40M LP and SP Take Off Angles

The F1 layer exists only in summer, and during the Northern Hemisphere Winter, our F2 layer means that we get more distance covered by each hop. At ZS they have both F1 and F2 because its their Summer.

ZS6CCY has a low take off, high gain antenna – 3 element yagi up high on 40M. This is why he always will be doing most of the work. Here is the Short Path:

My lower take off phased array works best after our sunset. I’m going to guess that my first hops – that would go over the US, would benefit if they did not bounce off land – so the lower angle prevents this. ZS6CCY has gain, low takeoff angle and salt water on both SP and LP for the first hops.

During the morning sunrise at my QTH, my rotatable dipole, with a higher take off angle does best – and I can only imagine it has more to do with me bouncing off water – and maybe its also because the F layer is rising. I’m still not sure why a higher take off angle is better . . .

Here’s another variable. My terrain. During the nightly SP – my east direction has an immediate hill that I have to try to go over. Why my lower take off angle antenna is best is a mystery. For the morning long path – I have a lower hill to get over.

  • Terrain seems to not matter
  • The charging of the ionosphere and the F1 and F2 composition seems to be one part of this puzzle
  • The fact that I am bouncing off salt water means whichever antenna supports more water and less land seems to be a second part of the puzzle

The wild card would be some kind of chordal hopping or ducting is happening during my morning sunrise. The higher angle would get the signal in the duct where the ionosphere is charging and rising, and it requires a higher angle to do so. If you look at the Long Path – both stations have sunlight. On the SP – both are in dark. This has to be a key variable. If I had to give my answer – I’d say chordal hop or ducting happens when both stations are in sunlight.

On page 49 of the Ian Poole (G3YWX) book “Radio Propagation – Principles and Practice”, this situation does seem to be a very strong possibility. He even shows a diagram where indeed – a higher angle would be helpful, and a low angle at ZS6CCY’s QTH would not matter.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: