I can see this clearly at my new QTH. Beaming toward Africa, I am shut out
below about 12 degrees by the mountains behind me. Some path statistics
that I have seen for 10 meters (W4ZV's qth to Europe) indicate that the
arrival on 10 meters is generally below 12 degrees. Sure enough, I am
at about a 30 to 40dB disadvantage in that direction (based on comparison
signal reports with other area station who have flat terrain in that
On 20 meters, where absorption is more of an issue, I seem to do better
in that direction. I haven't looked at the AOA statistics for 20 meters, but
I would wager that there is a higher likelihood of AOA's greater than 12
degrees on 20 meters as compared to 10 meters.
In contrast to the the view towards Africa, towards the Pacific I have a
negative terrain slope. In this direction I seem to hear and be heard just
as well as everyone else on 10 meters despite using just a trapped
I look forward to getting a copy of HFTA. Should be interesting.
73 de Mike, W4EF..........................................
> > 1. The models used for predictions contain statistical data, thus there
> > is no possibility of guaranteeing that a particular path's predicted
> > characteristics will be accurate or even that the path will exist at
> > I understand and accept this. However, it's kind of like reading
> > semaphore signals in the fog. If the fog is too thick, you won't see
> > the signaller. If it's somewhat thick you may be able to see him but
> > not make out 100% of what he is sending. No fog, no problem. BUT if
> > you're facing the wrong way you will never see the signaller, fog or no
> > fog. I'm looking to the predictions to tell me which way to face.
> Exactly so.. just so you recognize the limitations of your modeling
> by the way, I too am interested in... looking forward to HFTA, which will
> a lot of this)
> > 2. The models are based on smoothed numbers. The daily SFI/sunspot
> > numbers you get are not smoothed so aren't the right values to use.
> > On a 6 hourly basis you can get Effective SSN based on real time FoF2
> > observations from
> > http://www.nwra-az.com/spawx/ssne24.html
> > The USAF provides forecasts about a month ahead of K and SFI values.
> > Presumably these forecasts improve on the model, else why would they
> > bother. I think the forecast is for a longer period than the 27 day
> > rotation period of the sun.
> > IPS in Australia provides Hourly Area Prediction charts centred on any
> > location you choose. It shows what I presume to be Optimum Working
> > Frequency (it tells you on their website) to any point on the chart.
> > Why are they doing this if it doesn't mean anything on a particular day?
> > What I'm trying to say here is that it looks to me as if people are
> > doing meaningful path predictions (and others are buying them).
> IPS uses a different modeling approach more suited to short time range
> predictions. Not that the IONCAP models won't work, it's just that they
> don't have the statistical validity that models more suited to
> predicts might have. Think of it like predicting the stock market
> behavior... If your interest is in behavior over 20 years, a month or year
> at a time, you'd use a different technique than if you were interested in
> day trading. The day trading model might work real well in the short run,
> but have large divergences in the long run.
> Compare also, for example, climatology predictions and weather
> IONCAP is more like a climatological program (We predict that we'll get
> inches of rain this year, but we don't really know on what days)... Short
> run forecasting is more like weather prediction (it will be 95 degrees
> tomorrow afternoon).
> Different models, different analysis, different validations.
> > 5. Just because a path is open doesn't mean that there are Qs to be
> > made because a) there's no one there b) they all have their beams
> > pointing sideways to you working a different opening
> > a) I didn't mention it because I was trying to keep things simple. The
> > FOM includes the number of stations reachable via that path who entered
> > the contest last year.
> > b) Sad but true. I guess experience is the only teacher here. Say, I
> > could also plot paths for each location I'm trying to reach to see what
> > they're likely to be working.... oops, sorry, got carried away there.
> Actually, that IS a clever idea... As you mention, the "other end of the
> link" might have a gain antenna, pointed elsewhere. More practically, the
> band they'll be on is the band that's "hot" for them. However, bear in
> a path that's good from you to them, is probably also good from them to
> and that's where they'll be. (hope springs eternal).
> Jim, W6RMK
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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