WSPR vs SSB

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W6LVP
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Joined: 2015/03/08 - 03:56
WSPR vs SSB

Each each evening starting about 0230Z, a group of us in Canada, the US, and even some DX locations assemble to exchange signal reports with Danie, ZS3D, in South Africa. Danie gets up very early every morning to work with us and has been doing this now for more than 7 years. Based on frequency use and QRM, we try to operate on 7.156 MHz. This is an open informal net and everyone is welcome to join us.

We have implemented a protocol where the names and call signs of the participants collected between 0230 and 0300Z are provide to Danie via the Internet. Starting at 0300Z, Danie works down the list making contact with each person without a pileup or QRM.

Motivated by both poor summer conditions and the near bottom of the sunspot cycle, we use WSPR as a tool to give us an idea of how the SSB contacts might go. We have four dedicated 5 watt 40 meter WSPR transmitters in Southern California (my location), Arizona, Georgia, and South Africa. Using the exchanged WSPR reports from these four stations, we are learning how to correlate WSPR SNR reports with SSB reports.

Although the correlation is still evolving, it seems that a WSPR SNR of -17 dB from a 5 watt transmitter produces a 55 SSB signal report from a transmitter running 1 KW. For continuity, we use the same antennas for WSPR and SSB.

For simple arithmetic, assume that the lowest detectable WSPR signal report is -27 dB. That means that a half watt (10 dB lower than our 5 watt transmitter) WSPR transmitter produces a readable signal (-27 db SNR report) that requires 1 KW of SSB to equal with a 55 verbal report. That's a whopping 2,000 times (33 dB) advantage. Way to go, Joe and team!.

Larry
W6LVP