开云体育

I have always assumed that the "Not recommended for new designs" warning
implied only that the part was old and planned for obsolescence by the
manufacturer. That is important information if you are planning a large
volume production that will require long term access to the part. But for
one-off design for my own use, I have always ignored this.

Hi,
I'm facing the same issue with my new NanoVNA V2 and NanoVNA Saver version
V0.3.10 under Win64.

In 9 out of 10 calibration attempts I get the following error message:
“two of short, open and load returned the same values at frequency ...”

This is really annoying - does anybody have an idea if this is a hardware
or a software issue on my device?
Calibration on the device itself works fine but with the V0.3.10 on the PC
it's a nightmare.

BR,
Markus

On 2/4/22 8:36 AM, N2MS wrote:

I missed the trigger voltage. The Infineon triggers at 6.1 volts and clamps at a lower voltage depending upon current. I'll look for an equivalent or order the Infineon.

The Bourns part is more for telco and data applications. Ethernet, for instance, has a transformer isolation which is pretty robust to transients of short duration. I don't know that I'd use a part with 25V holding voltage on Ethernet which might be PoE at 48V, though <grin>.

When you find a new part, let us all know.? Low C and low voltages are a tough combination to find.

Here is the one I am using for my H4.



It has some padding, and pockets for cables, etc.

...Bob / AA2FD

On 02/04/2022 11:08 AM Jim Lux <jim@...> wrote:


On 2/4/22 7:59 AM, N2MS wrote:

I checked this Infineon diode on Mouser and it shows "Not recommended for new design:

<>

Has anyone used this Bourns part:

<>

It has low capacitance the the 0603 size with solderable ends may be easier to solder to the connector.

Mike N2MS

Very different parts.? The Infineon part triggers at a few volts. The
Bourns part triggers at 250V, and then clamps to 25V.

By the time the Bourns part triggers, your front end is dead.

On 02/04/2022 8:38 AM Reinier Gerritsen <r.gerritsen@...> wrote:


Solved this problem a few years ago. I protected my nanovna V2.2 with a
TVS diode: ESD101B102ELE6327XTMA1, a 5.5V TVS bi-directional diode from
Infineon, 0.1 pF capacitance.
Soldered directly at the input on the pcb. I did not see any difference
in return loss matching. You could introduce a series capacitor to
prevent DC connection related failures. I think (not for sure) that the
TX port does not have one, but the RX port does.
Had to replaced the input switches in 3 different nanovnaV2.2? units
failing in a timespan a few days. All units back to life now.
Reinier

So, after years of almost constant use (I got nanovna 2 the moment I could) I fried channel 0 because of my stupidity :-( I connected it to an antenna switch that had a short that send +12V DC from relay coil supply right to ch0. Of course this fried the infamous MXD8641 switch chip. The chip is not available from any electronics distributors here in Europe, but I found some on Aliexpress. Unfortunately it'll take months to arrive and I need my nanovna now. So, the official store being out of stock I bought a "black and gold" clone. It arrived in two days. Great.

What is not so great is that I managed to fry the same chip in the new nanovna in less than a day and this time no DC was involved. In fact there was nothing I could think of that could've caused it other than ESD.

So I did, what anyone else would. I butchered my previous nanovna to get the mxD8641 chip from it and I fixed the new one, but now I'm worried. If it broke in a day of use while my old one lasted years. Perhaps new chips have worse ESD protection? As such some sort of input protection should be possible to add. I would much prefer to install some extra parts inside than have to use a dingle etc. So I'm thinking of adding two back to back diodes as protection.

However, why reinvent the wheel. Perhaps someone has already found a good solution for this. If there is one please let me know.

What do you do to protect your nanovna?

For a proper Tektronix spectrum analyzer I have I use a DC block dongle and a pin diode dongle that shorts anything over 10dB to ground. Both are quite bulky.

I still have 3 more chips I can salvage from the old nanovna. I have to make do with them until my purchase comes from China. Please don't suggest I use personal ESD protection as a solution, because I'm working with vacuum tube amplifiers that have 5kV plus voltages. A grounded strap on my wrist, or a grounded mat is the last thing I would want to have around those things.

So, after years of almost constant use (I got nanovna 2 the moment I could) I fried channel 0 because of my stupidity :-( I connected it to an antenna switch that had a short that send +12V DC from relay coil supply right to ch0. Of course this fried the infamous MXD8641 switch chip. The chip is not available from any electronics distributors here in Europe, but I found some on Aliexpress. Unfortunately it'll take months to arrive and I need my nanovna now. So, the official store being out of stock I bought a "black and gold" clone. It arrived in two days. Great.

What is not so great is that I managed to fry the same chip in the new nanovna in less than a day and this time no DC was involved. In fact there was nothing I could think of that could've caused it other than ESD.

So I did, what anyone else would. I butchered my previous nanovna to get the mxD8641 chip from it and I fixed the new one, but now I'm worried. If it broke in a day of use while my old one lasted years. Perhaps new chips have worse ESD protection? As such some sort of input protection should be possible to add. I would much prefer to install some extra parts inside than have to use a dingle etc. So I'm thinking of adding two back to back diodes as protection.

However, why reinvent the wheel. Perhaps someone has already found a good solution for this. If there is one please let me know.

What do you do to protect your nanovna?

For a proper Tektronix spectrum analyzer I have I use a DC block dongle and a pin diode dongle that shorts anything over 10dB to ground. Both are quite bulky.

I still have 3 more chips I can salvage from the old nanovna. I have to make do with them until my purchase comes from China. Please don't suggest I use personal ESD protection as a solution, because I'm working with vacuum tube amplifiers that have 5kV plus voltages. A grounded strap on my wrist, or a grounded mat is the last thing I would want to have around those things.