[Amps] 1:9 un-un for grid driven tetrode

[jim.thom jim.thom@telus.net]

A buddy is trying to get a 1:9 un-un to work on his grid driven tetrode.
Terminated in a  450 ohm globar,  SWR is  1:1   but only up to aprx  20 mhz.
Above  20 mhz,  it rapidly all goes to hell....reaching  2.5:1   at 29.00
mhz.   ( this on the test bench)

He needs the  1:9  un-un to work from  80-10m.   What's the trick here ?
 What  is the ideal material to wind the trifilar onto ?

Once eventually installed into the amp, a small  coil is wired in parallel
with the 450 ohm globar to  cancel out the XC from the tube,  but that is a
normal procedure, and will not alleviate the high swr issue on the upper
bands.

Jim   VE7RF