开云体育

When you use a coaxial cable the RF current goes up and down the center
conductor and the inner surface of the coax shield. The reason I say inner
shield is that due to the "skin effect" the RF current only travels on the
surface of the inner surface of the shield and slightly below the surface.
The outer surface is effectively isolated and acts like a "third wire".

You are correct. A coaxial cable is really a 3-conductor topology for RF
energy.

1) The inner portion of the center conductor which only supplies
"bulk" to the conductor
and really does nothing for conducting RF energy.

2) The outer surface of the center conductor which conducts RF energy
(skin depth).

3) The inner surface of the shield which conducts RF energy (skin
effect).

4) The outer surface of the shield which only supplies "bulk" to the
conductor and really
does nothing for conducting internal energy. However, if not
correctly decoupled, may
carry common mode currents which distort antenna patterns and
introduce noise to the
receiving system (degrade receiver noise floor).

Now in your case you have the following. You have a microstrip
transmission line and only one side is connected to your helical radiator.
So what is the return path of the RF current? It is the ground side of the
microstrip which is connected to the ground plane. So your antenna
consists of the helical radiator and the other half is the transmission
line ground side and PCB ground plane. Both are radiating RF.

All correct.

When you connect your RG316 cable and nanoVNA the RF current flows on the
inner conductor and inner surface of the shield. The outer surface is
attached to the ground plane so it will radiate as well and is part of the
antenna system. When you wrap the coax around a ferrite you do not affect
the current flowing inside the coax - only the current on the outer shield
is reduced. The current flowing on the outer surface is known as "common
mode current" The common mode current reduction is due to the complex
impedance (R + X) of the inductor which is effectively in series with the
outer shield surface. If you google "braid breaker", "current balun" or
"RF Choke" you will find more info on this subject.

For your application I'd recommend a current choke consisting of 2 to 3
turns loosely spaced of your RG-316 on a small (1" OD or so) 61 material
ferrite toroid. Place this immediately at the connection of the coax braid
to the PCB with absolutely minimal pigtail.

Dave - W?LEV


On Sat, Mar 15, 2025 at 6:34?PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

On Fri, Mar 14, 2025 at 08:39 PM, Nico wrote:

It took me a few reading of your two last replies but I think I got it.

If I

understand correctly, the shield of my coax is now integral part of the
antenna system as it is connected to the ground pad which is the antenna

and

system ground and also the ground plane. In this case then, how will I

ever

achieve an accurate reading ?

When you use a coaxial cable the RF current goes up and down the center
conductor and the inner surface of the coax shield. The reason I say inner
shield is that due to the "skin effect" the RF current only travels on the
surface of the inner surface of the shield and slightly below the surface.
The outer surface is effectively isolated and acts like a "third wire".

Now in your case you have the following. You have a microstrip
transmission line and only one side is connected to your helical radiator.
So what is the return path of the RF current? It is the ground side of the
microstrip which is connected to the ground plane. So your antenna
consists of the helical radiator and the other half is the transmission
line ground side and PCB ground plane. Both are radiating RF.

When you connect your RG316 cable and nanoVNA the RF current flows on the
inner conductor and inner surface of the shield. The outer surface is
attached to the ground plane so it will radiate as well and is part of the
antenna system. When you wrap the coax around a ferrite you do not affect
the current flowing inside the coax - only the current on the outer shield
is reduced. The current flowing on the outer surface is known as "common
mode current" The common mode current reduction is due to the complex
impedance (R + X) of the inductor which is effectively in series with the
outer shield surface. If you google "braid breaker", "current balun" or
"RF Choke" you will find more info on this subject.

--

*Dave - W?LEV*


--
Dave - W?LEV

ST-LINK info:
/g/nanovna-users/topic/nanovna_bricked/34149616

On Sat, Mar 15, 2025, 10:40 AM SP1RAC via groups.io <sp1rac@...>
wrote:

Maybe you have a problem with the battery.
I would open the NanoVNA and disconnect the battery.
Check if it is working. Use a meter to check if there is voltage coming
out of it and what it is.
Also check the battery socket.

Geoff, this will download the program and documentation:



Brian

Brian,

When I go to this link:
I get the message that ham-radio.com domain has expired.

Is the above link you posted correct.
73,
Geoff - W8GNM

On Fri, Mar 14, 2025 at 08:39 PM, Nico wrote:

It took me a few reading of your two last replies but I think I got it. If I
understand correctly, the shield of my coax is now integral part of the
antenna system as it is connected to the ground pad which is the antenna and
system ground and also the ground plane. In this case then, how will I ever
achieve an accurate reading ?

When you use a coaxial cable the RF current goes up and down the center conductor and the inner surface of the coax shield. The reason I say inner shield is that due to the "skin effect" the RF current only travels on the surface of the inner surface of the shield and slightly below the surface. The outer surface is effectively isolated and acts like a "third wire".

Now in your case you have the following. You have a microstrip transmission line and only one side is connected to your helical radiator. So what is the return path of the RF current? It is the ground side of the microstrip which is connected to the ground plane. So your antenna consists of the helical radiator and the other half is the transmission line ground side and PCB ground plane. Both are radiating RF.

When you connect your RG316 cable and nanoVNA the RF current flows on the inner conductor and inner surface of the shield. The outer surface is attached to the ground plane so it will radiate as well and is part of the antenna system. When you wrap the coax around a ferrite you do not affect the current flowing inside the coax - only the current on the outer shield is reduced. The current flowing on the outer surface is known as "common mode current" The common mode current reduction is due to the complex impedance (R + X) of the inductor which is effectively in series with the outer shield surface. If you google "braid breaker", "current balun" or "RF Choke" you will find more info on this subject.

Below is an update on the schedule of speakers and presentations for the
Southeastern VHF Society Conference. The conference will be held at the
Quality Inn at Exit #4 in Clarksville, TN April 4-5, 2025. This is an
opportunity to meet other VHF+ enthusiasts, learn, exchange ideas, and have
FUN. The $69 registration fee for the conference is required, and it
includes a 1 year membership in the SVHFS. Details are here:
. Advance registration is highly
recommended as the hotel requires a head count in order to prepare the food
for the event. There will be door prizes given away at the banquet on
Saturday evening. Feel free to contact me via email if you have any
questions: RobinK4IDC@....

*Preliminary 2025 SVHFS Conference Schedule*

*Friday*

*8:00 AM Registration*

9:00 Charles Osborne -K4CSO – RF Zero - 30 min

9:30 Robin Midgett – K4IDC – RF Zero 2 Meter Beacon- 30 min

10:00 Bob Lear – W4ZST Power Dividers and Cable Loops – 30 min

10:30 15 Minute Break

10:45 Mike Stipick – KC4RI – 5.7 GHz SDR Transceiver - 45 min

11:30 Bill Pence – Grid Square Locator – 30 min

12:00 PM Lunch - Steve and Sandra Kostro – Designing a Multi Band
Transverter

1:15

2:00 Paul Wielozenski - K4PEW - VHF Nets – 30 min

2:30 Ben Lowe – Rover Radiators – 30 min

3:00 George Presley – 10 GHz Beacon – 30 min

4:00 Charles Osborne / Kent O’ Dell – 10GHz Antenna test Range - 30 min

5:00 Dinner –On your own

7:00 Swap Fest and Hospitality Suite

*Saturday*

9:00 AM Brian McCarthy – Lunar Rover Truck, 2.3GHz Amp – 1 hour

10:00 Peter Van Horne – KA6U - Moon Bounce Rover – 45 min

10:45 15 Minute Break

11:00 Chris Arthur - NV4B – 45 min

12:00 PM Lunch - On your own

1:30 Larry Cagle - K4WLO – Meteor Scatter with MSK144 - 45 min

2:15 SVHFS Business Meeting

3:00 – 5:00 Rover Round Up and 10GHz Antenna Range

6:00 Social Hour- Hotel Bar

7:00 Dinner Banquet followed by the Door Prize Extravaganza!


Thanks,
Robin Midgett K4IDC


Thanks,
Robin Midgett K4IDC

Maybe you have a problem with the battery.
I would open the NanoVNA and disconnect the battery.
Check if it is working. Use a meter to check if there is voltage coming out of it and what it is.
Also check the battery socket.

You wrote in the title that the unit is: NanoVNA-H v3.5 ?
If you have somehow managed to wipe the bootloader (highly unlikely) your
only
choice left is to connect to the micro directly, using a programer like
st-link (2-3 bucks and Ali, Ebay etc).

On Sat, 15 Mar 2025 at 15:38, Taracait via groups.io <tcdrennen=
[email protected]> wrote:

Thanks. Clyde - but my unit is not -H; I did try the BOOTP - VDD reset, no
good, and all the other sequences mentioned.

Nothing lets me connect to the unit via USB-C.

I do appreciate the response. ?

On Fri, Mar 14, 2025, 13:34 Clyde Lambert via groups.io <clyde.lambert=
[email protected]> wrote:

Hello,
In the files section you will find a process to recover from "White

Screen

Recovery". Follow it PRECISELY STEP by STEP!.
If that does not work you could try, for the lack of a better term, a
factory reset.
Push the jog switch down to the left and hold while turning the unit on.
Then try the screen recovery.
Clyde KC7BJE

How to remove the stored numbers in the recall/empty windows

Thanks. Clyde - but my unit is not -H; I did try the BOOTP - VDD reset, no
good, and all the other sequences mentioned.

Nothing lets me connect to the unit via USB-C.

I do appreciate the response. ?

On Fri, Mar 14, 2025, 13:34 Clyde Lambert via groups.io <clyde.lambert=
[email protected]> wrote:

Hello,
In the files section you will find a process to recover from "White Screen
Recovery". Follow it PRECISELY STEP by STEP!.
If that does not work you could try, for the lack of a better term, a
factory reset.
Push the jog switch down to the left and hold while turning the unit on.
Then try the screen recovery.
Clyde KC7BJE

R&L was where I got my SAA2N. I also contacted them about the clone issue and I didn't get a reply back, that was 2 yrs ago.
________________________________
From: [email protected] <[email protected]> on behalf of K3IY via groups.io <oconnorkl@...>
Sent: Saturday, March 15, 2025 5:33 AM
To: [email protected] <[email protected]>
Subject: Re: [nanovna-users] Erratic traces with SAA2N

I got an email response from NanoRFE support with some concerning information. They suggested that the hardware version of my SAA2N "is a clone" and many users have reported issues with it. I was puzzled because I did my research (or at least I thought I did), and all sources online said there's enough bad clones out there and if you're in the US avoid this by buying from R&L electronics. NanoRFE support pointed me to their website which has a listed of suppliers selling clones. To my surprise R&L electronics is on that list and they're noted to "keep selling clones despite not being asked to by the original developers". If this is indeed true I am very disappointed in R&L and will be giving them a call to discuss a possible resolution.

I got an email response from NanoRFE support with some concerning information. They suggested that the hardware version of my SAA2N "is a clone" and many users have reported issues with it. I was puzzled because I did my research (or at least I thought I did), and all sources online said there's enough bad clones out there and if you're in the US avoid this by buying from R&L electronics. NanoRFE support pointed me to their website which has a listed of suppliers selling clones. To my surprise R&L electronics is on that list and they're noted to "keep selling clones despite not being asked to by the original developers". If this is indeed true I am very disappointed in R&L and will be giving them a call to discuss a possible resolution.

@Dave :

Thanks, 1.86:1 was before I put the PCB into its final plastic case. Then within the case it jumped to 2.6. That's when I calculated the corresponding matching values. I've put an 8.2nHload inductor and a 3.9pF series capacitor. The resulting reading is on the 9th picture. It jumped the other way around. I think it has to do with what Roger says.

@Roger : It took me a few reading of your two last replies but I think I got it. If I understand correctly, the shield of my coax is now integral part of the antenna system as it is connected to the ground pad which is the antenna and system ground and also the ground plane. In this case then, how will I ever achieve an accurate reading ?

Thanks

I finally managed to implement renormalization for unequal port reference impedances. The images show unequal resistances for a 10.7 MHz Murata ceramic filter. I optimized them by hand for minimum group delay variation over 10.6 to 10.8 MHz, the passband of an FM broadcast signal. The optimization also flattened the passband and lowered the spurs.

I'm not quite ready to release this. The new renormalization algorithm I'm using can also handle a reactance shunting either port. This would let you include the standard 10 pF Murata test load. I think it might be useful for other kinds of filters and transformers as well. The problem is that I'm running out of screen real estate, at least on the bottom line. I'll figure out something. In the meantime, would there be any use for a shunt inductance? I don't recall seeing this, but it would be easy to implement.

Brian

Further addressing small values of inductance: There is really no need to
buy SM inductors which may or may not be apropriate. Small nH inductors
can easily be made of short lengths of appropriate single conductors. For
example and one I always remember is that AWG #18 solid copper wire
exhibits 18.1 nH / inch. The following calculator may be of use for this
purpose:



Dave - W?LEV

On Fri, Mar 14, 2025 at 8:51?PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

Nico,

So you have two issues here...

Th first one is that you will have difficulty knowing what the impedance
is near the matching network because your measuring system is affecting the
results. That was the point of my previous post.

The second is that even if you knew precisely what impedance you are
trying to match inductors and capacitors at 916 MHz. will not have the same
values as they do at lower frequencies. An inductor will have series
resistance that increases with frequency and parallel capacitance. A
capacitor will have lead inductance. So you need to purchase components
that have been characterized at 900 MHz.

--

*Dave - W?LEV*


--
Dave - W?LEV

Nico,

So you have two issues here...

Th first one is that you will have difficulty knowing what the impedance is near the matching network because your measuring system is affecting the results. That was the point of my previous post.

The second is that even if you knew precisely what impedance you are trying to match inductors and capacitors at 916 MHz. will not have the same values as they do at lower frequencies. An inductor will have series resistance that increases with frequency and parallel capacitance. A capacitor will have lead inductance. So you need to purchase components that have been characterized at 900 MHz.

On Fri, Mar 14, 2025 at 04:00 AM, Nico wrote:

Look at the picture and zoom it (not zoomed it does not show up properly),
you'll see a blurred larger line around the feedline. This is the return path
or, the other half of the transmission line. This is a ground line attached to
the ground plane on layers 2 and 3. I was unsure on how to terminate it close
to the antenna attachment point, so I've just ended it close to it

Nico,

In your case the purchased helical is one half of the antenna. The other half is the "buried" side of the transmission line and the ground plane of your board. When making measurements of the antenna the outer surface of the shield of your connecting RG316 cable is now also part of the antenna. Grab the coax with your hand or attach a wire to the SMA connector nut on the VNA and you will see the SWR change. The situation is similar to what happens on a handheld radio transmitter where the operator is capacitively coupled to the radios antenna system.

You can try reducing the RF current on the coax cable with ferrites but you will not get rid of it entirely. And at this high of a frequency you will still have a considerable length of coax shield radiating until the ferrites.

SUGGESTION: Forget about these "canned" solutions. Download and install
SIMSMITH.



There is also a accompanying tutorial at:



Dave - W?LEV

On Fri, Mar 14, 2025 at 5:51?AM shlomo537678 via groups.io <shlomo537678=
[email protected]> wrote:

Hi All.

I need to build a Pi Network for my circuit as shown in the fig below.

1741926237187.png

So I have a 'Pi Matching Network' in my circuit. The datasheet asked me to
build a Pi Matching Network. ( You know, how there is a series component, a
source shunt component and a Load shunt component. )

Anyway, my VNA keeps telling me this: The measured load impedance is
31.9-58.5j.

The VNA is automatically generating these four groups below ( group 1 thru
4 ) of available matching parameters on the screen:

1. 5.24pF capacitor for source shunt and 28.8nH inductor in series.
Does that mean, this group does not need a Load Shunt at all? Does this
mean that the proper tuning has been achieved with just a capacitor for
source shunt and an inductor in series?

2. 23.1nH inductor for source shunt and 12nH inductor in series.
Does that mean, this group does not need a Load Shunt at all? Does this
mean that the proper tuning has been achieved with just a inductor for
source shunt and an inductor in series?

3. 97.5nH inductor for load shunt and 23.3nH inductor in series.
Does that mean, this group does not need a Source Shunt at all? Does this
mean that the proper tuning has been achieved with just a inductor for load
shunt and an inductor in series?

4. 15.3nH inductor for load shunt and 5.21pF capacitor in series.
Does that mean, this group does not need a Source Shunt at all? Does this
mean that the proper tuning has been achieved with just a inductor for load
shunt and a capacitor in series?

If the answer is yes to all the 4 above questions, then I still cant
believe that a 'Pi matching Network' can exist with 1 of the 3 components
totally missing.

Ty for your reply!

--

*Dave - W?LEV*


--
Dave - W?LEV

It looks like the cal may not be taking. RESET......COMPLETE
CAL.......STORE in a register. Go back and verify that the OSL displays as
it should. If not, OPEN CASE....INSTALL PROPER LOAD......from the inside
VERIFY WITH DMM that 50-ohms is measured correctly. All this to confirm
the center pin is mating correctly to the connector. Also do same with the
short and DMM.

Dave - W?LEV

On Fri, Mar 14, 2025 at 7:21?PM K3IY via groups.io <oconnorkl=
[email protected]> wrote:

I have been using my nanovna SAA2N for months without issues, and I bought
it from R&L who is an authorized distributer of legitimate Nanovna's. This
morning my issue started after I calibrated the unit. All of my traces
were erratic (see attached picture). Smith chart is a mess of zig zags
instead of arcs. I tried the following and nothing has fixed the issue.
"Reset" and "Reset All" prior to calibration. Tried multiple frequency
ranges and trace points. Tried using both cables. Tested the cables for
shorts/continuity. Tested all three standards (short, open, load) with an
ohm meter, unfortunately I don't have another set to try. Flashed the
firmware. Opened up the case and confirmed good solder joints and
continuity from the N connectors to the board. Wiggled the connections and
nothing changed. Checked again when the battery was fully charged. Also
tried using VNA View and got the same results. The unit was safely stored
in the case between the last time it worked and now. What am I missing?

--

*Dave - W?LEV*


--
Dave - W?LEV

I have been using my nanovna SAA2N for months without issues, and I bought it from R&L who is an authorized distributer of legitimate Nanovna's. This morning my issue started after I calibrated the unit. All of my traces were erratic (see attached picture). Smith chart is a mess of zig zags instead of arcs. I tried the following and nothing has fixed the issue. "Reset" and "Reset All" prior to calibration. Tried multiple frequency ranges and trace points. Tried using both cables. Tested the cables for shorts/continuity. Tested all three standards (short, open, load) with an ohm meter, unfortunately I don't have another set to try. Flashed the firmware. Opened up the case and confirmed good solder joints and continuity from the N connectors to the board. Wiggled the connections and nothing changed. Checked again when the battery was fully charged. Also tried using VNA View and got the same results. The unit was safely stored in the case between the last time it worked and now. What am I missing?