blacklogo_orangetext.gif (13932 bytes)When will the eclipse effect the radio signals...

WB01547_.gif (1452 bytes)

An important thing to note is that the maximum effect on your radio signal WILL NOT be the same as the eclipse is at its maximum overhead.

The radio wave between you and your contact will experience the maximum effect from the eclipse when the eclipse shadow and the point where the radio wave bounces off the upper atmosphere, are the same. (See section on best locations ).

For instance you are in the Midlands in the UK and you are doing this experiment with someone if South Eastern France about 800 km away. Neither of you are actually under the path of totality, but still both within about 80% eclipsed region (see below) .You are may be working on about 4 to 5 MHz .

path0.gifBefore the eclipse
(click on image to enlarge)

At 11:11am on Wednesday 11th August  the eclipse will be a totally eclipsed in Cornwall and Devon. For you in the middle of the England the sun's face is at its maximum obscured at about 95% covered. You have been monitoring the strength of a CW transmission from your contact in France and the signal has started to increase .

path1.gifAt 11:11am  BST
(click on image to enlarge)

After 11:11am if you keep monitoring the strength of your radio signal from France, you will see it continuing to INCREASE in its level AFTER the eclipse has passed its optium for your location. The rate of increase in signal will probably be getting greater.

At about 11: 20am the signal will probably be at its maximum. This is because the eclipse shadow is now pass the approximate point where your radio wave is reflecting like a mirror off the ionosphere (see below).

path2.gifAt about 11:20am BST
(click to enlarge image)

The strength of signal (reading on your S-meter) will probably start to decrease now. The rate at which it falls could be quite different from the rise you experinced earlier.

At 11:30am (Bristish Summer Time which is the same as 10:30 Universal Time) your French contact will witness the maximum effect of the eclipse overhead. About 80% of the sun's face will be obsecured .

path3.gifAt about 11:30am BST
(click to enlarge image)

If you are under the path of totality in Devon or Cornawall...

Hopefully you will experince something similar especilly if your  contact also lies  ALONG the path of totallity or within the 90% eclipsed region.

path5.gifAt 11:11am

path6.gifAt about 11:20 am

path7.gifAt about 11:30 am

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11/05/1999 Ruth Bamford