Gray Line Notifier

I’ve always been kind of fascinated by gray-line propagation. The gray line is a band around the Earth where night is turning into day and day is turning into night. Theories differ as to why, but radio propagation along the gray line is often very efficient. NA5N has one explanation of the phenomenon.

This morning, while walking to our ham radio club breakfast get-together, I got to thinking about how I might be better able to take advantage of gray-line propagation.Because this phenomenon is so short-lived, it’s easy to miss the gray line. How cool, I thought, would it be if I could come up with a program that would inform me when my QTH was beginning its transit through the grayline.

I thought up several ways to get my computer to do this. Then, it occurred to me that I should be able to write a Web application that hams could sign up for that would either send them an e-mail or send them a Tweet when their QTH was about to enter the gray line. And, coincidentally, I might be able to sell some advertising to pay for this and maybe make a few bucks off it.

I’m tentatively calling this application the Gray Line Notifier. I talked up this idea a bit at our breakfast this morning, and the guys noted that there are already may gray line maps on the Web, but none of them can be programmed to send you notices. We chatted a bit more about this, and came up with a couple of features for this app, including:

  1. Will send either an e-mail or a Tweet, when a ham’s QTH is about to enter the gray line.
  2. Include information about other countries/grid squares that are also along the gray line.
  3. Perhaps interface with a DX spotter to see if there is good gray line propagation at the time.
  4. Beam headings to take advantage of gray line propagation.
What do you think? Would you sign up for this service? Can you think of any other features that I might include?


  1. Ned Davis WB4BKO says:

    Sounds like a great idea. I think it would be very useful. When and where do we start? Keep me posted.

  2. David Brodbeck N8SRE says:

    Many cell providers offer an email-to-SMS gateway. It would be nice to offer an option to generate a very short email message (less than 160 characters, including the subject) for users who want to send the notifications to their phones.

  3. The view through the window is a big clue about whether we are in greyline!

    I’d be more interested in a tool that calculates what times of year my greyline coincides with that for some DX station that I’m hunting on the low bands.

    73 Gary ZL2iFB

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