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