I have never seen a problem feeding a dipole directly with an unbalanced
feedline. The last dipoles I had up (which were for 40 and 30 meters) were
just fed by connecting the two leads of the coax directly to the antenna
wires attached to an insulator at the center of the antenna. SWR in both
cases, when the antenna was trimmed, were around 1.05:1. And I worked 180
countries on 40 m CW with that antenna and Japan fairly often on 30 m CW.
Zack W9SZ
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On Mon, Mar 31, 2025 at 7:59?AM 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?
