PSDR-1 (is a asembled SDR ready to use and comes with crystal)
it is also avible from Giga Techonology
PSDR is a compact module of powerful SDR receiver with crystal oscillator with exchangeable crystals and external input for oscillator. On input part is simple filter for separation of undesirable signals. Filter is followed by a mixer with a Johnson counter and a quadruple bandpass filter, ensuring a high selectivity and purity of the output signal. The filtered signal is further amplified by low noise amplifiers with bandwidth up to 140 kHz, CMRR = 100 dB (type).
SDR receiver block scheme, using computer sound card
The mixing signal is obtained from a crystal oscillator with contacts for easy insertion and removal of the desired crystal. Used crystals range is approx. 3 to 25 MHz. Or even more simply by changing the capacitors. The received signal is in this case always XTAL / 4. Another option for obtaining mixing signal is use input (with BNC type connector) with an external oscillator.
Also high frequency input signal from aerial (or even better from tunable aerial element) is connected using BNC type connector. Output I/Q signals are connected through isolating capacitors on 3.5 jack stereo type connector. From there is signal connected to Line-in audio input on computer (using classic stereo cable). Switch of left and right channel isn’t critical, it is possible to change configuration in application.
Pin layout details.
Here is an example of the free available SDR software.