The ISDR is developed for Students and Radio Amateurs. ISDR is a low cost 40 meter band receiver.
PC Sound card's MIC jack(stereo) is extensively used for the ISDR. So, the ISDR performance depends on the PC Sound card. The center frequency is 7056 KHz and typical frequency range the receiver covers is about +/- 48 KHz and depends on the PC sound card sampling rate which happens to be 96 KHz. The receivers performance depends on the usage of a good antenna.
A 28.224MHz crystal which is used to create stable oscillations. IC 74HC00 is used as a Local Oscillator of frequency 28.224MHz. The output of the local Oscillator is first divided by to provide True and Complement signals (0 degrees and 180 degrees) by IC 74HC74. These two signals are agian divided by 2 to provide 0 degree and 90 degree by one more IC 74HC74. These signals are given as L.O. input to the mixers to drive the P and Q amplifiers through transistor buffers. The output signals P and Q (mono-jacks) are low frequency signals which have a phase difference of 90 degrees. These signals are connected to the MIC jack (stereo) of the PC.
Front Panel : Outputs P & Q (mono jacks)
ON / OFF switch
LED indicator.
Back Panel : Antenna connector(UHF/ BNC)
12V D.C. binding posts.
Software to be used: Rocky, WinRad, PowerSDR etc. (all software used are free )
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