Tom,
As I recall, HFTA software has an ionospheric module that calculates the
predictability of arrival angle as a function of frequency, time of day,
season, etc. Learning that program has been on my "to do" list for a long
time. Perhaps others here can comment on whether the arrival angle
information goes down to 160m in that program. I believe the program was
designed for elevated antennas and hence the need to analyze terrain. So,
in addition to 160m relevance, I'm not sure it applies to base-fed
monopoles.
I think the important "take away" in these discussions is that the far field
pattern alone is not enough to show the real vertical profile from a
vertical monopole. The significance of the ionospheric element is another
issue altogether.
Paul, W9AC
----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: "Richard Fry" <rfry@adams.net>; <topband@contesting.com>
Sent: Wednesday, October 24, 2012 2:39 PM
Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
----- Original Message -----
From: "Richard Fry" <rfry@adams.net>
To: <topband@contesting.com>
Sent: Wednesday, October 24, 2012 2:23 PM
Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
from [Tom W8JI]:
The issue here is one of measurement distance and the assumed flat earth,
and how much the ground wave contributes to low angle radiation. We
obviously know radiation at zero degrees is not zero, as distant models
show.
<As to measured data, below with his permission is a quote from a
broadcast
consultant acquaintance of mine who has made helicopter measurements of
the
elevation patterns of MW monopoles.>
My point is that does not tell us what happens at the ionosphere.
If I just take a simple program like EZNEC, and use a small sense antenna
out in the distance, the results follow the trend you posted from the
helicopter. I certainly am not disputing that data, because it seems
reasonable.
AFAIK, we do not have measurements of arrival angles useful for long
distances or how lower angles from verticals might apply to that. All we
really know is using simple programs, low angle patterns are misleading.
73 Tom
_______________________________________________
Topband reflector - topband@contesting.com
_______________________________________________
Topband reflector - topband@contesting.com
|