On Mon, 20 Aug 2007 20:29:34 -0400, "Rick (W-A-one-R-K-T)"
wrote:

So, should I connect the unun to the balun as I have it, or should I
connect it at the transmitter end as MFJ advises?

Hi Rick,

Yes.

So much for the short answer. With an OCF, your line is so heavily
invested with a lack of symmetry that it will ring in the fields
surrounding the antenna. Hence it needs to be choked every quarter
wave away from the feedpoint (that is, the UnUn at the bottom of the
BalUn AND again in intervals of a quarterwave).

Now as the need for suppressing Common Mode currents (which are due
both to the off center feed AND the asymmetry). Unless you are
feeling the pain of a live chassis, or suffering from inappropriate
foldback of the transmitter (due to its circuits being confounded by
Common Mode currents); then you could live with it. Then, of course,
there is the perfectionist's point of view that this adds a vertical
radiator to an otherwise dipole design. Yes it does. How much it
contributes to the mix of fields is going to be a spin of the wheel
(just as how much CM is there going to be on the line?).

One last point. The OCF resonates at pretty much the same frequencies
as it would as a dipole, it is only the feedpoint Z that changes with
respect to placement. Some places are great for many bands, others
are abysmal, and some bring in bands that would be a nasty match for
the strictly balanced dipole. If you don't snub the feedline, you are
adding other opportunistic resonance's to the mix.

73's
Richard Clark, KB7QHC