Getting started with SDR radio using DVB-T USB dongle and gqrx

Some time ago I bought a cheap DVB-T USB dongle from ebay. I was inspired by several stories found on the internet how to use it as a primitive SDR (software-defined radio). Somehow I didn’t get around to do anything with it, partly because most of the instruction in net were for windows based PC’s and those I found at that time for linux were command line programs.

Recently I found a package called gqrx. It combines gnuradio and osmocom files into a nice package that resembles sdr# (sdrsharp). I decided to give it a try.

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2 x 200 = 240

And now for something completely different…

Last Summer I took my vanity call (OH2HA) into use and decided to try how long it would take to work 200 countries again starting from zero. First time it took 35 years with my other call (OH2BSC).

The goal was achieved on April 8th 2014, in 9 months. All qso’s were made on 100W, most of them with my trusty 15+ year old FT-1000MP. The main contributors were better antenna (6 element log periodic Tennadyne T6) and more extensive use of CW (1/3 of  countries were on CW). Maybe I even have learned something about working DX. Solar cycle 24 certainly helped, but I’ve seen better sunspot numbers in the past. Still I think the most important contributor was, that during the last 5 years my hamshack has been computerized.

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iGate with minimum hardware – the RasPi version

My friend Ari OH2BSF built his version using Raspberry Pi instead of a laptop. Othervise the setup is the same than described in the previous posts, soundmodem as TNC and xastir as APRS client.

Hugo XE1BEP has built a similar system, and he has also written an excellent document how to turn a Raspberry Pi into an iGate using xastir and soundmodem. His version includes the instructions how to connect a serial GPS into the system. Here is the link to his document:




APRS iGate setup with minimum hardware – part 4

It’s been a while since the last update. Let’s wrap this topic up by going through the final set-up for the minimum hardware (= soundmodem based) iGate.

Part 1 lists all the needed building blocks for the iGate. PC, linux/ubuntu operating system, soundmodem software, xastir software (aprs client), internet connection, 2m FM radio (only RX is needed for iGate) and an audio (stereo) cable with 3,5 stereo plugs are needed.

Part 2 shows how to configure the xastir for the connection to APRS-IS server. In this case there is no GPS, but your station location is entered as part of the station configuration. This makes sense for a fixed station, especially for an iGate.

Part 3 shows how to configure the soundmodem. When this is done it might be a good idea to test that the soundmodem works properly. This can be done with the soundmodemconfig’s Diagnostics functionality.

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APRS iGate setup with minimum hardware – part 1

I’ve had an Xastir APRS client running on my shack’s computer for years. There’s no GPS, so it shows fixed location. There’s no radio either, information flows both ways via APRS-IS server.

My IC-R5 receiver was sitting idle, so I started to wonder how to turn it and Xastir into a minimum hardware iGate. In Greater Helsinki area there’s no need to improve APRS coverage, but when has the real need been the driver in this hobby?

The minimum setup for an iGate requires:

  1. iGate capable APRS software (there are many options, but since I already had xastir up and running …)
  2. PC to run the software (ham shack PC is Acer Revo running Ubuntu 12.04 LTS)
  3. internet connection to an APRS-IS server (choose APRS Tier 2 server near you, most of them require a passcode based on your call sign)
  4. radio capable of receiving APRS packets (my trusty IC-R5, any 2m FM receiver will do)
  5. TNC (terminal node controller) to decode APRS packets (soundmodem acts as a minimum/nil hardware TNC)
  6. interface between radio and PC sound card (audio cable with 3.5mm stereo plug on each end)

The only tricky part is the soundmodem configuration. Instructions found on the net didn’t work with Ubuntu 12.04. In the next post I’ll show how I configured mine.