开云体育

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in
11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun
and one at the VNA S11 port. No body / coax inadvertent movements,
everything taped down near the antenna.

Thanks

If you have a close-by strong source of RF energy like FM or AM
broadcasters, police, ambulance, CB'ers, hams, ....... any of those and
more could be affecting the readings. This is not all that uncommon in
cities when the VNA is connected to a large antenna.

Dave - W?LEV

On Tue, Apr 1, 2025 at 7:51?PM kellogs via groups.io <mihai0226=
[email protected]> wrote:

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in
11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun
and one at the VNA S11 port. No body / coax inadvertent movements,
everything taped down near the antenna.

Thanks

If you have a close-by strong source of RF energy like FM or AM
broadcasters, police, ambulance, CB'ers, hams, ....... any of those and
more could be affecting the readings. This is not all that uncommon in
cities when the VNA is connected to a large antenna.

Dave - W?LEV

On Tue, Apr 1, 2025 at 7:51?PM kellogs via groups.io <mihai0226=
[email protected]> wrote:

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in
11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun
and one at the VNA S11 port. No body / coax inadvertent movements,
everything taped down near the antenna.

Thanks

--

*Dave - W?LEV*


--
Dave - W?LEV

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in
11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the balun
and one at the VNA S11 port. No body / coax inadvertent movements,
everything taped down near the antenna.

Thanks

Is the measurement frequency stable?
Dave
ZL3FJ

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Zack Widup via groups.io
Sent: Thursday, April 03, 2025 06:14
To: [email protected]
Subject: Re: [nanovna-users] Jittery , non steady readings

I have consistently had this problem measuring inductors, capacitors and
resistors. Just recently I measured a silver mica capacitor that was around
3400 pF. I measured at 475 kHz (630 meter amateur band). As I watched the
display, every time I got a new measurement I would see something like
3420.1
3416.3
3411.8
3418.6
3422.5
3424.2
etc.

I took the average of the measurements as the value. But I don't know why
this was happening. The same happens with resistors and inductors. I could
see the inductors as most likely to pick up radio signals. But I do not
live close to a radio station or any service that is transmitting near me
(as noted on a TinySA). I turned off my wifi and got the same results.

I use a right angle SMA connector with a wire about 3 inches long going
through the opening and soldered to the center pin contact, also another
wire about 3 inches long soldered to the SMA body. I solder the other ends
of the wires to the device under test.

Zack W9SZ

On Tue, Apr 1, 2025 at 2:51?PM kellogs via groups.io <mihai0226=
[email protected]> wrote:

Is it normal for the readings to fluctuate as much as 2-3 ohms ? As in
11+/-1.5 - j(70+/-1.5)

Dipole NMHA (antenna), balun, calibrated, two ferrites: one at the
balun and one at the VNA S11 port. No body / coax inadvertent
movements, everything taped down near the antenna.

Thanks

<

Virus-free.www.avg.com
<

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>