开云体育

Set up your number of points and start/stop so that measurement points/markers coincide with your desired frequencies. Hint: numbers of points ending in "1" like 201, 401, tend to make the math work more easily.
Example: I work with SATCOM IFs so I set my analyzer to 141 points, start 850MHz, stop 2250MHz and the points are exactly 10 MHz apart.
I think that the interpolation math to give continuous markers as opposed to discrete readouts may be computationally intensive.
Best regards, Don Brant

Great description, Roger,

A diagram which illustrates your description of the skin effect in coax is attached (hopefully),

73,

Maynard
W6PAP

I am using STMicroelectronics: DfuSeDemo.exe
The Dfu file is DIsLord Version 1.2.27 see the image below. My NanoVNA H4
is: HW version 4.3_MS. I reloaded the Dfu file once again. I've tried
several different WH versions with the same results. Once the 2.8" went
south I refuse to proceed with the download because of the message in the
second image.

Thanks for your interest.

[image: DfuFile.PNG]
[image: dfu.PNG]

On Mon, Feb 3, 2025 at 11:51?AM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

What software are you referring to?

Dave - W?LEV

On Mon, Feb 3, 2025 at 3:06?AM Richard Jamsek via groups.io <K8cyk56=
[email protected]> wrote:

Can anyone explain this problem? I'm afraid to proceed on my H4. I FAFO

and

bricked my 2.8" H.

RJ K8CYK



Attachments:

- dfu.PNG <

>

--

*Dave - W?LEV*


--
Dave - W?LEV

Dave made some very good points but perhaps some clarification is needed for those new to the topic. What follows is a simplification of the RF theory involved. For more details see any textbook on antennas and transmission lines.

There is a phenomena known as the "skin effect" where at RF frequencies the current flow is present on the surface of a conductor and has a reduced magnitude deeper in the conductor. . The depth depends on several factors with frequency being one of them.

A coaxial cable used as a transmission line consist of an inner conductor and a shield. The transmission of power takes place between the center conductor and the inner surface of the shield because of the skin effect. . The outer surface of the shield acts as a "3rd wire" and if the far end is connected to a resistive dummy load does not have any current on it. Now when you connect the coaxial cable to an antenna like a dipole the leg connected to the shield is in effect connected to two conductors: the inner shield and the outer shield. The outer shield is now an element of the antenna and RF current can flow on it and radiation can occur.

Now what happens if you connect a hamstick to the center conductor and nothing is connected to the shield? Since the inner and the outer shield are connected at the cable end the outer shield will now be the other radiating element. There is an antenna called the "sleeve dipole" which is built using this technique.

The radiation on the shield is usually undesirable because it can lead to radiation in the shack and for receiving purposes it can lead to picking up noise because it is close to RFI generating devices around the home. The other drawback is that the feedpoint impedance of the antenna will change depending on the length of the coax and objects close to the coax cable. Any ground connection at the transmitter end or in the case of a VNA holding it in your hand will also effect results.

The solution to this is an RF choke. This is an inductor, placed inline close to the antenna feedpoint, which puts a high impedance in series to reduce the level of RF current. . The easiest implementation is multiple ferrite toroid cores with a permeability factor that is suitable for the frequency of operation. The coaxial cable passes through or is wrapped around the toroid. Only the outer surface of the shield is affected by this technique.

In summary to install the hamstick on a vehicle mount it in place with a good ground connection at the antenna feedpoint. Use an RF choke suitable for the frequency of operation. Run the coax to the operating position and then use your VNA to measure SWR. Set the marker to the desired operating frequency and then adjust the stinger for lowest SWR. If running you hand along the coax or holding the VNA significantly affect the results your RF choke is inadequate.

On Mon, Feb 3, 2025 at 01:39 PM, <mattscott2@...> wrote:

Am I missing something? This should be a common feature. I need the ability to
dial in the exact freq of markers.

There is no capability on the NanoVNA device itself to enter a marker frequency. It is easy to use the jog switch to set the marker frequency. It will quickly jump between frequency measurement points

On PC programs like NanoVNA app and Saver you can enter the marker frequency but it only goes to the nearest frequency where a measurement was made.

Roger

Am I missing something? This should be a common feature. I need the ability to dial in the exact freq of markers.

What software are you referring to?

Dave - W?LEV

On Mon, Feb 3, 2025 at 3:06?AM Richard Jamsek via groups.io <K8cyk56=
[email protected]> wrote:

Can anyone explain this problem? I'm afraid to proceed on my H4. I FAFO and
bricked my 2.8" H.

RJ K8CYK



Attachments:

- dfu.PNG <>

--

*Dave - W?LEV*


--
Dave - W?LEV

BS...... The NANOVNA is well shielded. How many times do we,
collectively, have to remind others that holding onto the VNA while making
measurements is allowing your conductive body to become part of the antenna
and its fields.

READ THE REPLIES, PLEASE. Several of us have made it as clear as we
possibly can that "shielding" or "earthing" IS NOT A SOLUTION!!!! You and
the coax outer surface of the shield are becoming part of the antenna if
means to decouple the coax shield are not taken.

READ THE REPLIES. Several of us have responded in best engineering
practices, not here-say, snake oil, or witchcraft!!!! Read the previous
replies, PLEASE!!!!!!!!!!!!!!!!!!!

Dave - W?LEV

On Mon, Feb 3, 2025 at 6:20?PM Patricio A. Greco via groups.io
<patricio_greco@...> wrote:

Hello: I’m reading this topic since a couple of hour. Its clear that
NanoVNA has a poor shielding. These instruments are very cheap …the good
news is that there are many things to enhance on them. A metallic case
would be a good idea with many grounding points, the problem is the display
it should be outside the RF sections… enhance the design requires more
money so this is . You need first an electrically stable setting prior VNA
calibration. I’ve a NanoVNA and let me tell that you are getting
everything this tool can give. In other posts some people are trying to
measure very low series resistance from an inductor , this is out of
NanoVNA possibilities. I measured the RF generator output and this is
square wave, another source of error in the instrument.
That it does is the limit of his technology.

Regards, Patricio.

On 3 Feb 2025, at 15:04, Roger Need via groups.io <sailtamarack=

[email protected]> wrote:

On Sun, Feb 2, 2025 at 05:06 PM, Coyote wrote:

When using my NanoVNA to adjust length of a 20m hamstick, the readings

kept

changing depending on what the NanoVNA was sitting on (truck hood,

pelican

case, my thigh, or in my hand).

How do I get a reliable reading that I can count on for a properly

adjusted

antenna?

A hamstick is a helically wound whip antenna with an adjustable stinger

for tuning the antenna to a desired frequency. But it is only "one half"
of an antenna system. The other half can be another hamstick (which makes
a dipole) or some type of ground plane or counterpoise. The vehicle body
act as the other half for mobile installations.

What happens if you just connect the coaxial cable and secure the

antenna to a non-metallic structure as some posters have suggested? In
this case the outer surface of the coaxial cable will become the other half
of the antenna and will radiate RF in addition to the hamstick. If you
tune using the stinger you will get a minimum SWR point but if you increase
the length of the cable, touch the cable or VNA with your hand or put the
antenna over something metallic the readings will change.

The proper way to adjust the antenna is to mount it in the way it will

be operated and then adjust the stinger. Be aware that the outer surface
of the shield will still act as part of the antenna system and will radiate
RF. The level of RF will depend on what type of structure the antenna is
mounted over. A metal vehicle body acts as a good ground plane and you
will have less cable radiation than just a trunk lid.

You can get a significant reduction in the cable radiation by using an

RF choke on the coaxial cable like Juan Pablo suggested. You can make your
own or buy one from several vendors.

Roger

--

*Dave - W?LEV*


--
Dave - W?LEV

Thank you, Roger! How many times do we (collectively) need to write
something like you (and I) have!!??? The reader evidently doesn't read the
replies.

SUGGESTION to PROVE A POINT: One additional requirement is that the guy or
gal doing the testing of the antenna have a selection of large clamp-on
ferrite beads of either 31 or 43 material for HF. If you're not interested
in 160 or 75/80 meters, go with only 43 material. At least 10 of each is
good.

OK, here goes. Set up your hamstick or equivalent as you normally would.
Connect the NANOVVNA as you normally would to the far end (transceiver end)
of the coax. Go ahead and hold onto the NANOVNA and/or sit it on something
conducting and large. Make measurements as you normally would. Write
down ALL these measurements where you can compare them to what is coming
further.

Next, leave the setup as above, BUT: Install at least five of your
clamp-on ferrites right at the base of the hamstick (or equivalent) right
where the coax feeds the antenna. If the clamp-ons are large enough, make
one additional turn through each bead. After installing the ferrites, make
measurements as you normally would. Go ahead and hold onto the NANOVNA.
Grip it tightly as though your life depended on it. Write down ALL these
measurements.

Compare the two sets of measurements. I'll bet they are quite different.
What you have done with the clamp-on ferrites is isolate the outer surface
of the coax and YOU from the measurements.

POSSIBLE SUBSTITUTE for the FERRITES: Wind a roughly 10 to 12-inch
diameter loose coil of coax of about 10 or so turns and lay the coil
directly on the soil surface. Don't make the coil too tight.

I've done both while camping in the field off grid. Both show quite a
change form allowing the coax, you, and the environment from becoming part
of the antenna.

Dave - W?LEV

On Mon, Feb 3, 2025 at 6:04?PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

On Sun, Feb 2, 2025 at 05:06 PM, Coyote wrote:

When using my NanoVNA to adjust length of a 20m hamstick, the readings

kept

changing depending on what the NanoVNA was sitting on (truck hood,

pelican

case, my thigh, or in my hand).

How do I get a reliable reading that I can count on for a properly

adjusted

antenna?

A hamstick is a helically wound whip antenna with an adjustable stinger
for tuning the antenna to a desired frequency. But it is only "one half"
of an antenna system. The other half can be another hamstick (which makes
a dipole) or some type of ground plane or counterpoise. The vehicle body
act as the other half for mobile installations.

What happens if you just connect the coaxial cable and secure the antenna
to a non-metallic structure as some posters have suggested? In this case
the outer surface of the coaxial cable will become the other half of the
antenna and will radiate RF in addition to the hamstick. If you tune
using the stinger you will get a minimum SWR point but if you increase the
length of the cable, touch the cable or VNA with your hand or put the
antenna over something metallic the readings will change.

The proper way to adjust the antenna is to mount it in the way it will be
operated and then adjust the stinger. Be aware that the outer surface of
the shield will still act as part of the antenna system and will radiate
RF. The level of RF will depend on what type of structure the antenna is
mounted over. A metal vehicle body acts as a good ground plane and you
will have less cable radiation than just a trunk lid.

You can get a significant reduction in the cable radiation by using an RF
choke on the coaxial cable like Juan Pablo suggested. You can make your
own or buy one from several vendors.

Roger

--

*Dave - W?LEV*


--
Dave - W?LEV

Hello: I’m reading this topic since a couple of hour. Its clear that NanoVNA has a poor shielding. These instruments are very cheap …the good news is that there are many things to enhance on them. A metallic case would be a good idea with many grounding points, the problem is the display it should be outside the RF sections… enhance the design requires more money so this is . You need first an electrically stable setting prior VNA calibration. I’ve a NanoVNA and let me tell that you are getting everything this tool can give. In other posts some people are trying to measure very low series resistance from an inductor , this is out of NanoVNA possibilities. I measured the RF generator output and this is square wave, another source of error in the instrument.
That it does is the limit of his technology.

Regards, Patricio.

On Sun, Feb 2, 2025 at 05:06 PM, Coyote wrote:

When using my NanoVNA to adjust length of a 20m hamstick, the readings kept
changing depending on what the NanoVNA was sitting on (truck hood, pelican
case, my thigh, or in my hand).

How do I get a reliable reading that I can count on for a properly adjusted
antenna?

A hamstick is a helically wound whip antenna with an adjustable stinger for tuning the antenna to a desired frequency. But it is only "one half" of an antenna system. The other half can be another hamstick (which makes a dipole) or some type of ground plane or counterpoise. The vehicle body act as the other half for mobile installations.

What happens if you just connect the coaxial cable and secure the antenna to a non-metallic structure as some posters have suggested? In this case the outer surface of the coaxial cable will become the other half of the antenna and will radiate RF in addition to the hamstick. If you tune using the stinger you will get a minimum SWR point but if you increase the length of the cable, touch the cable or VNA with your hand or put the antenna over something metallic the readings will change.

The proper way to adjust the antenna is to mount it in the way it will be operated and then adjust the stinger. Be aware that the outer surface of the shield will still act as part of the antenna system and will radiate RF. The level of RF will depend on what type of structure the antenna is mounted over. A metal vehicle body acts as a good ground plane and you will have less cable radiation than just a trunk lid.

You can get a significant reduction in the cable radiation by using an RF choke on the coaxial cable like Juan Pablo suggested. You can make your own or buy one from several vendors.

Roger

The timeline for submission of papers and presentations has been extended to March 17th.

The VNA and you, when hold on hand, are part of antenna. You must change the installation, feeder route, ground if possible properly.
Any trick to allow a reliable measure if removed later for normal operation then the SWR will become unstable again.
Usually a line choke isolates the antenna feeder side from outside world (shack...)

Not familiar with windoze tools but it seems that it is complaining that the
firmware is in the wrong format. Try the .dfu firmware file?

Anyway you can't brick these devices, even in the worst case scenario you can
always connect to it with a $3 ST Link clone and flash it.

On Mon, 3 Feb 2025 at 04:06, Richard Jamsek via groups.io
<K8cyk56@...> wrote:

Can anyone explain this problem? I'm afraid to proceed on my H4. I FAFO and
bricked my 2.8" H.

RJ K8CYK



Attachments:

- dfu.PNG <>

Insertion Loss method ( this is resonance with VNA) uses to produce Q values higher than Q meter. Take note that Q meter measurements are absolute , independent of residual capacitance on inductor, you set the frequency and reach the resonance with Q-meter variable capacitor and read Q. This is that will happen in a classical RF circuit (narrowband radio amplifiers). Today the components are used in different way and the Q value can be computed using the equivalent inductance, this includes Cp . To compute more accurately the Q with VNA you must to remove this capacitance by calculation. I my example Q= 156 and removing the parasite capacitance (Cp) Q=151. This is a ratio of 1.033 ( this is another coil and frequency) but in general when you remoce Cp the resulting inductance goes down Q is proportional to L…

I hope that explanation would be useful. I’m just trying to help.

Regards. Patricio.

Thanks for thinking about this. I went back and measured the #22 coil several ways and everything seems to agree within known errors. With the 260, I just use the capacity scale (they call it mmfd !), the frequency dial and assume all is correct. The last tries at this were around 255 nH. I have tried to get about 1/2-inch leads, but that is hard to say down amongst the terminal posts! I did a real careful VNA measurement with very short leads and got 239nH. If one adds on the missing leads you are back up in the 255 or 260 range. This is all fun, but enough is enough!! Oh, also, MicroMetals says they don't guarantee anything but typically the Al value is within 5%.

This is good education, and thanks to all.

I think your wire is #22 also. Mine comes from a Belden 8051 roll and looks like yours in the picture.

Those correction factors for old inductance standards are interesting. It would be fun to know more about them.

73, Bob

Can anyone explain this problem? I'm afraid to proceed on my H4. I FAFO and
bricked my 2.8" H.

RJ K8CYK



Attachments:

- dfu.PNG <>

Thanks a lot for the prompt reply Colin. Shall come back to you in case it
doesn't work out.

73
Jon, VU2JO

On Mon, Feb 3, 2025 at 7:13?AM Colin McDonald via groups.io <colinrmcdonald=
[email protected]> wrote:

The steel table may have an effect. But based on your description, the
antennas are some distance away from that table. The table will likely
not have any impact on the antenna system if it's separated from the
antennas by distance.
To prevent any possible interaction just put the NanoVNA on a non
conductive insulator or surface like a piece of cardboard or plastic or
rubber mat or something.
The radio is insulated from the table by its insulated feet on the case,
so you want to mimic that to some extent if you are using the NanoVna to
tune the antenna system from the radio end of the coax.
In the previous scenario, the OP was working in a mobile situation which
has different variables to a fixed installation at home.

73
Colin, VA6GG
On 2025-02-02 6:33 p.m., Jon via groups.io wrote:

I am waiting for NanoVNA to be delivered this week. My FT-710 radio is

on a

steel table. I am planning to use an SMA to SO239 patch cable of 1m

length

to connect NanoVNA to PL 259 of my antennas.

From this discussion, it seems that I will have to get a wooden table to
keep the NanoVNA?

I have not used NanoVNA yet.

73
Jon, VU2JO

On Mon, Feb 3, 2025 at 6:53?AM Colin McDonald via groups.io

<colinrmcdonald=

[email protected]> wrote:

Put the NanoVNA on a non conductive surface well away from where the
antenna is mounted.

The reason you are getting different readings is because you are
changing the ground plain of the antenna system with your body or metal
surface or non metal surface. I would guess the antenna itself doesn't
have a sufficient ground plain to work off of and so any small changes
to the ground side of the system, IE where the coax is finding ground,
will alter the measurements.

When you say it's changing, how much is the SWR changing? If by a couple
points it's not a big deal. If it's changing from say 1.1 to 1 to 3 to 1
or 4 to 1 by placing the NanoVNA on the hood verses in your hand then
you've got a antenna ground issue.

You can try connecting a counterpoise to the ground side of the antenna
mount if you can't electrically ground it to the vehicle. That would be
a quarter wave of wire or so on the band you are trying to tune.

I would say that the most accurate reading will be the one where the
NanoVNA is on the insulated pelican case.

Is the radio you are using going to be chassis grounded to the vehicle
or floating inside or outside the vehicle during operation? If floating
you want the NanoVna to most accurately represent where the radio will

be.

You can cross check this by tuning with the NanoVna, then checking the
swr with the radio itself. If they are close, within .5 or so, you'll
be good to go on SWR.



73

Colin, VA6GG

On 2025-02-02 6:04 p.m., Coyote via groups.io wrote:

When using my NanoVNA to adjust length of a 20m hamstick, the readings

kept changing depending on what the NanoVNA was sitting on (truck hood,
pelican case, my thigh, or in my hand).

How do I get a reliable reading that I can count on for a properly

adjusted antenna?

Thanks, Coyote

Sent with [Proton Mail]() secure email.

The steel table may have an effect. But based on your description, the antennas are some distance away from that table. The table will likely not have any impact on the antenna system if it's separated from the antennas by distance.
To prevent any possible interaction just put the NanoVNA on a non conductive insulator or surface like a piece of cardboard or plastic or rubber mat or something.
The radio is insulated from the table by its insulated feet on the case, so you want to mimic that to some extent if you are using the NanoVna to tune the antenna system from the radio end of the coax.
In the previous scenario, the OP was working in a mobile situation which has different variables to a fixed installation at home.

73
Colin, VA6GG

I am waiting for NanoVNA to be delivered this week. My FT-710 radio is on a
steel table. I am planning to use an SMA to SO239 patch cable of 1m length
to connect NanoVNA to PL 259 of my antennas.

From this discussion, it seems that I will have to get a wooden table to
keep the NanoVNA?

I have not used NanoVNA yet.

73
Jon, VU2JO

On Mon, Feb 3, 2025 at 6:53?AM Colin McDonald via groups.io <colinrmcdonald=
[email protected]> wrote:

Put the NanoVNA on a non conductive surface well away from where the
antenna is mounted.

The reason you are getting different readings is because you are
changing the ground plain of the antenna system with your body or metal
surface or non metal surface. I would guess the antenna itself doesn't
have a sufficient ground plain to work off of and so any small changes
to the ground side of the system, IE where the coax is finding ground,
will alter the measurements.

When you say it's changing, how much is the SWR changing? If by a couple
points it's not a big deal. If it's changing from say 1.1 to 1 to 3 to 1
or 4 to 1 by placing the NanoVNA on the hood verses in your hand then
you've got a antenna ground issue.

You can try connecting a counterpoise to the ground side of the antenna
mount if you can't electrically ground it to the vehicle. That would be
a quarter wave of wire or so on the band you are trying to tune.

I would say that the most accurate reading will be the one where the
NanoVNA is on the insulated pelican case.

Is the radio you are using going to be chassis grounded to the vehicle
or floating inside or outside the vehicle during operation? If floating
you want the NanoVna to most accurately represent where the radio will be.

You can cross check this by tuning with the NanoVna, then checking the
swr with the radio itself. If they are close, within .5 or so, you'll
be good to go on SWR.



73

Colin, VA6GG

On 2025-02-02 6:04 p.m., Coyote via groups.io wrote:

When using my NanoVNA to adjust length of a 20m hamstick, the readings

kept changing depending on what the NanoVNA was sitting on (truck hood,
pelican case, my thigh, or in my hand).

How do I get a reliable reading that I can count on for a properly

adjusted antenna?

Thanks, Coyote

Sent with [Proton Mail]() secure email.