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Hello,<br>
<br>
Did some more antenna measurements tonight. The Ubiquiti sectors
were the new contenders for the "official sector" title.<br>
<br>
The <a
href="https://www.hamwan.org/t/tiki-index.php?page=Ubiquiti+5G-16-120&structure=HamWAN">5G-16-120</a>
didn't do so well. Gain is dreadful and the radiation pattern is
nearly omnidirectional. Blah!<br>
<br>
The <a
href="https://www.hamwan.org/t/tiki-index.php?page=Ubiquiti+5G-19-120&structure=HamWAN">5G-19-120</a>
did a lot better. It looks to be a 90 degree sector though, if
we're honest. -3dB points were measured just 81 degrees apart. The
+/- 60 degree points look to be -8dB, not the -6dB I've come to
expect from some manufacturer beamwidth claims. The radiation
pattern is also a bit weird in its shape, but not awful. The
frequency response is pretty good though. The final drawback of
this sector is price. It's about $150 a piece. Although that is
cheaper than the Laird sector which is $180 a piece. This Ubiquiti
sector is also dual polarity, so if we ever do MIMO, antennas won't
have to change.<br>
<br>
More contenders have arrived though! I'll get them tested soon.
Hopefully they blow all these expensive sectors out of the water.
:)<br>
<br>
Now, on the "official high gain antenna" front, I've measured two
new contenders as well.<br>
<br>
The <a
href="https://www.hamwan.org/t/tiki-index.php?page=ARC+ARC-DA5834SD1&structure=HamWAN">ARC-DA5834SD1</a>
does not disappoint. It is well constructed and weighs less than
you'd think. The frequency response is the flattest of ANY of the
antennas tested so far. The radiation pattern is THE most
directional of any of the antennas tested so far as well. Just look
at that gorgeous rejection, all at least -30dB down. This is the #1
choice if you've got the $300 (shipped) to spend on it. It is also
a dual polarity antenna with a fair amount of isolation between the
polarities. On the rear are N-connector to waveguide adapters.
They combine to feed one solid circular waveguide that protrudes
from the center of the dish. At the end of the waveguide structure
the metal turns to plastic and the waves are allowed to radiate
through the plastic shield/support onto the subreflector at the very
tip. This subreflector has a really cool wavey pattern milled into
it on the underneath to collimate all the waves properly to/from the
main reflector dish. I found the N connectors somewhat hard to
start threading for whatever reason. Was not getting alignment.
The mounting system is well thought out and a pleasure to use,
especially to adjust the tilt of the antenna! You just turn one nut
to raise/lower the tilt. To rotate you can loosen both U-bolts.
Now, normally this would make the antenna slide down. But they're
thought of that and provide you with a stopper you install on the
mast before hand. The weight of the antenna rotates on this base.
When angled right, you just tighten the antenna's u-bolts. There's
also a built-in mini-mast section to bolt a radio to. Very well
thought out. A very nice antenna. But still, $300 shipped from
Streakwave isn't cheap. WLANmall <a
href="http://www.wlanmall.com/arc-34dbi-dual-pol-4-94-5875ghz-dp-dish.html">looks
to have it</a> for much less shipping. Streakwave tried to jack
the shipping on this antenna by another $50 *after* I placed the
order. It would have been $350 if I let them have their way.<br>
<br>
The <a
href="https://www.hamwan.org/t/tiki-index.php?page=Poynting+K-GRID-003-06&structure=HamWAN">Poynting
K-GRID-003-06</a>, henceforth known as "<a
href="http://en.wikipedia.org/wiki/Die_Antwoord">Die Antwoord</a>",
is a surprisingly well performing high gain antenna. It is designed
and manufactured in <a
href="https://maps.google.com/maps?hl=en&ll=-26.10403,28.079563&spn=0.012689,0.009495&sll=-26.103982,28.079655&layer=c&cid=11252272406233210136&cbp=13,3.3,,0,2.79&panoid=inPysFz8CF29sKnrYx1ziw&gl=US&t=h&z=17&cbll=-26.104026,28.079467">South
Africa</a>, just like its musical namesake. It may indeed be "the
answer" for HamWAN's directional antenna needs. While I do not have
official trustworthy absolute gain comparison figures yet for any of
the antennas, the preliminary numbers make it look like Die Antwoord
gets about 5dB over its similar-in-size cousin, the <a
href="https://www.hamwan.org/t/tiki-index.php?page=Laird+GD5W-28P&structure=HamWAN">Laird
GD5W-28P</a>. It also looks like the $300 dish is only 1dB
better. Die Antwoord also features a much flatter frequency
response, and a far better radiation pattern than the Laird. You
know you're doing something right when the <a
href="http://cdn.entelectonline.co.za/wm-43814-cmsimages/A-K-GD-003-06%20Datasheet.pdf">manufacturer's
published H-plane pattern</a> strongly resembles your own
results. Notice the distinctive side-lobes touching -20dB on either
side of the main lobe. Notice the containment of all other lobes
within the -30dB limits. This is a FINE antenna! And for not lying
about the patterns like so many others do, Poynting gets my "fine
manufacturer" seal of approval. Poynting and I disagree on the
frequency response, but the difference is 1dB, so I'll let it go.
:) The gain is really quite flat. A surprising achievement for
such a broadband antenna. In fact, the gain flatness is only bested
by the $300 ARC dish mentioned in the previous paragraph. What does
all this wonderful performance cost? Would you believe <a
href="http://www.titanwirelessonline.com/Poynting-5-8GHz-31dBi-Grid-p/at-30gr-58.htm">a
mere $95 shipped</a>? NOTE: Do *NOT* follow the advice of the one
gentleman who commented on this product at the link I just gave
you. The man is a fool who ruined his antenna. :) The radiating
element is meant to be unconventionally oriented. Follow the
assembly instructions.<br>
<br>
The physical size difference between the $95 Die Antwoord (bottom)
and the $300 ARC dish (top) is small. Here they are both enjoying
my couch, just yearning to RF @ each other:<br>
<br>
<img src="cid:part11.07080102.03070107@bartk.us" alt=""><br>
<br>
To truly measure the real long distance gain of these antennas, I've
got to test them over a longer range. Something like 100m should be
enough to make the EM waves mostly perpendicular to the DUT antennas
instead of hitting them at weird angles. This straightening of
geometry should allow for real-world gain measurements and
comparison of absolute gain performance. A 3ft dish on a 20ft range
may not get the chance to focus correctly, and it may be losing gain
because of this. I've taken steps so that I can take the
measurement lab mobile and deploy in a large field.<br>
<br>
I also screwed up the measurement process enough times that I
finally sat down and documented it, step-by-step, at the bottom of
the <a
href="https://www.hamwan.org/t/tiki-index.php?page=Antenna+Analysis&structure=HamWAN">Antenna
Analysis</a> page. Who could possibly screw up executing a 57
step sequence from memory? :)<br>
<br>
Finally, I also had a discussion with a microwave antenna measuring
friend of mine, and figured out how to measure the absolute gain of
each antenna. This is different from measuring "comparison of
absolute gain", aka "absolute gain delta between antennas". This
would be deriving that actual dBi you'd print on a box of a product
and you'd have to stand by it. I'm not sure if the process is worth
it though, since it's only the deltas which lead to antenna
selection decisions. We'll see.<br>
<br>
Now, where are those new sectors ...<br>
<br>
--Bart<br>
<br>
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