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Sad to report that, for the second time, my nanovna is broke from RF over exposure or ESD. My question is: can I protect the input with some fuse- or similar over-load protection device? Yes, I will treat this one with extra care.
Terry. K3JT

Terry,

Can you please explain the RF exposure or ESD which caused the failure so
that I can take precautions?

73
Jon, VU2JO

On Fri, May 16, 2025 at 8:43?PM Terry Wassell #1398 via groups.io <k3jt.wv=
[email protected]> wrote:

Sad to report that, for the second time, my nanovna is broke from RF over
exposure or ESD. My question is: can I protect the input with some fuse-
or similar over-load protection device? Yes, I will treat this one with
extra care.
Terry. K3JT

Which one? NanoVNA V2 frontend is quite different from H4 (for example).

On Fri, 16 May 2025 at 17:13, Terry Wassell #1398 via groups.io <k3jt.wv=
[email protected]> wrote:

Sad to report that, for the second time, my nanovna is broke from RF over
exposure or ESD. My question is: can I protect the input with some fuse-
or similar over-load protection device? Yes, I will treat this one with
extra care.
Terry. K3JT

Permanent installation of the following would go a long ways in protecting
the S11 or source port:

VLM-33W-2W-S+

From Minicircuits. It's presently under re-design, but is available and is
designed to limit large and possibly damaging RF levels on the ports where
it is installed.

Dave - W?LEV

On Fri, May 16, 2025 at 3:26?PM Dragan Milivojevic via groups.io
<d.milivojevic@...> wrote:

Which one? NanoVNA V2 frontend is quite different from H4 (for example).

On Fri, 16 May 2025 at 17:13, Terry Wassell #1398 via groups.io <k3jt.wv=
[email protected]> wrote:

Sad to report that, for the second time, my nanovna is broke from RF over
exposure or ESD. My question is: can I protect the input with some

fuse-

or similar over-load protection device? Yes, I will treat this one with
extra care.
Terry. K3JT

--

*Dave - W?LEV*


--
Dave - W?LEV

As Dave mentioned limiters like mini-circuits VLM-33W-2W-S+ are a good solution. Unfortunately these are hard to get as they are being re-designed, and ebay sellers know this and have jacked up prices to mafia levels.
Fortunately for us, another great solution is the equivalent TAPR, their limiter can be purchased from here

Please *Note* that the TAPR version is only spec'ed up to 6M (54 MHz) and is not as wide bandwidth as the mini-circuits that goes up much higher. Please read the description on the above page before buying.

Another option is the receiver guard from DX engineering

This has an operating range 500 kHz to 150 MHz - still not as wide band as the mini-circuits and has limitation on the lower frequencies unlike the mini-circuits or the TAPR limiters. This unit has BNC connectors and not SMA.

There are many pin-diode based limiters on eBay/Aliexpress, none of them have clear specs, so buyer beware.

Also please note the presence of such limiters still does not guarantee full protection due to limits of input power, output leakage, recovery time and non linear behavior outside the defined bandwidth. In any case you cannot willy-nilly pump watts into these, things will still go up in smoke! You still need to attenuate and/or use a good quality sampler (see w2aew's videos on these topics, all of his videos are so excellent)
If you are so inclined, I can suggest starting with this and then search for all related videos


--
73 de ws1m
bammi

There is also a large family of low-capacitance limiter diodes from a
number of (non-Chinese) sources designed specifically for the purpose if
you choose to build your own. They are readily available from standard
suppliers like Mouser and Digikey. They are not expensive.

Again, the use of these limiters does not guarantee a silver bullet in
preventing damage.

Dave - W?LEV



On Fri, May 16, 2025 at 5:21?PM WS1M - bammi via groups.io <jbammi=
[email protected]> wrote:

As Dave mentioned limiters like mini-circuits VLM-33W-2W-S+ are a good
solution. Unfortunately these are hard to get as they are being
re-designed, and ebay sellers know this and have jacked up prices to mafia
levels.
Fortunately for us, another great solution is the equivalent TAPR, their
limiter can be purchased from here

Please *Note* that the TAPR version is only spec'ed up to 6M (54 MHz) and
is not as wide bandwidth as the mini-circuits that goes up much higher.
Please read the description on the above page before buying.

Another option is the receiver guard from DX engineering


This has an operating range 500 kHz to 150 MHz - still not as wide band
as the mini-circuits and has limitation on the lower frequencies unlike the
mini-circuits or the TAPR limiters. This unit has BNC connectors and not
SMA.

There are many pin-diode based limiters on eBay/Aliexpress, none of them
have clear specs, so buyer beware.

Also please note the presence of such limiters still does not guarantee
full protection due to limits of input power, output leakage, recovery time
and non linear behavior outside the defined bandwidth. In any case you
cannot willy-nilly pump watts into these, things will still go up in smoke!
You still need to attenuate and/or use a good quality sampler (see w2aew's
videos on these topics, all of his videos are so excellent)
If you are so inclined, I can suggest starting with this and then search
for all related videos


--
73 de ws1m
bammi

--

*Dave - W?LEV*


--
Dave - W?LEV

It was the H4 . Purchased from R&L. I accept the blame for the damage. The nano was not defective.

Thanks for all the information and suggestions. I will chose a low cost option and have learned to be more thoughtful and careful with this wonderful tool. I have learned a lot from it and have a replacement on the way. Thanks again for your expert advice.
Terry K3JT.