>> 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.
Or perhaps using an antenna with tunable element lengths (SteppIR/UltraBeam)
and changing them to optimize the antenna pattern based on the location of
the other end of the QSO and current conditions.
For weak signal work, the experiment I had in mind was using the estimated
incoming angle only as a starting point to choose from a collection of
pre-computed element lengths optimized for gain or F/B by incoming angle,
and tweaking up or down from there. (I'm not expecting a big effect, but
modeling wih EZNEC and 4nec2 shows reasonable trade-offs are possible). It
wouldn't compensate for fast QSB, but that's not the goal.
If anyone else has tried something similar, I would be interested in hearing
about it.
73, Rick ZL2HAM
-----Original Message-----
From: cq-contest-bounces@contesting.com
[mailto:cq-contest-bounces@contesting.com] On Behalf Of David Gilbert
Sent: Wednesday, June 27, 2012 4:54 AM
To: cq-contest@contesting.com
Subject: Re: [CQ-Contest] Estimating arrival angles?
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.
73,
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
angle.
> 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
> _Good_Old_Softwares_.
>
>
> 73,
> Jukka
>
>
> 2012/6/25 Zack Widup<w9sz.zack@gmail.com>:
>> 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<kiessig@gmail.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
> _______________________________________________
> CQ-Contest mailing list
> CQ-Contest@contesting.com
> http://lists.contesting.com/mailman/listinfo/cq-contest
>
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|