Transitional frequencies every 2 MHz between the night and
frequencies will be needed to maintain 24-hour communication.
For nets in which all stations are within 25 miles of one another, a
frequency between 12-20 MHz will make the best use of the ground wave
using a 15-foot whip.
Using a 15-foot whip you can expect only a 30 percent reliability for
a 24-hour period.
Using a 32-foot whip you can expect only a 50
percent reliability for a 24-hour period.
Using a doublet, sloping
wire (quarter wave long) for inverted vee you can expect a 90 percent
reliability for a 24-hour period.
Four frequencies should be
available, anything less, reliability will decrease.
A change in
frequency at other than the times indicated will vary. There will be
times when fewer frequencies are required.
See page 121 for
MUF - Maximum Usable Frequency.
FOT - Optimum Working Frequency.
LUF - Lowest Usable Frequency.
SSN10 - Low Sunspot Number 10.
To make communication more difficult, most of our HF nets have
frequencies assigned in the 2 and 3 MHz range. On closer examination
those assignments are flawed. Even though the LUF is 2 and 3 MHz and
should work for distances less than 100 miles, look closer, it is for
We should use the whip's LUF not the doublet,
because of power loss it's the worst antenna to use.
whip's LUF in most cases is the MUF. A better frequency assignment
for day and night is 6.7 and 3.4 MHz. Even so the reliability is 0-