GNU Radio

Articles and blogs about the GNU Radio, written by Alexandru Csete OZ9AEC.

Smaller dish for tracking UNITEC-1

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As you probably already know the UNITEC-1 launch got scrubbed today (17th May). Fortunately, there is a launch window every day for the next few weeks.

During the last few days I learned that tracking UNITEC-1 will be very difficult because the available trajectory data can be very uncertain. Therefore, we decided to use a smaller antenna with wider beam width in the first few days after launch. One option was to mount the IKEA dish to piggyback the 7m dish, another option was to use a 90cm dish which is currently equipped with a 2.4 GHz feed. We decided to go for the second option.

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Preparing the 7m antenna for UNITEC-1

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AMSAT OZ staff are preparing the 7 meter dish for tracking the UNITEC-1 interplanetary spacecraft. Related articles: UNITEC-1 Link Budget C-band Receiver Hardware for UNITEC-1 UNITEC-1 5.8 GHz Receiver Test Using OZ7IGY Smaller dish for tracking UNITEC-1 5.8 GHz Helical Feed for the 90cm dish UNITEC-1 Tracking Report

C-band Receiver Hardware for UNITEC-1

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With only a few days left until the launch of UNITEC-1 (May 17) to Venus, we are getting ready to track it and I am trying to catch up on the documentation part – this time a brief description of the receiver hardware.

Recall the system architecture where the 5.84 GHz RF signal is converted to 640 MHz using the KU LNC 5659 C PRO low noise down converter, and…

C-band receiver architecture

This article gives a high level walkthrough of the receiver used to convert the 640 MHz IF to digital baseband, i.e. the blue box called USRP in the above diagram.

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SSTV Robot OZ9STV with USRP and WBX

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I was fooling around with the USRP / WBX on the 2 meter band tonight when I suddenly stumbled upon some very strong SSTV transmission. It turned out to be the OZ9STV robot located only a few kilometers from me. That explained why I had more than 40 dB SNR even though I was only using a bad whip antenna indoors.

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Binaural CW Receiver with GNU Radio and USRP

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Today I felt like doing an experiment that is not quite on my TODO list – a binaural CW receiver. A binaural CW receiver is a receiver that gives a spatial feeling while you are tuning. As I understand it, you have to use stereo where the signals move from one side to the other as you tune and are in the middle when you are tuned to the frequency.

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Frequency xlating filter vs. complex multiplication

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When I upgraded the simple GNU Radio receiver to single side band, I decided to separate the band pass filter and the frequency xlating filter and the frequency xlating filter got equipped with a wide low pass filter instead. The low pass filter is useful but really not important. Therefore, I decided to replace the frequency xlating filter with a simple complex multiplication (aka. local oscillator) and thereby save some CPU cycles – I figured that removing a filter would save something.

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