[TowerTalk] Question concerning Hard Line

[Van Fair]

A friend has 60 to 70 feet of hard line (type unknown) buried to his tower and then RG8 up the tower. On the transmitter end it has 10 feet of RG8 before the hard-line. 

He is having a problem with high SWR on his beam. In checking it out I put a 52 ohm dummy load at the end of the hard line at the base of the tower and found a 1-1 SWR at 12.53, 20.71 and 16.63 MHZ. Over the rest of the freq the SWR was much higher including 2-1 at 14.2, 1.9-1 at 21.3 and 1.5 -1 at 28.6 MHZ.  This seems abnormal and my experience says it should be close to 1-1 on all freq. but I have only used 52 ohm coax. The hard-line may be 72 - 75 ohms. Would this cause the above type of readings or does this indicate some other problem.?  It seems to me that mixing hardline and coax of different impedance is not good but does it work??   Thanks Van