QRP Ferrite Core Coupled Magnetic Loop Antenna 14-30 MHz Antenna Party

21 April 2012

The River City ARCS Magnetic Loop Build Party was held on Saturday, April 21, 2012 9:00 AM - 2:00 PM at the Sacramento County Corp Yard, 5026 Don Julio Blvd, Sacramento, CA 95842 . QRP Ferrite Core Coupled Magnetic Loop Antenna 14-30 MHz Plans ANTENNA BUILDING IDEAS ASSEMBLY & TEST RESULTS The Club purchased and had the following kit of parts on hand at the party for those who signed up and pre-ordered :

RG-8/U cable for loops and RG-58 or RG-59 cable for coupling loops

two PL259 and SO239 UHF connectors for each loop,

one female BNC or SO239 feed line connector for each loop,

RCA plugs and jacks (optional for coupling loop)

NE-2 neon glow lamp,

necessary bolts, nuts, spacers and washers,

½ inch PVC conduit clamps

6:1 reduction drive

butterfly capacitor plates

polycarbonate end plates for capacitor frames (pre-cut and drilled by W6FT)

polypropylene enclosures for capacitors Our default feed method was a small coupling loop of RG-58/U cable, 1/5 the size of the main loop. You may provide and use your own ferrite toroid core if you prefer that coupling method. The club had free donated coaxial cable on hand for loop material. You may provide your own building materials if you have another preference, such as hardline, or aluminum or copper tubing or strap, or weatherproof and UV resistant enclosures. See the tables on this page as loops thicker than RG-8/U can require more capacitor plates. A feed line and antenna analyzer were available for testing the loops. At the time of this project the estimated parts costs were: $4 for each 3 inch capacitor plate set*

$6 for each 5 inch capacitor plate set*

$10 for each 8 inch capacitor plate set*

$11 for the 6:1 reduction drive

The cost of the other parts was added on (about $20). * Each capacitor plate set consists of one rotor plate and two stator plates.

You may order capacitor plate sets from Bob Leschyna, VE3UK of Monarch Capacitors or Vasile Pop, VA6POP.

Magnetic Loop Antenna Party

Although the event has passed and no spare parts remain, you may e-mail us with specific questions about planning your antenna.





Freq. Range 14-30 MHz

Loop dia. 3 ft. Circ. 113 in. Wire dia. 0.4” RG-8/U

Cap. range: 10-50 pF Wire dia. 1” tubing

Cap. range: 13-62 pF Power

Watts Max

Voltage Plate

spacing No. of

3” sets No. of

5” sets No. of

3” sets No. of

5” sets 50 3000 .04” 1 mm 3 1 4 2 100 4300 .06” 1.5 mm 4 2 5 2 200 5900 .08” 2 mm 6 2 7 3

Freq. Range 10-22 MHz

Loop dia. 4.2 ft. Circ. 158 in. Wire dia. 0.4” RG-8/U

Cap. range: 13-65 pF Wire dia. 1” tubing

Cap. range: 16-80 pF Power

Watts Max

Voltage Plate

spacing No. of

3” sets No. of

5” sets No. of

3” sets No. of

5” sets 50 3000 .04” 1 mm 4 2 5 2 100 4300 .06” 1.5 mm 5 2 7 3 200 5900 .08” 2 mm 7 3 9 3

Freq. Range 7-15 MHz

Loop dia. 6 ft. Circ. 226 in. Wire dia. 0.4” RG-8/U

Cap. range: 18-86 pF Wire dia. 1” tubing

Cap. range: 22-104 pF Power

Watts Max

Voltage Plate

spacing No. of

3” sets No. of

5” sets No. of

3” sets No. of

5” sets 50 3000 .04” 1 mm 5 2 6 2 100 4300 .06” 1.5 mm 7 3 9 3 200 5900 .08” 2 mm 9 4 11 4



The Yahoo Magnetic Loop Antenna group is a discussion forum for design and construction of magnetic loop antennas.



CAUTION: Due to the high voltages and strong radiation field this antenna may produce, take care to avoid close proximity to this antenna while transmitting significant power levels. Refer to Table 17 in the FCC Compliance OET Bulletin 65 and Safety Distances for Small HF Loop Antennas