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Re: Nano VNA BASIC WORKSHOP via Zoom

 

Kirk
No, I did not record them because I wanted to encourage questions/comments and when you record these sessions,
(some) folks are hesitant to ask questions or respond.
Barry
Re: Nano VNA BASIC WORKSHOP via Zoom

 

Hi, Barry,
Did you happen to record those previous sessions?
Thanks,
--Kirk, NT0Z

My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)

On Sunday, November 13, 2022 at 06:21:03 AM CST, Barry K3EUI <k3euibarry@...> wrote:

The ¡°Five County Digital Training Net¡± (Philadelphia region) is hosting a series of Zoom Workshops on Monday evenings at 7-9 pm. The topic: Nano VNA Fundamentals
All are welcome to join.
Link:

We have already held two sessions covering the fundamentals of what a VNA is capable of measuring and the second session covered how to CALIBRATE the VNA over a frequency range.

The 3rd Zoom session on November 14th will cover what a Nano VNA measures and what it calculates: the forward and the reflected signals are compared (S11) and the following are calculated:

1) Reflection Coefficient (rho) - a fraction from 0 to 1.0 representing the ratio of returning signal to incident signal. In an antenna, you do not want any reflected (return) signal, so the ideal reflection coefficient is zero.

2) Return Loss (dB) - this is based on the reflection coefficient and represents the loss of signal, but measured in decibels (dB) rather than as a percent or fraction. Hams rarely use this measurement. Why?

3) SWR - standing wave ratio? -? We all use this term but what does it mean? What is an ¡°acceptable¡± SWR in terms of antenna performance.

I will tie these three measurements into what a Smith Chart reveals.

Come join the discussion.
I am not an RF Engineer - so I try to keep this at a moderate level of mathematics.

De k3eui
Barry? (k3euibarry - at - gmail.com)
Five County Digital Net manager
Philadelphia PA
November 13 2022
Nano VNA BASIC WORKSHOP via Zoom

 

The ¡°Five County Digital Training Net¡± (Philadelphia region) is hosting a series of Zoom Workshops on Monday evenings at 7-9 pm. The topic: Nano VNA Fundamentals
All are welcome to join.
Link:

We have already held two sessions covering the fundamentals of what a VNA is capable of measuring and the second session covered how to CALIBRATE the VNA over a frequency range.

The 3rd Zoom session on November 14th will cover what a Nano VNA measures and what it calculates: the forward and the reflected signals are compared (S11) and the following are calculated:

1) Reflection Coefficient (rho) - a fraction from 0 to 1.0 representing the ratio of returning signal to incident signal. In an antenna, you do not want any reflected (return) signal, so the ideal reflection coefficient is zero.

2) Return Loss (dB) - this is based on the reflection coefficient and represents the loss of signal, but measured in decibels (dB) rather than as a percent or fraction. Hams rarely use this measurement. Why?

3) SWR - standing wave ratio - We all use this term but what does it mean? What is an ¡°acceptable¡± SWR in terms of antenna performance.

I will tie these three measurements into what a Smith Chart reveals.

Come join the discussion.
I am not an RF Engineer - so I try to keep this at a moderate level of mathematics.

De k3eui
Barry (k3euibarry - at - gmail.com)
Five County Digital Net manager
Philadelphia PA
November 13 2022
Re: MOSFET as RF on/off switch and how to measure/what to expect #circuit

 

Sorry ... I meant to say:

These parts are designed for turning on MOSFET gates so I suspect they stack as many photodiodes in series as they need to get the required voltage.

Eamon
Re: MOSFET as RF on/off switch and how to measure/what to expect #circuit

 

I don't know of any PV output optos that have 10V kind of outputs, which
is what you're going to need for Vgs on a big FET.

An isolated supply is fairly easy - as in an off the shelf DC/DC
isolated converter. You could use it as the gate drive directly, since
you're not looking for high speed.


For improving off isolation, you could put multiple identical switches in
series. I would start by simply taking the device and measuring its off state,
to see how many I might need to chain up.

Or a configuration that has a series switch followed by a shunt to ground.
Here's one that will do 10V (it's far from the only one). These parts are designed for turning on MOSFET gates to I suspect they stack as many LEDs in series as they need to get the required voltage.

Besides being cheaper than an isolated DC/DC converter, they probably have lower capacitance across the isolation barrier.

Eamon
Re: MOSFET as RF on/off switch and how to measure/what to expect #circuit

 

On 11/12/22 9:39 AM, Manfred Mornhinweg wrote:
Miro, yes, Elecraft uses such high voltage rectifiers as PIN diodes in several of their products. They use true PIN diodes in some others, and sometimes they even mix them. What kind of diodes they use in each case, is surely a trade-off between total cost and performance.
Apparently, those 1000V PIV (the 1n4008) *are* PIN diodes - something about the voltage rating - the 800V versions are not.

However, there's some commentary about different manufacturers being different, and needing to check the data sheet for the reverse recovery time trr - it needs to be "long enough" (which I guess implies a big I region that has to be swept clear when reverse biased)

This is the issue - As a mfr can use the JEDEC number if your part meets the required datasheet values. If, you as a circuit designer are depending on "not on datasheet" numbers, some might work, some might not. (noise properties are notorious for this..)





Many schematics are available on theyr website. Just download them and look! For example download the manual of the KPA100, which has such diodes, and also the crystal-locked DC-DC converter I mentioned. And download the K3 schematics file, where you can see the KPA3 using a combination of SMD high voltage rectifier and true PIN diodes. Also the low power final amp of the KPA3 uses a rectifier as a PIN diode. The TR switch on the K3 RF board uses a combination of rectifier and PIN diodes. Same thing with the K3S.
Re: MOSFET as RF on/off switch and how to measure/what to expect #circuit

 

Miro, yes, Elecraft uses such high voltage rectifiers as PIN diodes in several of their products. They use true PIN diodes in some others, and sometimes they even mix them. What kind of diodes they use in each case, is surely a trade-off between total cost and performance.

Many schematics are available on theyr website. Just download them and look! For example download the manual of the KPA100, which has such diodes, and also the crystal-locked DC-DC converter I mentioned. And download the K3 schematics file, where you can see the KPA3 using a combination of SMD high voltage rectifier and true PIN diodes. Also the low power final amp of the KPA3 uses a rectifier as a PIN diode. The TR switch on the K3 RF board uses a combination of rectifier and PIN diodes. Same thing with the K3S.
nanovna_remote.py - Python tool for remote control of the NanoVNA-H from the PC #nanovna-h #scripting #python #nanovna-tools

 

Hi,
as written just around the corner /g/tinysa/topic/tinysa_remote_py_python/94944540 there's a new tool in my toolbox:



Remote control for the NanoVNA or tinySA - mirror the screen to your PC and operate the device with the mouse. The keys + and - zoom in and out, s takes a screenshot with timestamp, ESC quits the program.

usage: nanovna_remote.py [-h] [-d DEVICE] [-t | -n] [-z {2,3,4}]

optional arguments:
-h, --help show this help message and exit
-d DEVICE, --device DEVICE
connect to serial usb device
-n, --nanovna use with NanoVNA (default)
-t, --tinysa use with tinySA
-z {2,3,4}, --zoom {2,3,4}
zoom the screen image

Martin
Re: NanoVNA-H4 no longer measures SWR or Smith Chart

 

Dave - LogMag for S11 just sits there at 10db/0.05db no matter what connector i put on the unit, OPEN, SHORT or LOAD. It doesn't fluctuate at all. Smith Chart stays at -133mOhms 521nH. No fluctuation using any of the three, OPEN, SHORT or LOAD.
No other traces for S11.

The screen also shows two S21 values. LogMag for S21 shows a constant 10db but the number next to it is fluctuating all over the place, typically between -70 and -99. Also below LogMAG it shows Phase Angle. It shows 90 degrees and to the right of that is another angle that is fluctuating all over -110 to +10 and many values in between over and over randomly.

I didn't tell the thing to show S21 values at all. It just did it.

John
Re: NanoVNA-H4 no longer measures SWR or Smith Chart

 

Tom - I've ordered a couple to have on hand. Will take the one out.
Thanks for the suggestion.

John
Re: NanoVNA-H4 no longer measures SWR or Smith Chart

 

Doug, i checked all the cables and popped the lid and checked inside for a cracked solder connection possibly. Took off the shield and checked that also. No problems that I could see.
Thanks for the suggestion.

John
Re: New firmware features request - testing toroids ( I hope for . . . .)

 

Hello,
The PDF file works fine for me also.
Maybe you need to download it again?
Clyde KC7BJE
Re: HANDHELD CALCULATOR Scattering Parameter Routines

 

Mutiple parties interested. So for now spoken for... THANKS!
Great not to send to the landfill.
Re: NanoVNA-h4 stuck in DFU mode

 

Paul,

thanks i tried this; was able to see the device in the DeFuse and it completed the update but the machine still acts like its in DFU mode.
Re: NanoVNA-h4 stuck in DFU mode

 

tried this today and it did not fix it.
HANDHELD CALCULATOR Scattering Parameter Routines

 

If you own or still use the ol HP 65/67/41C series RPN machines, I have a copy of Medleys microwave routines text.
Routines include analysis and synthesis of networks driven by S data.

If interested, reply offline direct. TNX...

73' Alan W4AMV
Re: New firmware features request - testing toroids ( I hope for . . . .)

 

For me too
Opens fine
Dg9bfc sigi

Am 11.11.2022 12:57 schrieb "Max via groups.io" <kg4pid@...>:




It opens fine for me.
Max
On Friday, November 11, 2022, 05:41:36 AM CST, DougVL
<k8rftradio@...> wrote:

On Thu, Nov 10, 2022 at 11:36 PM, Michael wrote:
Michael -

Found this a long time ago and not sure if this will be useful to
anybody. See
attached.
Your "cross_ref_list.pdf" sort of opens - appears blank and closes
immediately.
--
Doug, K8RFT
Re: MOSFET as RF on/off switch and how to measure/what to expect #circuit

 

Power MOSFETS are specified in terms of max Rdson. At high frequencies one must also include the drain/source capacitance as well as gate-drain and gate-source capacitances. Spice models typically include those capacitance parameters so an AC simulation at the frequency of interest should shed light on the performance as a ¡°switch¡±.

-CT
Re: MOSFET as RF on/off switch and how to measure/what to expect #circuit

 

On Thu, Nov 10, 2022 at 07:53 AM, Manfred Mornhinweg wrote:


Elecraft went another path, and used an RF oscillator to generate the high
voltage needed to bias 1N4007 and 1N5408 diodes pressed into PIN diode
service.
Is this saying that they use 1N4007/5408 as PIN? If so, any details?
Re: New firmware features request - testing toroids ( I hope for . . . .)

 

It opens fine for me.
Max

On Friday, November 11, 2022, 05:41:36 AM CST, DougVL <k8rftradio@...> wrote:

On Thu, Nov 10, 2022 at 11:36 PM, Michael wrote:
Michael -

Found this a long time ago and not sure if this will be useful to anybody. See
attached.
Your "cross_ref_list.pdf" sort of opens - appears blank and closes immediately.
--
Doug, K8RFT
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