1. Magnetic loop antennas
Roger reini, kd8cse
febrUary 2017

2. Two types of loop antennas
Large Loop – size ison the order of a wavelength (quad, delta)
Small Loop – size is much smaller than a wavelength
This presentation will deal with SMALL loop antennas

3. Magnetic loop antenna? Alternate term for the small loop antenna
Refers to the fact that they respond better to the magnetic component of an EM wave and transmit a large magnetic component in the extreme near field (< 0.1 wavelength distance)
In far field (>1 wavelength), the EM waves naturally have E and M components

4. Antenna basics
Diagram of a small loop antenna
Equivalent Circuit

5. ANTENNA PARAMETERS Pick any TWO of the following:
Small size (in terms of wavelength)
Efficiency
Bandwidth
Magnetic loop antennas are small and tend to be efficient
Their bandwidth, therefore, is very narrow

6. Tuning capacitor
For maintaining low losses, and for handling large voltages (kV), a vacuum variable capacitor is preferred

7. antenna performance
When vertically polarized, nulls are perpendicular to face of loop
Strongest directionality in plane of loop
Easy to null out QRM/QRN

8. Antenna performance (cont’d)
When horizontally polarized, antenna acts like a vertical antenna
Omnidirectional radiation pattern
Does not require a ground plane

9. Some benefits Antenna is low profile, so it is easily concealed
Stealth antenna built into a table:

10. references http://www.aa5tb.com/loop.html
Burger and Dvorsky, Magnetic Loop Antenna: Slightly Different Each Time, Ostrova, 2015
Leigh Turner, VK5KLT, “An Overview of the Underestimated Magnetic Loop Antenna,)