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

Siegfried Jackstien

hmmm ... their dac and adc could make a nice sdr backend with high quality

dg9bfc sigi

Am 12.03.2018 um 13:45 schrieb Ken Alexander:

I'd be interested to know if anyone has ever tried one of these.  It's a "USB decrapifier", meant for audio systems.  It isolates computer's USB power from (in our case) the Airspy and replaces it with cleaned-up power from its own linear power supply.  Kind of expensive at US $99 compared to ferrites and better cables.  I've had my eye on them and just wondering.

From: jdow <jdow@...>
Sent: Monday, March 12, 2018 12:58 AM
Subject: Re: [airspy] 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


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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