MAG - LOOP AERIAL


This is my example of a "magnetic-loop" receiving antenna.
There is plenty of info on the web about how and why these things work.
I would recommend the following as a very good example.
Loop antenna website
I have used the hula-hoop (75cm diameter) as a means of supporting the coil turns needed for the "loop"
Using a discarded hula-hoop; I ground 2 small slots on the outer-facing surface, approx 10cm apart, each side of the 'double-bung' joiner.
I then fed two 4 pair cables (16 turns) through the hoop. (CAT 5 ethernet cable)
All I would then need to do, is to join the finish and starts of successive turns (in "series-aiding") to give me a 14 turn primary, and 2 turn secondary.
As all cores are colour coded and traced, this is relatively easy.
See schematic below for details of the connection.
I have included a 12 position single pole rotary switch.
This achieves both the purpose of a tap-changing coil, and uses the switch connection as termination points for all of those wires!
Coil inductance for various tap switch positions was measured and tabulated using my LC meter : see schematic.
The combination of the selectable taps and the tuning capacitor, should allow the loop to be tuned over all of the MF and much of the HF spectral assignments
i.e. 300 - 3000KHz, and 3000KHz - 30MHz
The switch, 500 pF tuning capacitor and all wiring are included in a weatherproof, electrical junction box.
The J.B. is affixed to a length of metal tube,
and also a flat polycarbonate strip to which the (light-weight) hula-hoop is fastened with some cable ties.
From surburban Perth WA (during winter nights mostly) I regularly listen to MW broadcast station 1566 KHz - 3NE Wangaratta (N-E Victoria), at good strength, on an untuned 'long wire' aerial.
This is a (DX) distance of 2850 Km. (Great circle path)
However, on the same channel there is a 1 Megawatt ( YES! 1 Megawatt ) broadcaster in Nagpur India which causes some interference.
This powerful Indian station has been monitored in Europe and Russia (google: 1566 KHz for Info')
As Nagpur and Wangaratta subtend an angle of about 150° at my QTH,
I should be able to use my loop to null out the interfering and magnify the desired station!
Nagpur 'nulled' and Wangaratta 'boosted' !