Hi
In a YouTube Video i saw Someone built a esd safer for the NanoVNA. The circuit wasn’t clear to me as had drawn. I’m wondering if anyone built such a esd safer for his device and can share the latest circuit?

yt-Video https://m.youtube.com/watch?v=totwu4IbavE

YouTube is going to be our technical undoing.

The video is factual useless nonsense. A GDT will not protect a VNA of
any type, it will barely help a much more robust communications
receiver. Adding a GDT and ground strap is a total waste of time and money.

There are two reasons a VNA is damaged:

1.) Steady state voltages either from local signals or bias voltage on
the device under test. We can look for or measure for these issues
before connecting. Just a volt or two will damage some VNAs, and most
all of them will go at 20-50 volts. (My Nano VNA is useless on my 200ft
high 500 foot long 630-meter antenna because it overloads, and I am many
miles from any significant broadcast systems.  Even with a 15-ohm dcr
2.5MH RF choke dc static drain I puckered when I connected it. It has
+10dBm or more of accumulated signal level from external distant RF
sources!)

2.) Static or residual charge from a large high antenna and feed line
capacitance being charged,  or perhaps a capacitor in the system
accidentally left charged from some previous bias voltage.

The three most effective ways to handle this and protect the VNA are:

1.) Don't connect to an active circuit unless you know what you are
doing, things like a bias-T can be a disaster

2.) Short the external load or have a static drain like a resistor or
choke across the external load before connecting

3.) Don't test antenna systems in inclement weather

The very worst thing you can have is a false sense of being protected. I
would never even bother with a GDT system of any type, the threshold
voltage is far too high and the ground strap is silly. The VNA is
damaged by differential mode voltage between center and shield...not
shield common mode voltage. If you damage a VNA from lack of ground you
have a very dangerous system and deserved the damage as a wake up call.

73 Tom




On 7/29/2023 4:02 PM, Max DM5MK wrote:
> Hi
> In a YouTube Video i saw Someone built a esd safer for the NanoVNA.
> The circuit wasn’t clear to me as had drawn. I’m wondering if anyone
> built such a esd safer for his device and can share the latest circuit?
>
> yt-Video https://m.youtube.com/watch?v=totwu4IbavE
>

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Seems to me that the best practices of good esd bench work and shorting any leads together of the devices you are going to measure before making your measurements are all you need. These practices have worked for me for over 40 years including using highly sensitive esd equipment.

The circuits describe in the video are well understood when trying to protect equipment from esd but should not be needed when using a nanoVNA.

Very well said. I use my nanoVNA for passive components like filters. For
antennas, I use a good dedicated antenna analyzer like the rugged RigExpert
series.

Bob

On Sun, Jul 30, 2023 at 9:59 AM Tom W8JI <w8ji@w8ji.com> wrote:

> YouTube is going to be our technical undoing.
>
> The video is factual useless nonsense. A GDT will not protect a VNA of any
> type, it will barely help a much more robust communications receiver.
> Adding a GDT and ground strap is a total waste of time and money.
>
> There are two reasons a VNA is damaged:
>
> 1.) Steady state voltages either from local signals or bias voltage on the
> device under test. We can look for or measure for these issues before
> connecting. Just a volt or two will damage some VNAs, and most all of them
> will go at 20-50 volts. (My Nano VNA is useless on my 200ft high 500 foot
> long 630-meter antenna because it overloads, and I am many miles from any
> significant broadcast systems. Even with a 15-ohm dcr 2.5MH RF choke dc
> static drain I puckered when I connected it. It has +10dBm or more of
> accumulated signal level from external distant RF sources!)
>
> 2.) Static or residual charge from a large high antenna and feed line
> capacitance being charged, or perhaps a capacitor in the system
> accidentally left charged from some previous bias voltage.
>
> The three most effective ways to handle this and protect the VNA are:
>
> 1.) Don't connect to an active circuit unless you know what you are doing,
> things like a bias-T can be a disaster
>
> 2.) Short the external load or have a static drain like a resistor or
> choke across the external load before connecting
>
> 3.) Don't test antenna systems in inclement weather
>
> The very worst thing you can have is a false sense of being protected. I
> would never even bother with a GDT system of any type, the threshold
> voltage is far too high and the ground strap is silly. The VNA is damaged
> by differential mode voltage between center and shield...not shield common
> mode voltage. If you damage a VNA from lack of ground you have a very
> dangerous system and deserved the damage as a wake up call.
>
> 73 Tom
>
>
>
>
> On 7/29/2023 4:02 PM, Max DM5MK wrote:
>
> Hi
> In a YouTube Video i saw Someone built a esd safer for the NanoVNA. The
> circuit wasn’t clear to me as had drawn. I’m wondering if anyone built such
> a esd safer for his device and can share the latest circuit?
>
> yt-Video https://m.youtube.com/watch?v=totwu4IbavE
>
>
>
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> Virus-free.www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> <#m_1380364117553627140_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
>
>

QUOTE (from Tom, W8JI): YouTube is going to be our technical undoing

AMEN and again A M E N ! ! !

Youtube provides an avenue for proliferation of snake oil, witchcraft, and
sorcery within (and with out) the hobby. The majority of the presentation
are technically flawed and many dead wrong!

I avoid YouTube, period.....

Dave - WØLEV

On Sun, Jul 30, 2023 at 1:59 PM Tom W8JI <w8ji@w8ji.com> wrote:

> YouTube is going to be our technical undoing.
>
> The video is factual useless nonsense. A GDT will not protect a VNA of any
> type, it will barely help a much more robust communications receiver.
> Adding a GDT and ground strap is a total waste of time and money.
>
> There are two reasons a VNA is damaged:
>
> 1.) Steady state voltages either from local signals or bias voltage on the
> device under test. We can look for or measure for these issues before
> connecting. Just a volt or two will damage some VNAs, and most all of them
> will go at 20-50 volts. (My Nano VNA is useless on my 200ft high 500 foot
> long 630-meter antenna because it overloads, and I am many miles from any
> significant broadcast systems. Even with a 15-ohm dcr 2.5MH RF choke dc
> static drain I puckered when I connected it. It has +10dBm or more of
> accumulated signal level from external distant RF sources!)
>
> 2.) Static or residual charge from a large high antenna and feed line
> capacitance being charged, or perhaps a capacitor in the system
> accidentally left charged from some previous bias voltage.
>
> The three most effective ways to handle this and protect the VNA are:
>
> 1.) Don't connect to an active circuit unless you know what you are doing,
> things like a bias-T can be a disaster
>
> 2.) Short the external load or have a static drain like a resistor or
> choke across the external load before connecting
>
> 3.) Don't test antenna systems in inclement weather
>
> The very worst thing you can have is a false sense of being protected. I
> would never even bother with a GDT system of any type, the threshold
> voltage is far too high and the ground strap is silly. The VNA is damaged
> by differential mode voltage between center and shield...not shield common
> mode voltage. If you damage a VNA from lack of ground you have a very
> dangerous system and deserved the damage as a wake up call.
>
> 73 Tom
>
>
>
>
> On 7/29/2023 4:02 PM, Max DM5MK wrote:
>
> Hi
> In a YouTube Video i saw Someone built a esd safer for the NanoVNA. The
> circuit wasn’t clear to me as had drawn. I’m wondering if anyone built such
> a esd safer for his device and can share the latest circuit?
>
> yt-Video https://m.youtube.com/watch?v=totwu4IbavE
>
>
>
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> Virus-free.www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> <#m_-8229002786314544430_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
>
>

--

*Dave - WØLEV*

It isn't that they are "not needed".  The truth is the method in the
video will NOT protect the VNA.

The worst thing in the world we can do is be lulled into a false sense
of being protected.  That sets us up for failure.

73 Tom


On 7/30/2023 9:55 AM, Mark Libner wrote:
> Seems to me that the best practices of good esd bench work and
> shorting any leads together of the devices you are going to measure
> before making your measurements are all you need. These practices have
> worked for me for over 40 years including using highly sensitive esd
> equipment.
>
> The circuits describe in the video are well understood when trying to
> protect equipment from esd but should not be needed when using a nanoVNA.
>

--
This email has been checked for viruses by AVG antivirus software.
www.avg.com

On 7/30/23 8:13 AM, W0LEV wrote:
> QUOTE (from Tom, W8JI): YouTube is going to be our technical undoing
>
> AMEN and again A M E N ! ! !
>
> Youtube provides an avenue for proliferation of snake oil, witchcraft,
> and sorcery within (and with out) the hobby.  The majority of the
> presentation are technically flawed and many dead wrong!
>
> I avoid YouTube, period.....
>
Well, there are things on youtube that are correct and useful, but the
problem really is separating the good from bad.

I personally am not a fan of "video explanations", I'd prefer a good
written explanation, but that's me.

And sometimes, when walking through menus or an application, a well done
video is a compact way of showing how to do it.


The modern internet is more rapid - so weird stuff propagates more
easily than when you had to have someone edit it and publish it. But,
hey, there's plenty of bogus stuff in old 73, CQ, and QST, no?

And you want wild, check out people's online "interpretations" of
electrical code.

Do you think the rig expert would do better on my 630M antenna?

On 7/30/2023 10:36 AM, Bob W0EG wrote:
> Very well said.  I use my nanoVNA for passive components like filters.
> For antennas, I use a good dedicated antenna analyzer like the rugged
> RigExpert series.
>
> Bob
>
> On Sun, Jul 30, 2023 at 9:59 AM Tom W8JI <w8ji@w8ji.com> wrote:
>
> YouTube is going to be our technical undoing.
>
> The video is factual useless nonsense. A GDT will not protect a
> VNA of any type, it will barely help a much more robust
> communications receiver. Adding a GDT and ground strap is a total
> waste of time and money.
>
> There are two reasons a VNA is damaged:
>
> 1.) Steady state voltages either from local signals or bias
> voltage on the device under test. We can look for or measure for
> these issues before connecting. Just a volt or two will damage
> some VNAs, and most all of them will go at 20-50 volts. (My Nano
> VNA is useless on my 200ft high 500 foot long 630-meter antenna
> because it overloads, and I am many miles from any significant
> broadcast systems.  Even with a 15-ohm dcr 2.5MH RF choke dc
> static drain I puckered when I connected it. It has +10dBm or more
> of accumulated signal level from external distant RF sources!)
>
> 2.) Static or residual charge from a large high antenna and feed
> line capacitance being charged,  or perhaps a capacitor in the
> system accidentally left charged from some previous bias voltage.
>
> The three most effective ways to handle this and protect the VNA are:
>
> 1.) Don't connect to an active circuit unless you know what you
> are doing, things like a bias-T can be a disaster
>
> 2.) Short the external load or have a static drain like a resistor
> or choke across the external load before connecting
>
> 3.) Don't test antenna systems in inclement weather
>
> The very worst thing you can have is a false sense of being
> protected. I would never even bother with a GDT system of any
> type, the threshold voltage is far too high and the ground strap
> is silly. The VNA is damaged by differential mode voltage between
> center and shield...not shield common mode voltage. If you damage
> a VNA from lack of ground you have a very dangerous system and
> deserved the damage as a wake up call.
>
> 73 Tom
>
>
>
>
> On 7/29/2023 4:02 PM, Max DM5MK wrote:
>> Hi
>> In a YouTube Video i saw Someone built a esd safer for the
>> NanoVNA. The circuit wasn’t clear to me as had drawn. I’m
>> wondering if anyone built such a esd safer for his device and can
>> share the latest circuit?
>>
>> yt-Video https://m.youtube.com/watch?v=totwu4IbavE
>
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> Virus-free.www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
>
> <#m_1380364117553627140_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
>

--
This email has been checked for viruses by AVG antivirus software.
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Bob, could not agree more.
In a heavy rain storm, and sometimes not so heavy too, I see spikes on my 120 ft long antenna.  I would dread to think what this would do to my VNA.
Connecting any antenna to a VNA without having grounded it properly first, before attaching it, is inviting BIG Trouble and the potential death of your VNA.
I too use the RigExpert... I've got the 650Zoom here. Best purchase ever made,
Albert
EI7II.

Never gone that low. I think that it would be safer, less likely to be
damaged. I like that it can be operated with one hand so safer on top of a
tower. Easy to save a sweep and print later from a PC.

On Mon, Jul 31, 2023 at 1:00 AM Tom W8JI <w8ji@w8ji.com> wrote:

> Do you think the rig expert would do better on my 630M antenna?
> On 7/30/2023 10:36 AM, Bob W0EG wrote:
>
> Very well said. I use my nanoVNA for passive components like filters. For
> antennas, I use a good dedicated antenna analyzer like the rugged RigExpert
> series.
>
> Bob
>
> On Sun, Jul 30, 2023 at 9:59 AM Tom W8JI <w8ji@w8ji.com> wrote:
>
>> YouTube is going to be our technical undoing.
>>
>> The video is factual useless nonsense. A GDT will not protect a VNA of
>> any type, it will barely help a much more robust communications receiver.
>> Adding a GDT and ground strap is a total waste of time and money.
>>
>> There are two reasons a VNA is damaged:
>>
>> 1.) Steady state voltages either from local signals or bias voltage on
>> the device under test. We can look for or measure for these issues before
>> connecting. Just a volt or two will damage some VNAs, and most all of them
>> will go at 20-50 volts. (My Nano VNA is useless on my 200ft high 500 foot
>> long 630-meter antenna because it overloads, and I am many miles from any
>> significant broadcast systems. Even with a 15-ohm dcr 2.5MH RF choke dc
>> static drain I puckered when I connected it. It has +10dBm or more of
>> accumulated signal level from external distant RF sources!)
>>
>> 2.) Static or residual charge from a large high antenna and feed line
>> capacitance being charged, or perhaps a capacitor in the system
>> accidentally left charged from some previous bias voltage.
>>
>> The three most effective ways to handle this and protect the VNA are:
>>
>> 1.) Don't connect to an active circuit unless you know what you are
>> doing, things like a bias-T can be a disaster
>>
>> 2.) Short the external load or have a static drain like a resistor or
>> choke across the external load before connecting
>>
>> 3.) Don't test antenna systems in inclement weather
>>
>> The very worst thing you can have is a false sense of being protected. I
>> would never even bother with a GDT system of any type, the threshold
>> voltage is far too high and the ground strap is silly. The VNA is damaged
>> by differential mode voltage between center and shield...not shield common
>> mode voltage. If you damage a VNA from lack of ground you have a very
>> dangerous system and deserved the damage as a wake up call.
>>
>> 73 Tom
>>
>>
>>
>>
>> On 7/29/2023 4:02 PM, Max DM5MK wrote:
>>
>> Hi
>> In a YouTube Video i saw Someone built a esd safer for the NanoVNA. The
>> circuit wasn’t clear to me as had drawn. I’m wondering if anyone built such
>> a esd safer for his device and can share the latest circuit?
>>
>> yt-Video https://m.youtube.com/watch?v=totwu4IbavE
>>
>>
>>
>> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>> Virus-free.www.avg.com
>> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>> <#m_-7255998555519005371_m_1380364117553627140_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>>
>
>
>

What does the rigexpert make rugged? I mean that needed to have also some kind of input protection to deal with statics  if it’s not a mysterious magical device.

There are very low capacitance ESD diodes which could help. They were mentioned here some time ago. But not against overload, I think.  I heard that a good HF antenna gives 1W of total power at the connector. Probably more from huge antennas.
This is the ESD diode  https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559

The RF Power Snitch can be used as a tool to protect sensitive equipment against too much power. But for ESD situations I don’t think there is a solution.

Oh boy. The real undoing is when people watch only the first few minutes of
the aforementioned video, and then rush to the keyboard. I watched the
whole thing, and not only is the information presented accurate, but also
interesting. Joe is an expert with both nanovnas and ESD/transient testing.

So perhaps you should give it the full 35 minutes and come back, you might
learn something.

PS. If you watch all the way to the end you can see Joe applying transients
(both air and contact) to his nanovna, using his suppression circuits to
protect it.

Regards,

Josh VK4JNA

On Sun, 30 Jul 2023 at 11:59 pm, Tom W8JI <w8ji@w8ji.com> wrote:

> YouTube is going to be our technical undoing.
>
> The video is factual useless nonsense. A GDT will not protect a VNA of any
> type, it will barely help a much more robust communications receiver.
> Adding a GDT and ground strap is a total waste of time and money.
>
> There are two reasons a VNA is damaged:
>
> 1.) Steady state voltages either from local signals or bias voltage on the
> device under test. We can look for or measure for these issues before
> connecting. Just a volt or two will damage some VNAs, and most all of them
> will go at 20-50 volts. (My Nano VNA is useless on my 200ft high 500 foot
> long 630-meter antenna because it overloads, and I am many miles from any
> significant broadcast systems. Even with a 15-ohm dcr 2.5MH RF choke dc
> static drain I puckered when I connected it. It has +10dBm or more of
> accumulated signal level from external distant RF sources!)
>
> 2.) Static or residual charge from a large high antenna and feed line
> capacitance being charged, or perhaps a capacitor in the system
> accidentally left charged from some previous bias voltage.
>
> The three most effective ways to handle this and protect the VNA are:
>
> 1.) Don't connect to an active circuit unless you know what you are doing,
> things like a bias-T can be a disaster
>
> 2.) Short the external load or have a static drain like a resistor or
> choke across the external load before connecting
>
> 3.) Don't test antenna systems in inclement weather
>
> The very worst thing you can have is a false sense of being protected. I
> would never even bother with a GDT system of any type, the threshold
> voltage is far too high and the ground strap is silly. The VNA is damaged
> by differential mode voltage between center and shield...not shield common
> mode voltage. If you damage a VNA from lack of ground you have a very
> dangerous system and deserved the damage as a wake up call.
>
> 73 Tom
>
>
>
>
> On 7/29/2023 4:02 PM, Max DM5MK wrote:
>
> Hi
> In a YouTube Video i saw Someone built a esd safer for the NanoVNA. The
> circuit wasn’t clear to me as had drawn. I’m wondering if anyone built such
> a esd safer for his device and can share the latest circuit?
>
> yt-Video https://m.youtube.com/watch?v=totwu4IbavE
>
>
>
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> Virus-free.www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> <#m_-1959378213660832048_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
>
>

I think the addition of the aforementioned ESD diode is worthwhile, bearing in mind unforseen events, like a nearby lightning strike (with say a small telescopic still attached to the VNA), or some unexpected very close proximty QRO. Obviously, that'd be rare, but simply fitting a diode to help prevent any potential damage seems a good idea. But I think the diode in question is 0402 encapsulation, so it's not the easiest to solder in for most people (I've yet to attempt it).

By rugged, I mean physically. The Type N connector on the RigExpert is
less subject to damage than the SMA connectors on the NanoVNA. SMA
connectors mounted directly to a PCB are easily damaged by stress. Best to
connect the supplied cables once and calibrate through the short cables.

The RigExpert likely has low capacitance Schottky diodes on its input for
static protection. One thing is that the RigExpert has a much lower upper
frequency limit so it can tolerate more circuit protection. The Nano works
to I think 3 GHz. If you are working with microwave antennas then the
RigExpert is not the right instrument.

Bob

On Tue, Aug 1, 2023 at 2:06 AM Max DM5MK <DM5MK@t-online.de> wrote:

> What does the rigexpert make rugged? I mean that needed to have also some
> kind of input protection to deal with statics if it’s not a mysterious
> magical device.
>
>
>

On 7/31/23 2:36 PM, Leif M wrote:
> There are very low capacitance ESD diodes which could help. They were
> mentioned here some time ago. But not against overload, I think.  I
> heard that a good HF antenna gives 1W of total power at the connector.
> Probably more from huge antennas.
> This is the ESD diode
> https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559

I've used parts like that.
In a receiver, one wants low parasitic C so you don't "shunt" the signal
to ground.

In this application, the reduction in sensitivity would theoretically be
compensated by the calibration (assuming sufficient dynamic range).
Furthermore, one also probably isn't as concerned about harmonics, since
you're making single frequency measurements, and, in fact deliberately
using harmonic content of the LO.

There's sort of two distinct problems that one might want to protect
against:
1) ESD - a transient - stored energy discharging through the input circuitry
2) overload - your DUT has gain, or receives enough power that it
presents the receiver with enough power to saturate or worse, damage it.

Diode clamps and series resistors are the usual way to deal with #1 -
you want to limit the energy dissipated in internal junctions. It's a
one shot thing so the energy you need to dissipate is limited.

#2 is a bit trickier - the signal is there continuously and the
potential energy to be dissipated is larger. A shunt diode clamp might
work. But the voltages might still be too high, and you need to limit
the current through the clamp, or the clamp fails.
60 years ago, a series incandescent light bulb into a diode clamp was
one solution, but has a lot of disadvantages.

Or, you design the input circuits to just be tough.

A simple bleeder circuit consisting of a 2.2M resistor and NE2 bulb will bleed off the sferics charges from your antenna as it always has since the 1950’s.



W4JDY

Here is my approach, how I constructed external simple ESD protection for Nanovna, written about two years ago:
https://www.qsl.net/o/ok1vaw//protector/NanoVNA%20input%20protector.pdf
this is a link to a directory with other files:
https://www.qsl.net/o/ok1vaw//protector/
BR,
Vojtech, OK1VAW.

Here is my article written about two years ago with some measurements.

https://www.qsl.net/o/ok1vaw//protector/NanoVNA%20input%20protector.pdf?fbclid=IwAR3jtUNMJiZBeNrvFh4sciTE4_4vNSzYfC0jvH1q_nDp1cXzh7jSZUREGRw

BR,

Vojtech, OK1VAW.

People like to pile on and most of them have no idea what they are talking
about.

On Tue, 1 Aug 2023 at 15:30, Josh A <lexusjosh@gmail.com> wrote:

> Oh boy. The real undoing is when people watch only the first few minutes
> of the aforementioned video, and then rush to the keyboard. I watched the
> whole thing, and not only is the information presented accurate, but also
> interesting. Joe is an expert with both nanovnas and ESD/transient testing.
>
> So perhaps you should give it the full 35 minutes and come back, you might
> learn something.
>
> PS. If you watch all the way to the end you can see Joe applying
> transients (both air and contact) to his nanovna, using his suppression
> circuits to protect it.
>
> Regards,
>
> Josh VK4JNA
>
>

Antenna analyzers and VNAs are not nearly as static-rugged, signal level
damage immune,  and overload dynamic range as a common modern solid
state receiver.

As far as static immunity and signal damage old tube radios are
generally tough, although the old tube radios we fondly remember are
generally not that great for overload or IMD.

In the big scheme of things analyzers are probably the most damage prone
pieces of gear we have. With a total 9kZ to 30 MHz antenna power level
of around -10dBm from my big 630M Inverted L, my nanoVNAs are useless.
My  bench top real Network Analyzers are much better, but I have to
measure things in a shielded box if the impedance are terribly far away
from 50 ohms.

The diodes in the old out of date MFJ antenna analyzer had to be V<10
volts PRV microwave diodes. The most common failures by far are the
bridge diodes.

A common failure of the 50-100 PRV diodes in antenna tuners is charge on
dc floating antennas charging the air variables and the air variable
dumping into the bridge when  it is "full".  Those bridges will take
several kilowatts of power when assembled correctly, but antennas can
actually "get them".

With the VNA or antenna analyzer being by far the most sensitive piece
of gear we have, I would make darned sure with any outside cables or
antennas are shorted immediately before being connected. There are some
low voltage clamp diodes, and I have built some dc biased diode clamps
that go hard limit at a few volts but are wide open below that, and now
we have things like this:

https://www.ti.com/product/TPD1E01B04

but even 3V is a horse race to the finish line if protecting a VNA. The
best policy is to know what we are connecting, and to short those big
cables and long floating from ground antennas before connecting. A
resistor and a gas tube aren't going to do much.

73 Tom

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On Tue, Aug 1, 2023 at 02:30 PM, Josh A wrote:

>
> "Joe is an expert with both nanovnas and ESD/transient testing."

Josh... VK4JNA... Josh. U are SPOT ON. Joe has forgotten more about VNA's and other matters than most of us will EVER hope to learn.
I run his NANOVNA Solver 64  program here. Brilliant does not begin to even describe it !
Albert. EI7II.

Seriously, watch the video.

On Wed, 2 Aug 2023 at 2:49 pm, Tom W8JI <w8ji@w8ji.com> wrote:

> Antenna analyzers and VNAs are not nearly as static-rugged, signal level
> damage immune, and overload dynamic range as a common modern solid
> state receiver.
>
> As far as static immunity and signal damage old tube radios are
> generally tough, although the old tube radios we fondly remember are
> generally not that great for overload or IMD.
>
> In the big scheme of things analyzers are probably the most damage prone
> pieces of gear we have. With a total 9kZ to 30 MHz antenna power level
> of around -10dBm from my big 630M Inverted L, my nanoVNAs are useless.
> My bench top real Network Analyzers are much better, but I have to
> measure things in a shielded box if the impedance are terribly far away
> from 50 ohms.
>
> The diodes in the old out of date MFJ antenna analyzer had to be V<10
> volts PRV microwave diodes. The most common failures by far are the
> bridge diodes.
>
> A common failure of the 50-100 PRV diodes in antenna tuners is charge on
> dc floating antennas charging the air variables and the air variable
> dumping into the bridge when it is "full". Those bridges will take
> several kilowatts of power when assembled correctly, but antennas can
> actually "get them".
>
> With the VNA or antenna analyzer being by far the most sensitive piece
> of gear we have, I would make darned sure with any outside cables or
> antennas are shorted immediately before being connected. There are some
> low voltage clamp diodes, and I have built some dc biased diode clamps
> that go hard limit at a few volts but are wide open below that, and now
> we have things like this:
>
> https://www.ti.com/product/TPD1E01B04
>
> but even 3V is a horse race to the finish line if protecting a VNA. The
> best policy is to know what we are connecting, and to short those big
> cables and long floating from ground antennas before connecting. A
> resistor and a gas tube aren't going to do much.
>
> 73 Tom
>
> --
> This email has been checked for viruses by AVG antivirus software.
> www.avg.com
>
>
>
>
>
>

That's a nice article. My only question is can the VNA being protected
safely handle 15 volts, and why not have a surface mount drain resistor,
perhaps a 47k or higher resistor? An earth ground is of course not
necessary since it is the differential voltage across the port that we
are concerned with and not the common mode potential.

My procedure for connecting now is to make sure the cable is not
energized by a source, and short the feedline immediately before
connecting. I feel this is relatively safe based on measurements of my
300ft insulated base tower in various weather conditions. Even in
inclement weather when corona was present the current was very low on
the scale of a 50-microampere meter. (However, distant lightning strikes
would pin the meter.)
Even on clear sunny days a brisk breeze would produce a few microamperes
of charging current, and the ungrounded tower could rise to spark gap
voltages every several minutes.

I have not measured my 630M Inverted L charge current, but that might be
interesting. I keep thinking I should put a choke from the antenna to
ground, but right now I just let it drain through my radio gear. I've
never heard the connector arc or gotten a poke on a normal day, but of
course I disconnect when storms are possible or not running WSPR. The
more I talk about this the more I know I need to fix the Inverted L feed
point with a shunt inductor.  My countering mental argument is the 630M
inverted L is feet away from a ground 318 ft tower, 200ft high, and runs
horizontally to a second taller tower shunted to ground.  So the
likelihood it has a dry weather charge problem is at least a little bit
diminished.

Having that float is a bad idea, isn't it. :) I better fix that soon.

My insulated base ~300ft tower is less than 50uA, so a 20k resistor
would hold that tower to 1 volt. The exception would be the big spikes
during distant or closer local lightning strikes, but someone would be a
little crazy measuring at that time anyway.

The rest of my antennas have fairly low leak paths to ground with the
exceptions of wire dipoles, more typical of Ham stations. The only
reason I bring the big ones up is to give a perspective of the typical
charge current we might have to bleed off on big floating antennas.

73 Tom


On 8/1/2023 3:50 PM, OK1VAW Vojtech wrote:
>
> Here is my article written about two years ago with some measurements.
>
> https://www.qsl.net/o/ok1vaw//protector/NanoVNA%20input%20protector.pdf?fbclid=IwAR3jtUNMJiZBeNrvFh4sciTE4_4vNSzYfC0jvH1q_nDp1cXzh7jSZUREGRw
>
> BR,
>
> Vojtech, OK1VAW.
>
>

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This email has been checked for viruses by AVG antivirus software.
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On 8/1/23 10:46 AM, W4JDY1953_G wrote:
> A simple bleeder circuit consisting of a 2.2M resistor and NE2 bulb will
> bleed off the sferics charges from your antenna as it always has since
> the 1950’s.
>
> W4JDY

The "turn on" voltage of a neon bulb, like a gas discharge tube, is
substantially higher than the damage threshold of most semiconductor
devices.

That's assuming you were talking about a series combination.
If they're in parallel, the high value resistor as a bleeder works
fairly well, and the NE2 is a ~60V clamp.

One advantage of a gas tube clamp is that it doesn't have the potential
IMD problem that a semiconductor device might have. However, the modern
semiconductor protection devices are not just a diode clamp (which
starts flowing current from the get go, as a square law device at low
signal levels). They have a distinct threshold, so they don't have the
IMD problem.

|Hello Tom,
I am reacting to your question. You have to consider two different effects. One is the voltage across the DUT (for example coaxial cable center and shield), which in case of not DC connected legs of antenna could easily charge the coax like a high voltage capacitor. 1m cable is typically about 75pF, so 20m of cable charged to 1kV could carry significant energy.
The second effect come from different voltage potentials - one potential level is your antenna itself and the second could be VNA for example held by hand on an insulated floor. In case of connecting something to SMA you could connect center pin first and the whole transient current/voltage equalize.
This is a direct application of ESD human body model.
Most of the SMD capacitors are sure not for kV voltages and if something with so high charge gets on semiconductor, the problem could appear.
BR,
Vojtech.

I understand that, and it would always be nice to connect the cable
shield to the analyzer before the analyzer center is connected, but a
ground path from the cable does not guarantee anything at all unless the
analyzer is common to that ground.

There is an increase in danger if the analyzer has a different ground
path than the cable.  If we are going to anything for shield voltage, it
should be to jumper the shield to the analyzer case before the center is
connected.

Let me give an example of a danger we all face. If the analyzer is
connected to a line operated power supply or a computer system that is
not properly earthed rather than battery power and floating off ground
(which is always what I do, even with a laptop, the analyzer case can be
well above ground. Connecting the center first, even if the shield is
grounded and the feed line fully discharged, can result in damage.

Any ground on the cable being tested should actually be to the analyzer
case to avoid this.

I feel this is a small risk for me, because I never power a laptop
externally while using it with any VNA, and I never externally power the
VNA. I would feel a lot better if the VNA had onboard S parameter storage.

I learned this lesson when an expensive bench VNA was damaged by
connecting the port to something powered by an internal switch mode
supply. On bench tests with an expensive VNA everything ties to the
bench common ground bus since that day, and I am a little more discrete
about what I connect. This includes my bench computer.


I care a lot less with a $100 throw away, although I try to avoid doing
easily avoidable things.

This whole thing is worthy of a peer reviewed comprehensive article with
input from many skilled people.

The important point is gas tubes and grounds on cables probably are not
worth much, 15V diode systems might be better, but it probably takes a
great deal of thought to do what we need. It might need $100 of thought
to protect a $50 device.

73 Tom




On 8/2/2023 12:42 PM, OK1VAW Vojtech wrote:

> |Hello Tom,
> I am reacting to your question. You have to consider two different
> effects. One is the voltage across the DUT (for example coaxial cable
> center and shield), which in case of not DC connected legs of antenna
> could easily charge the coax like a high voltage capacitor. 1m cable
> is typically about 75pF, so 20m of cable charged to 1kV could carry
> significant energy.
> The second effect come from different voltage potentials - one
> potential level is your antenna itself and the second could be VNA for
> example held by hand on an insulated floor. In case of connecting
> something to SMA you could connect center pin first and the whole
> transient current/voltage equalize.
> This is a direct application of ESD human body model.
> Most of the SMD capacitors are sure not for kV voltages and if
> something with so high charge gets on semiconductor, the problem could
> appear.
> BR,
> Vojtech.
>

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This email has been checked for viruses by AVG antivirus software.
www.avg.com

What is really needed is a "transorb" see:
https://www.wagneronline.com.au/transorbs-devices/transorbs/semiconductors/electronic-components/458/fl/
these work at 1ns and ..... well just go look at the specs.

Mike C. Sand Mtn GA

On 7/31/2023 5:36 PM, Leif M wrote:

> There are very low capacitance ESD diodes which could help. They were
> mentioned here some time ago. But not against overload, I think.  I
> heard that a good HF antenna gives 1W of total power at the connector.
> Probably more from huge antennas.
> This is the ESD diode
> https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559
>
>

Wel, if you only need audio or low frequency range this may be useful.
But with capacitance in the many 100 pF range, no chance for real RF
work. The device I use is a 0.1 pF ESD diode, designed for high
frequency signal protection. Hardly any effect at 1 GHz. It will give
you ESD protection, not protection agains lightning or discharge of a 
long coax cable. Just discharge before connecting to the VNA. It is near
impossible to make it really fool proof.

Op 9-8-2023 om 04:52 schreef Mike C.:

>
> What is really needed is a "transorb" see:
> https://www.wagneronline.com.au/transorbs-devices/transorbs/semiconductors/electronic-components/458/fl/
> these work at 1ns and ..... well just go look at the specs.
>
> Mike C. Sand Mtn GA
>
> On 7/31/2023 5:36 PM, Leif M wrote:
>> There are very low capacitance ESD diodes which could help. They were
>> mentioned here some time ago. But not against overload, I think.  I
>> heard that a good HF antenna gives 1W of total power at the
>> connector. Probably more from huge antennas.
>> This is the ESD diode
>> https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559
>
>

With respect to the transorb suggestion: I'm a technician not an engineer, but I could find no indication in the data sheet that those devices are suitable for use at RF.
What am I missing?

Sent with [Proton Mail](https://pr.tn/ref/NV8FZHYH5PG0) secure email.

------- Original Message -------
On Tuesday, August 8th, 2023 at 9:52 PM, Mike C. <mg@mgte.com> wrote:

> What is really needed is a "transorb" see: https://www.wagneronline.com.au/transorbs-devices/transorbs/semiconductors/electronic-components/458/fl/ these work at 1ns and ..... well just go look at the specs.
>
> Mike C. Sand Mtn GA
>
> On 7/31/2023 5:36 PM, Leif M wrote:
>
>> There are very low capacitance ESD diodes which could help. They were mentioned here some time ago. But not against overload, I think. I heard that a good HF antenna gives 1W of total power at the connector. Probably more from huge antennas.
>> This is the ESD diode https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559
>
>

Usually Transorbs have a relatively large capacitance and may be unsuited
for applications in front of the TinySAs and NANOVNAs.

Dave - WØLEV

On Wed, Aug 9, 2023 at 7:29 PM W0FAA - JJ via groups.io <W0FAA=
protonmail.com@groups.io> wrote:

> With respect to the transorb suggestion: I'm a technician not an engineer,
> but I could find no indication in the data sheet that those devices are
> suitable for use at RF.
> What am I missing?
>
> Sent with Proton Mail <https://pr.tn/ref/NV8FZHYH5PG0> secure email.
>
> ------- Original Message -------
> On Tuesday, August 8th, 2023 at 9:52 PM, Mike C. <mg@mgte.com> wrote:
>
> What is really needed is a "transorb" see:
> https://www.wagneronline.com.au/transorbs-devices/transorbs/semiconductors/electronic-components/458/fl/
> these work at 1ns and ..... well just go look at the specs.
>
> Mike C. Sand Mtn GA
> On 7/31/2023 5:36 PM, Leif M wrote:
>
> There are very low capacitance ESD diodes which could help. They were
> mentioned here some time ago. But not against overload, I think. I heard
> that a good HF antenna gives 1W of total power at the connector. Probably
> more from huge antennas.
> This is the ESD diode
> https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559
>
>
>
>
>

--

*Dave - WØLEV*

It is accepted practice to place the transient protection device at the source. Adding as much protection as is warranted. So, if you have a big antenna that is likely to be struck by lightning you will have all sorts of transient protection devices long before the signal gets to the input of the detector.

One worries about the capacitance of the protective device when it will have an effect on the fidelity of the signal which will be more pronounced as the frequency increases.

If it is really a concern, then use QUCS to simulate the effect of the protection device to the overall performance of your test circuit. I'll use any excuse known to mankind to beat the QUCS drum as it is the most fantastic of all tools.


73
________________________________

For all the discussion and a really bad circuit on this thread, there is an
excellent commercial solution designed for the purpose from MiniCircuits:

VLM-33W-2W-S+

https://www.minicircuits.com/pdfs/VLM-33W-2W-S+.pdf

It costs about $70 from Mouser:


https://www.mouser.com/ProductDetail/Mini-Circuits/VLM-63-2W-S%2B?qs=hWgE7mdIu5SsPTT3lqlQ7Q%3D%3D

However, just being careful per the procedures which have been well
described many times in this thread (and others) will save you the $70.

Dave - WØLEV




On Thu, Aug 10, 2023 at 7:03 PM wizard cybinlabs.com <wizard@cybinlabs.com>
wrote:

> It is accepted practice to place the transient protection device at the
> source. Adding as much protection as is warranted. So, if you have a big
> antenna that is likely to be struck by lightning you will have all sorts of
> transient protection devices long before the signal gets to the input of
> the detector.
>
> One worries about the capacitance of the protective device when it will
> have an effect on the fidelity of the signal which will be more pronounced
> as the frequency increases.
>
> If it is really a concern, then use QUCS to simulate the effect of the
> protection device to the overall performance of your test circuit. I'll use
> any excuse known to mankind to beat the QUCS drum as it is the most
> fantastic of all tools.
>
>
> 73
> ------------------------------
> *From:* NanoVNAV2@groups.io <NanoVNAV2@groups.io> on behalf of W0LEV via
> groups.io <davearea51a=gmail.com@groups.io>
> *Sent:* Wednesday, August 9, 2023 1:41 PM
> *To:* NanoVNAV2@groups.io <NanoVNAV2@groups.io>
> *Subject:* Re: [nanovnav2] ESD safer circuit
>
> Usually Transorbs have a relatively large capacitance and may be unsuited
> for applications in front of the TinySAs and NANOVNAs.
>
> Dave - WØLEV
>
> On Wed, Aug 9, 2023 at 7:29 PM W0FAA - JJ via groups.io <W0FAA=
> protonmail.com@groups.io> wrote:
>
> With respect to the transorb suggestion: I'm a technician not an engineer,
> but I could find no indication in the data sheet that those devices are
> suitable for use at RF.
> What am I missing?
>
> Sent with Proton Mail <https://pr.tn/ref/NV8FZHYH5PG0> secure email.
>
> ------- Original Message -------
> On Tuesday, August 8th, 2023 at 9:52 PM, Mike C. <mg@mgte.com> wrote:
>
> What is really needed is a "transorb" see:
> https://www.wagneronline.com.au/transorbs-devices/transorbs/semiconductors/electronic-components/458/fl/
> these work at 1ns and ..... well just go look at the specs.
>
> Mike C. Sand Mtn GA
> On 7/31/2023 5:36 PM, Leif M wrote:
>
> There are very low capacitance ESD diodes which could help. They were
> mentioned here some time ago. But not against overload, I think. I heard
> that a good HF antenna gives 1W of total power at the connector. Probably
> more from huge antennas.
> This is the ESD diode
> https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559
>
>
>
>
> --
>
> *Dave - WØLEV *
>
>
>
>
>

--

*Dave - WØLEV*

"A GDT will not protect a VNA of any type, it will barely help a much more robust communications receiver."

The GDT is to quench the higher energy.

"The truth is the method in the video will NOT protect the VNA."

Please share your expert opinion as to why and we can discuss.

OK, I'm ignorant, but what is a "GDT"?

Dave - WØLEV

On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=
yahoo.com@groups.io> wrote:

> "A GDT will not protect a VNA of any type, it will barely help a much more
> robust communications receiver."
>
> The GDT is to quench the higher energy.
>
> "The truth is the method in the video will NOT protect the VNA."
>
> Please share your expert opinion as to why and we can discuss.
>
>
>

--

*Dave - WØLEV*

Hi Dave,

Guessing ‘Gas Discharge Tube’, similar to the old NE-2 neon bulbs, but perhaps a bit more refined for specific ‘firing’ voltage.

Again, just a guess.

Ken – WBØOCV

From: W0LEV
Sent: Friday, August 11, 2023 01:59 PM
To: NanoVNAV2@groups.io
Subject: Re: [nanovnav2] ESD safer circuit

OK, I'm ignorant, but what is a "GDT"?

Dave - WØLEV

On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=yahoo.com@groups.io> wrote:
"A GDT will not protect a VNA of any type, it will barely help a much more robust communications receiver."

The GDT is to quench the higher energy. 
"The truth is the method in the video will NOT protect the VNA."

Please share your expert opinion as to why and we can discuss.


--
Dave - WØLEV

Gas Discharge Tube, GDT.
On Friday, August 11, 2023 at 01:59:18 PM EDT, W0LEV <davearea51a@gmail.com> wrote:

OK, I'm ignorant, but what is a "GDT"?
Dave - WØLEV

On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=yahoo.com@groups.io> wrote:


"A GDT will not protect a VNA of any type, it will barely help a much more robust communications receiver."

The GDT is to quench the higher energy. 

"The truth is the method in the video will NOT protect the VNA."

Please share your expert opinion as to why and we can discuss.







--
Dave - WØLEV

"W0LEV 2023/08/10 19:47 ... and a really bad circuit on this thread,"

So, you don't know what a GDT is but you feel it is a bad circuit.  Explain why. On Friday, August 11, 2023 at 02:04:31 PM EDT, Joe Smith <joeqsmith49@yahoo.com> wrote:

Gas Discharge Tube, GDT.
On Friday, August 11, 2023 at 01:59:18 PM EDT, W0LEV <davearea51a@gmail.com> wrote:

OK, I'm ignorant, but what is a "GDT"?
Dave - WØLEV

On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=yahoo.com@groups.io> wrote:


"A GDT will not protect a VNA of any type, it will barely help a much more robust communications receiver."

The GDT is to quench the higher energy. 

"The truth is the method in the video will NOT protect the VNA."

Please share your expert opinion as to why and we can discuss.







--
Dave - WØLEV

GDT= Gas Discharge Tube.

73,
geo - n4ua

On Fri, Aug 11, 2023 at 1:59 PM W0LEV <davearea51a@gmail.com> wrote:

> OK, I'm ignorant, but what is a "GDT"?
>
> Dave - WØLEV
>
> On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=
> yahoo.com@groups.io> wrote:
>
>> "A GDT will not protect a VNA of any type, it will barely help a much
>> more robust communications receiver."
>>
>> The GDT is to quench the higher energy.
>>
>> "The truth is the method in the video will NOT protect the VNA."
>>
>> Please share your expert opinion as to why and we can discuss.
>>
>>
>
> --
>
> *Dave - WØLEV*
>
>
>
>
>

Hi Joe,

In Dave’s defense -- I have to admit I am clueless as to what voltage will challenge (a.k.a, “fry”) the input circuitry of a NanoVNA. Single-digit volts, ten-of-volts, more??? Considering that most GDTs are designed for a discharge voltage of ~70-volts or more, I would wonder if that is sufficient to protect the relatively-sensitive solid state input circuitry of a NanoVNA.

In the “good ole’ days” of vacuum tube radios, the venerable NE-2 neon bulb would likely provide the necessary protection for such receivers, even with its 65 VAC or 90 VDC ‘breakdown’ voltage. Considering that static charge is likely DC, that would suggest an NE-2 used as a GDT wouldn’t ‘protect’ a device unless the voltage on the antenna was greater than ~90 VDC. If the capacitive charge stored on a coax cable was slightly less than 90 VDC (i.e., below the breakdown voltage that would discharge the charge), and it was connected to an unprotected NanoVNA, would the NanoVNA survive? Again, I will admit I am clueless, but I suspect it wouldn’t. Just my humble opinion, based on clueless ignorance.

Ken -- WBØOCV

From: Joe Smith via groups.io
Sent: Friday, August 11, 2023 03:59 PM
To: nanovnav2@groups.io
Subject: Re: [nanovnav2] ESD safer circuit

"W0LEV 2023/08/10 19:47 
... and a really bad circuit on this thread,"

So, you don't know what a GDT is but you feel it is a bad circuit.  Explain why.
On Friday, August 11, 2023 at 02:04:31 PM EDT, Joe Smith <joeqsmith49@yahoo.com> wrote:


Gas Discharge Tube, GDT.
On Friday, August 11, 2023 at 01:59:18 PM EDT, W0LEV <davearea51a@gmail.com> wrote:


OK, I'm ignorant, but what is a "GDT"?

Dave - WØLEV

On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=yahoo.com@groups.io> wrote:
"A GDT will not protect a VNA of any type, it will barely help a much more robust communications receiver."

The GDT is to quench the higher energy. 
"The truth is the method in the video will NOT protect the VNA."

Please share your expert opinion as to why and we can discuss.


--
Dave - WØLEV

Thanks! Suppose I could have guessed if in the right state of mind (needed
more coffee).

Dave - WØLEV

On Fri, Aug 11, 2023 at 7:59 PM Ken Sejkora <kjsejkora@comcast.net> wrote:

> Hi Dave,
>
>
>
> Guessing ‘Gas Discharge Tube’, similar to the old NE-2 neon bulbs, but
> perhaps a bit more refined for specific ‘firing’ voltage.
>
>
>
> Again, just a guess.
>
>
>
> Ken – WBØOCV
>
>
>
> *From: *W0LEV <davearea51a@gmail.com>
> *Sent: *Friday, August 11, 2023 01:59 PM
> *To: *NanoVNAV2@groups.io
> *Subject: *Re: [nanovnav2] ESD safer circuit
>
>
>
> OK, I'm ignorant, but what is a "GDT"?
>
>
>
> Dave - WØLEV
>
>
>
> On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=
> yahoo.com@groups.io> wrote:
>
> "A GDT will not protect a VNA of any type, it will barely help a much more
> robust communications receiver."
>
> The GDT is to quench the higher energy.
>
> "The truth is the method in the video will NOT protect the VNA."
>
> Please share your expert opinion as to why and we can discuss.
>
>
>
> --
>
> *Dave - WØLEV*
>
>
>
>
>
>
>
>
>

--

*Dave - WØLEV*

The ionization potential of a GDT is around 70 volts. It would be fine of you had a tube front end. Not applicable for solid state devices. You are better off using two low voltage Zener diodes. or a transorb.

I might also point out that there are resistor networks on the two ports. On the bright side even if you did blow out the electronics, all the components are easy to replace.

If you are trying to measure an antenna, then put the protective device at the antenna. NOT at the VNA.

cg


________________________________

Ken,

There is no one size GDT that fits all.  There is a reason we have datasheets.   Ignorance is easy enough to address assuming you want to learn.  It just takes time and willingness to research.

I went over most of the the basics in that video, but as we can see, many posts suggest it's "factual useless nonsense".   If you decide to watch, feel free to ask any questions you may have or do your own research after.  Most of this is pretty basic and the information is readily available for free on the internet.  While I do cover it in the video, my goal was not to design a turn key solution but rather show the basics that you would need to consider.

Linked to the 9:00 in.  Watch carefully.  Best part is the comments.
https://youtu.be/tCHAa-sjgcQ?t=535

This thread goes on and on with occasional good and a lot of bad
suggestions. Early on there was a long video link with a mix of a couple
minutes of good information in with a lot of meaningless "protection"
like the assumption a small resistor will clamp at the resistor's rated
voltage.

Ten volt and higher protection devices and devices with a lot of
capacitance really do not belong in the protection system.

These are not expensive devices so we just want some reasonable
protection that does not compromise the "instrument".  I bought a sample
collection of these from Amazon and have been using them in place of my
old trusty but limited range MFJ analyzers and have not damaged one yet.
First I follow some simple rules.

I'm not fan of attenuator pads because the transient suppression, at
least below the surprisingly high catastrophic mortality point of even a
small resistor, is only by pad attenuation. If we use a 3dB pad, which
then takes at least 3dB from the dynamic range of measurements, we
reduce unwanted voltage to about 71% of the original port voltage. A
six-dB pad is only a ~50% voltage reduction. The resistors are not
remotely as good at fusing as real fuses, and fuses are notoriously slow
and unreliable enough in transient response. We sure don't want to
depend on such a meaningless protection return for a hit on the already
too-low signal levels of these devices. The silliest thing is where
resistors appear as glitch fuses in amplifiers, and yes I have measured
their protection contribution. If they are unreliable as fault "fuses"
in a simple rugged tube amplifier, they are an even worse fuse in a
fragile semiconductor system.  They are first and foremost just resistors.

GDTs are off the charts in voltage breakdown but can handle current in
the hundreds or kilo-ampere range, and just look like a few pF of
capacitance when not ionized. They are great for protecting high voltage
high power systems.

About the only choice with fast response and low enough voltage is a
simple TVS diode. They are readily available in low voltage-threshold
and very low capacitance devices, like the Littlefuse SP3022 series.
Link to this diode:
https://www.mouser.com/datasheet/2/240/Littelfuse_TVS_Diode_Array_SP3022_Datasheet_pdf-3193388.pdf

I use them on my expensive bench VNA, so I am sure they will work with a
nanoVNA. They are not nearly as robust as a GDT and unsuitable in high
power circuit protection (like linear amps), but are the component of
choice in low voltage systems.

I would also use a suitable series capacitor between the DUT port and
the TVS diode, or make it a symmetrical T with two suitable value MLCC
(multi-layer ceramic capacitors) and a shunt TVS diode in the center.

Beyond this we are likely doing more measurement and cost harm than we
are protection and failure cost good.

I've connected two or three unprotected nanoVNAs to various things
without issue, but I use some common sense precautions. My worst case
antenna is a 290ft vertical section and 230ft horizontal section
Inverted L antenna that totally floated from ground. During approaching
severe weather  I measured a few kV charge voltage on the floating coax
but the charge current is very low microamperes even in horrible
weather. Once the coax center is grounded to shield and released it
takes 30 seconds to build to ~5kV, the breakdown of the UHF connectors. 
  When measuring this antenna I followed these rules:

1.) I did not measure when the weather radio was going off with alerts.
I made sunny fair weather measurements for both myself and the equipment.

2.) I shorted the center pin to the shield using the nanoVNA connector
outside shell immediately before connecting. I've taught myself to
always connect this way out of habit. It is smooth, fast, and requires
no tools.

3.) I don't measure things fed with bias-T feed, and my outdoor cable
shields are all grounded.

My L has near zero to +10 dBm (one to ten  milliwatts) of accumulated
VLF to upper HF energy. This is enough to make impedance measurements
with a nanoVNA useless, but it does not harm the nanoVNA. I also have
some rental services that run, there are a few ~100W VHF/UHF repeaters
that are on and off and maybe 50 feet from the L. There is also a 1500W
HF and six meter system about 300 feet away that runs quite a bit. None
of this has harmed the nanoVNA although it sure does mess up any readings.

Last week I installed 230V GDTs and a 50K 7 watt static drain on that
big Inverted L so it no longer has a dc charge build problem, plus I
finally installed 10,000pF of shunt impedance matching capacitance (so
the SWR is 1.2:1 instead of 10:1 on 472kHz). The nanoVNA's now read that
antenna perfectly fine because the overall power level has dropped to
-20 to -40dBm. Take the capacitors out and it goes to impedance reading
hell again.

My biggest problem with the nanoVNAs are overload and the difficult time
getting S-parameters into the computers. But if I use it like a fancy
MFJ-259 it is great, and common sense when connecting protects it.

By the way, if I build a system with a dual TVS diode I would still
connect the diode protector to the load first, and THEN connect the
nanoVNA to the protector. I would not hang it on the nano and
willy-nilly connect things. I would move the protection block to the
load first, and then connect the VNA. Good connection habits are worth
far more than anything.

73 Tom

--
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Gas discharge tube AKA neon bulb 😊

Hi all!

I think there are some missunderstanding on how to properly protect
electronics from high voltage/high current surges.

I also find the video linked in the beginning to be good. It describes the
same method of protection as I use in my designs.

First missunderstanding is assuming the GDT is there to protect the VNA.
It’s not. The whole protection strategy is based on using several element
in a cascade to achive proper protection of the VNA. Each element protects
the next.

The surge is a fast ramping voltage pulse. This is described in any
standard for ESD or surge protection. And in most datasheets for tranzorbs,
GDT, and other protection devices.

The circuits from the video (at about 21 minutes in). Consists of the
following elements: (from the VNA side)

1. Capacitor, blocking DC from damaging the VNA.
2. Tranzorb (low capacitive, low voltage) - protecting the VNA from danages
due to high voltage.
3. Attenuator. This introduces a series resistor liminting the current
through the Tranzorb at the same time letting the GDT see a high voltage if
the current is high enough. These resistors can ser a voltage up to the
ignition voltage of the GDT. This is why the voltage rating matter.
4. GDT - protecting the Tranzorb and resistor attunator if the surge has
more energy than these devices can handle on their own.

There are of course many other ways of doing this. But the cascade approach
works in both low power and high power applications with aporopriate
selected components for the application.



Cheers!
Bernie

søn. 13. aug. 2023 kl. 07:24 skrev cocopuppy <cocopuppy@bellsouth.net>:

> Gas discharge tube AKA neon bulb 😊
>
>
>
> *From:* NanoVNAV2@groups.io <NanoVNAV2@groups.io> *On Behalf Of *W0LEV
> *Sent:* Friday, August 11, 2023 12:21 PM
> *To:* NanoVNAV2@groups.io
> *Subject:* Re: [nanovnav2] ESD safer circuit
>
>
>
> OK, I'm ignorant, but what is a "GDT"?
>
>
>
> Dave - WØLEV
>
>
>
> On Fri, Aug 11, 2023 at 4:04 PM Joe Smith via groups.io <joeqsmith49=
> yahoo.com@groups.io> wrote:
>
> "A GDT will not protect a VNA of any type, it will barely help a much more
> robust communications receiver."
>
> The GDT is to quench the higher energy.
>
> "The truth is the method in the video will NOT protect the VNA."
>
> Please share your expert opinion as to why and we can discuss.
>
>
>
> --
>
> *Dave - WØLEV*
>
>
>
>
>
>
>
>

Thanks for linking that video, it will be fun to watch how many people
figure it out.

On Sun, 13 Aug 2023 at 07:24, Joe Smith via groups.io
<joeqsmith49=yahoo.com@groups.io> wrote:

>
> Ken,
>
> There is no one size GDT that fits all. There is a reason we have datasheets. Ignorance is easy enough to address assuming you want to learn. It just takes time and willingness to research.
>
> I went over most of the the basics in that video, but as we can see, many posts suggest it's "factual useless nonsense". If you decide to watch, feel free to ask any questions you may have or do your own research after. Most of this is pretty basic and the information is readily available for free on the internet. While I do cover it in the video, my goal was not to design a turn key solution but rather show the basics that you would need to consider.
>
> Linked to the 9:00 in. Watch carefully. Best part is the comments.
> https://youtu.be/tCHAa-sjgcQ?t=535
>

Just as an aside; If you consider yourself an advanced user and use the
NanoVNA primarily as a bench instrument, you may want to consider checking
out Joe Smith's excellent NanoVNA PC software. I have two versions
installed, the 32-bit NanoVNA and the 64-bit NanoVNA solver64. Both
written by Joe using LabView.

To install correctly, you must follow Joe's instructions exactly and in
order. Don't skip steps or guess. My understanding is that Joe had to stop
development on the 64-bit version when National Instruments changed the
licensing for Lab View to a subscription service. Too bad.

Here is my interpretation of the installation procedure but read and follow
the instructions on the site carefully and it will work..

Installing Joe Smith’s software for the NanoVNA V2Plus

Install 7-zip (free)

Download all 21 NanoVNA_V2Plus_Installer.zip.nnn files from here:

https://github.com/joeqsmith/NanoVNA_Software/releases/tag/0.10

open NanoVNA_V2Plus_Installer.zip.001 with 7-zip (all 21 installer zip
files will then be extracted.

Run the installer. You will then have version 1 installed at C:\Program
Files (x86)\NanoVNA_V2Plus

Confirm that it works than get the latest version of the exe at:

https://github.com/joeqsmith/NanoVNA_Software/blob/NanoVNA_V2Plus/NanoVNA_V2Plus_2p08.zip

Replace the version 1 NanoVNA_V2Plus.exe in C:\Program Files
(x86)\NanoVNA_V2Plus
with new version exe.


On Fri, Aug 11, 2023 at 1:07 AM W0LEV <davearea51a@gmail.com> wrote:

> For all the discussion and a really bad circuit on this thread, there is
> an excellent commercial solution designed for the purpose from MiniCircuits:
>
> VLM-33W-2W-S+
>
> https://www.minicircuits.com/pdfs/VLM-33W-2W-S+.pdf
>
> It costs about $70 from Mouser:
>
>
> https://www.mouser.com/ProductDetail/Mini-Circuits/VLM-63-2W-S%2B?qs=hWgE7mdIu5SsPTT3lqlQ7Q%3D%3D
>
> However, just being careful per the procedures which have been well
> described many times in this thread (and others) will save you the $70.
>
> Dave - WØLEV
>
>
>
>
> On Thu, Aug 10, 2023 at 7:03 PM wizard cybinlabs.com <wizard@cybinlabs.com>
> wrote:
>
>> It is accepted practice to place the transient protection device at the
>> source. Adding as much protection as is warranted. So, if you have a big
>> antenna that is likely to be struck by lightning you will have all sorts of
>> transient protection devices long before the signal gets to the input of
>> the detector.
>>
>> One worries about the capacitance of the protective device when it will
>> have an effect on the fidelity of the signal which will be more pronounced
>> as the frequency increases.
>>
>> If it is really a concern, then use QUCS to simulate the effect of the
>> protection device to the overall performance of your test circuit. I'll use
>> any excuse known to mankind to beat the QUCS drum as it is the most
>> fantastic of all tools.
>>
>>
>> 73
>> ------------------------------
>> *From:* NanoVNAV2@groups.io <NanoVNAV2@groups.io> on behalf of W0LEV via
>> groups.io <davearea51a=gmail.com@groups.io>
>> *Sent:* Wednesday, August 9, 2023 1:41 PM
>> *To:* NanoVNAV2@groups.io <NanoVNAV2@groups.io>
>> *Subject:* Re: [nanovnav2] ESD safer circuit
>>
>> Usually Transorbs have a relatively large capacitance and may be unsuited
>> for applications in front of the TinySAs and NANOVNAs.
>>
>> Dave - WØLEV
>>
>> On Wed, Aug 9, 2023 at 7:29 PM W0FAA - JJ via groups.io <W0FAA=
>> protonmail.com@groups.io> wrote:
>>
>> With respect to the transorb suggestion: I'm a technician not an
>> engineer, but I could find no indication in the data sheet that those
>> devices are suitable for use at RF.
>> What am I missing?
>>
>> Sent with Proton Mail <https://pr.tn/ref/NV8FZHYH5PG0> secure email.
>>
>> ------- Original Message -------
>> On Tuesday, August 8th, 2023 at 9:52 PM, Mike C. <mg@mgte.com> wrote:
>>
>> What is really needed is a "transorb" see:
>> https://www.wagneronline.com.au/transorbs-devices/transorbs/semiconductors/electronic-components/458/fl/
>> these work at 1ns and ..... well just go look at the specs.
>>
>> Mike C. Sand Mtn GA
>> On 7/31/2023 5:36 PM, Leif M wrote:
>>
>> There are very low capacitance ESD diodes which could help. They were
>> mentioned here some time ago. But not against overload, I think. I heard
>> that a good HF antenna gives 1W of total power at the connector. Probably
>> more from huge antennas.
>> This is the ESD diode
>> https://www.digikey.fi/en/products/detail/infineon-technologies/ESD101B102ELE6327XTMA1/4759559
>>
>>
>>
>>
>> --
>>
>> *Dave - WØLEV *
>>
>>
>>
>
> --
>
> *Dave - WØLEV*
>
>
>
>
>

Bob, I am using the 64 version. Supurb S/W. Joe cannot be beaten at this game. Labview really screwed him. The story is worth reading. He did document it on YouTube.
Albert. EI7II.

Nice job Vojtech, I may also try it. Thanks.

Mike C. Sand Mtn GA

On 8/1/2023 3:34 PM, OK1VAW Vojtech wrote:

> Here is my approach, how I constructed external simple ESD protection
> for Nanovna, written about two years ago:
> https://www.qsl.net/o/ok1vaw//protector/NanoVNA%20input%20protector.pdf
> this is a link to a directory with other files:
> https://www.qsl.net/o/ok1vaw//protector/
> BR,
> Vojtech, OK1VAW.
>

I've got 713 more msgs to go to get to the top, so bear with me. Only 1
question. Regarding shorting the antenna PRIOR to attaching the VNA or
any other instrument, would it be a better fix just to have a Transfer
Relay/Switch to dump any charge then IMMEDIATELY connect the VNA?

Mike C. Sand Mtn GA

On 8/1/2023 8:25 PM, Tom W8JI wrote:

> Antenna analyzers and VNAs are not nearly as static-rugged, signal
> level damage immune,  and overload dynamic range as a common modern
> solid state receiver.
>
> As far as static immunity and signal damage old tube radios are
> generally tough, although the old tube radios we fondly remember are
> generally not that great for overload or IMD.
>
> In the big scheme of things analyzers are probably the most damage
> prone pieces of gear we have. With a total 9kZ to 30 MHz antenna power
> level of around -10dBm from my big 630M Inverted L, my nanoVNAs are
> useless. My  bench top real Network Analyzers are much better, but I
> have to measure things in a shielded box if the impedance are terribly
> far away from 50 ohms.
>
> The diodes in the old out of date MFJ antenna analyzer had to be V<10
> volts PRV microwave diodes. The most common failures by far are the
> bridge diodes.
>
> A common failure of the 50-100 PRV diodes in antenna tuners is charge
> on dc floating antennas charging the air variables and the air
> variable dumping into the bridge when  it is "full".  Those bridges
> will take several kilowatts of power when assembled correctly, but
> antennas can actually "get them".
>
> With the VNA or antenna analyzer being by far the most sensitive piece
> of gear we have, I would make darned sure with any outside cables or
> antennas are shorted immediately before being connected. There are
> some low voltage clamp diodes, and I have built some dc biased diode
> clamps that go hard limit at a few volts but are wide open below that,
> and now we have things like this:
>
> https://www.ti.com/product/TPD1E01B04
>
> but even 3V is a horse race to the finish line if protecting a VNA.
> The best policy is to know what we are connecting, and to short those
> big cables and long floating from ground antennas before connecting. A
> resistor and a gas tube aren't going to do much.
>
> 73 Tom
>

Hi Tom,

OK, you got my attention, how about some pictures of your tronic
radiators for the rest of us droooooooling to see what ya got?

Mike C. Sand Mtn GA

On 8/2/2023 7:11 AM, Tom W8JI wrote:

>
> That's a nice article. My only question is can the VNA being protected
> safely handle 15 volts, and why not have a surface mount drain
> resistor, perhaps a 47k or higher resistor? An earth ground is of
> course not necessary since it is the differential voltage across the
> port that we are concerned with and not the common mode potential.
>
> My procedure for connecting now is to make sure the cable is not
> energized by a source, and short the feedline immediately before
> connecting. I feel this is relatively safe based on measurements of my
> 300ft insulated base tower in various weather conditions. Even in
> inclement weather when corona was present the current was very low on
> the scale of a 50-microampere meter. (However, distant lightning
> strikes would pin the meter.)
> Even on clear sunny days a brisk breeze would produce a few
> microamperes of charging current, and the ungrounded tower could rise
> to spark gap voltages every several minutes.
>
> I have not measured my 630M Inverted L charge current, but that might
> be interesting. I keep thinking I should put a choke from the antenna
> to ground, but right now I just let it drain through my radio gear.
> I've never heard the connector arc or gotten a poke on a normal day,
> but of course I disconnect when storms are possible or not running
> WSPR. The more I talk about this the more I know I need to fix the
> Inverted L feed point with a shunt inductor.  My countering mental
> argument is the 630M inverted L is feet away from a ground 318 ft
> tower, 200ft high, and runs horizontally to a second taller tower
> shunted to ground.  So the likelihood it has a dry weather charge
> problem is at least a little bit diminished.
>
> Having that float is a bad idea, isn't it. :) I better fix that soon.
>
> My insulated base ~300ft tower is less than 50uA, so a 20k resistor
> would hold that tower to 1 volt. The exception would be the big spikes
> during distant or closer local lightning strikes, but someone would be
> a little crazy measuring at that time anyway.
>
> The rest of my antennas have fairly low leak paths to ground with the
> exceptions of wire dipoles, more typical of Ham stations. The only
> reason I bring the big ones up is to give a perspective of the typical
> charge current we might have to bleed off on big floating antennas.
>
> 73 Tom
>
>
> On 8/1/2023 3:50 PM, OK1VAW Vojtech wrote:
>>
>> Here is my article written about two years ago with some measurements.
>>
>> https://www.qsl.net/o/ok1vaw//protector/NanoVNA%20input%20protector.pdf?fbclid=IwAR3jtUNMJiZBeNrvFh4sciTE4_4vNSzYfC0jvH1q_nDp1cXzh7jSZUREGRw
>>
>> BR,
>>
>> Vojtech, OK1VAW.
>>
>
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