Topband: Ladder line + tuner

[D Rodman MD]

I designed a loop for 100 ohm impedance and fed with coax and 1/4 wave 
transformer.  It has worked well for years.  I got the bright idea to 
replace the coaxial feed with 35' of 450 ohm ladder line and a Bliss 
remote tuner.  This combination would not match.  I experimented.  A 
nice dip in VSWR was noted about 400kHz lower than the bottom of the 
band where that combination of antenna plus ladder line was almost 
perfectly resonant.  A versa tuner WOULD tune it but I needed to add 
about 90' of ladder line for the remote tuner to produce a reasonable 
lower complex impedance inside the band (actually it was reduced to 
about 58 + j6).  The impedance with 35' of line was over 1K and this is 
too large of a value for that tuner to accept.  (That is a previously 
made tuner with vacuum capacitor and large roller inductor.)  Does 
anyone have knowledge or experience with impedance transformation on 
ladder lines that might be able to teach me something here about the 
effects I noted???  Thanks.

-- 
David J Rodman MD
Assistant Clinical Professor
Department of Ophthalmology
SUNY/Buffalo

Office 716-857-8654