Since Hy-gain didn't include a frequency chart to help customers initially set the SWR, I added this frequency chart that will get you close to the perfect length setting.
24.960 (center of 12 meter band)- 23 ft & 5 1/4 in,
28.000 (start of 10 meter band)- 20 ft & 10 23/32 in,
28.100- 20 ft & 9 27/32 in,
28.200- 20 ft & 8 15/16 in,
28.300- 20 ft & 8 1/16 in,
28.400- 20 ft & 7 3/16 in,
28.500- 20 ft & 6 11/32 in,
28.600- 20 ft & 5 15/32 in,
28.700- 20 ft & 4 5/8 in,
28.800- 20 ft & 3 3/4 in,
28.900- 20 ft & 2 15/16 in,
29.000- 20 ft & 2 3/32 in,
29.100- 20 ft & 1 1/4 in,
29.200- 20 ft & 7/16 in,
29.300- 19 ft & 11 19/32 in,
29.400- 19 ft & 10 25/32 in,
29.500- 19 ft & 9 31/32 in,
29.600- 19 ft & 9 3/16 in,
29.700 (end of the 10 meter band)-19 ft & 8 3/8 in
re:ky2v