[600MRG] LF-MF antenna advice

[Rudy Severns]

In 1947 Woodrow Smith published the following advice on LF-MF antennas:

 

"The main object in the design of low frequency transmitting antenna systems
can be summarized briefly by saying that the general idea is to get as much
wire as possible as high in the air as possible... and an extensive ground
system..."

 

Take this advice literally!

 

In order of priority:

 

1)      Make the antenna a tall as practical (H).  In an electrically short
vertical the radiation resistance (Rr) varies as the square of the height.
The inductance required to resonate falls roughly as 1/cube root of H.

2)      Maximize top-loading.  Capacitive top-loading reduces the required
inductance to resonate, which reduces loading inductor loss.  Rr increases
with top-loading.  Compared to a bare vertical Rr can increase by a factor
of up to 4 although 2X is more typical.

3)      The higher the tuning inductor Q the lower the losses

4)      When you've maxed out the above then get to work on the ground
system.

 

In a separate note to follow I'll explain how I applied this advice to my
own antenna.

 

73, Rudy N6LF