WSPR-SNR-Plot-v-WWCR

I am interested in investigating sunrise/sunset enhancements. Over the years I have done long-term checks on signals from various locations. These have been tropical band broadcast stations and time signal stations.

Some time ago I looked at signals from WWCR, Nashville Tennessee and Cuba. I established that on this path to my location at the South of England that there were few signs of any dusk/dawn enhancements. In general signals gradually rose to a broad peak in the middle of the night and then gradually dropped. I have always recorded signal strength, the SNR of received signals is sometimes maintained due to reduction of noise level after dawn. My charts below show this with WWCR's signal.

When I was using WSPR on 60 metres, 5MHz, a few spots from American stations seemed to indicate an improvement at my dawn. I decided to investigate.

So far I have not done many checks but it seems that sometimes there is a broad peak when USA stations receive my signal at a better SNR. This does not seem consistent with dusk/dawn enhancements seen on other paths. Unfortunately WSPR does not report actual signal and noise levels which would show exactly what is happening.

I use "SpecLab" to record signal and noise NOTE:- IGNORE MY SpecLab SNR MEASUREMENTS This signal is much stronger than I usually look at, sideband energy has affected my noise readings. I hope I have corrected this. levels from simple "Softrock" receivers. The chart below shows my reception of WWCR on 4840KHz with spots of my WSPR signals on 5.2287MHz as received by K9AN added. K9AN is about 280 miles from WWCR, not too far when propagation has settled for the night.

At the top are the WSPR spots, SNR dB, joined by lines.

Below is the trace of WWCR's signal strength. The dB scale is not calibrated, just relative.

At the bottom the dark blue line is the received background noise level around WWCR. The light blue trace is the difference between them, the SNR as measured by SpecLab. IGNORE

The two SNRs are not comparable, one represents how I receive WWCR, the other how K9AY receives me. But if K9AY's noise level varies like mine then that would explain the variation in the WSPR SNR he reports.

If an average is drawn then the WSPR SNR more closely follows the WWCR signal strength trace.

This is assuming that propagation of WWCR and K9AN between my station in the South of England is similar and that the path is reciprocal. From simultaneous monitoring of signals on different frequencies and different locations I believe this is a reasonable assumption BUT paths are not always reciprocal.

Below, the next day. W8AC, 480 miles from WWCR, provides some early spots, K9AN later.

Again the average follows the WWCR signal strength trace. W8AC seems to have better reception as it looks as if my signal strength would have been lower than when K9AY appeared. But K9AY must have the record for the number of -33dB SNR spots he gives!

WWCR does not start transmission until 01.00, clearly seen in the top chart, not so obvious in the lower but the SpecLab waterfall indicates it is the stronger signal, on a slightly different frequency.

On the night 21-22 November 2011 several USA stations were on, including K9AN and W9AC.

This time the two USA stations reported an increased SNR around my sunrise. This does not really follow the WWCR signal. This shows a short peak, maybe 2dB above the 03.20 level.

Around 08.40 the US station's reports of my SNR is still high considering that WWCR's signal is dropping considerably. At 09.22 when W8AC last spotted me, -29SNR, WWCR was at -70dB.

G3TQH was given -25 at 09.32 by W8AC.

I need to know the noise level at the other end.....

Over this night no real peaks. But the SNR again seems to be maintained when WWCR is dropping. My last spot from W8AC at 09.24 was -24. WWCR was at -65dB.

All I can do is speculate whether the noise drops in America or whether TX/RX propagation is not reciprocal. I know the frequency and paths are slightly different but in my experience propagation would be similar, at least in one direction.

The "enhanced" SNR is not too common, this is the next time I observed it. Again no correlation with WWCR (or 5025KHz Cuba). Again, one way enhancement or drop in K9AN's noise?

What is needed is SpecLab observations at each end of the path.

Even two way WSPR reports would be a help, one day I may try 80m but I don't think my 1 watt will be so effective and the database is likely to be much larger.

Index to some of my many recordings, other paths do show significant dusk/dawn enhancements!