Old Receiving Magnetic Loop Antennas _006

ANTENTOP- 02- 2004, # 006			Old Receiving Magnetic Loop Antennas


switched to the feedline instead of crosspieces between clamping contacts K1K2 and K4K5. These contacts were established inside the box. Feedline contacts K3K6 were installed at a cheek of the box. However 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 Receiving basket 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. Basket 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
A 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 [3]). So, at a small own capacity a loop has high Q. There 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		that is 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 used.

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