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@earthlink.net
<mailto:jimlux@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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