[Elecraft] Toroids frequency range and baluns

[Solosko, Robert B (Bob)]

Hello All,

	There have been several e-mail threads recently about ferrite
cores and about baluns and transmission line loss with high SWR. Related
to this is a question that I haven't seen addressed anywhere - toroids
all have a specified frequency range but what happens when they're used
outside of that range?

	To be more specific, I have a multiband fan dipole fed with
ladder line into a 4:1 current balun that then connects to my rig
through about 5 feet of RG-8. I made the balun using a pair of T200-2
powder iron cores, which have a specified frequency range of 0.25 to 10
MHz. Since I'm using this single antenna from 160m to 10m, I'm way
beyond the specified frequency range of the cores - is the balun likely
to be very inefficient above it 10MHz? The antenna seems to work very
well on 40m and 20m and OK on 15m. Since the band conditions haven't
been particularly good in the last few years that I've been using this
antenna, I can't tell whether my lack of many QSOs on 15m and above is
due to inefficiencies in the balun or to band conditions? What do you
think?

Bob W1SRB