I think the link below is the right Webinar. I hope so, But I remember
one had some very good information on this very subject.
The Original Rolling Ball Clock
On 6/26/2012 11:54 AM, David Gilbert wrote:
> VOACAP does indeed predict optimum arrival angle for any particular
> path, but that's based upon statistical averages -->by month<-- and has
> no bearing at all to instantaneous conditions ... which can change
> DRAMATICALLY in a matter of seconds. And, of course, there are indeed
> multiple arrival angles at play much of the time anyway.
> I have an Elecraft K3 with identical receivers that can be phase locked
> for diversity reception. I also have a tribander and 40m yagi on the
> same tower spaced about 12 feet apart vertically. One night on 40m I
> fed the signal from the tribander into one receiver and the signal from
> the 40m yagi into the other receiver ... and then fed the stereo audio
> output into my computer sound card with a dual-channel audio
> oscilloscope application running. I tuned to a 40m broadcast signal so
> that I could get a pure carrier when the announcer was not speaking. I
> sync'd the oscilloscope to one signal while observing both on the
> screen, and while I couldn't determine the exact phase angles because I
> didn't know the electrical lengths to each antenna, I was able to watch
> the phase difference in real time (relative phase is retained in the
> frequency down conversion to audio). Based upon the 12 foot spacing and
> the amount of phase shift I was seeing on the computer screen, I
> calculated that the NET arrival angle was changing as much as 20 degrees
> within fractions of a second ... which is not unrealistic in light of
> other more rigorous studies that have been done by the government over
> the past several decades. That net arrival angle could have been due to
> a single signal changing in angle or the sum of multiple arrival angles
> individually changing in amplitude, but the net result would be the same
> to a listener ... perceived fast fading.
> HFTA, the terrain analysis program written by N6BV that comes free with
> the ARRL Antenna Book, uses the VOACAP arrival angle data for its
> optimization algorithm and that's about as good as you're going to get
> for planning purposes. For actual real time optimization, you are
> pretty much stuck with either using stacked antennas to eliminate
> notches or somehow being able to quickly raise/lower your antenna as
> conditions require.
> Dave AB7E
> On 6/26/2012 3:27 AM, Jukka Klemola wrote:
>> Luckily the world is not that simple we really could measure the arrival
>> There are often more than one sky wave propagation models happening
>> all the time if you are in ZL2.
>>> From ZL2, you work a JA, a W6 or anything else that is 'close by' ..
>> the propagation usually happens through at least two F2 hops.
>> To estimate how the propagation works out, I have used a DOS program
>> Miniprop for that purpose.
>> W6EL that works in WinXP machines, might have the same feature.
>> At least you can set the minimum radiation angle also in W6EL so you
>> can experiment by software the phenomena you are after.
>> Maybe also VOACP has some possibilities for that, but I found VOACAP
>> to be largely inferior comparing to even Miniprop when I was
>> experimenting the low angle propagation models for long-haul paths.
>> I gave OH6BG a set of feedback, so VOACAP may have been corrected or
>> at least improved, I do not know.
>> I have been very happy experimenting by software with W6EL and Miniprop.
>> ..yes. I still have even DOS computers around so I can use the
>> 2012/6/25 Zack Widup<firstname.lastname@example.org>:
>>> You would need at least two separate antennas and the ability to
>>> measure the phase angle between the signals received by the two
>>> On 6/25/12, Rick Kiessig<email@example.com> wrote:
>>>> Can anyone suggest a good way to estimate the incoming RF arrival angle for
>>>> a given QSO? Are there any software tools to help in that type of analysis?
>>>> 73, Rick ZL2HAM
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