[TowerTalk] CURIOSITY question

[JAMES HEADRICK]

A new 3el Steppir was installed and it performed properly for several days. 
But then during a QSO the VSWR abruptly went very high.  A DC Ohm meter 
measurement of the coax line going to the Steppir indicated a very high 
resistance.  Steppir says input to their antenna should be a DC short 
circuit.

Now to the question. I tried using my MFJ tuner and on 20 and 15 meters 
found I could get enough of a match for the transceiver, a Yaesu FT1K. 
Performance seemed about the same!! The next time the radio was turned on it 
was back to normal and then the problem started occurring intermittently.  I 
operated in the recent ARRL DX SSB with use of the tuner required about half 
of the time.  Of course no quantitative measure but performance seemed about 
the same when the fault existed.  How can that be?

A bit more info: The input to the antenna balun does measure a DC short when 
performances is normal.  The Steppir is on a mast at 65 ft on a 55 ft 
crankup tower, and the coax run from shack is about 170 ft.  The coax up to 
the base of the tower looks OK, and as soon as possible I'll get the tower 
down and find the problem.  I just can't understand how the antenna can work 
with one side of the transmission line open.  Can some one explain?

73,  Jim  w3cp