Easy-SDR
Hello. I am a 4th year student of Brest State Technical University. For a long time I was interested in SDR technology. However, I could not find the devices for self-production with a detailed description. After that it was decided to make a project combining various devices for cheap SDR receivers.
At the moment, sponsorship for this project was provided by companies RTL-SDR.COM, Mini-Circuits, LCSC.
What are the objectives of this project?
Creating affordable, easy-to-manufacture layouts of PCBs to working and expand the capabilities of existing low-cost SDR receivers available to ordinary users. All the created elements of the project will have a detailed description of the manufacturing process, with all the existing features and possible problems.
Currently availiable modules:
Example of HF Upconverter module:
HF Upconverter was based on the idea of an shifting the frequency up by a certain value (I use 125 MHz value), after this conversion your receiver will be able to correctly process frequencies below 30 MHz with less loss of useful signal.
For example: We want to receive a signal with frequency 4625 kHz. But if we try to receive this signal directly to SDR receiver, without any transformations, we most likely will not hear anything. Why? Answer is simple - RTL2832U can not process a signal with such a low frequency. The sensitivity of the receiver in this range is extremely low, which at best will allow us to receive only powerful broadcast stations. Sure, now some SDR recievers allows to use Direct Sampling mode which transform signal directly to RTL2832U bypassing R820T/R820T2 chips (perfect realisation for example at RTL-SDR.COM V.3) and allows you to receive signals up to 30 MHz.. But this method confidently receives signals only with frequency lower than 14400 kHz and also has a low sensitivity.
However exist method shifting frequency by a certain value up, this method named Up-сonverting. For implementation, an auxiliary generator is used, to shift the original signal with a certain frequency (in this module we will use 125 MHz, this is important, since the output filters are designed specifically for operation with a this frequency) and a mixer where the input signal is additioned to the generator signal. When we using a generator at 125 MHz, the frequency shift of our received radio station will look like this: 4.625 MHz + 125 MHz = 129.625 MHz. Also, we need to use input (Low-pass filter) and output (High-pass filter) filters to suppress unnecessary signals and reduce noise. After all transformations, our SDR receiver will be able to process the signal of this frequency without any problems.
After that, we can also set the amount of offset in the software used for reception. The last step is necessary for the frequency of our radio station to be displayed exactly as 4.625 MHz and not 129.625 MHz.
At the moment, the method described above is the best way to work with the SDR receiver in the frequency range up to 30 MHz (subject to the availability of an appropriate antenna).
Example of the finished device:
I hope for a positive decision on sponsorship for my project. In the case of a positive response, I will post information about sponsorship from PCBWay on the main page of the project.
Apply for sponsorship >>
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