Topband: [TowerTalk] Advise needed on phased beverages

[Herbert Schoenbohm]

 Jim, yes, I suspected they might interact of course. But can I avoid it?
> ungrounding both ends of the unused beverage would also not eliminate
> coupling I am afraid?

If the feedlines are a half wave or multiples of a half wave you should try
terminating the unused shack end.  This electrically places the termination
right at the feed point.

Herb Schoenbohm, KV4FZ

On Tue, Sep 11, 2018 at 11:10 AM jimlux <jimlux at earthlink.net> wrote:

> On 9/11/18 6:19 AM, Tonno Vahk wrote:
> > Jim, yes, I suspected they might interact of course. But can I avoid it?
> > ungrounding both ends of the unused beverage would also not eliminate
> > coupling I am afraid?
>
> Exactly... no convenient way to change it in the field.
>
> A model can tell - run the model with the wire in and wire not in and
> see what the difference is.
>
>
> >
> > Height is ca 2m +/- 0.5m.
> >
> > I did not model switching in any other way than simply creating
> > feedpoint for both beverages. No feedlines in the model. Could such long
> > feedlines even if the same length, create a trouble?
>
> Sure - the feedline is an impedance transformer, so it changes the
> impedance at the feed end of the antenna. For instance, if it were a
> quarter wavelength (or an odd multiple), if you short the shack end,
> it's an open at the antenna end, and vice versa.
>
> I'm not sure how sensitive a beverage is to end termination impedance.
>
> If you're using NEC or a derivative, you can put a TL card or NT card in
> to do the transmission line and the model will show the effect.
>
>
> >
> > On 11 Sep 2018, at 15:19, jimlux <jimlux at earthlink.net
> > <mailto:jimlux at earthlink.net>> wrote:
> >
> > On 9/11/18 5:00 AM, Tonno Vahk wrote:
> >> Hi,
> >> Last weekend I finally got into experimenting with phased beverages,
> >> something I was planning for some time.
> >> I installed 3 broadside 219m (718ft) long beverages into the forest
> >> looking at 90 degrees and separated 60m (200ft) from each other (120m
> >> between the outer ones).
> >> I took great care to make sure the wires are straight and fully
> >> parallel to each other as well as starting from the the same line.
> >> I use DXE 9:1 beverage transformers and DXE 470 ohm termination
> resistors.
> >> I brought 150m (500ft) 50 ohm cable from each beverage feedpoint to
> >> the shack and connected to Microham Stack Switch (like Stackmatch).
> >> All the cables were of identical length to ensure same phasing.
> >> So I presume this system gives me full ability to test any combination
> >> of those 3 beverages alone or phased with each other?
> >> Well, all the 3 beverages alone are quite identical indeed which is
> good.
> >> But now when switched in pairs or all 3 together I am not seeing much
> >> effect. I do know what the patterns should look like and I presumed
> >> the effect would be strong especially with signals coming from side
> >> but most of the time I notice no difference with any signals when
> >> comparing any single beverages to combinations.
> >> This is puzzling. Modelling suggests I should for example have very
> >> big improvements in suppressing signals 45 degrees off on 160m when
> >> using 2 phased beverages 120m apart as well as when using all 3
> >> beverages on 80m but I did not notice such drops of 10-20db almost in
> >> any signals from any off directions.
> >> I could hardly notice sometimes the expected 3-5db increase in the
> >> signals from the right direction but not always as well.
> >> Can some of you having experiences with phased beverages tell me if I
> >> have done something wrong in my setup?? Should I test them
> >> differently? Are the phased beverages overrated and in real life there
> >> is seldom a significant improvement over 1 single wire beverage that
> >> is already long enough like 220m in my case?
> >> Look forward to any input. I can send the modelled patterns and maps
> >> of my beverages in picture files to anyone interested.
> >
> >
> >
> > 60m (your separation) is about 3/8 wavelength on 160, and the elements
> > are long (1 1/8th wavelength) so they'll interact signficantly, even if
> > disconnected from the feed (just like parasitic elements on a Yagi).
> >
> > How high off the ground are the wires?
> >
> > How did you model the switching?
> >
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