the feedline instead of crosspieces between clamping contacts K1K2
and K4K5. These contacts were established inside the box. Feedline
contacts Ê3Ê6 were installed at a cheek of the box.
small-sized magnetic loop antennas were used not only to Broadcasting
Radio Centers. Earlier, in 30-50 years of the 20 Century such antennas frequently
installed inside broadcasting receivers. Some designs of
the inner loop antennas
are shown below.
Basket Magnetic Loop Antenna
loop antennas were widely used for work with LW and MW receivers
of direct amplification since of the end of 20s of the 20 Century.
As a matter of fact, basket loop antennas are ones of the first
types of magnetic loop antennas used by radio amateurs. Basket loop
antennas were used both as to stationary receivers as to so called
“suitcase receivers’, i.e. tube receivers made inside a suitcase
and intended to a movable work. Old radio magazines of 30- 50s of
the last century contained hundreds designs of basket loop antennas.
loop antennas were earlier so popular because, in the first, ever
a radio amateur having
a minimal experience of designing easily can make this one, in
the second, a basket loop antenna can be made of any improvised
material, and in the third, a basket loop antenna made even in
home conditions works very effectively. The essence of the design
of a basket loop antenna is that at its winding the step between
turns is constant and equal to the diameter of the used wire (practically
this step even bit more).
Figure 3 Small-sized receiving loop of a rural Broadcasting Radio Center
coil, which has been reeled - up with such step, has rather small
own parasitic capacity of turns to each other. It is possible
to show, that the more parasitic own capacity of a coil is the
less its Q is (see, for example, reference ).
So, at a small own capacity a loop has high Q.
are several basic points to pay attention at design of a basket
loop antenna. A basket loop antenna can be reeled up on a plate
from any dielectric stuff having small losses on frequencies where
the antenna works. A basket loop antenna of LW- MW ranges can
be made of a cardboard, wooden plate, PC- board, getinaks or ebonite.
Pay attention, that some grey cardboard made of so-called "not
washed" recycling paper (a paper
not washed off typographical paint) can have a big losses at LW-
MW ranges, at least, in a microwave this cardboard is strongly heated
up. Certainly, do not use the grey cardboard for a form of a basket
loop antenna. Odd number slots are made in this dielectric plate,
the more slots are done, the winding has more density Number of
turns and sizes of an antenna form are depended on frequencies range