WØIVJ's Receive Loop Project
(Click on pictures to enlarge)
Email: w0ivj@arrl.net
About a year ago I noticed a strong interfering signal on the 40 meter band.  Since the interference was coincident with the work day and week, I suspected it was coming from the industrial building just behind our house.  But, in order to be sure, I decided to build a receive loop to track the noise down.  The loop is made of 1/4 inch copper tubing and a piece if 1 X 2 lumber.  The large loop is 24 inches in diameter and the small loop is 6 inches in diameter.  The large loop is connected in series with a 220 pF siver mica capacitor which is in parallel with a 26 to 170 pF air variable capacitor.  This is a nominal capacitance of 318 pF to resonate the loop.  The 6 inch pick up loop is fastened to the other side of the 1 X 2 and connected to a short feed line of RG-58 coax.  The loop is connected to a receiver and the variable capacitor is adjusted for maximum noise on the 40 meter band.  Pictures A, B, and C show the construction of the loop.

A..Hi Res..B..Hi Res..C..Hi Res

By the way, the noise turned out to be a switching power supply in a halogen track light, but that is another story.