Finally finished, after two full days of tuning. This is the K5RP loop as discussed in ARRL Antenna Compendium no. 2. What a mechanically awkard antenna. It is extremely narrowband, covering only 40kHz of the band between 2:1 swr points and ground interaction is wicked. I could change the dip frequency by retensioning the wires. The 1:1 bandwidth is 10khz. This narrowness makes tuning more of a challenge because it has to be smack dab on the frequency of choice. The purpose of building this is to help in finishing up my 5 band dxcc award. I still need 8 countries on 80 and the simple verticals of the past have just not been enough from Colorado. This loop is supposed to provide 3db gain over a vertical. The goal is to be able to work cw, psk31, and jt65. That’s more than 40kHz so I compromised. After multiple trips up and down the step ladder, I was able to get a dip at 3.573 mHz, half way between psk and jt65. SWR is 1:1 and resistance is 50 ohms. Very nice. No matching network needed. For the cw portion down to 3.500 I can switch in a tuner. Antenna gain only works with this design at it’s resonant point. Have you played with these loops? I’d really like to hear your experiences.
Wire is 14 guage stranded insulated antenna wire from DX Engineering – 560 feet.
Support posts are Army surplus camoflage netting fiber glass poles – 28 feet tall.
I used clothes line pulleys at the 8 corners.
The antenna is two full wave 80 meter loops connected as a two turn coil.