I would like the NaNoVNA to help me steer my dual dipole array.  I have 2 15m dipoles running E/W, so there is a S. Antenna and a N. Antenna.  Currently I have the same length of quad shielded feed cable running from each antenna to a splitter box.  The S. Antenna has a 1/4 wave phasing cable along with the basic cable length with a goal of steering the detection to 65/70 degrees above the S. Horizon.  My questions are:

1/ Can I use the NanoVNA to determine the phase angle between the two feeder cables?  Ideally I would like to hook North up to S11 and the other (South) to S21 to confirm no phase difference.  This would confirm that both feeder cables were the same length and the beam was 90 degrees straight up.

2/ I'd then like to check my phase cables to the S. Antenna to confirm they are 90 and 135 degrees compared to the N.

I have some basic understanding of engineering/physics but what I could really use is a procedure and some guidance to interpret the results.  Any assistance (including saying you can't do that with a NaNoVNA) would be appreciated.

For background, the application is a Radio Jove antenna to detect Solar and Jupiter Radio Bursts at 20.1 MHz.  I have linked a photo of the set up.

Thanks in advance,
Bob

Short answer - not directly.
You can measure the S21 between the antennas, but that includes the coupling between the antennas which has a phase lag due to the physical distance), and your feedlines get into the equation too.

You could measure your two feedlines, independently, disconnected from the antenna and from the S11 know what the electrical length is. But that still doesn't tell you what the radiated phase shifts will be, because the antennas interact.


I'm facile with modeling, so what I would do is make a quick model in NEC, and then adjust the length of the transmission line until it matched what I measured at the two feed points. Do the measurement on one antenna at a time, leaving the other antenna feedline connected, but not terminated. Do the same in NEC (open circuit is "put a load of 1E7 ohms" on it)

The other thing is that this is a variant of the Christman feed, used for two VHF monopoles - so you could probably use a spreadsheet or tool designed for that to get whatever phasing you want. (see attached for an example)

If I understand your requirements, you are essentially trying to
calibrate your transmission lines at 20.1 MHz. Here is how I would try
to do that. Note that I am referring to the NanoVNA Saver application in
the following.

First I would disconnect one of the feed lines and bring both ends to
the test bench.

Second I would connect the NanoVNA Port0 to one end and Port1 to the
other end of the feed line. Be sure to calibrate the NanoVNA.

Third I would perform an S21 measurement selecting "Phase" for display
and in the marker menu. After scanning, the phase of that length of
cable at 20.1 MH can be read out directly using the marker.

Finally repeat for the other cable and compare and adjust the cables as
necessary.

Obviously this is a calibration process and not meant for ongoing
monitoring.

Hope this helps.

73
Dave VE3TLY

That method is likely the best way to measure phase length. However, if it
is not practical to remove the cables at this point, you could place a
short on the far end and measure S11 for each and adjust the lengths to get
equal phase. Not accurate.

On Fri, Jun 13, 2025 at 11:00 AM Dave VE3TLY via groups.io <dave.green=
ncf.ca@groups.io> wrote:

> If I understand your requirements, you are essentially trying to calibrate
> your transmission lines at 20.1 MHz. Here is how I would try to do that.
> Note that I am referring to the NanoVNA Saver application in the following.
>
> First I would disconnect one of the feed lines and bring both ends to the
> test bench.
>
> Second I would connect the NanoVNA Port0 to one end and Port1 to the other
> end of the feed line. Be sure to calibrate the NanoVNA.
>
> Third I would perform an S21 measurement selecting "Phase" for display and
> in the marker menu. After scanning, the phase of that length of cable at
> 20.1 MH can be read out directly using the marker.
>
> Finally repeat for the other cable and compare and adjust the cables as
> necessary.
>
> Obviously this is a calibration process and not meant for ongoing
> monitoring.
>
> Hope this helps.
>
> 73
>
> Dave VE3TLY
>
>
> --
> Dave VE3TLY
>
>
>

Or, measure the electrical length at something like twice the frequency - The
dipole will be close to an open circuit, and a healthy mismatch. Using the
TDR function will do nicely. Or, measure S11 at 40 MHz find the phase shift
of the reflection, divide by 2 then multiply by (frequency of use/40E6)



Warning, though - the two antennas interact. So “transmission line length” is
NOT “radiated phase of the array element”.











> On Jun 14, 2025, at 04:28, Bob W0EG via groups.io
<morrisnc7=gmail.com@groups.io> wrote:
>
>

> 

>

> That method is likely the best way to measure phase length. However, if it
is not practical to remove the cables at this point, you could place a short
on the far end and measure S11 for each and adjust the lengths to get equal
phase. Not accurate.

>

>
>

>

> On Fri, Jun 13, 2025 at 11:00 AM Dave VE3TLY via
[groups.io](http://groups.io)
<dave.green=[ncf.ca@groups.io](mailto:ncf.ca@groups.io)> wrote:
>

>

>> __

>>

>> If I understand your requirements, you are essentially trying to calibrate
your transmission lines at 20.1 MHz. Here is how I would try to do that. Note
that I am referring to the NanoVNA Saver application in the following.
>
> First I would disconnect one of the feed lines and bring both ends to the
test bench.
>
> Second I would connect the NanoVNA Port0 to one end and Port1 to the other
end of the feed line. Be sure to calibrate the NanoVNA.
>
> Third I would perform an S21 measurement selecting "Phase" for display and
in the marker menu. After scanning, the phase of that length of cable at 20.1
MH can be read out directly using the marker.
>
> Finally repeat for the other cable and compare and adjust the cables as
necessary.
>
> Obviously this is a calibration process and not meant for ongoing
monitoring.
>
> Hope this helps.
>
> 73

>>

>>
> Dave VE3TLY
>
>

>>

>>
> \--
> Dave VE3TLY

_._,_._,_

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