WD8DSB Small Tuned DF Loop For 7 to 32 MHZ

• 1 turn Main Loop (12 3/8" wide by 12 1/4" tall) 12 gauge bare wireNote: if I were to build it again I would make the main loop 1/16" to 1/8" wider and 1/16" to 1/8" taller to make sure it can tune down to slightly below 7.0 MHz as mine just barely does (6.990 MHz). This will reduce the maximum frequency slightly.

• 1 turn Pickup Coil ( 6" wide x 4 1/2" tall) 20 Gauge insulated wire spaced 5/8" up from main loop.

• 13 - 385 pf variable capacitor

• Feedpoint impedance approximately 50 ohms at resonance.

• Note 1: I just cut halfway though the wood with a saw to allow placement of the bottom of the main loop and the bottom of the pickup loop, and then back fill the cuts with wood glue to maintain good strength of the wooden mast. I drilled holes through the wood to pass the top of the main loop and the top of the pickup loop through the wood mast.

• Note 2: This antenna does not provide perfect balance (not exactly the same depth of nulls) and this is more noticeable as you go higher in frequency (like 28 MHz), but it's still more than adequate for direction finding. Placement of a common mode choke on the coax using 12 to 14 turns of the coax on an FT240-31 toroid core right before it connects to the twisted wires from the pickup loop would likely improve balance, but I've never needed to do this for my direction finding activities.

Website created and maintained by Don Kirk (wd8dsb) Feb 4th, 2021