Approximately 12 turns of 18 gauge speaker wire on a 2" diameter
ferrite ring will do the job.

Ferrite material with Mu = 200 to 500, ordinary LF to HF grade will be
OK.

If Mu = 10 then the core material is iron dust. Permeability is much
too low. Many turns would be needed to obtain sufficient inductance
at 80m. Too many turns prevent correct operation at 20 and 10m. And
the wire would be too thin for operation at 200 watts.
----
Reg, G4FGQ.

========================================

"Fred W4JLE" wrote in message
...

It is to be used in a transmission line. I need to cover 10-80
meters. The
core has m=10 and uH per hundred turns of 218.

"Reg Edwards" wrote in message
...


Using a T200A-2 for a 1:1 balun, what is the optimum number of
turns
and
best wire size? 200 watts max power.


What sort of circuit is it in?
Between what things is it to be used?
What frequency range?
We are not mind readers!

Without further information try 12 turns of Radio Shack, 18 or
16-gauge, twin, stranded, speaker wire. It might work.