Software-defined radio, or SDR short (Software Defined Radio) is a radio communication system in which the usual hardware components (such as mixers, filters, amplifiers, modulators / demodulators, detectors, etc.) created by PC software or firmware embedded in system. This is not a game-changing technology.
The first mention can be found at the end of the seventies, when Walter Tuttlebee described the concept of VLF radio, utilizing A/D converter and microprocessor Intel 8085th Furthermore followed SpeakeEasy project, focusing on the U.S. defense system. His aim was to use digital signal processing, and range from 2 to 2,000 MHz replace up to ten existing military radios. The historical sequence we must not forget also, the year 1991 when Joseph MITOL created and a year later published extensive work on the subject, designed for a wide field of technology. More information on the historical development of SDR receivers can be found on the Internet.
Today the situation is much better than it was in the early days of his birth. Since the SDR receiver typically consists of several functional units separately, it is possible to create a variety of different approaches. From the highest when the input filter placed in one or more of fast A / D converter, followed by a configurable gate array (FPGA), taking care of the basic signal processing to the simpler designed especially amateur construction. They are used to digitize the signal usually Line-In input of your sound card (see block diagram in Figure 3). Sampling frequency is equal to the received range yet. Ie. when you use a sound card with a sampling frequency such as 192 kHz is also available software tunable range of 192 kHz. Greater extent then provides for the exchange of crystals in the receiver or tunable oscillator (VCO).
PSDR is easy to use SDR receiver module "Software Defined Radio", for connection to a PC sound card. It is based transistor crystal oscillator (crystals for 80 meters and 160 meters inside Gaza), Johnson counter with 7474 circuit group and Tayloe detector circuits 4053rd After treatment, there are four signals shifted by 0, 90, 180 and 270 degrees, which pass through the low-pass band filtrate and the operational amplifier (typ. NE5532) of them after amplification signals generated I / Q.
Signals I / Q also lead to a stereo line-in audio card and another decoding and listening to old software. The advantage is that this is a diagram useful in a very wide frequency range and the possible addition of switchable input bandpass filters with their properties rivaling professional, the amateur radio receivers.
Unlike similar solutions, however, are modules PSDR supplemented with external input generator and the switch. Instead crystal oscillator can use any tunable generator, like this: PGEN45 - Generator 8 kHz to 45 MHz
FREE - Two crystals for 80 meters and 160 meters band - FREE
Using SDR receiver is very versatile and is based on a wide frequency range. Virtually can be used to receive all services in long, medium and short waves AM, NFM, WFM, LSB, USB, DSB, CW and CW-L-U modulation. In addition to radio stations can also receive amateur radio broadcasts, synoptic maps, military installations, submarines, navigation beacons, and much more.
Example of use (frequency in kHz):
Installing the receiver
PSDR modules are supported by all standard SDR software. Among the most common are: WINSDR, HDSDR or a new open source SDR# (SDR Sharp). Since this is a very interesting project, which is for non-commercial use completely free of charge, we describe the use PSDR module together with SDR#.
Application does not need to install, just download and unzip the following address:
After unpacking the software SDR# ready to use! It is not necessary to install anything!
The first use PSDR module
After unpacking SDR# files can immediately start the application SDRSharp.exe that after reading the following window:
For starters, you can try such as receiver for receiving the classic AM radio broadcast:
1) First, connect the antenna to
the module, power supply (12V DC) and 3.5 jack to connect the
Line-In input of the sound card
2) Enter the desired crystal or potentiometer to adjust the VCO frequency
3) Next, run the application SDRSharp.exe
4) Set the recording from line-in (no microphone)
5) In addition to the Play button to select "Other (Sound Card)"
6) Select the type of modulation
7) Click the play button
5) Section Frequency set the receiving frequency
6) If everything works as it should, it should show the received spectrum from PC speaker should hear noise or music