Spurs - what to do about them?

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W9MDO's picture
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Joined: 2013/07/28 - 19:56
Spurs - what to do about them?

Hi all,

I routinely see stations that are being received with high signal strength at my location showing one or more pairs of sidebands on adjacent frequencies, generally 25-35dB lower than the apparent intended signal. Yesterday, I received an email from a ham notifying me that he and others had heard my station with such signals. I have terminated all WSPR operations pending a resolution, but frankly, am at a loss to understand what may be going on that would cause such unintended interference.

My operations have been based on the following equipment:

Kenwood TS-590S
Raspberry Pi controller running Raspian and WSJT-X (latest version)
Double G5RV (204 foot length off center fed dipole at about 50 feet.
Everything is properly grounded, and ferrite clamp on cores are in use on all cables to limit ground loops and common mode problems.

I ran the TS-590S at minimum power (5W), and did not use transmit processing. I adjusted the audio drive such that it was the minimum level needed to achieve 5W, and without any ALC showing.

The radio connected to the RPi with USB - both the audio (transmit and receive) as well as the CAT control via the USB. No analog audio cables at all.

I do have some good test equipment including spectrum analyzers and oscilloscopes, but can see nothing wrong in the RF domain,

I'm not sure what else to do. Any ideas?


Chuck Kelly W9MDO/VE1MDO