[TowerTalk] Propagation / Beam Headings Responses

[Sylvan Katz]

Well Tom,

>  Propagation prediction tools are useful IF you recognize their
 > limitations.

You are indeed correct. I only build the front end stuff - I leave the
propagation details  to the RSGB propagation committee
(http://www.rsgb.org/society/psc.htm and
http://www.keele.ac.uk/depts/por/psc.htm#members) which I believe has
some propagation experts (maybe even a physicist or two) sitting on it.
They seem to know what they are doing. In fact at the moment they have
mounted a serious effort to calibrate the new tools we are using by
collecting real data. It will take a couple of  years to complete this
project.

>  First, since they are based on AVERAGES, they typically

Are you suggesting that 'averages' do not provide some useful insight
into propagation for the 'average' amateur during a particular part of
an 'average' sunspot cycle using an 'average' K-index and SSN in a
particular 'average' season? Hmmm - I guess that is why they are called
'propagation prediction' programs.

>  Some propagation "experts" have done the DX community > a serious
disservice with inaccurate low band propagation

>From the details you provided it would seem that your personal
requirement is more of a commercial-like requirement and not really an
amateur requirement. My  DXing  needs, I guess, are less sophisticated
than yours and thus I am rather content with averages. And I think that
knowing the average probablity of a path being open at a particular time
(e.g. plus or minus 30-60 mins) under average conditions would be
reasonable for most amateur requirements. I tend to look at the
propagation table, fill my coffee cup, sit in front to the rig and have
a listen ---  I am always prepared for the prediction to be wrong (a)
because it is just that a prediction and (b) because I live in the
auroral zone and no model can handle that problem.

>   Theoretical models of ANTENNAS have been shown to be
>  accurate.  IMHO, simplistic propagation prediction programs
>  leave a LOT to be desired.  Theory must be backed up by
> observation and confirmation.

Well I guess you might have to wait a few life times or longer to get
this kind of accuracy. Propagation theory falls into the larger study of
dynamical, deterministic,  non-linear systems (or chaotic systems) and
like the weather and other turbulent systems, they are highly sensitive
to intial conditions and very unpredictable past a certain point no
matter how accurately can describe them. However, even though the
weather is unpredictable even two or three days into the future most of
us look at the weather channel to see what is coming even though we know
the prediction could be wrong. It seems that average predictions have
some sort of usefulness in our society even though they are  not very
accurate. In addition, unlike antenna theory which can be model antennas
with a great deal of accuracy because they are 'not' dynamical system,
they are static non-linear systems, I think we will have to remain happy
and content with predicting propagation that use averages and predict
averages. Perhaps we will have to leave the actual detail to Mother
Nature. Oh - and by the way many good propagation models are backed up
with observation (look around http://www.its.bldrdoc.gov/Home.html)

Thanks for the interesting comments

73 .... sylvan

ps - I hope this is not too far off the TT theme :-)

--
Sylvan Katz
Saskatoon, Sask
VE5ZX & G0TZX



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