A simple voltage divider with two resistors will work fine here. first in path a series resistor, with a shunt resistor from signal to ground on the receiving end. You could make the series resistor a pot and dial it to the needed level reduction. I might try a 5K pot with a 1K resistor shunt; that's a guess. Scale both up or down as needed depending on the pot you have or can get easily, scale resistor smaller relative to full pot value if it's not enough reduction. Don't scale the entire thing below 2K, I would guess.
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even easier; just use a 5K or 10K pot as-is, take signal from sweeper into receiving device. connect it as close to receiving device as possible.