[Elecraft] K3 diversity phase drift

Thu Apr 9 17:01:28 EDT 2026

Hi, Alan.

Yes, that could rather easily be done.  Of course it's not possible to 
independently assign "phase" to an individual signal since that would 
require some sort of independent phase reference, but the app I build 
already measures the relative phase between them and that is all that is 
needed.  The app also already measures the relative amplitude between 
the two signals, so it should be possible to have an app (either this 
one or a similar one) do exactly as you propose.

I'm not sure yagis work so well for this sort of thing.  Yagis operate 
by manipulating phase, and some of my tests involving the two yagis on 
my tower instead of the purpose-built horizontal dipoles gave REALLY 
squirrely results.  I have some EZNEC models of various yagis and when I 
look at the far field data under the "FF Tab" the phase is dramatically 
different for different elevation angles.  As best I can tell, that 
means that the incoming phase would be corrupted by the antenna itself 
and almost certainly in a different manner for a horizontally oriented 
yagi than a vertically oriented yagi.  I suspect that two crossed 
dipoles would be best. If I remember correctly, a KL7 did a bunch of 
work tracking polarization shifts a few years ago.  I don't remember his 
callsign but he's pretty active on the TowerTalk reflector.

Again ... I haven't waded this far into the swamp before so I'm mostly 
in "explore" mode as far as capturing all the nuances.

By the way, I wrote the app using a PowerPoint diagram for the layout of 
the user interface and a list of prompts on what I wanted the app to 
do.  I fed that into Codex and I've spent maybe 5X more time working on 
the video describing the app than I spent with Codex refining it.  I 
literally did not write a single byte of the actual code myself.

73,
Dave   AB7E

On 4/9/2026 12:41 PM, Alan wrote:
> Hi Dave,
>
> Have you  given any thought to using this technque to measure the 
> polarity of the incoming signal?  One receiver input would go to a 
> horizontal dipole and the other to a vertical dipole, with the two 
> dipoles co-located (feedpoints at the same location).  It could also 
> be done with two Yagi antennas mounted on the same boom.
>
> If you can measure the phase of each signal as well as the amplitude, 
> the polarity can be calculated with a little trigonometry.
>
> This is something i've wanted to do for years "when I get time". :-)
>
> Alan N1AL
>
>
> On 4/9/2026 6:43 PM, David Gilbert via Elecraft wrote:
>>
>> 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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