Topband: strange SWR readings at tower base vs inside shack

[Mike & Coreen Smith]

Hi Guys,

I want to thank you all once again for all the private emails, articles and 
pix you've sent of your shunt fed tower installations
and great words of wisdom !  The outpouring of support and advice has been 
great. . . but I digress.

I am using my MFJ-259 antenna SWR analyzer on a ~10' chunk of coax to my 
series matching capacitor near the base of the tower that I am attemping to 
resonate on 160m and tuning the series Gamma cap and moving the Gamma wire I 
can get the match real low on 160m (like 1.2:1 or so) but when I measure it 
in the shack, it's over 3.1:1.. and the resonant frequency is not even close 
!.......initially I thought I must have had a bad remote antenna switch at 
the tower base, or a bad run of coax, but I have a spare ~180' run of coax 
and readings using it are nearly identical. Both runs are probably close to 
the same length.  One has a remote switch in line and the other does not.  I 
added a 2nd cap (a la Ohmega Match) this afternoon between rain showers but 
it made little if any difference in the strange SWR readings I am seeing. 
(good SWR and freq at tower base and poor in shack.)

What's going on ?

Scratching my head in NB

Mike VE9AA