Topband: 160m loop VSWR question

[David J Rodman MD]

I have two stations, lets call them RIGHT and LEFT.  With regard to my 
loop antenna they are as follows.  The antenna is apex UP and fed about 
30' up from a bottom corner from the B tower.  There is a 75 ohm 
transformer and the RG213 remaining goes through a surge protector at 
the base of the tower (POINT 1).  The loop itself is tilted slightly 
away from the base of the tower, probably about 20'.  The antenna has 
been up for a year now.  Continuing, the coax goes 25' to a six position 
dual feed coaxial switch (WX0B SixPak) (POINT 2) then another 180' with 
buried hardline to the second tower.  A two position coaxial switch 
(ICE) (POINT 3) feeds the signal to the house (200' underground hard 
line).  The switch allows me to separate off the stations if one needs a 
front tower antenna (A tower or a rear tower B).  A second surge 
protector at the house breaks the hardline from RG213 which continues to 
the station which is located over the garage.  The two stations are 
about 25' away from each other.  That is the only difference in the two 
coax lengths.  Both stations use the same equipment, a Yaesu XCVR for 
the low bands, a 781 for the high bands and an Alpha87 amp.

I was going to operate the ARRL 160m from the LEFT station, but I 
noticed the VSWR on the loop was quite high.  It was at least 3:1 and 
the amp kept tripping out.  The RIGHT station had its normal VSWR which 
is quite low.  I abandoned the test and decided to trouble shoot.

Since my Autek device never measured 160m antennas well, I took a 751A 
transceiver to POINT 1 and POINT 2 and found the VSWR to be quite like 
the LEFT station.  As a matter of fact, there was a small dip going to 
the bottom of the band, so I shortened the bottom corners by 6' per side 
and the antenna looked quite good with a 1.2"1 at 1815 or so.  I 
measured the VSWR at POINT 2 and it was also good.  I went to the 
station and found the RIGHT station VSWR now had INCREASED at the amp to 
about 100w reflected from about 20 before I started.  I wish I could say 
that the LEFT station was great now, but a relay problem with the SixPak 
prevented the station from transmitting and I will just need to repair 
the unit.

So you probably want to know why the RIGHT and LEFT setup?  The LEFT is 
for contesting and the RIGHT shares three transceivers (also an Orion) 
which is my internet remote control station rig.  So, I rarely use the 
LEFT station.  My questions are why could a VSWR that was seemingly so 
bad look terrific at one station and so bad at the other with the only 
difference being an extra 25' of coaxial cable and different equipment?  
I am presuming the CORRECT VSWR is the reading of the radio at the base 
of the tower and each point down the line.  I never adjusted the antenna 
for VSWR last year as I presumed the number I was seeing was identical 
on the LEFT station, mistake.  Should I now see some better performance 
from the loop as the VSWR is less?  Why would an extra 25' of coax 
matter the station POINT 3 and not POINT 1 vs POINT 2?

Thanks for the help and I appreciate any insight from my learned colleagues!