29 December 2012

HF DRM Broadcast with KX3 and Dream

I've just got Dream working with my KX3's I/Q output and have been able to receive the "Voice Of Nigeria" DRM transmission on 15.120MHz.






9 December 2012

Feeding baudline with the KX3's I/Q Output

After someone mentioned in ##rtlsdr that it was possible to pipe I/Q data into baudline via stdin, I wondered if I could do the same with I/Q data from the KX3.  As I'm already feeding the I/Q data from the KX3 into gr-kx3 using pulseaudio, I needed to use pulseaudio as the source for baudline but it isn't supported, so I used parec to pipe the I/Q signals into baudline.

#!/bin/sh
# blkx3 - a bash script to feed I/Q data from a pulse audio device into baudline
SAMPLE_RATE=48000
BL_BIN=~/bin/baudline_1.08_linux_x86_64/baudline

parec --format=s16le --channels=2 --rate=$SAMPLE_RATE --latency-msec=5 | \
$BL_BIN -scrollcontrol -record -stdin -channels 2 -quadrature -samplerate \
$SAMPLE_RATE -basefrequency $1

You may need to change the path to baudline in the script and maybe also the sample rates. The script takes the baseband centre frequency as its only parameter.


$ blkx3.sh 7184500


2 December 2012

1 December 2012

L-band SARSAT doppler tracks in gqrx



High Altitude Balloon tracking

This might be a kind of live-blog. Perhaps. We'll see what happens.

Project info: http://ukhas.org.uk/

Tracking online: http://track.spacenear.us/

I'm using a discone in the loft and a preamp at the wrong end of the coax.  With this arrangement, I can here (but not well) some priates on UHF-SATCOM,  quite a few 70cm sat transponders and faint signals from L-Band SARSATS, so it works okish.

A screenshot of gqrx, using a USRP B100 & wbx daughterboard.


 One of dl-fldigi, using an AOR8600mk2 and a Signalink-USB.

Apparently that's PROM i can see.

Bob too now:
Now, I'm decoding Bob, but with bad checksums:
There's a bunch of loons going up, so I thought I'd monitor a whole MHz of spectrum in gqrx and look for them all at the same time, then tune in the strongest for decoding.  This is the playing field, below.  Bob is where the receiver is tuned to, and PROM is up at 434.167, faintly visible.
I popped up to listen to FO-29 and when i came back, there was another signal:

Apparently, it was TRUSS:
A little while later, I spotted ROLL in the waterfall:
But the decodes weren't so good as it was in a noisier part of the band:

I continued to monitor, alternating between TRUSS and ROLL depending on which seemed stronger at the time.  I didn't get many good decodes.