Here is one of my favorite antennas. I cut my Delta Loop according to the ARRL formula:
Length = 1005 /7.040 = 142 ft. 9 inches.
I used vinyl covered #14 wire and configured it as an inverted delta loop and feed at the upper corner. When I first put it up, I connected a quarter-wave 75 ohm coaxialransmission line transformer to the upper corner. Then I connected 50 ohm coax from the transmission line transformer right into my rig.
The delta loop is up about 35 feet at the top of the loop and it slopes downward at about a 45 degree angle. One leg passes through several tree branches.
The table below shows the SWR by frequency. I used an Autek RF-1 connected at the end of my 50 ohm coax, not at the antenna feed point. As you can see, this antenna has it's lowest SWR around 7.200 ---NOT around 7.040.
As suggested on the QRP-L, it may be better to use 1030 or 1040, instead of 1005 in the formula to get your Delta Loop to resonate at the appropriate frequency.