Bob,
Would you suggest a voltage balun or current balun at antenna feedpoint?
One ham told me that if you use a voltage balun, it can bring down the high
noise I have on 80m.
Regarding the original question, I am tempted to think like Milt. I see a
lot of harmonic resonance in NanoVNA tracings when I set the range high on
purpose. In fact I use them to work higher bands. I am able to work North
America from VU on 12m, using my 80m center-fed dipole mounted at just 5m
height and 100W, with a little bit of touching up with the N7DDC tuner.
That would be the seventh harmonic resonance!
73
Jon, VU2JO
On Mon, Mar 31, 2025 at 6:29?PM Bob Ecclestone VK2ZRE via groups.io
<becclest@...> wrote:
Hello Hobride,
Unfortunately you have not supplied a photo of your test setup.
A dipole is balanced at the feedpoint, your VNA is unbalanced.
I suspect your problem is that you do not have a balun or choke at the
antenna feedpoint to prevent the feeder from affecting the measurement.
I won't make any guess as to why the VSWR appears lowest at 513MHz, but
I do suggest you use a balun or choke at the antenna.
HTH...Bob VK2ZRE
On 31/03/2025 11:25 pm, Milton Engle via groups.io wrote:
You did not indicate the range of your sweep.
Try setting the sweep range to 150MHz to 190MHz, recalibrate
open/short/load, then measure.
I suspect that you will find the lowest VSWR near 171MHz, indicating
that the element lengths are a bit long.
The third harmonic of 171 is 513
Milt
N3LTQ
On Mar 31, 2025, at 03:51, hobride via groups.io <hobride=
[email protected]> wrote:
?Hello everyone,
I have bought a NANO VNA H4 to build simple dipole antennas.
Now I have made a simple dipole antenna for testing. This should be
tuned for 172 MHz. The total length is ~83 cm (2,72 feet), one leg is ~41.5
cm (1,36 feet).
When I now connect this antenna and try to measure it, the result is a
lowest SWR (1.15) at 513 MHz.
Can this be possible? I am not a radio specialist. I am an IT guy.
I have flashed the NANO VNA H4 to the latest firmware (tried DiSlord
and Hugen) and also calibrated it.
Perhaps I need to make further settings after flashing?
