Hello Frank and All,
First you must tell us what you are expecting to make better with a Hi-Z
array. Do you want Better front to back? Do you want Front to side? Do you want
better signal to noise ratio? You want narrower beam width? Not ALL things get
better at once with size.
To my knowledge, with this phasing scheme Just changing the spacing on
your current 8A array will do more harm than good to the overall performance.
The front to back will remain about the same. The front to side lobe will get
severely worse to where the side lobes are only down about 8 dB. The RDF or
signal to noise improvement of the 8A is the highest commercially available
anywhere. It only changes 0.2 dB better theoretically going to 300 feet
diameter. There is NO conventional wisdom that I am aware of that tells us the
array should be better with a larger footprint. This array has ALL elements
active all the time. Raising the foot print to 300 feet and going to 4 elements
active per direction will only improve the front to side rejection but suffer
from a 0.5 dB or so less signal to noise improvement. I could change the
phasing on the 200 foot diameter array and lower the side lobes easily. I
choose to stay with the higher RDF.
Theoretically it is possible to model 8 elements like this and get over 16
dB of RDF ( I have the Eznec model) or signal to noise improvement.
Unfortunately theoretics and reality don't match. The current array from Hi-Z
(8A) requires all of the transformers and components plus the cable lengths and
element placement to be quite accurate (around 1% for each sub part) to even do
the 13.5 dB of RDF. It is at this time likely NOT within a Ham budget to
actually build an array accurate enough to even attempt getting more RDF or
signal improvement out of 8 Elements with 8 directions. I even tried 12
elements in 12 directions all active.
There are installations using two arrays phased together to get
approximately 3 dB higher RDF. Even this is tricky but it is being done. At
this time phasing two or more arrays has the best chance. First we know the
smaller arrays work but can be affected by other antennas and power lines etc.
A higher RDF array gets affected by the same things only worse. So phasing two
arrays that are not affected as bad have a better chance of working in the
environment than a single SUPER RDF array.
Now, If it seems your 8A only array just simply does not have enough
gain or the noise level from it remains extremely low because of your low noise
area contact me directly as we have a pilot program going on right now that
reduces the Noise figure of this array by nearly 9 dB. Its not really simple
but it works. This does NOT change the lobes or front to back or anything about
the patterns only the VERY VERY weak signal performance.
I get questions all the time about; can I make it better if I make it bigger.
NO: if changing size would have been better I would have provided it a long
time ago. I have 100's of acres here to try things like that. I even looked at
a 4-square of 8 element arrays. The beam gets so narrow you have deep gaps
between the main lobe.
Ahhh so many antennas so little time. Thanks for the question Frank, I hope
this has been helpful.
73, Lee K7TJR Hi-Z Antennas.
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of
dl8yhrfrank--- via Topband
Sent: Saturday, March 03, 2018 11:30 AM
To: topband@contesting.com
Subject: Topband: HIZ 8 Circel Diameter.....
Hi everyone...
Did annyone has experience in using more wide spacing the 8 circel rx arrya?
Im running the hiz 8a lv2 160-2 arrya in a 200 foot spacing in the fields on a
litel hilltop away from man made noise and have lots off space their so i think
about to get it up to 300 foot spacing to optimize it for 160 Annyone tryed it
ore can model it maybe if that will give more performace on 160?
Anny comments vy welcome
Best wishes
Frank
DL8YHR
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