good clean sky access I believe it helped. The interferance that did result I believe was down mainly to fading due to circular polarisation and also the bad weather we were having (heavy cloud and rain – indeed, you notice in the image you can not make out Tassie other than for the computer generate outline). Here are the details from WxToImg of the predicted pass:

2013-07-02 UTC
Satellite Dir MEL Long Local Time UTC Time Duration Freq
NOAA 19N 71E 150E 07-02 14:04:18 04:04:18 11:54 137.1000

As you can see, a nice high elevation (71 degrees) and a good long duration.

Also, for those who have not played with this before, here is the combination image that is received and then later processed to generate the multitude of other formats (the land mass outlines and lat/long grid are added in WxToImg):

NOAA-19 0404UTC - Full Image

NOAA-19 0404UTC – Full Image

And so that you have a comparison, following is the pass prediction and image (same format) that I received just before 2am this morning – which left me wondering if there was any hope. But note the lower elevation and the fact it is to the West – which is where the land slopes up and away from me, so really the pass would have been much shorter in duration.

2013-07-01 UTC
Satellite Dir MEL Long Local Time UTC Time Duration Freq
NOAA 19S 49W 140E 07-02 01:42:59 15:42:59 11:43 137.1000
NOAA-19 1542UTC - Not so flash

NOAA-19 1542UTC – Not so flash

I’ve still got the setup in place and am looking forward to another four more passes before tomorrow night (two to the East, two to the West) which will provide for some interesting comparisons.

Unfortunately I have no CAT cable, otherwise I could have WxToImg automatically change frequency and attempt to grab the other two satellites as well. One day.. maybe..