First steps with Software Defined Radio

It has been about 10 years since I bought a Softrock lite kit for 40 meters. At the time SDR seemed a promising technology and hardly any equipment was either available or very expensive. Buying a 20 dollar kit seemed a good idea, I could at least get a taste of it. The kit ended up in a drawer and I forgot about it. Until last week, when a friend demonstrated a RTL-SDR dongle to me and I got intrigued again. I build the kit in 2 evenings, it comes with a very good build description.
softrock Lite II 40 meter receiver kit
Top and bottom side of the PCB (about 2x6 cm) and the added enclosure

It is probably the cheapest way to get a taste of Software Defined Radio and it's software. This 40m design by KB9YIG uses a crystal oscillator, a divider and a mixer to produce I and Q signals which are injected into your sound card, so it basically is a direct conversion receiver. Demodulation is done in software.

I have had a try using Quisk on linux. You get a nice waterfall and spectrum display with selectable modes and filters. In order to get things running the configuration file needed a bit of tweaking. Create a file called in your home directory with the following entries:

import quisk_hardware_fixed as quisk_hardware
softrock_model = "fixed"
fixed_vfo_freq = 7056000
sample_rate = 96000

You might need to adjust the sample rate so it suits your sound card. The higher the sample rate, the more of the 40m band you will see.

                quisk on Linux

Performance is amazing. Good selectivity and audio. Using a full size 40 meter dipole seemed to be no problem for the receiver.

Some Links:
Webshop of WB5RVZ with several softrock kits
Homepage of quisk, a python based multi-platform SDR