MagLoop Antennas What Are They Why Use Them

Mag-Loop Antennas What Are They, Why Use Them, and Can I Make My Own? ?

What We Hope to Accomplish Basics of a Mag-Loop Antenna – Keep It Simple Absolute minimum of math My “first” Mag-Loop – example Resources

What is a Mag-Loop A loop antenna <1/4 wavelength A tuned circuit with an inductor and variable capacitor

Why Use a Mag-Loop? Small size – Allows stealth – Covenants, Homeowner Ass. Ease of handling Less sensitivity to ground – Doesn't need great height Low noise pickup, especially on lower bands

Some Details

Details Lots of current – Use minimum of connections If > ¼ wavelength circumferance – Self oscillations - unstable

Details – Loop Coupling Easiest method of coupling - Some variations reduce noise pickup

Details - Capacitors High Voltage & High Current unless QRP Vacuum Split Stator

Details - Capacitors Trombone

Details - Capacitors Butterfly

Details - Capacitor Trombone, Split-Stator, and Butterfly Half the capacitance Twice the voltage rating Less series resistance Butterfly ¼ turn min to max

Best Practices Use vertically – FAR less sensitivity to ground Elevation above ground Slight effects on coupling Some effect on take-off angle Clearance from other metal objects Null out interferences if good contact is made Gear reduced motor drive for tuning

My Mag-Loop Antenna

My Mag-Loop Antenna - Results The antenna was compared to a trap-dipole 28' elevation at the center, approx. 8' at the ends. Legs on ground- bottom of loop 2' above ground Good receive, 2 S-units below trap dipole Perfect match at tuned frequencies (20 m) – 1: 1 SWR No contacts made Legs on chairs – bottom of loop 3. 5' above ground Receive still 2 S-units below trap dipole Match increased to 1. 5: 1 SWR. Readjust coupling loop? ? Contacts in plane of the loop were also 2 s-units from trap dipole (contacts were in Oklahoma and Texas)

My Mag-Loop Antenna - Results Tuning: Extremely touchy – absolutely requires a gear reduction and motor drive! ~50 k. Hz bandwidth at 2: 1 SWR for a given tuning in the 20 m band. Need to reduce number of capacitor plates to raise frequency and reduce frequency swing Switch in door-knob caps for lower band(s)

Future Mag-Loop Projects 80/160 m Loop

Future Mag-Loop Projects Convoluted Mag-Loop

Future Mag-Loop Projects

Web Resources http: //www. brisdance. com/vk 4 amz/files/Download/Under. Mag. Loop. pdf http: //www. aa 5 tb. com/loop. html http: //www. aa 5 tb. com/aa 5 tb_loop_v 1. 22 a. xls http: //www. 66 pacific. com/calculators/small_tx_loop_calc. aspx http: //viennawireless. net/wp/wp-content/uploads/2017/01/Magnetic -Loop-Antennas-W 4 RAX. pdf http: //www. on 4 ceq. net/ant_en. htm

Material Covered Mag-Loop Antennas – What and Why Some Technical Details Use Some Possible Variations Resources

Questions