Posts

Measurement of noise figure of HF103 rc1

Image
Fairly accurate comparative measurements may be made with HDSDR.  Please remember the method used, without reference to a suitably calibrated source measurements will not be absolute. But this method might provide an experimenter with a useful way of comparing equipment. “  Source:   Signal Measurement with HDSDR  Thanks to the HDSDR Authors and to G4ZFQ.My RF reference is a 14 pin metallic dip crystal oscillator at 20MHz with sine wave output. It’s output is 400 mVpp sine wave on 50 Ohm resistor. I placed a  20dB attenuator at the output so that the reference on a 50 Ohm load is  40mVpp,  -24dBm.  I measured the levels with an Hantek Oscilloscope.  The procedure to measure NF is as follow:- Connect the reference generator to HF103 antenna input and run the HDSDR application.- Set RFgain to 0dB attenuation.- Select the Smeter to rms mode (click with the mouse on peak/rms indication to toggle mode). This is important as peek/rms ratio is different for sinewave or noise. We need rms to…

HF103 rc1

Image
HF103 is a HF only prototype of BBRF103 that started at the end of 2019. Thanks to Andrew G4XZL for ideas, test reports and advice.  Here after the modifications.Hardware:- It is designed for LW-MW-HF band only: 0-30MHz.- A Low Noise Amplifies has been added to improve NF of receiver.- The Clock reference used is a low noise xtal oscillator with lower phase noise and spurs than Si5351a.    - The RF attenuator of HF103 uses  DAT-31-SP+- The PCB has been made larger 100x100 mm to increase spatial separation between components' groups (COVID style) Here the scheme and PCB layout.Some pictures of hardware Case 
ADC and RF layout
LNA, filter, attenuator and xtal oscillator
Software (still in evolution):- The reference clock oscillator, that is the ADC sampling frequency has accuracy error. The error is compensated with a software trimming value into the ExtIO.dll's user interface dialog.- The ExtIO.dll will be compiled in Visual Studio 2019 and will not use pthreads library.- The FX3 f…