[Elecraft] K3 diversity phase drift

[David Gilbert]

Hi, Mike.

I haven't done any searching, but I'm sure that such studies have been 
made ... probably many decades ago.   A good friend of mine told me that 
a long time ago he was a consultant for the Army on a project that used 
an array of several antennas to track instantaneous changes in arrival 
angle using phase determination. He said that significant changes could 
be seen in fractions of a second, but I wouldn't be surprised if they 
were also experiencing multipath diffraction patterns.

In my case, I think several factors are at play.  I'm using two short 
(non-resonant) horizontal dipoles 18 feet high spaced about 12 feet 
apart that are both broadside to WWV, and I'm using a really narrow 
bandwidth on the K3 to filter out the sidebands so I get only a mostly 
clean carrier.  Given the results I see, I think these are the possible 
effects:

1.  Simple multipath reflections due to ionospheric propagation effects.
2.  Reflections from the sloped ground beneath the antennas (I live on a 
hillside) that would have different effect with different arrival angles 
... AND different effect caused by #1 above.
3.  Reflections from surrounding terrain.  I not only live on a hillside 
with a mountain range to the south and west of me, but there is a deep 
(50 foot deep, 120 foot across) ravine roughly 100 feet to the south of 
the two dipoles.

I don't think it is possible to accurately model any of that unless it 
was possible to actually measure and plot a ground conductivity profile 
of the entire area that would show where the actual RF ground plane is.  
The sides of that ravine show how variable the earth is here ... soil in 
some places, iron-based rocks in some places but limestone or quartz in 
others, and rocks varying from the size of an orange to the size of a 
garage.

I have to admit, though ... even if I can't get unambiguous numbers for 
arrival angle, the application accurately displays the relative phase 
between the signals that are coming from the two dipoles and it's rather 
fascinating to see the rapid and significant changes over time.

The application may be better suited to displaying the azimuth angle of 
a signal ... presumably using vertical antennas.  I suspect that there 
is less multipath propagation azimuth-wise than there is elevation-wise 
... but I could be wrong about that as well.  ;)

73,
Dave  AB7E



On 4/9/2026 10:18 AM, Michael Carter via Elecraft wrote:
> Hi Dave,
>
> I've been interested in your experiments since you first posted news of them and the app you developed for angle-of-arrival estimation.  Your latest post really piques my curiosity.  Is there new science to be uncovered for the effects you describe as anomalous, or is there professional academic literature that already has reported such effects?  I have not ventured into that literature, but would be surprised if some ionosphere scientists had not conducted similar experiments.
>
> Thanks for a very interesting thread, and keep the reports coming!
>
> 73,
> Mike, K8CN
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