RadioBanter - Modified MFJ Cobweb Antenna

An article in QST several years ago, described an "Octopus" antenna
consisting of four pairs of mobile whips arranged as dipoles, all fed in
parallel with a single co-ax. Since then, I have been using one in my
attic with 80, 40, 20 and 15 Meter whips. I added a 4 foot vertical
whip for 10 Meters.

With a tuner, the Octopus antenna works OK on 20 through 10 Meters.
However it stinks on 80 and 40. So a few months ago I added an MFJ-1788
36" loop antenna for use on 40 Meters. It is a pain to use, but works
better than the 40 Meter mobile whip dipole.

This arrangement still left a lot to be desired, so I recently replaced
the Octopus with an MFJ-1835 "Cobweb" antenna. This is a horizontal
loop antenna with 5 sets of dipoles covering 20 through 10 Meters. It
is built-in to the attic, and would have to be Un-built to remove it!

A tuner is still needed for wider bands, but the Cobweb definitely works
better than the Octopus. The 36" loop antenna is still a nuisance due
to its EXTREMELY sharp tuning, so I added a 40 Meter element to the
Cobweb. Using insulated wire, I stapled two quarter wave wires to the
rafters inside the attic. They were connected in parallel with the
other Cobweb elements.

The first try resonated at the low end of 40 Meters, but had a "notch"
in the SWR curve. It seems that the nearby 36" loop was interacting
with it. By completely removing the 36" loop from the attic, and
folding back about 3 inches of each element, the antenna now resonates
at the center of 40 Meters. It seems to be working at least as well as
the 36" loop, and better than the mobile whip dipole on 40 Meters!

One feature of the Cobweb arrangement, is it is somewhat
omnidirectional. The mobile whip dipoles are somewhat directional, in
addition to being less efficient.

Fred
K4DII