Jim,
I ran the models of 2 beverages (any combination of the 2) with and without the
3rd passive wire present. And interestingly the models show almost no effect
for the 3rd wire. Sort of makes sense maybe as it is grounded and 60m away…
As for the feedline, I made sure the coax ground is isolated from the beverage
ground. The coax is running on the lawn and I don’t believe it might have much
effect on the pattern. And even if it did, the phasing effect of some sort
should still be there. The impedance is rather constant along the coax and SWR
curve flat.
One somewhat unexpected modelling result is that the pattern surely seems best
on 160, 80 as well as on 40 meters when all 3 beverages combined. I get clean
and narrow patterns then on all bands with sidelobes supressed. This seems to
contradict what I have read that when stacking beverages more is not better and
2 is ideal...
So all in all I guess I need to do more testing when I get back to my QTH...
ES5TV
On 11 Sep 2018, at 17:10, jimlux <jimlux@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@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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