40-meter Groundplane with 4 Sloping Radials
Free Space
7.150 MHz
8 wires, feet
5    0 0 30     -23 0 7   #12
5    0 0 30      23 0 7   #12
5    0 0 30     0 -23 7   #12
5    0 0 30     0 23 7    #12
2    0 0 30     0 0 40    1"
2    0 0 40     0 0 49.5  .875"
2    0 0 49.5   0 0 58    .75"
2    0 0 58     0 0 63    .625"
1 source
20,100,0
0 loads

The sloping radials raise the input impedance to 50 ohms.  This antenna
illustrates how MN can model radiators employing telescoping tubing.  Try
making the entire radiator of 1" tubing to see the effects of the tapered
radiator.