[mythtv-users] Attic Antenna: simple question.

[Daryl McDonald]

On Sep 7, 2014 9:23 AM, "Saul A. Peebsen" <jaglover at gmail.com> wrote:
>
> On Sun, 7 Sep 2014 12:24:45 +1000
> blind Pete <0123peter at gmail.com> wrote:
>
> > On Sat, 06 Sep 2014 13:18:44 -0400
> > Bert Haskins <bhaskins at chartermi.net> wrote:
> >
> > >
> > > I have been trying to recover at least a few channels after charter
> > > effectively  bricked my HDHR. One, CH8 is marginal and in an attempt
> > > to improve it I want to modify a existing antenna. The antenna has
> > > all of the elements including the center point of the dipole
> > > connected (grounded) to the main beam which then is bolted to the
> > > grounded mast. This just doesn't seem right to me, i.e. it seems
> > > like the dipole should be insulated from all the other parts(?).
> > > I've searched the net and found lots of other information but
> > > nothing on this.
> >
> > Antenna design is a bit of a black art.
> >
> > With a Yagi-Uda design all of the directors and the reflector are
> > simple conductors insulated from the boom.  There might be a bunch
> > of plastic washers and sleeves where they are not obvious to the
> > casual glance.
> >
> > If you doubled the length of the passive elements there
> > would be a node at the centre, so electrical connection
> > would be OK.  But that would make the antenna twice as
> > large as necessary.  Such a design would surprise me.
> >
> > With a log-periodic antenna there are two parallel booms.  half
> > of the elements are electrically connected to one and the other
> > half are connected to the other.
> >
> > Many, many, weird and wonderful designs are possible.
> >
> > If you like mucking about with this stuff, go for it.
> >
> > If you just want a marginal signal to be a bit better
> > consider buying a new (corrosion free), slightly larger antenna.
> > Make sure that it is pointing in the right direction.
> > Check that there are no obstructions, hills, neighbour's
> > new attic, wet trees, etc.   Yes, at some frequencies a mess
> > of leaf sized conductors will block a signal.  Dry leaves
> > don't conduct enough to matter.  Then all of the usual stuff,
> > check the cables and connectors.  Is anything generating
> > electronic noise nearby?
>
> I've used Yagi antennas where all elements are grounded in the middle.
> Dipole is not insulated. As much I remember of this type of design
> insulation is not necessary because there is never any voltage in
> center point (although it is the point of max current).
>
> --
> Cheers, Saul
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Since E = I x R, how can there be no voltage (E) and max current (I) at any
point?
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