What signal level should there be from the Ch0 port? I'm seeing nothing on a scope. After a Cal the VNA traces are full-screen rubbish, and there is no change irrespective of any load on the connector. I suspect one of the analogue switches is faulty, does anyone know what type they are?
Blue LEDs under ADF devices are on. Sweeping signals present on a large cap in the middle of the board.

I have tried a full reset - makes no difference. Has been working fine, bought late 2021.

Any ideas short of buying another one?

On 4/10/23 1:49 AM, Simon G8DMN via groups.io wrote:
> What signal level should there be from the Ch0 port?

Around 0dBm.


I'm seeing nothing
> on a scope. After a Cal the VNA traces are full-screen rubbish, and
> there is no change irrespective of any load on the connector. I suspect
> one of the analogue switches is faulty, does anyone know what type they are?
> Blue LEDs under ADF devices are on. Sweeping signals present on a large
> cap in the middle of the board.

I don't know that my old NanoVNA2 schematic (attached) is the right one,
but those rf switches are quite ESD and DC sensitive. It doesn't take
much to destroy them. Back in the archives more than a year ago,
there's suggestions for protection devices that have low parasitic C.

>
> I have tried a full reset - makes no difference. Has been working fine,
> bought late 2021.
>
> Any ideas short of buying another one?
>

That's sort of what I thought (0dBm). Last successful use was tuning up a 7MHz wire dipole - could well be static.
Thanks for schematic.

I wonder how well it would work with permanent 3dB pads on the connectors? (when fixed).

Simon

The Nano VNA 2 Plus 4 is a fine instrument for the price. I use it to
measure passive components, such as filters, and for education. However,
measuring antennas involves risk to the VNA as static charges can damage
the unprotected inputs and strong signals can degrade accuracy.

On Tue, Apr 11, 2023 at 8:58 AM Simon G8DMN via groups.io <simon.rundle=
talk21.com@groups.io> wrote:

> That's sort of what I thought (0dBm). Last successful use was tuning up a
> 7MHz wire dipole - could well be static.
> Thanks for schematic.
>
> I wonder how well it would work with permanent 3dB pads on the connectors?
> (when fixed).
>
> Simon
>
>
>

We live and learn.
It turns out there's quite a lot of info about and sufferers of this problem. Perhaps there could be larger / louder warnings about this on the various web pages about this device.

Perhaps the next generation of these VNAs could include some protection - I realise it might result in poorer accuracy.

Simon

On 4/12/23 1:19 AM, Simon G8DMN via groups.io wrote:
> We live and learn.
> It turns out there's quite a lot of info about and sufferers of this
> problem. Perhaps there could be larger / louder warnings about this on
> the various web pages about this device.
>
> Perhaps the next generation of these VNAs could include some protection
> - I realise it might result in poorer accuracy.
>

I don't know that it would result in poorer accuracy - most of the
protection devices effectively put a small (few pF) shunt C on the port,
and that would probably come out in the calibration.

Hi, all ESD protection devices we tested degraded the linearity of S11 measurements to an unacceptable level, so they are not used. In the VNA6000 series we switched to components with a higher ESD rating instead. The frontend ICs are now rated for 4000V HBM instead of 1000V to reduce the occurrence of damage. However, we recommend following ESD precautions when performing measurements. Thanks

On Wed, Apr 12, 2023 at 08:11 PM, nanov2support wrote:

>
> Hi, all ESD protection devices we tested degraded the linearity of S11
> measurements to an unacceptable level, so they are not used. In the
> VNA6000 series we switched to components with a higher ESD rating instead.
> The frontend ICs are now rated for 4000V HBM instead of 1000V to reduce
> the occurrence of damage. However, we recommend following ESD precautions
> when performing measurements. Thanks

This is interesting  and good to keep in mind.

I wonder if there are SMA adaters( or others) with low capacitance ESD diodes built in. They could be usefull elsewhere if not here.

If you can afford one, consider using a dedicated antenna analyzer,
essentially a one port VNA but rugged. The RigExpert units are very good
( made in Ukraine).

On Fri, Apr 14, 2023 at 12:32 AM Leif M <leif.michaelsson@gmail.com> wrote:

> On Wed, Apr 12, 2023 at 08:11 PM, nanov2support wrote:
>
> Hi, all ESD protection devices we tested degraded the linearity of S11
> measurements to an unacceptable level, so they are not used. In the VNA6000
> series we switched to components with a higher ESD rating instead. The
> frontend ICs are now rated for 4000V HBM instead of 1000V to reduce the
> occurrence of damage. However, we recommend following ESD precautions when
> performing measurements. Thanks
>
> This is interesting and good to keep in mind.
>
> I wonder if there are SMA adaters( or others) with low capacitance ESD
> diodes built in. They could be usefull elsewhere if not here.
>
>
>

I've previously posted this, but here it is again:

MiniCircuits VLM-33W-2W-S+ SMA Limiter

You can look up the complete specifications on the MiniCircuits site.

Dave - WØLEV

On Fri, Apr 14, 2023 at 4:32 AM Leif M <leif.michaelsson@gmail.com> wrote:

> On Wed, Apr 12, 2023 at 08:11 PM, nanov2support wrote:
>
> Hi, all ESD protection devices we tested degraded the linearity of S11
> measurements to an unacceptable level, so they are not used. In the VNA6000
> series we switched to components with a higher ESD rating instead. The
> frontend ICs are now rated for 4000V HBM instead of 1000V to reduce the
> occurrence of damage. However, we recommend following ESD precautions when
> performing measurements. Thanks
>
> This is interesting and good to keep in mind.
>
> I wonder if there are SMA adaters( or others) with low capacitance ESD
> diodes built in. They could be usefull elsewhere if not here.
>
>
>

--

*Dave - WØLEV*

On 4/14/23 8:38 AM, W0LEV wrote:
> I've previously posted this, but here it is again:
>
> MiniCircuits        VLM-33W-2W-S+          SMA Limiter
>
> You can look up the complete specifications on the MiniCircuits site.
>
> Dave - WØLEV

Of course, at $63 each, buying a pair of these costs more than the
instrument its protecting <grin>