"Rick (W-A-one-R-K-T)" wrote in message
news

On page 7-10 of the 20th edition of the ARRL Antenna Book is a description
of an off-center fed dipole. I have the necessary materials around here
so I thought I'd experiment with that a bit and see how it does.

I'm a little confused about the balun.

I don't have a 4:1 or 6:1 current balun, but I do have a 4:1 W2AU-type
balun and an MFJ-915 RF Isolator, what they call a "1:1 current balun"
(actually an unun). I figured on connecting the latter to the former with
a double male PL-259 adapter and then connecting the coax to the other end
of the unun ... rather heavy, and no way to support it at the balun, and
it'll no doubt droop like a 400-pound beer belly, but I guess I'll jump
off of that bridge when I come to it...

The instruction sheet for the MFJ-915 says I should put the unun in the
line at the transmitter end, and yet the discussion of the OCF dipole in
the Antenna Book shows the 4:1 current balun at the antenna and a length
of coax to the transmitter.

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?

It does seem that if the objective is to keep RF off the outside of the
coax, the unun really should go up at the antenna end.

What say you?


I would not worry too much about it, Just stick up something and see what
hapens. Wire is not that expensive. I have an OCF up about 45 feet and it
seems to work ok. Usually beter on 80 meters than an 80 meter dipole at 20
feet that is at right angles to it. The OCF is around 125 feet long and has
a 4:1 balun of somekind about 1/3 of the way on the horizontal wire, then
about 40 feet drooping rg8x to about 10 turns of coax on a piece of pvc pipe
and then into the shack. Seems to work ok on 80 and 40 meters. I have a
beam up for 20/15/10 so don't care how it works there, but sometimes it does
not do too much less thant he beam in some directions. The beam is usually
much beter most of the time as it is at 60 feet.