[Top] [All Lists]

Re: [CQ-Contest] Estimating arrival angles?

To: "David Gilbert" <xdavid@cis-broadband.com>, <cq-contest@contesting.com>
Subject: Re: [CQ-Contest] Estimating arrival angles?
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Wed, 27 Jun 2012 20:20:24 -0400
List-post: <cq-contest@contesting.com">mailto:cq-contest@contesting.com>
> Arriving signal polarity is indeed something that others have found to
> be quite variable at times.

It varies million of times a second. :-)

>It is generally accepted that HF skywave
> signals arrive with an elliptical polarization, but the shape of the
> ellipse can change pretty dramatically.  And 20 to 30 db impact is not
> unusual at all.  Lots of Field Day stations will orient adjacent
> antennas with different polarization to minimize cross-band overload.

A horizontally polarized dipole, or Yagi, is only perfectly horizontal 
straight off the broadside of the element. I made that mistake installing a 
160 dipole to null my vertical, and quickly learned to null the vertical my 
dipole had to be broadside to the vertical, and not nearly off the ends. One 
of those "duh" moments for me.

> I've thought about feeding the signals from two cross polarized antennas
> to the two phase locked receivers of my K3 to investigate the real time
> effects ... maybe some day I'll get around to it.

My K3 is phase locked between channels on any given frequency, but not phase 
stable at one fixed phase difference between channels as the VFO is moved. 
You can observe this effect by combining the sub and main into one channel 
in and audio into one channel out, and tuning any band while listening to 
background noise. You will hear peaks and nulls as phase rotates as much as 
180 degrees with frequency settings.

This does not hurt diversity stereo for me, like not having phase lock and 
phase stable (common in most radios) does, but be aware of it in 
measurements. Don't tune while measuring phase.

>What I really need to
> do is learn how to program (probably with something like Python) so that
> I can record the audio to a wave file and then analyze the result
> properly.  Maybe I'll live long enough to do that ... maybe not.

I use Audacity for recording. It will let me zoom enough to see phase, and 
there might be a way to get an X-Y sum.

I don't see much real rotation of polarization and of phase between 
spatially separated antennas, but there is a little varying tilt. Nothing of 
any real fading consequence, in what I have recorded and looked at. I 
decided it was a waste of time for me.

73 Tom 

CQ-Contest mailing list

<Prev in Thread] Current Thread [Next in Thread>