A.M. Broadcast Antennas
by W5CDT
Shown below is my 1st prototype of an A.M. broadcast antenna for 1610KHz.
Don't laugh!!!….it's resonant, has a 1.1:1 VSWR, and works AMAZINGLY well.
The goal was to keep it under 9.8 feet in length to comply with FCC part 15.219.
Tuning is very touchy and bandwidth is always narrow for such short antennas for
1.6MHz operation. The capacitive "hat" (a pieplate) was my lazy way of lowering
the frequency by adding capacitance. To be strictly FCC legal you should
resonate your antenna without the capacitive "hat".
Shown Below is my 2nd prototype with tuneable loading coil
Below is a close up of the tapped loading coil and tuning capacitor arrangement
3D simulation of antenna radiation pattern
cross sectional power plot relative to 1/4 wave antenna
After getting it all working I weatherproofed the air variable
capacitor in a nice box as shown below in the two photos...
it's hard to see the box in the right photo but it IS there.
Updated 12/3/1999