This is a rear view of my Jeep with the homebrew 20,40 and 75m antenna mounted. The design of this antenna was done to allow the greatest size possible without excessive wind load. Assuming most interstates allows for 13'6" truck clearance, this antenna is 13'4" from the road bed. So the first option to be eliminated was a capacity hat. This called for a bit more coil but I found that the capacity hat didn't reduce the coil enough to make a significant difference. I also wound a farily large coil to maximize the Q, so some tradeoff was required regarding wind load.
A bandswitch was added because I didn't want to play with alligator clips, and the resistive losses of such a poor connection. I used a heavy (20Amp) type porcelin based switch from a decade power resistor substitution box. I'll detail as much as I can here and in the following pages. I have more photos to scan in on some of the construction technigues so you may want to check back in a few weeks as I develop the details further, but everything will be described for now.
The mounting required that a standoff bracket be attached to the roof. I made this from Lexan and brass plate. Lexan is incredibly tough, much more so than Plexiglass. It had to be waterproof and UV tolerant. I also offers some slight flex which isn't a bad thing.
Next Page