¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. Nanovna-Users
  2. Messages
Expanded Topics Messages
Date
Re: Tone control capability

 

On Mon, Mar 1, 2021 at 10:12 AM, John Brent - VA7WPN wrote:

Can I change the tone? or does anyone even know what the tone generated is? IT
would help a LOT with using it as a tone generator.
When you put the NanoVNA in CW mode it generates a square wave at that frequency. So you have a fundamental and harmonics of that frequency.

I don't know what you mean by using the NanoVNA as a "tone generator". If you mean generating an AM signal like 455 kHz. with a modulation tone of say 1000 Hz. you need a different device. I suggest the TinySa which has the same 2.8" case style but can operate as a spectrum analyzer or signal generator with CW, AM and FM capability.

Roger
Re: 450-OHM WINDOW LINE........OR IS IT?

 

A quick look at the line would be put a 450 ohm resistor at the far end and
check at an odd quarter wave for the z on the nano.

A given length of line has an odd number of quarter waves at numerous
frequencies. The wave length,at velocity factor for the line, should show,
1 to 1 swr, a high return loss, or if TDR is on the nano variant should
show the z.

The velocity factor usually supplied by the manufacturer. In this case the
velocity factor is a result of the air window and the polyethylene spacer.
In this case I'd determine an adjusted quarter wave at a short length of
line shorted at one end, near the higher frequency of the instrument, and
verify the resonant frequency. That would verify the suppliers velocity
factor.

For hf through low uhf, six 2700 ohm carbon 1/4 w resistors in parallel
with short leads should be a easy load with whatever connector.

On Mon, Mar 1, 2021, 1:01 PM Donald S Brant Jr <dsbrantjr@...> wrote:

All: Unless one is building a tuned circuit like a tuning stub or a series
matching section, and in the typical use case of an untuned feeder for a
non-resonant dipole, the exact impedance and velocity factor are mostly
irrelevant. 73, Don N2VGU
Re: #measurement Problems for reading SWR, Graph always mooves ! #measurement

 

Hi Pierre,

What do you advise to me in order to has the most precise result.
Operating a handheld transceiver has many imperfections, not the least of which is the operator himself who is a pretty good conductor (70% salty water in a human body) and will absorb or reflect some of the RF.

For an end-fed vertical antenna (which is the typical antenna design on a handheld radio) the optimal ground plane would have a 1/4" wavelength diameter. That sounds at first glance easy to achieve but there is a serious problem hidden in that statement. The wavelength is inversely proportional to the frequency and you probably want to operate that handheld device on one (or more) amateur radio band and not just on a single fixed frequency. To optimize for single frequency operation you take 1/4 of the wavelength and use a circular metal disk with that length as radius. That will result in a high-Q antenna + groundplane system that has a low SWR only in a very narrow frequency range.
A compromise is to use a square groundplane for testing which means that the radius of the groundplane varies in every direction and the resulting system of antenna + groundplane has a low-Q (wide bandwidth). This should result in low SWR values over an entire band assuming the square groundplane is sized such that length of each side is less than 1/2 wavelength of the highest frequency in the band and the length of the diagonal is more than 1/2 wavelength of the lowest frequency in the band. The 1/2 wavelength corresponds to the desired 1/4 wavelength radius when the antenna is mounted in the center of the square groundplane.

I explain : i would like to try to have the result closest to reality.
Because of the many variables that you will encounter when operating in real life, it sadly isn't realistic to simulate it. The best you can do is ensure a consistent environment in which you are testing the antennas to make sure you test each antenna under the exact same conditions. This does mean to keep the human being as far away as reasonably possible from the device under test.

Maynard's suggestion of using a 1/4 wavelength wire to improve the antenna performance of a handheld radio works well and does result in a measurable gain (about 3dB). Those wires are often referred to as Tiger Tails and you can find more information by searching for Tiger Tail Antenna. It is a very inexpensive way to improve the performance of a handheld radio.

73.
Thomas
Re: Sun Shield?

 

On 3/1/21 9:38 AM, Larry Rothman wrote:
How about using a piece of privacy glass/plastic - the type that allows you to see the display straight-on?
I think it would block out light from the side.? Of course, it would be useless if the sun was behind you....
There's two kinds of these - one is little tiny louvers (Light Control Film), the other is a circular polarizer (the reflection flips the polarization, so it gets blocked on the way back out). I'm not sure how the CP ones would work on a LCD display (since the light from the display is polarized).


(I'm looking into this for another application, so I've just started researching it)
Re: #measurement Problems for reading SWR, Graph always mooves ! #measurement

 

There is a Japanese Web magazine, published in English, that had a 3 part series on testing "rubber duck" and other antennas on portable radios (HT's). They did SWR and field strength tests (Tx and Rx) using a modified Icom handheld radio as a test jig. I think members of this group will find the results interesting.....

Part1
Part2
Part3

Roger
Re: Tone control capability

 

Can I change the tone? or does anyone even know what the tone generated is? IT would help a LOT with using it as a tone generator.

thanks,

John
Re: 450-OHM WINDOW LINE........OR IS IT?

 

All: Unless one is building a tuned circuit like a tuning stub or a series
matching section, and in the typical use case of an untuned feeder for a
non-resonant dipole, the exact impedance and velocity factor are mostly
irrelevant. 73, Don N2VGU
Re: #measurement Problems for reading SWR, Graph always mooves ! #measurement

 

Pierre,

the SWR fluctuations you see on the NanoVNA simply show you how a handheld antenna performs in normal use! It doesn't offer fixed, good SRW to the radio. Instead it varies according to what's around, how you hold the radio, etc. The SWR you see on the NanoVNA is not the same the radio will see, because the NanoVNA is different from the radio. But there will be wild fluctuations in both cases.

To find the best antenna for your radio, don't watch the SWR. Instead experiment which of them makes the radio transmit and receive the best.

Go to an open place, and enlist the help of some fellow ham at a few km distance who can transmit at variable power, and who has a radio with a real S-meter. Test each of your antennas while communicating wth that ham. In each case, ask him to reduce the power until you hear him with significant noise, and then swap antennas and move the radio around and find out which antenna receives best, in which position. Also set your power so that his S-meter points somewhere in the middle of its range, and ask him to report the signal level for each of your antennas, while you move the radio in several ways. These tests should bring out which of the antennas provides the best performance, and whether any is more position-critical than any other.

Be sure to make these tests on at least two or three frequencies spread over the band, because small antennas are often quite frequency-selective. Testing on just one frequency might give a wrong idea.

SWR is very far from telling everything about an antenna. A 50? dummy load gives you perfect SWR, but no radiation! A very poor antenna might be so lossy that it behaves largely like a dummy load. And most handheld radios are rather uncritical regarding SWR. They need to be, since SWR varies so much depending on what's around the antenna.

When I take my handheld radio into the field, I use a telescopic whip antenna, which I can extend just the right amount for the frequency in use. I marked these lengths for quick use. It allows me using the same antenna both on the ham band and on the marine band, with good performance. And the performance is significantly better than that of any rubber duckie.
Re: Sun Shield?

 

Hmmm...I¡¯ve had to use those at work where my cubicle let sunlight impinge on my monitor. They work pretty well particularly if the sun is behind one and shining directly onto the screen.

I wonder if soneone makes ¡°little¡± ones?

DaveD

On Mar 1, 2021, at 12:38, Larry Rothman <nlroth@...> wrote:

How about using a piece of privacy glass/plastic - the type that allows you to see the display straight-on?
I think it would block out light from the side. Of course, it would be useless if the sun was behind you....

On Monday, March 1, 2021, 9:54:51 a.m. EST, Kent Borg <kentborg-nanovna@...> wrote:

The NanoVNA is great, among various reasons, because it is so small and
light (and inexpensive if damaged) and great for use in the field!
Otherwise known as "outside", where there is often bright light, which
can make it hard to see the screen.

Any suggestions for making a sun shield? This weekend I grabbed a handy
piece of light cardboard and cut into pieces that I then taped together
to make a rectangular tube. It works sort of¡­I need a darker cardboard,
and it sometimes triggers the touch screen.

Anyone with experience or advice?


Thanks,

-kb
Re: Sun Shield?

 

How about using a piece of privacy glass/plastic - the type that allows you to see the display straight-on?
I think it would block out light from the side.? Of course, it would be useless if the sun was behind you....

On Monday, March 1, 2021, 9:54:51 a.m. EST, Kent Borg <kentborg-nanovna@...> wrote:

The NanoVNA is great, among various reasons, because it is so small and
light (and inexpensive if damaged) and great for use in the field!
Otherwise known as "outside", where there is often bright light, which
can make it hard to see the screen.

Any suggestions for making a sun shield? This weekend I grabbed a handy
piece of light cardboard and cut into pieces that I then taped together
to make a rectangular tube. It works sort of¡­I need a darker cardboard,
and it sometimes triggers the touch screen.

Anyone with experience or advice?


Thanks,

-kb
Re: 450-OHM WINDOW LINE........OR IS IT?

 

Thank you so much. Some really good measurements. Excellent site.

Dave - W?LEV

On Mon, Mar 1, 2021 at 2:49 PM joe gay via groups.io <hamop=
[email protected]> wrote:

Hi Dave,

I measured wireman #553 at 390 +/- 5 ohms with AA-600. John K5NL has data
he has measured in the Simsmith feedline data table for several versions of
LL - see his site for lots of info on LL using Nano's & others -

73 Joe W4RYW





--
*Dave - W?LEV*
*Just Let Darwin Work*
Re: Sun Shield?

 

That¡¯s a good idea. If one could find one of those Tektronix ¡®scope hoods that had the right dimensions so that the nanoVNA could be ¡°tucked¡± into the hood such that it would fit tightly towards the narrow end of the hood might work quite nicely.

DaveD

On Mar 1, 2021, at 11:59, Dave Fugleberg <dave.w0zf@...> wrote:

I¡¯m envisioning the green plastic/rubber hoods we had on the old Tektronix
oscilloscopes... the ones that were shaped to fit tightly against your face
around your eyes...
Nowadays the test equipment is smaller than the scope hood !

On Mon, Mar 1, 2021 at 8:54 AM Kent Borg <kentborg-nanovna@...> wrote:

The NanoVNA is great, among various reasons, because it is so small and
light (and inexpensive if damaged) and great for use in the field!
Otherwise known as "outside", where there is often bright light, which
can make it hard to see the screen.

Any suggestions for making a sun shield? This weekend I grabbed a handy
piece of light cardboard and cut into pieces that I then taped together
to make a rectangular tube. It works sort of¡­I need a darker cardboard,
and it sometimes triggers the touch screen.

Anyone with experience or advice?


Thanks,

-kb
Re: Sun Shield?

 

I am thinking that, short of using a 3D printer to create a hood, a small box maybe twice the length and breadth of the nanoVNA that opens by the top lifting off, hinged at the back and with flaps that tuck into the sides of the box when closed would work if spray painted flat black. I think I might havevone of those lying around.

DaveD

On Mar 1, 2021, at 11:59, Dave Fugleberg <dave.w0zf@...> wrote:

I¡¯m envisioning the green plastic/rubber hoods we had on the old Tektronix
oscilloscopes... the ones that were shaped to fit tightly against your face
around your eyes...
Nowadays the test equipment is smaller than the scope hood !

On Mon, Mar 1, 2021 at 8:54 AM Kent Borg <kentborg-nanovna@...> wrote:

The NanoVNA is great, among various reasons, because it is so small and
light (and inexpensive if damaged) and great for use in the field!
Otherwise known as "outside", where there is often bright light, which
can make it hard to see the screen.

Any suggestions for making a sun shield? This weekend I grabbed a handy
piece of light cardboard and cut into pieces that I then taped together
to make a rectangular tube. It works sort of¡­I need a darker cardboard,
and it sometimes triggers the touch screen.

Anyone with experience or advice?


Thanks,

-kb
Re: Sun Shield?

 

I¡¯m envisioning the green plastic/rubber hoods we had on the old Tektronix
oscilloscopes... the ones that were shaped to fit tightly against your face
around your eyes...
Nowadays the test equipment is smaller than the scope hood !

On Mon, Mar 1, 2021 at 8:54 AM Kent Borg <kentborg-nanovna@...> wrote:

The NanoVNA is great, among various reasons, because it is so small and
light (and inexpensive if damaged) and great for use in the field!
Otherwise known as "outside", where there is often bright light, which
can make it hard to see the screen.

Any suggestions for making a sun shield? This weekend I grabbed a handy
piece of light cardboard and cut into pieces that I then taped together
to make a rectangular tube. It works sort of¡­I need a darker cardboard,
and it sometimes triggers the touch screen.

Anyone with experience or advice?


Thanks,

-kb
Re: #measurement Problems for reading SWR, Graph always mooves ! #measurement

[email protected]
 

What a beautiful suprise to see all theses answers ! Thanks to all ! Many Many Thanks to all !
Now i understand, i begin to understand.
Why i try to do this : in order to try to get the best antenna for the handheld, in order to have the minimum of reflected power, and test all my handys antennas
I love handheld radio and i've done incredibles contact on top point (mountains)

What do you advise to me in order to has the most precise result. I explain : i would like to try to have the result closest to reality.
I think to try to mesure this evening the swr with the VNA vertical, the antenna directly mount on the VNA and the VNA in my hand, close to my head : like in the reality when i transmit.

Many thanks to all, it's incredible : One question ask this morning : 5 answers coming from all around the world this evening....
Long life to radio
Long life to hams
Long life to all

73 QRO

Pierre.
Re: Sun Shield?

 

On 3/1/21 7:45 AM, Karel Gol wrote:
Seems to me there is work to be done for those with a 3D printer.
I was thinking something collapsible so it would be very small when not in use, but maybe that could be done by some clever 3D printer wrangler. (I've never played with any 3D printing.)


-kb
Re: Sun Shield?

 

Simples! Blackboard paint !
Re: #measurement Problems for reading SWR, Graph always mooves ! #measurement

 

Very good advice.?? Another possibility would be to cut a quarter wave wire, attach it to the shell of the antenna's connector, and let it hang down vertically while the antenna is oriented vertically upward.? How effective this is would depend on the electrical (not necessarily the same as physical) length of the wire and how it is affected by objects around it, but it would be easy to try.

Note that an extensive ground plane ought to exhibit a very low impedance while an ideal quarter wave wire would be somewhere around 35 or 40 ohms, but we get the same sort of mismatch when we feed an ideal halfwave dipole with 50 ohm coax.

73,

Maynard
W6PAP

On 3/1/21 5:27 AM, Ken Sejkora wrote:
Hello Pierre,

Great observations and questions. I am not an expert at this, but I do recall a response to a similar question a few weeks about using the nanoVNA for antenna measurements. I recall that the recommendation for measuring the characteristics (including SWR) of a vertical antenna is to have the antenna situated upon a good metal ground plane that is at least one-half (perhaps even more) of a wavelength in diameter around the base of the antenna, and that the coaxial cable length between the antenna and nanVNA should be at least two wavelengths. Thus, if you are measuring response of a 2-meter antenna, the antenna should ideally be placed on a metal ground plane that is two meters in diameter (1-meters in each direction around the base), and the coax between the antenna and VNA should be at least four meters long. Following these guidelines should help minimize the inconsistencies you described in your post.

Another thing to consider is that when an antenna is placed on a portable/hand-held radio, you most likely will not have the same conditions as compared to those present when the antenna was tested as described above. In the case of hand-held radios, the human body makes up a portion of the ground ¡°plane¡± for the radio, and the SWR in actual practice can be highly dependent on orientation of the radio (horizontal vs. vertical vs. tilted), proximity to the radio to the face, use of an external microphone, etc. Therefore, measurements made with a nanoVNA under ideal conditions may or may not represent what the radio is actually seeing when in use.

Good luck. 73

Ken - WB?OCV


From: pjbellin@...
Sent: Monday, March 1, 2021 07:59 AM
To: [email protected]
Subject: [nanovna-users] #measurement Problems for reading SWR, Graph always mooves !

Hi all,

First time I post a question because i've an issue with my nanoVNA. Thanks to all for intersesting to it and many thanks for all your post ! I've learn so much things with all of you !
So when i try to measure the SWR with my NanoVNA, calibration is OK, but when I connect directly a small VHF / UHF Handheld in order to see how the swr is the lowest, the graphs always mooves. When i put my hands near the VNA i can read SWR is 1,5 at 140 MhZ, when i pull back my hands, i can read, 2,5 at 145 Mhz.... When a put the VNA verticaly i can read another measure, horizoly, another measure and it depend if i'm on a wooden table or a glass table.... So... it's really difficult for me to get a good and constant measure in order to see how the antenna work exactly !
Have you any idea ? I'm sure the nanovna is a good instrument but i do something wrong but i don't now what !

Thank's a lot for reading me and perhaps help !

73'S QRO

F4COH

Pierre
Re: Sun Shield?

 

Seems to me there is work to be done for those with a 3D printer.

Op ma 1 mrt. 2021 15:54 schreef Kent Borg <kentborg-nanovna@...>:

The NanoVNA is great, among various reasons, because it is so small and
light (and inexpensive if damaged) and great for use in the field!
Otherwise known as "outside", where there is often bright light, which
can make it hard to see the screen.

Any suggestions for making a sun shield? This weekend I grabbed a handy
piece of light cardboard and cut into pieces that I then taped together
to make a rectangular tube. It works sort of¡­I need a darker cardboard,
and it sometimes triggers the touch screen.

Anyone with experience or advice?


Thanks,

-kb
Re: #measurement Problems for reading SWR, Graph always mooves ! #measurement

 

Small handheld antennas are affected by close proximity to conductive and dielectric sources such as your body or hand.

This is also true when you attach th antenna to your handheld radio. The SWR will vary but you don't have to worry about transmission line loss since the antenna is directly connected to the radio.

You can measure the swr in a lab environment by mounting the antenna on a ground plane and attaching the vna to the connector underneath the ground plane. Keep in mind this down not replicate the real world operating situation.

Mike N2MS

On 03/01/2021 3:13 AM pjbellin@... wrote:


Hi all,

First time I post a question because i've an issue with my nanoVNA. Thanks to all for intersesting to it and many thanks for all your post ! I've learn so much things with all of you !
So when i try to measure the SWR with my NanoVNA, calibration is OK, but when I connect directly a small VHF / UHF Handheld in order to see how the swr is the lowest, the graphs always mooves. When i put my hands near the VNA i can read SWR is 1,5 at 140 MhZ, when i pull back my hands, i can read, 2,5 at 145 Mhz.... When a put the VNA verticaly i can read another measure, horizoly, another measure and it depend if i'm on a wooden table or a glass table.... So... it's really difficult for me to get a good and constant measure in order to see how the antenna work exactly !
Have you any idea ? I'm sure the nanovna is a good instrument but i do something wrong but i don't now what !

Thank's a lot for reading me and perhaps help !

73'S QRO

F4COH

Pierre
18761 - 18780 of 39481