I've been futzing with the Termaline.
Inside there is about a 14" long copper 'shell' that is the 'exponentially tapered line section'.? Inside the shell (which is the coaxial shield) is a 3/4" copper 'center conductor' that clamps to a plain ol' 6"x1" 50 ohm Carborundum tubular resistor (Type SP--rated for use in oil).
I have cleaned all the conducting junctions and substituted the resistor with another, and have checked multiple Bird QC connectors.? Sweeping the unit (outside of the oil bath) shows little change (VSWR ~ 2.7:1 at 435 MHz).
I'm thinking that the only thing left to go wrong is the oil itself.? The oil has some dielectric constant on the order of 2.5-3.0 (so I shouldn't expect to see 1:1) but I wonder (1) does Bird use some specific silicone oil that is controlled for dielectric constant?? and (2) would overheating the oil be a sufficient cause to make the input sweep so poorly when it's all put back together?
The Bird silicone oil is quite expensive and it would be good to have some comfort level for my diagnosis before possibly throwing good money after bad.
TIA,
