KA7U

Noise at roughly 60 KHz intervals

KA7U

December 2018

Nick,
I think 10mbits will run the KiwiSDR. I applied the ethtool utility with your parameters to my KiwiSDR's. The first one was imperceptible change, then the 2nd one showed improvement on the… (more) KiwiSDR that has the most interference, then the 3rd one and at that point the SDR with the most interference showed a 6dBm improvement and the interference lines seem to have less density on the spur, as though interfering signals are missing. The KiwiSDR antenna with the worst spurs is about 30 feet from the equipment, the 2nd KiwiSDR antenna is about 250 feet from the equipment, and the 3rd KiwiSDR antenna is about 350 feet from the equipment. So antenna 1, 2, and 3 for future reference. Antenna 3 is a 210' top dipole with 350' of RG213/U underground in conduit, and the KiwiSDR shows the least interference, ka7u.no-ip.org:8073. Antenna 2 is a 120cm copper active loop antenna with 250' of shielded CAT6 4 pair, ka7u.no-ip.org:8074. Antenna 1 is a 100cm coax active loop with 50' of shielded CAT6 4 pair, ka7u.no-ip.org:8075. The dipole is not amplified, the two loops both use the same design of differential amplifier and matching baluns and power supplies.

When there is no amplifier on the loop antennas the interference is there. With amplification the spurs increase. The differential amplifiers are well balanced for hfe and bias, so common mode signals should be seriously attenuated. Which point has been verified by accident with shielded and unshielded RJ5 connector mismatches. So my theory is most of my spur interference is actually received at the antenna and not common mode. Hence antenna 1 has the greatest interference, and the interference subsides greatly in antenna 2, and is practically nonexistent on antenna 3, the dipole. Now your ethtool parameters have improved the situation even more, but not eliminated it. There remain 3 network switches, one shielded and 2 not shielded, and 2 computers, and 2 monitors, running in the radio shack with the KiwiSDR's.

I think my next best move is to move antenna 1 out to where antenna 2 is located or nearby, and expect that the interference will be reasonably abated. Replace the unshielded network switches with shielded ones should help too.

You might find that moving your antenna to the barn and keeping the KiwiSDR where it is, will give the best results.
Ron
KA7U (less)

DRM Heard

KA7U

January 2020

15325KHz Voice of Russia GRFC loud and clear at grid DN14lf. I was able to decode on all antennas. This video is testing the KiwiSDR using the BeagleBone AI in 4 channel mode. All 4 channels were in… (more)