1. HF Propagation
Direction of Maximum Radiation h

2. Propagation in the Atmospherekm
F2: Separate during daylight, merge w/F1 at night.
F1: Separate during daylight
250 km
E: Daylight Only, Ultraviolet Radiation
Ionospheric Layers
140 km
D: Daylight Only, Particle radiation
90 km
50 km
Presence of ionized particles causes variation in er , leading to reflection/refraction at the boundaries.
fv : the frequency below which vertical transmissions are reflected, 4 – 5 Mhz.

3. “Skip” Commmunication
Multi-hop sky wave q1
Line of sight condition: hr ht
Skip Zone

4. Atmospheric Absorption Attenuation

5. Space Loss/Space Attenuation
Spreading Loss
Space Attenuation
EIRP
Space Loss

6. DO NOT use eq 15-43, 15-44, or 15-45 on page 653!!
Use this Equation!!
DO NOT use eq 15-43, 15-44, or on page 653!!
R and l must have the same units!
Example: Determine received power if transmitted power is 2 watts, f = 450 Mhz, transmit antenna gain is 12 dB, receive antenna is ¼ wave whip, range is 50 km.
=3 dBw + 12 dB – dB + 2 dB
= dBw = dBm ( ~56.0 pW)