Re: USB cable quality and QRM in a spyserver setup with an Airspy Hf+ and Raspberry PI3. 6 microUSB cable test. #airspyhfplus #bestpractice #raspberrypi


Put some ferrite on every lead that goes out of the Pi. Any one of them can radiate and create problems. Try using a longer cable for the HF+ and placing it further away from the Pi. You are in the near field for at least the HF noise. So doubling distance from the noise source will bring as much as a 9 dB improvement. It will help at much as 6 dB at VHF. A 5 meter cable would not be out of line. But don't go beyond that without careful testing with a powered USB extension.


On 20180311 12:38, ea5ehs@... wrote:
Hello David,
I decided to go de Orange Pi UNO way for different reasons; low cost, Gigabit ethernet outside the usb bus, only one usb 2.0 port.
My theory about the usb qrm from cables is that there is a RPI USB design allowing for this. I have tested one Rpi2B and two Rpi3B with identical results.
QRM is only generated when an active data connection is on, ie when a client connects to spyserver and start sdr#.
When I connect the airspy HF+ to a usb port of my Laptop and rin SDR#, no noise is generated with any of the six tested cables' using the same antennas.
I was considering the Tinkerboard SBC but as I'm runing on solar power, every mW  of power consumption counts. Tinkerboard seems to draw more power than Rpi an Orange pi. Rpi3+airspy accounts for 630mA at 5V during an active connection. I have also taken additional power saving measures like turning off the on Board leds and the HDMI.
Best Ni

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