VNA 2180

[killy]

Am about to receive the 2180, ordered 10 days ago.
From what i've read, this is THE instrument one should have among
his toys.
I'm just wondering why there is absolutely no mention of this VNA
on this forum; so here we go.

For me, toying with wire antennas all my ham life, the Autek RF1 has
just been upped.
Try putting up a 4 element 80M yagi in trees and towers, sloping, skewing and at different heights, on a granite hilltop where the ground is "somewhere".

Have modeled with three different pgm to get a good starting point,
but i'm picky and want to tune the elements for max. gain only.

I dont care about F/B, but want to maximize gain; so no reflector, only
1 DE and 3 directors. (maximizing f/b makes you lose up to 1.3db
gain; besides, the extra director gives more gain than adding a
reflector).

i intend to put port 1 to the DE, and put port 2 to the first director,
then measure S12 and S21 and hope to see the current magnitude and phase. (the 2180 allows you to "null out" the 1/2 wave coax and
current balun to put the instrument as if it is at the antenna terminal).

With these readings, then change the length of the DE and/or director to get what it should be as per modeling.
Then repeat the process, adding more directors.

Anyone with ideas about, or having toyed with "funny" yagis and
other VNA (or this one) and able to comment?

Anxious to get my new toy, and if no one knows about the 2180,
i'll surely provide my feedback.

[dl4raj]

Killy,

I'm not sure if your intended test setup will work.
You are planning to load a parasitic element with the
50Ohm load of port B of your VNA and you would have to
open it in the middle for connection to the analyzer.

BTW,I have my VNA since about four weeks.

73
Clemens
DL4RAJ

[killy]

Tks Clemens for the comment.
Just received the 2180 today and have not connected it to the computer yet.
You make a valid point; you cannot open the director without affecting the whole setup.
I will model this condition, but will put the biggest resistor that does not affect mag/phase,
then in real life i will wind a toroid with the ratio required to still have 50 ohms at the VNA but
showing that modeled resistor (pbly half or one ohm) in the center of the director.
Stay tuned, i have not begun playing with my new toy yet. BTW my call is va2gu on top of
a 300m hill near salt water.

73,
roy (killy is my web user name)

[killy]

Clemens,
forgot to mention, i've brought down a half wave coax from the center of that director and the shack
end is normally kept shorted, unless i want to make it invisible to the DE.

killy

[dl4raj]

Roy,

it will be difficult if not impossible to build a transformer
with an impedance ratio of 1:50 or even 1:100 for 80m.

73
Clemens

[killy]

Well, if i cannot build enough Z on the primary with all those turns of wire for pri
and sec, we'll resort to the old trick and pass the short of the director through
a toroid and sense on a secondary winding the current to a dual trace scope.

The other trace will sense the current in the DE, thus giving me the phase diff.

Good toughts Clements, and again thanks. Forces me to think a bit more.

73's
killy