[TenTec] Open Wire Line - A CASE FOR OCFD

[Wade Staggs]

*Sorry about calling you Bob .... Rob, my eyes are getting old.....*

On Tue, Oct 20, 2015 at 9:17 AM, Rob Atkinson <ranchorobbo at gmail.com> wrote:

> >Perfect example. Another would be a full wave dipole. :)
>
> A full wave center fed dipole will be voltage fed and have a Z of
> around 5K ohms and put a vswr on the line of around 10:1.  The line
> loss is negligible because it is a balanced line with an air
> dielectric.  I will go up against a horizontal 1/2 wave balun and coax
> fed dipole on 40 m. with my balanced line fed horizontal 1 wave center
> fed dipole on 40 any day of the week and I will come out ahead across
> 40 m.   Both same height.
>
> >
> >But more generally, I'm talking about putting up a single dipole, whether
> center-fed or off-center fed, feeding it with open wire or window line, and
> loading it on all bands.
> >
>
> Brown, you are off in your own world of open wire line hating and you
> are free to be irrational about it to your heart's content but you
> occasionally pop up in some on-line forum somewhere and I see your
> dis-information.  Perhaps you attempted the folly of feeding an
> unbalanced (i.e. off center fed) dipole with balanced line as you
> included it in your description above.   Surely you understand the
> concept of unbalanced load fed with unbalanced line and balanced loads
> fed with balanced line.  You don't feed an unbalanced load directly
> with balanced line.
>
> A high dipole 1/2 wave on the lowest frequency of interest and fed in
> the center with decent open wire line with a characteristic impedance
> of at least 600 ohms and matched with a correctly designed and
> constructed truly balanced link coupled matching network, will run
> rings around any coax fed dipole, especially on 80 meters where the
> band is 500 kc wide.  You won't need a ridiculous ferrite core balun
> at the feedpoint, sitting there adding to your losses with heat
> reactance; you won't need a dozen dipoles to cover HF, and such a
> system will deliver more power to the load on average on any HF
> frequency than some hammy coax fed dipole will.   If any ham wants to
> be obsessed with feeding a balanced load with an unbalanced line he is
> free to do so and live in denial (I work everyone I hear blah blah)
> but professionally designed and constructed shortwave broadcasting
> plants always use balanced antennas and feed them with balanced line.
> If they didn't work they wouldn't do it.
>
> To be objective, there is one problem with a low band dipole used on
> the high bands, and that is the pattern you wind up with.  An 80 m.
> half wave dipole on 10 meters has many lobes going off in all
> directions and even though the system in terms of power transfer is
> efficient, the pattern is not reliable if the operator wants a good
> idea of where is signal is going.  For that reason, I employ a second
> dipole, 1/2 w. on 20 meters to cover the high bands.
>
> 73
>
> Rob
> K5UJ
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