Welcome fellow Radioamateur.
If you read this page it is perhaps because you have had a HF contact with me and were intrigued by my home brewed SDR.
A description of the work in progress will be provided soon. In a nutshell, to satisfy your immediate curiosity, my SDR hardware is as follows:
Antenna is connected through a T/R /Band selector switch to a bank of bandwidth limiting filters, one for every band. These filters also provide antenna impedance matching.
This is followed by a digitally controlled AGTC (Automatic Gain Time Control) device. The AGTC output is then conditioned and presented to a 500MSS Analog to Digital converter .
The output of the ADC is presented to a TriCore TI DSP running at 1GHZ per core.
From here on all all processing is done in Firmware. All oscillators are a Cordic algorithm, and many IIR and FIR filters and Demodulators are composing the bulk of the down converter. The detectors and demodulators follow and their data is pushed to a simple DAC to 50mW audio amplifier connected to my ear buds.
In reverse direction (on Transmit) the microphone is connected to a simple audio amplifier Converted to Digital by a ADC and pumped into the DSP where all audio processing is done. If you were impressed by the audio quality of my transmitter it is in part that the audio signal is oversampled 250 times and about 7000 lines of code are dedicated just to this task.
The audio then is pumped into a Gilbert Cell that creates the two necessary and selectable sidebands. The Low level modulator contains modulation Firmware to accommodate SSB, AM and FM . Addition of other modulation schemes is just a mater of more code to be added. The local oscillators for this section is, again constructed from the Cordic algorithm.
Once the modulated signal is generated and filtered accordingly, the data is pushed to an external Digital Converter at a rate of 1MS per second. This fact contributed greatly to the quality of the transmitted signal as it makes the following Analog filter work much easier.
Once the signal passed these filters it is ready to transmit. Output power at this stage is 10mW. The signal now is is presented to a single stage PushPull Power Amplifier which consumes about 650mA at 12 Volts(on peaks).
Now the signal is passed back to band limiting filters and then to the antenna.
And this is all Folks. Simple enough
About the antenna
This is a 160m wire hanging in the trees about 60 foot high of the ground. The wire bends in all directions and it loops back onto it self where the beginning meets the end into a one to four ballun. The fact that you hear me so well with only 5W has nothing to do with my construction. It is simply because my house is 336feet above the water level of the Hudson River and I just have a good oppening to the West, South and North
OK… More to comme. Should you wish you can allways write me to the address in QRZ
73, N2NNU