In June 2008 I started the most
complex antenna project since I got a ham:
The first antenna should be a full size 80m dipole. To handle lightning
protection the dipole will be build in some distance from the house.
A rented skid loader helped a lot to dig grooves for the
cables.
These pictures show the longest groove from the house the to
antenna in about 60m distance.
Unfortunately this groove crosses our doorway. Therefore I
hade to remove and later to replace the pavement which was a lot of work.
Every 10 meters I build an inspection point which makes it
easier to draw the cables into the burried pipes.
In the background you can see the ground strap. This will
also be the mounting point for the lightning protectors.
The other end of the pipe ends at the antenna tower. Another
pipe with all cables then ends directly below the shack.
Antennas for the lower bands 80m and 40m:
for a long time I evaluated different multi
band antennas, like
FD4, Trap Dipoles, Multi Band Dipoles from Kelemen or Fritzel etc.
As ideal solution I choosed a full-size 80m and a full-size 40m Dipole
connected to a single 1:1 balun. With an angle of over 60 degrees the two
dipoles do not effect each other in any way. The big advantage is that I
can feed it over a single cable and do not need any components for tuning.
Measurements:
the dual band dipole was measured with the FA-NWT network
tester, published in the German Funkamateur magazine.
After only 2 tries for 80m and one try for the 40 m band the antenna
was tuned to the right length and worked perfectly.
The picture on the left shows the SWR on both bands.