Simple SDR transceiver 4Z5KY

sdr radio diagram There was a desire to do something SDR transceiver . And began the search for information and transceiver circuits for SDR. As it turned out complete transceivers, there is little, except for the different variants of SDR-1000 . But for many, this transceiver and expensive and complicated. Also published various versions of key boards , synthesizers , etc., ie individual functional units . Has done a lot in the development and popularization of simple SDR technology Tasa YU1LM, who also made ​​a complete transceiver "AVALA", and can recommend his design for beginners in this area and want to try what SDR at minimal cost. In the end, decided to make his own, as simple as possible and at the same time, quality SDR transceiver . In the development of materials used YU1LM and other publications. The mixer was decided to make the 74HC4051 - once did a direct conversion receiver Sergei US5MSQ, with the mixer on the chip . And the use of 74HC4051 in the transceiver allows you to make a very simple mixer - the total for receiving and transmitting tract.
The quality of this mixer is quite satisfied . Detail the history of the development of the transceiver can be read on our TFR ( Krasnodar site).
And if you're going to do this or any other simple SDR transceiver , then I highly recommend reading forum - there is detail painted my entire path from idea to make the transceiver to complete the construction and running and a lot of other useful information that just does not really fit in this article. 
The transceiver circuit is constructed by direct conversion of the working frequency audio frequency signal processing computer's soundcard . So much is written about the technique of direct conversion applies to the SDR. In particular, the need to suppress the non-working side band ( in SDR second channel ) phase method . It was decided to make a simple single-board single-band transceiver with a crystal oscillator to the fundamental frequency and QRP power , ie completely finished unit . Chose the 14 MHz range , the most interesting for me. If desired, will not be difficult to make the radio to any other bass range .
At frequencies above 14 MHz transceiver has not been tested , and the lower frequencies should work well . Resulting in the end transceiver has the following parameters :
Operating Frequency Range 14.140 - 14.230 MHz. (When using a crystal oscillator to the frequency of 14.185 MHz and a sound card with a sampling rate of 96 kHz)
The sensitivity of about 1 mV and depends heavily on the quality of the sound card.Intermodulation free dynamic range greater than 90 dB - more precisely nothing to measure.
Suppression carrier for transmission over 40 dB (I turned 45 - 60 dB) , depending on the particular instance of 74HC4051, as well as the quality setting.
Image rejection greater than 60 dB in the program correction.
The output power of about 5 watts. 

It is clear that for SDR transceiver control program is needed , and I chose a program because of the possibility M0KGK program for correcting the amplitude and phase over the entire operating range of the sound card and store the calibration points . This is very important. This feature allows you to program very well to suppress the second channel . Due to lack of storage in the program Power SDR calibrations at several frequencies sound card from its use declined - this program works great with SDR transceivers with integrated frequency synthesizers , where the rearrangement frequency synthesizer is a question , not the frequency of the sound card.

Подробнее sdr ерансивер

The concept is simple , and describe the operation will not. It can be read at Tasa YU1LM, though in English language . Errors in the printed circuit board is not detected. For ease of soldering signed the component values ​​in Figure circuit board, not the serial numbers of the elements . 
Transceiver requires virtually no setup , and proper installation will start immediately . With the right settings you certainly M0KGK. This data can also be read on the forum. It is clear that many have difficulty with the acquisition of a quartz resonator. Therefore, in case of his absence or because of the desire to have a full range of 20 meters , you can simply use an external synthesizer or GPA to the operating frequency , the signal from which you want to apply for the 1st 74HC04 output via a capacitor 10nF . Capacitors C63 and C64 are not set . Work on this SDR transceiver is very nice and comfortable. All control a computer mouse .
See the whole spectrum in the band of 96 kHz , and a mere indication or " dragging " of the filter program instantly rebuilds the interest on the station.
Very quickly and clearly . After working on this radio , working on a standard has something missing - the visual information about the situation on the range.
Sergei 4Z5KY
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