Thursday 29 January 2009

Greyline Propagation

I few years back I was working on grey line propagation studies as part of my work with the RSGB's Propagation Studies Committee. For those who do not know what grey line is, here is a feature that was written for the RSGB's RadCom magazine. It is available in HTML form without images here or as an Adobe Acrobat PDF file with images (701kb) here.
Feel free to download them.
The first part of the research looked at trans-terminator propagation on 10m. That is, signal enhancements that are sometimes seen when signals arrive from areas to the west that are currently experiencing their local sunset. For this, Geoclock software was used (see, but the parameters are changed to show the illumination at both the D and F layers. This is done by following the instructions in the package. Signals were logged using DL4YHF's excellent Spectrum lab software (see
The resultant data are processed using MS Excel and graphs can be produced like the one here. Enhancements were seen on signals from the OH9TEN and SV3AQR beacons, but it didn't happen every day. The phenomenon was called skip focusing.
Updates You can also look at the latest trans-terminator results on 3210kHz (October 2005). Radcom published the results of the first round of tests in May 2005 - you can download it in PDF format (500kb) This is the original presentation on Greyline and the studies given to the RSGB Convention in 2005 (20Mb download - PDF.
Download the "3Y0X Propagation Predictions to G v Reality" presentation given at the RSGB's HF convention in October 2006 in either Adobe Acrobat PDF or Powerpoint formats (both 5mb). While not strictly about greyline it does show the effect of morning/sunrise enhancements on 80m very well. (October 2006)

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