Dear Tom,
Rant mode on:
YES, BUT... The same problem I ran into the last time I tried to
chase down VALIDATION of this angle business.
The N6BV "STUDY" you quote is a RE-REPRESENTATION OF MODEL DATA. The
presentation of the model has been revised to make it more useful.
It's still just IonCap.
Where are the original actual incoming angle measurements and
measurement methods for all this stuff? Where is the "How to make an
incoming angle detector" section in the ARRL Handbook.
Everything I've been able to find on it is a model, based upon a
model, based upon a model, based upon a model....
WHERE'S THE BEEF????? WHERE'S THE REAL DATA, THE PEER REVIEWED
METHODS? ANYBODY KNOW?
Worse, you construe the method as being RESTRICTIVE (if the model
doesn't predict it, it can't occur or only rarely) when the text I
have read about it honestly represents the method as merely PREDICTIVE
(if the model predicts it, it's attempting to predict the MOST LIKELY
occurrence).
Beyond that, it makes no statement regarding unusual or non-pro-forma
propagation.
I am struck by the persistence of arguments based upon "authoritative
sources". The whole premise of the scientific movement was to remove
"authoritative sources" from the loop and make such things based on
reproducible experimental data and methods, with both data and methods
in the open for peer review.
As to skip angles, and your stated method, then just how DO you
explain working all the adjoining states from Kentucky using 50 watts
and a 15 foot high 15 meter dipole? All sunspots you say? Doesn't
N6BV's methodology take sunspots into account? Don't we still get
sunspots?
And you can quit bringing up your 40 foot comparison. I never argued
about that. I just said a low dipole would beat a C31XR operating on
18.1., a frequency it wasn't designed for. You said most of the
radiation would go into outer space. I quoted Kentucky. You quoted
N6BV.
There was a period of time when we didn't know about radio.
Authoritative sources said there was no such thing. There was a period
of time where we didn't know about the E layer or the F2 layer.
Authoritative sources made no mention. There was a long period we
thought 160 meters went dead when the sunspots were up. Authoritative
publications said so.
For a long time the ARRL published a 468/f as the measurement for a
dipole. It's no longer in their publications. We learned that the
complexity of ground interaction varied the length of a resonant
dipole. I have my own story to tell about blind acceptance of the
ARRL-ingrained 468/f.
There is a lot of unexplained anecdotal material about propagation
floating around. Now unless everyone with an unexplained happening is
a liar, idiot, or non compos mentis...
Might there not be something yet undiscovered about propagation, that
will seminally revise our models and predictions?
Or has everything already been discovered and explained? And all
propagation doomed to obey IonCap.
When NEC first came out, there was a great deal of glee trying out the
new antenna designer programs. Peer review kept coming up with
anecdota where what was happening was NOT what was predicted. In a
progression of maturations we got stepped diameter corrections, ground
conductivity corrections, bent wire corrections, etc, etc, and a host
of carefully defined boundary conditions that caused the models to go
haywire, and had to be avoided or worked around. NEC 4 is **STILL** an
ongoing collaborative evolution.
Where is this maturation process for the incoming angle prediction
models? We seem to have lots of anecdota, no matura.
Rant mode off:
73, Guy
----- Original Message -----
From: <n4kg@juno.com>
To: <TOWERTALK@CONTESTING.COM>; <k2av@CONTESTING.COM>
Sent: Monday, June 24, 2002 3:59 PM
Subject: Re: [Towertalk] Re: [Force 12 Talk] XR dilemma
> On Mon, 24 Jun 2002 10:20:24 -0400 "Guy Olinger, K2AV"
> <k2av@contesting.com> writes:
> > The original post was about using a C31XR on EIGHTEEN POINT ONE
MHz.
> > That's a band it was not designed for. And that a low dipole would
> > beat it.
> >
> > Where did you get **TEN** meters from? Stick to the subject.
>
> My TEN Meter note was in response to a private note from another
> reader who was asking about very low 10M antennas (at 20 ft).
> I did not want to publicly post his comments without permission
> but I thought my response might be of interest to others so I
> posted it (without inclusion of the original 10M comments).
>
> My computer crashed and apparently multiple copies got
> sent out under the original XR dilemma heading without my
> knowledge. I resent the same text under the title '10M Takeoff
> Angles'. Sorry if that confused anyone. N4KG
>
> >
> > Propagation on 18 is a lot most like TWENTY meters, anyway.
> >
> > And will anyone mention that this angle business is a very
sparsely
> > supported "science" with a lot of unanswered questions and modes,
> > and lots of unexplained contrary anecdotal material.
>
> N6BV has made EXTENSIVE studies of takeoff angles from NA
> to the rest of the world on ALL BANDS using Ioncap models.
> His original work was published by ARRL in the Handbook
> (and / or Antenna Handbook). He *assumed* 60 ft high antennas
> for 10 through 15M and 100 ft high antennas for 17 through 80M
> in his original work. He later revised these studies using
isotropic
> sources to avoild the pattern nulls of the antennas at fixed
heights.
> This data is available on the ARRL Web Site and on CD in the
> latest ARRL ANTENNA HANDBOOK. I 'believe' the
> highest angle supported by the ionosphere at 18 MHz to be
> around 30+ degrees, assuming an MUF of 50 MHz. I have
> other privately supplied data which also supports this conclusion.
> de N4KG
>
> A simplistic approach to determining the maximum waveangle
> that is supported by the ionosphere is to merely *observe* the
> closest stations heard on a given band and look up the SKIP
> distance vs. TAKEOFF Angle in any ARRL Antenna Book.
> Of course, it is necessary to distinguish between F2 propagation
> and E Layer propagation. de N4KG
>
> > Used a 15 foot high fifteen meter dipole as a teenage Novice
> > operator
> > in Kentucky. Since nobody had tried to tell me that all that
energy
> > would go straight into outer space, I went ahead and worked a
couple
> > thousand contacts on it, more USA than not. I got lots of 599/589
> > reports running a mere 50 watts, at a time where you had to get
the
> > QSL address over the air because you couldn't afford a call book,
> > and the automatic 599 hadn't been invented yet.
> >
> > I worked all the surrounding states on 15 meters. This on a
> > frequency higher than in the original post. How does one do that
if
> those
> > angle formulas are really absolute and trustworthy?
> >
> > ***!!!>>> Or is it really that the angle formulas describe a
rather
> > broad and fuzzy center of probability, with a lot contrary
evidence
> > suggesting that there is something yet to be discovered?
> >
> > 18 MHz dipole at 20 feet will work. Easy experiment. Try it. See
how
> > many Europeans you work and get 5NN as a report.
> >
> > 73, Guy.
>
> My guess is that your Teenage experiences were in the mid 1950's,
> when we enjoyed the highest sunspot activity of the last 50 years.
>
> I'm not saying that a very low antenna won't radiate any energy
> that gets reflected, only that a somewhat higher antenna will
> radiate MORE energy that gets reflected. I notice that you
> did NOT have a comparison dipole antenna at 40 or 50 ft.
>
> My bet is that a 40 or 50 ft high dipole would have beaten
> your 20 ft high antenna. Your example proves the theory
> that "any antenna is better than NO antenna" but does not
> prove that it is better than one which radiates ALL of it's energy
> within the range of angles supported by the ionosphere.
>
> One last comment. ALL of my comments ASSUME
> FLAT TERRAIN. Sloping foregrounds tend to favor
> even lower antennas.
>
> Tom N4KG
>
> >
> >
> > ----- Original Message -----
> > From: <n4kg@juno.com>
> > To: <TOWERTALK@contesting.com>; <swca@swbell.net>
> > Sent: Monday, June 24, 2002 8:39 AM
> > Subject: Re: [Towertalk] Re: [Force 12 Talk] XR dilemma
> >
> >
> > > Hi Mark,
> > >
> > > I think our main disagreement comes over the the maximum
> > > angle that is supported on 10M. I believe that to be around
> > > 20 degrees (at very high MUF's).
> > >
> > > Some time ago, someone plotted his 10M SS contacts on
> > > a map. The vast majority were at skip distances of 900 miles
> > > or more, which corresponds to a 20 degree takeoff angle.
> > >
> > > At 18 ft, a 3L 10M Yagi places the majority of it's radiation
> > between
> > > 20 and 30 degrees. 3 dB points are 15 and 40 degrees. Over
> > > 80% of the energy is above 20 degrees, i.e. going into outer
> > space.
> > >
> > > At 35 ft, the 3 dB points are 7 and 22 degrees with the vast
> > > majority of the energy falling in the range of angles supported
> > > by the ionosphere. I see NO BENEFIT in going lower than
> > > 35 ft on 10M.
> > >
> > > Tom N4KG
> > >
> > >
> > >
> > > ________________________________________________________________
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> > >
> >
> >
>
>
> ________________________________________________________________
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