You don't have the space to put up a full-size dipole for 40m ? No problems ... here comes the SHORTYFORTY !
This antenna is quite critical, so it is important to construct is with utmost care, especially regarding symmetry ! In general, what 'looks nice' will work very well !
|2x 20,5 turns of 2.5mm˛
ordinary copper wire PVC insulated on PVC tube (resistant to heat, 3mm
thick wall) dia 50mm
In the centre, flatten the tube with a file to position the SO-239 connector.
Start the 4 windings quite wide, this because you will have to connect the feed. Make them absolutely symmetrical!
|Detail of the SO-239 connector. It is riveted, the copperwire is
fixed with solder lugs, which are soldered to the connector for a
perfect connection. You see the tap at 2 turns, this gave the best SWR
Windings are kept in position with PVC glue (preferably the 'hard type')
|Inside of the tube, you see the small hookup wire going from centre
of SO-239 to the 2nd winding.
Before affixing the SO-239, prepare this wire and insulate with heat shrink tube to protect against moisture
Then, with long nosed pliers, insert through hole you drilled next to second winding
|Detail of connection to dipole wire, which is flexible copperwire
2.5mm˛ PVC coated, each arm 4m53 long (cut at least 20 cm longer to trim
for your construction!)
Use crimp lugs which you solder and cover with heat shrink tube. Apply grease/vaseline to hardware (M5 bolt / nut / grower)
|When everything is ready and tested, protect the coil with coating (I use a spray for car body protection - it is flexible and resistant to UV light|
|The completed antenna, only 9m40 long about
As the centre coil is quite heavy, I recommend to feed it with RG-58 instead of RG-213