HF103 rc1

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 firmware will be modified to use the new IOs


Results :


The receiver 32MHz bandwidth with a 50 Ohm dummy antenna. The only spurs are the noise of FX3 board switching regulator of 1.2 V at 1.36 MHz and harmonics at 2.72, 4.08, 5.44, 6.80 MHz.  There is a noticeable tone at 20.550 MHz. No other signals with 20 dB LNA and without attenuation.

Comments

  1. Its strongly needed FPGA between ADC and FX3 for buffering, synchronization and performance improving. Direct connection to FX cannot give guaranteed bandwidth on USB3 with nonReal time operating system like windows or linux. This mean that you can drop from time to time samples or group of samples. Think about adding FPGA between ADC and FX3.Yes, it will raise cost and complexity of the board, but there are no free lunch nor full happiness.

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    1. I agree that non-real-time operating systems require intelligent programming to process the broadband signal as a full HF band with low latency. However, this is not related to the stability of the super speed USB3.0 transfer. My programming of FX3 is naive, however it shows continuous transfer. Here a video "HF103 : HF spectrum accelerated elapsed time, 24 hours in 2:30 minutes" (https://www.youtube.com/watch?v=2jvBGXheA0M&ab_channel=ik1xpv).

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  2. I appreciate your article. You truly share relevant and extraordinary knowledge. Thank you for keep sharing these valuable thoughts.

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