Best method would be a O-scope with H input to ant 1 and V input to ant 2.
Use feedline, identical length and characteristics. Feed the same low
level signal to both antennas with whatever switching you have available.
If your signals are in phase you are perfectly in phase. At the
feedpoints, if the feedpoints are equidistant from the boom. However I bet
they aren't. Cheap way. Low level signal again to both antennas use a
remote receiver at a comfortable distance. O-scope again will show 2
superimposed sine waves out of phase if they are not in phase. Now turn
the antennas to a new heading 90 degrees in same direction. I bet the
results will be different. To the dx they are going to be phased at some
random angle. Different dx, different angle. Worth the trouble? Probably
not, unless there is on heading you want to favor. BTW you can tell the
phase difference by the fraction of the wavelength difference. To tell
which signal is which add a few feet of feedline to 1 antenna.
Jim K0XU
jim@rhodesend.net
On Tue, Mar 10, 2026, 10:29 George Fremin III <geoiii@kkn.net> wrote:
>
> I have posed this question to a number of people over the last few years -
> and I have gotten some interesting ideas but I am not sure any of them have
> provided a simple or repeatable way of making such a measurement. I have
> not tried any of they yet but I think I am getting to that point.
>
> So, I thought I would cast a larger net.
>
> On the simple side of things - if I have two antennas - lets say verticals
> at some distance from each other with coax coming from them is there some
> way to measure the phase difference? Could I get some value out so that I
> know how much delay I need to add to one to get them in phase for a given
> signal?
>
> Or lets say I have two yagis on a tower fed with coax and I would like to
> verify they are in phase or at least close - can I measure this in some way?
>
> What if I have say a 48 foot boom 10m yagi and a 24 ft boom 10m yagi on a
> tower at 60ft over 30ft. If there a way for me to measure the phase
> difference?
>
> The last question is a real use case - and on the air use of this antenna
> seems to show that I might have lucked into these antennas being in phase -
> at least they work better together for EU and the USA. But it would be
> nice to repeat this luck or measure it.
>
> It would be nice if this did not require $100k in test equipment.
>
>
> George Fremin III
> K5TR
>
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