Greyline Index Page:- Propagation research. Recordings of Signal Strength to Observe any Dusk/Dawn Greyline Enhancements.  These will also give a record of the propagation on the paths during the recording period. Please excuse any missing pages and images, I only have limited space so have to delete older pages, sometimes leaving something behind. Hopefully I can find it all if anyone is interested.

CURRENT OBSERVATIONS March 2015. I am still making recordings, currently 5025, 4840, 4450, 4835, 3320KHz.Recent  monthly zip files here in the same format as those below. My Charts, SpecLab text files and waterfall captures are available if you contact me. 

Believed Pyongyang November 2009  December 2009 January 2010  February 2010 March 2010 April 2010 May 2010  June 2010 July 2010  August 2010 September 2010 October 2010 November 2010  December 2010 3250.03KHz. Not yet identified but the only station listed and results consistent with those expected. January 2011 Continuing but with the addition of 2850KHz, another Pyongyang station.  February 2011  3480KHz added, a station near Pyongyang. March 2011 3250, 2850 and 3480KHz

2310KHz and 2325KHz Another look at Northern Territory stations, Alice Springs and Tennant Creek. SDR enables one receiver to monitor both, so a comparison of propagation. 2310/2325KHz Jan 2011   2310/2325KHz February 2011  2310/2325KHz March 2011

Sao Paulo Brazil on 3325KHz. 3325 January 2011 3325 February 2011 3325 March 2011

Screenshots of the OK0EU beacons on 3.594.5MHz https://sites.google.com/site/g4zfqradio/ok0eu-beacon-screenshot-3-4-august-2010 These SpecLab waterfalls are optimised to show frequency variations. This shows the variations  in frequency due to movement in the refracting layers. Often several different paths from different layers can be seen. 

Understanding my Charts. Click here A note regarding signal to noise ratio. https://sites.google.com/site/g4zfqradio/signal-to-noise-wspr-users-note?pli=1

SUMMARY:-  I have been observing various low frequency paths for at least six years now. The RSGB study intrigued me and these enhancements are mentioned by DXers, some who seem to claim to be able to predict them. I have not found any detailed studies, most references give a fairly vague summary.

I have not examined many paths, suitable continuous, identifiable transmissions are rare. Two I have looked at in detail are  the paths between here and Africa and  Australia . While these paths show enhancements they are by no means consistent or regular. Many times there are no peaks, when they do occur the time of peaks varies and often the strength of peaks is lower than signals at other times during the night. It seems to me that the longer paths with a relatively short-lived darkness path are more likely to show significant dusk/dawn enhancements. I think this may be because although many signals do show an increase in strength around dusk and dawn "normal" overnight propagation is likely to produce stronger signals. Different paths may vary a lot. From North America I see little in the way of enhancements, in general signals rise and fade, are weaker around dusk and dawn. The signal from Ecuador is different, usually it gradually increases through the night, a peak after dawn here is not unusual, I continue to monitor this. The path from here to Korea is showing dusk/dawn enhancements. July 2011 I'm looking at Sao Paulo, Brazil, signs of enhancements but like other paths not very regular and often not significant..

Observations that are made only at dawn and dusk can be misleading, it is not unusual to see a drop in strength after dusk before the signal rises to a significantly higher level. There is often a drop in strength before a smaller peak around dawn. 

Some seem to suggest that when both stations are mutually in sunrise or sunset signals are especially strong. Opportunities to look at this situation are rare, it happens for short periods each year on only a few paths, except for stations near the antipodes. ZLXA, 3935KHz,  is close to that with me but the problem then is that there is no non-greyline propagation to compare. I do not feel that signals from there peak particularly strongly, even on that path the timing of actual peaks are variable. The path to ZL is open regularly on 80 metres, maybe because many variations in the path are possible. The RSGB conducted tests with VP8FI, the African stations are mutual at times but I have yet to see any exceptional propagation effects.  Sao Paulo, Brazil, 3250KHz, seems to refute this along-the-greyline path. No sign of enhancements during the mutual period but occasionally some good ones when there are a few hours difference.

This along-the-grayline effect may well be true for higher frequencies. Since WSPR has been in use some seem to have observed peaks around sunrise and sunset. BUT reporting when "greyline enhancement" occurs also requires reporting when it does not, how reliable is it?

The effect has been reported on higher frequencies, but I am not aware of any suitable transmissions that are on for long periods. The amateur beacons are an exception. The NCDXF beacons are continuous although they only transmit for 10 seconds every 3 minutes and can be subject to interference. VE3NEA has a program to monitor them but it is shareware.  Using this during the trial period I have seen no greyline peaks. The beacon DK0WCY on 10.144MHz could be observed, but mode changes make this difficult. Most other regular ones are on 10 metres or above although some personal QRP amateur beacons are setup..

Note I mark sunrise and sunset times on my charts as a reference. Sunrise and sunset at the ionosphere is likely to be more relevant.

I mainly use broadcast stations, a few in the tropical bands are identifiable and on all night. They could be observed and recorded from most places around the world. I would be interested if anyone else could join in. Can anyone demonstrate reliable Greyline? I will do my best to help someone get started. I have tried to describe my techniques on other pages, see my index below. 

 November/December 2008,  I am looking at Guayaquil 3810KHz 3810 January 2009 3810 February 2009 3810 March 2009  Around this time the signal is definitely peaking after my dawn!  3810 April 2009  3810 May 2009  3810 June 2009  3810 July 2009  3810 August 2009   3810 September 2009  3810+3340 October 2009  3810(off air) +other S. Americans. November 2009   3810+other S. Americans. December 2009  3810+other S. Americans. January 2010   3810+other S. Americans. February 2010  3810+other S. Americans. March 2010  3810+other S. Americans. April 2010    3810+other S. Americans. May 2010   3810+other S. Americans. June 2010  3810+other S. Americans. July 2010    3810+other S. Americans. August 2010   3810+other S. Americans. September 2010  3810+other S. Americans. October 2010  3810+other S. Americans. November 2010 3810+other S. Americans. December 2010

Recordings of North American stations. 5070/5025/3330KHz. August 2008. 5070/5025/3330KHz. September 2008. 5070/5025/3330KHz. October 2008. 5070/5025/3330KHz. and also Boston 1510.02KHz November 2008. .. 5025/3330/1510.02KHz December 2008. 5025/3330/1510.02KHz January 2009 5025/3330/1510.02KHz February 2009 5025/3330/1510.02KHz March 2009 5025/3330/1510.02KHz April 2009 5025/3330/1510.02KHz May 2009  5025/3330/1510.02KHz June 2009 5025/3330/1510.02KHz July 2009 5025/3330/1510.02KHz August 2009  5025/3330/1510.02KHz September 2009 Mid September:- stopping 5025 & 3330, year of these with little sign of dusk/dawn enhancements. Continuing 1510 1510.02KHz October 2009 

 Tajik Radio 4765KHz .. Continuing December 2008 4765KHz January 2009 4765KHz February 2009 4765KHz March 2009 4765KHz April 2009  4765KHz May 2009 Not particularly good because of a break in Transmission over Tajik night.

December 2008 A Look at Australians? on 1701Khz Continuing January 2009 February 2009 March 2009

Recordings of 3396KHz Gweru Zimbabwe to end of June 2007:  4828KHz. July 2007: 4828/3396KHz. August 2007. Including a simultaneous look at RSG Meyerton 3320KHz. 4828/3396/3320KHz. September 2007.  4828/3396/3320KHz. October 2007: 4828/3396/3320KHz. November 2007: 4828/3396/3320KHz. December 2007:  4828/3396/3320KHz. January 2008.  4828/3396/3320KHz. February 2008. 4828/3396/3320KHz. March 2008. 4828/3396/3320KHz. April 2008. 4828/3396/3320KHz. May 2008. 4828/3396/3320KHz. June 2008. . 4828/3396/3320KHz. July 2008. 4828/3396/3320KHz. August 2008.   4828/3396/3320KHz. September 2008. 

ZLXA 3935KHz. Identity was unlikely to be positively confirmed. But thanks to it's distinctive carrier and ZL1BPU....! August/September 2006   Recordings of ZLXA 3935KHz. July 2007   Recordings of ZLXA 3935KHz. August 2007  Recordings of ZLXA 3935KHz. September 2007  Almost daily recordings from September 2006 to September 2007 - contact me.

Notes on using SpecLab to observe and make recordings

 Some Examples of Dusk/Dawn Enhancements on Various Stations. Some Techniques used to identify stations.

 Recordings from VP8FI on Various Frequencies    These are attempts to record "true greyline". November-December 2004. Note my 2011 observations of Sao Paulo, Brazil, (See above) seem to be showing that NO enhancements can be expected when sunrise and sunset are mutual. BUT do occur when they are NOT mutual.

Notes About Some Stations Observed.  Although I am reasonably certain of the identity of stations recorded some depend on observations made by others. All seem to conform to expected propagation along the stated path.


Below, a list of most of the many recordings I have made. My ISP only gives me 10MB of space here. Please email if interested. 

3 Sept 2006 ZL1BPU on 3518.0000KHz based on Rubidium standard. 

Recordings of ZLXA 3935KHz. October 2006 November 2006 December 2006 January 2007 and carrying on through June 2007

Recordings from 5019.874KHz Reported to be Solomon Islands but unlikely to be absolutely positively confirmed. Shows some peaks around Solomon Is. dawn.  November 2006 December 2006 January 2007 and carrying through June 2007.

12 Recordings 10-15 May 2006 of various stations

Recordings. 15 May 2006 on - Mainly Christian Voice Lusaka 4965KHz with some others mixed in. 

Christian Voice, VOA 4930KHz etc. July 2006 August 2006 Including mutual greyline period.

Recordings of Radio Sonder Grense, Meyerton. 3320KHz. May/ June  2006, July 2006, August 2006. Including mutual greyline period. September 2006. Recordings restarted August 2007 as a comparison for the Zimbabwe stations.

Recordings showing the few recordings from Alice Springs 2310KHz when signal strength was higher than normal. Jan-April 2005

Recordings on 2310KHz from Alice Springs Australia .  Jan-April 2005

Australia Continued  Recordings from Northern Territory stations. 120 metre band. Mainly Alice 2310KHz. October 2005. November 2005  December 2005 January 2006 February 2006.  March 2006. April 2006

Recordings from Perth Western Australia on 1619.965KHz  October/November/December 2005

Recordings from Sydney? New south Wales Australia on 1701.076KHz  November/December 2005

Recordings from Sydney? & some others Australia on 1701/1620KHz January 2006 1701/1620KHz February 2006

Some more recordings of AM, Medium Wave stations. Oct 2005

More miscellaneous recordings of Medium Wave stations. February 2006 

A Study of WDHP 1620KHz USA Virgin Islands.

Recordings on 3210KHz from Nashville USA Dec 2004 onwards Oct 2005. On 3215KHz now some from July 2008.

Recordings on 5070KHz from Nashville USA. Oct 2005 Restarting July 2008 to November 2008.

A Comparison of reception from Alice Springs 2310KHz and Perth 1620KHz on 31 October 2005. Shows SpecLab "waterfall" (sideways) and Excel chart derived from the saved data. A similar reception pattern seen.


G4ZFQ Index page.

Click link to email  If you see no link or it does not work Click HERE  Please include "Greyline" in  the Subject Line. Make the subject VERY relevant - with the amount of spam I get an email from an unknown source can easily be discarded!

Grayline - alternative spelling.