On 1/5/2024 12:53 AM, Robin wrote:
One thing to bear in mind throughout any analysis of such designs
for 160M is that the total focus of the Broadcast designs and
measurements and proofs is energy at zero degrees elevation. Our
needs benefit from low angle radiation, for certain, but, little
attention is paid by the broadcasters and by the modeling programs to
position and shape of elevated lobes, or for that matter, the shape
of the main lobe above zero elevation
Not exactly true. Many "modern" broadcast facilities are designed to
minimize high angle lobes that cause destructive *self-interference*
at the outer edges of the [night time] ground wave coverage.
73,
... Joe, W4TV
On 1/5/2024 12:53 AM, Robin wrote:
Milt Jensen, N5IA (SK) constructed his original (circa 1990s) 160M
station TX antenna based on a similar design I encouraged him use. He
built a 180 ft tower with an insulator at 50 ft, Four elevated quarter
wave radials, each made of a box of four pieces of # 12. This was on
his "city" lot where buried radials were impossible
It worked very well, We did not have the tools to make real field
strength measurements to compare to a model, but on air performance was
excellent
It worked well enough for him to use the concept in several similar
installations and to make his 8 circle array
The radial height above ground clearly did not need to be 50 feet,. It
did need to be high enough to easily be well above a tall truck, or more
commonly, a horseback rider.
We used a single element elevated radial 160M TX antenna, and for the
80M 4 square at XZ0A with considerable success.
The concept of exciting a tower from the inside is very interesting.
The reposting this article a has me thinking about one situation I have
available to me that can not have a complex installation outside the
general dimensions of the tower (large but not tall)
One thing to bear in mind throughout any analysis of such designs for
160M is that the total focus of the Broadcast designs and measurements
and proofs is energy at zero degrees elevation. Our needs benefit from
low angle radiation, for certain, but, little attention is paid by the
broadcasters and by the modeling programs to position and shape of
elevated lobes, or for that matter, the shape of the main lobe above
zero elevation
Robin Critchell, WA6CDR
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