40M Mini-loop Antenna for QRP
 By Rob L. Dey, KA2BEO  1/24/99

Specifications

SIZE: 4'W x 4'H x 0.5"D approx.
FEEDPOINT IMPEDANCE: Balanced, 50-ohms approx.
CENTER FREQUENCY: 7.200 MHz
SWR: 1.1:1
BANDWIDTH (2:1 SWR): 300 kHz, 7.000-7.300 MHz
POWER RATING: 15 W rms (QRP only), 150 W rms (if 5kV caps are used)
TUNING: None required, pretuned design.
GROUND: None required, balanced design. Also, no balun required for coax feed.
MAINTAINANCE: None required, completely weatherproof.
MOUNTING: Hang vertically in any convenient location, even in the basement.
 Feedpoint is at the top.
RADIATION PATTERN: Major lobes in front and back at all elevation angles.

Additional Features of a Small Tuned Loop

* High selectivity increases dynamic range of receiver.
* Sharp nulling can isolate stations apart by 10 to 170 with 60dB
 of attenuation or more.
* Approximately 26dB of electrostatic noise reduction quiets man-made,
 precipitation, and other noise sources.

Parts Required

16'   14/2WG Romex Cable 3 x 14 AWG 600V
2     PVC Strip 4"L x 5/8"W x 1/8"Thk
       (Drill one with a 3/8"D hole in center for BNC,
       and one with six holes for capacitors)
1     BNC Female Connector, lock-washer, solder lug, and nut
2     27pf 5% 500V Silver-mica Capacitor or equiv.
1     33pf 5% 500V Silver-mica Capacitor or equiv.
1     20pf 5% 500V Silver-mica Capacitor or equiv.
       (Solder this cap across the 33pf cap, or use
       a 50pf variable capacitor across the 33pf cap)
      Solder
      Electrical Tape

See the other 40-meter Mini-loop Antenna for any details that may be 
missing here. Use the above construction technique for 2' square, 
and 1' square loop antennas for 20-meters and 10-meters also. 
Capacitor values will need to change accordingly.