Propagation

Question 1

What does electromagnetic radiation comprise of, what’s always the case with this

Answer 1

An electrical field and a magnetic field, at 90 degrees to each other

Question 2

How does ground wave propagation work

Answer 2

No bouncing off the ionosphere.

Straight to other station, bent down by ground as signal gets absorbed

Low range, espcially at high HF

Question 3

What does sky wave refer to

Answer 3

Using the ionosphere to refract signals back down to each

Distance you can refract signals depends on which layer is used

Question 4

D-layer:
What is it, how far above ground does it sit

Whats the problem with using it for propagation
What time is this worst at

Answer 4

Lowest layer within the atmosphere, about 60-90km above earth

Molecules are closer together, so when they become charged (peaking at noon), they absorb radio waves below certain frequencies

Usually anything below 6MHz during the day won’t work
But works at night as D-layer vanishes

Question 5

D-layer:
What are Lowest Useable Frequency and Maximum Useable Frequency

What happens if LUF is higher than MUF

Answer 5

LUF: Lowest frequency possible that can pass through the D-layer without significant absorption

MUF: Maximum frequency that can be used for transmission over a given path at a given time

Both constantly changing, if LUF is higher than MUF then you can’t use propagation (for the given path at that time)

Question 6

E-layer:
How far above ground does it sit

Answer 6

90-150km