WiNRADiO G305 VHF/UHF Receiver
60
Both DDS circuits derive their reference frequency from a 20 MHz reference
oscillator.
The 12 kHz IF output is then fed to the right channel of the
Line
input of the PC
sound card. You can hear what it sounds like if you use the sound card mixer
panel to listen directly to this input (rather than using the G305 Demodulator
software).
The AGC is performed in the first IF stage, based on the level of the last IF
output (at 12 kHz IF). As the IF bandwidth of the first IF stage is 15 kHz, the
AGC action is delayed until the dynamic range of the first IF stage is fully
utilized – this is in order not to cause desensitization of the receiver in the
presence of neighboring strong signals, falling within the 15 kHz IF bandwidth.
The resulting variation in audio output is then compensated for in software,
using
Audio AGC
in the software demodulator.
The final IF bandwidth is then adjusted entirely in software. If the
Professional
Demodulator
is used, this bandwidth is continuously variable from 100 Hz to
15 kHz.
Did you know?
The G305 receiver's hardware front-end is a dual conversion superheterodyne – the
rest of the signal processing, including further down-conversion, is done entirely in
software domain. The superheterodyne was patented in 1918 by American inventor
Edwin Howard Armstrong, an author of many radio related inventions, including the
regenerative circuit and frequency modulation.
