开云体育

Thanks Larry

I will pull it apart and have a look. regardless if the replacement switch is sent I will replace the switch with SMT switches as in your mod.

Andy "thats buying from China" As the saying goes buy the first model for your enemy, the second for your friend and the 3rd for yourself. But you dont even have these options from China since these units I believe are bulk manufactured and are mostly distrubuted by anyone and anything. I dont know why Ebay allows these people to tell lies when stating they in your home country when they clearly shipping from China.

Thanks all

Rune,
I just checked out your Latest commit, 0.0.10a and loving the fact that on my 1366x768 display I can see the whole screen without needing scrollbars. All the charts size very nicely at font size 7, even with show data turned. I think the pop up windows for Files, Calibration, Display setup, and About are nicely thought out. I wish at some point in the future you could add a setting under "Display setup" that would allow the user to add a centered caption at the top of the graphs for documentation purposes. Keep up the great work!

On Sat, Sep 21, 2019 at 09:46 PM, Ken Buscho wrote:

Any special calibration considerations to minimize other signals coming in? If
I don't have a test device hooked up, whatever Ref sees is outside world, can
it be calibrated or filtered out someway?

Use the zero span option.
That way the display only reports your "channel"
I think that would work.

73 de Andy

Rune,
Thanks for all of your work on this. I know from personal experience the effort and dedication that something like this requires. When I bought my NanoVNA, I had no idea that I was "surfing" the early adopters wave. I am a recently retired electrical engineer and the intellectual stimulation has been welcome, especially when dealing with a well designed software application like yours. The "bleeding edge" apps are not always this well thought out. It is quickly getting to the point where the first digit of the version number can be an integer greater than zero.

I do have a suggestion....

I have a 4k UHD monitor and one of the issues that I have is that most apps use fonts that have a single pixel stroke width which can be quite hard to read. I know that you have a font size option, which helps, however, I found that simply going to the Bold version of a font can widen the font stroke width and make big improvements in readability on a UHD monitor without changing the font size. Perhaps, you could put this option on your to do list for a future version.

73
Logan, KE7AZ

Warren,
Thanks for the kudos, I always try to figure out a way to find new uses for existing things, Sadly, these ideas usually pop in when my mind is idling right before bedtime, and then I'm up for another hour or two testing it out. Sleep is overrated, that's why they invented coffee

Thanks for all the comments and suggestions. For current batch of the tests, my reference antenna has been a normal car 2m/440 mag mount car antenna on top of a metal file cabinet with about 2m of coax, so we are out of nearfield for both of the ranges I care about for now. Any special calibration considerations to minimize other signals coming in? If I don't have a test device hooked up, whatever Ref sees is outside world, can it be calibrated or filtered out someway? Seems there should at least be a software way to acknowledge that value as a floor/base value and kick it to the curb.

73,
Ken

Hi Rune,

Attached is the calibration File.

Thanks Again.

Jim K. K8SLC

Hi all,
just for your records, attached is a VNWA plot of the NanoVNA RX input impedance.

73, Norbert, DG1KPN

if nothing there in your firmware (no info in boot logo or no version menu) try simply "version" or "info" via serial terminal. But honstly, who cares? just download the latest version and enjoy latest features, no need to care about someone programmed once in your nanovna

Hello,

Allow us, please, to we report that in order to be adequately
prepared to estimate the uncertainty in NanoVNA
measurements using complex differential error regions
and real differential error intervals, that is to attempt for the
first time scientific measurements using NanoVNA with the
only available method we know and with the currently
available software tools, we need, in addition to a correctly
working version of the interpreted foss [maxima-cas] to run
the /f/l/o/s/s/ [derdei.mc], a foss compiled language to we
be able to independently cross-verify the computation
results, and as a such one we intend to use for now the
[openwatcom][fortran].

Also, allow us, please, to we report that in a correctly working
operating system [wxp64p&sp2] we know that the following
versions of these two languages are respectively the last
ones which are correctly working under the 32-bit emulation
mode of an AMD x86-64 cpu:

[maxima-cas][5.38.1]:


[openwatcom-fortran][1.9]:
ftp://ftp.openwatcom.org/install/open-watcom-f77-win32-1.9.exe

Sincerely,

yin&pez@arg

2

The FFT assumes that you have a perfect fit of the (co)sinus in the sample range.
At higher frequencies the 5kHz start to deviate so the samples may no longer fit perfectly in the fft and you may get spectral bleeding.
This bleeding will vary with the error of the 5kHz signal
Can you apply a window to the input of the fft and see if that clears out the spectral bleeding?

Ok, looked at the source code and it seems that 2mA is used in fundamental mode and 8mA for harmonic (above 300MHz). This should make a big difference in Si5351 output impedance, isn't it? The question is, it's the bridge excitation source and detector impedances matched at least while in fundamental mode?

Carlos

What is the Si5351 drive strength being set? 2mA? Is it being increased at >300MHz harmonic bands? It's output impedance may not be 50ohm, and it could be even changing depending on the band. Also older Si5351 revisions specified 85 instead of 50ohm output impedance at 8mA. AFAIK, this excitation source impedance and detector impedance should be matched in order for the bridge to work correctly.

Receiver port is also badly matched above 600MHz. I don't understand the atenuator arrangement, although looks partly copied from DG8SAQ VNWA. A friend's VNWA3 shows a much better port match than nanoVNA.

BTW, one month ago i characterised the SA612 input impedance up to 900MHz and it's much higher than specified 1.5K||3pF. The circuit model i extracted from each IN_x to ground is:
o----[3.5nH]---------------[2.5K]---------->
L-----[1.2pF]----[50R]--->

Carlos

I've been continuing my investigation into improving the nanovna's
dynamic range above 900MHz, and have some further results to share.

Theory tells us that dynamic range can be improved by increasing the number
of readings that are correlated in the DSP - every doubling should increase
the dynamic range by 3 dB.

At the moment the firmware processes just one "frame" of 48 readings, 1
millisecond's worth at 48KHz sampling rate. It's astonishing that the
nanovna is so accurate with so few samples at frequencies below 300MHz.
It's almost trivial to modify the code to perform the correlation over a
number of frames; indeed there are vestiges of code there to do just that.
However, when I implemented the changes to correlate over 8 frames, which
should have improved the dynamic range by around 9dB, it actually got
worse! This surprise has led me to look further at the raw data.

My earlier investigation and work-around to the usb command instabilities
has been serendipitous in that I discovered a large chunk of memory that's
used only for screen-display. My stability workaround disables updates to
the screen, allowing this memory to be re-used. I've therefore created a
firmware version that dumps 10 consecutive frames worth of raw data via the
usb port. I run a FFT on this data. The FFT's 5KHz bucket tallies exactly
with what the firmware dsp calculates (apart from scaling).

What follows are some results.

*Attachment 1 - 190MHz with a cable connecting the 2 ports (48 samples
only)*
This is a "benchmark" reading showing normal operation. The upper graph is
of the raw data returned from the nanovna. The lower graph charts the
results of an FFT on the raw data what is plotted is logFFT =
10*log10(abs(FFT)). The Peak above noise floor calculation is max(logFFT) -
mean(logFFT). This calculation is a bit crude because the average also
includes the peak value, so understates the dynamic range.

*Attachment 2 - 190MHz with a cable connecting the 2 ports (48*10
samples)*
The same charts are displayed as in attachment 1, but with all 10 frames or
480 samples.
Note that the peak for both ref and sample is improved by ~9dB, and that
the noise floor remains at a similar level. This results tallies with
theory.

*Attachment 3, 4 - 1.23GHz with a cable connecting the 2 ports 48 samples,
and 480 samples*
These attachments are same as the first two, except at 1.23GHz. The
increased number of samples shows approx 8dB improvement (from 23dB to 30
dB for ref, and from 21dB to 30 dB for sample). Again this is about what is
expected. However the FFT shows some strong peaks at 1KHz rate (the frame
rate), hinting at one possible source of noise.

So far this is as expected. The problem arises a different frequency is
chosen:

*Attachment 5, 6 - 1.29GHz with a cable connecting the 2 ports 48
samples, and 480 samples*
The peak improvement here is negligible at only 3 dB and 0 dB. Note also
that the peaks are now very spread.

*Attachment 7, 8 - 1.29GHz, 6KHz offset with a cable connecting the 2
ports 48 samples, and 480 samples*
The same as the previous result, except with a 6KHz offset. The underlying
cause of the frequency spread appears to be unrelated to the offset value.

Different frequencies give a range of results, with the two at 1.23GHz and
1.29GHz appearing to be at two extremes.

I have no explanation for what causes these results, only guesses. However,
if we want to improve the dynamic range we need to get to the root cause -
no amount of averaging is going to help.

Any thoughts appreciated.

Rgds,
Dave




[image: 1_190MHz_48_samples.png]

[image: 2_190MHz_480_samples.png]
[image: 3_1.23GHz_48_samples.png]
[image: 4_1.23GHz_480_samples.png]
[image: 5_1.29GHz_48_samples.png]
[image: 6_1.29GHz_480_samples.png]
[image: 7_1.29GHz_48_samples6KHz.png]
[image: 8_1.29GHz_480_samples6KHz.png]

On Sat, Sep 21, 2019 at 07:27 PM, <bryburns@...> wrote:

I think that calibration after installation of such a device should readily
compensate for an extra 0.06 pF of stray capacitance in the circuit. I suggest
that manufacturing tolerances alone will have more variation in input
capacitance than this. Am I wrong about in these assumptions?

yes, you're wrong with these assumptions. First, voltage suppressor diodes have about 10-15 pF. It works like low-pass filter with cut-off at about 400 MHz. VNA can compensate it by calibration, but dynamic range will be lost. Because noise floor is here and if you attenuate signal, you lose dynamic range.

The second issue with voltage suppressor diode is that they make non-linear distortions. You cannot calibrate VNA for non-linear distortions. It just ruins RF signal with no way to restore it.

Here are a few comments about diodes and ESD issues for your consideration.

I agree that limiter diodes will cause issues; however, the devices I suggested above are not typical limiter diodes. Limiter diodes do function as a mixing device, even at amplitudes below their limiting voltage. So, I would not recommend them either.

The device I referenced above (PGB010603) contains back-to-back zener diodes designed for ESD protection. They have a threshold voltage of about 24 volts not 0.7 volts like a typical diode. My understanding is that the diode only appears as a small capacitance at low-amplitude signals (< -9 dBm or about a little more than 0.1 volts pk in 50 ohms) which are normally present at the front-end of the nanovna. The leakage current , even at a 6 volts, is < 1 nanoAmp. These ESD diodes will not protect against high RF levels on the device; however, during an ESD event they will limit the voltage (and energy) during the ESD event. A plot of the resulting voltage spike during an ESD event is shown on page 2 of the data sheet I attached above. What really matters is that the total energy which gets past the diode is quite low by comparison to the full ESD event. This is what helps prevent damage to sensitive RF components.

Yes, it would be better to not have the ESD event in the first place by taking appropriate cautions. However, in some dry parts of the world where relative humidity can be less than 10%, ESD events are more common and difficult to prevent in all situations.

Here are a few suggestions from my experience. A good practice in a lab or garage environment is to use an ESD wrist strap and resistive mat to protect against the human introduced ESD event. Perhaps this approach has the least impact to RF measurements in the lab or office environment. However, when climbing around on a tower or trying to make outdoor measurements such practices are more difficult. I suggest making it a habit to put a temporary short on coaxes prior to connecting them to the nanovna to avoid charge buildup on any antennas being measured.

I hope these suggestions will prevent someone going through my ESD experience of blowing up a switch in a VNA.

I think that calibration after installation of such a device should readily compensate for an extra 0.06 pF of stray capacitance in the circuit. I suggest that manufacturing tolerances alone will have more variation in input capacitance than this. Am I wrong about in these assumptions?

--
Bryan, WA5VAH

On Sat, Sep 21, 2019 at 06:55 PM, Dr. David Kirkby from Kirkby Microwave Ltd wrote:

I don’t think it will be possible to *objectively* measure HT antennas. So
much depends on how they are held, the size of the person etc.

It is possible. For example 145 MHz antenna has near field range about 1 meter. So, you can place two antennas for example 4 meters away from each other. Signal loss at 4 meters for 145 MHz will be 28 dB. It is well fit into NanoVNA dynamic range :)

For 433 MHz near field region is just 0.35 meter. So, you can place two 433 MHz antennas 1-2 meters away from each other. Signal loss at 2 meters 433 MHz will be 31 dB. It is also well fit into NanoVNA dynamic range.

The same for 27 MHz antenna. 27 MHz antenna has near field range about 5.6 meters. Signal loss will be about 21 dB for 10 meters and 27 dB for 20 meters. So, you can place two antennas 10-20 meters away from each other and use NanoVNA to compare antenna efficiency.

On Fri, 20 Sep 2019 at 18:33, Ken Buscho <kb6kob@...> wrote:

Hi, Folks,
My whole NanoVNA process started because I went out on eBay looking for an
antenna analyzer for ham VHF/UHF use and got my white model because it
intrigued me at what was being done at that price point. No prior personal
experience with VNAs, although I've been aware of them for years. Big
learning curve to get started, but it did almost everything I was looking
for once I could see SWR and a Smith Chart. It's been well worth the $60,
and I'm getting a VNA education to boot reading here.

I say almost because I would like to be able to get some values to at
least compare HT Antenna A to HT Antenna B for gain. To get started, I put
a test antenna on CH0 and a reference antenna on CH1. I can tell the CH1
antenna is "seeing" the CH0 antenna because logmag dB values change
with/without something on CH0, and I can also see that dB values go up/down
as antenna distances change.

What I'm looking for is suggestions on how to do this the right way, or at
least a better way. Now I'm using a scanner-type antenna for reference,
it's about 30cm/12" away from the test antenna.

I don’t think it will be possible to *objectively* measure HT antennas. So
much depends on how they are held, the size of the person etc.

If I were you, I would get some experience measuring antennas where the
gain can be predicted in advance - half wave dipoles etc. There are at
least 3 ways to determine the gain of an unknown antenna

1) Measure loss between two antennas, one of which is known - eg half wave
dipole

2) Measure loss between two identical antennas.

3) Three antennas, none of which are known. You measure A to B, A to C and
B to C. Then you have 3 measurements and 3 unknowns, so can solve the 3
simultaneous equations to determine the gain of each antenna.

Appreciate the input...

Ken Buscho
KB6KOB

Good luck

Dave.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

I assume this is the firmware changing what is output depending on what
mode is selected on the device. If there's a command to reset it, I guess I
could do that, but it didn't exist when I made the software initially :-)

--
Rune / 5Q5R

Er...one moment, please.

The gentleman who wrote that, and, might I say, the engineer or

academic who might favor that approach, does not have dirt under the
finger nails. The hard fact is that in Big City; saturated as it is by
truly stupendous microvolt per meter levels from a.m. broadcasting,
television broadcasting and no end of communication services clamoring
to get in; a non linear stage like that ahead of the receiver is a
mixer. That the diodes are not conducting does not mean that there is no
mixing going on.

Yes, those without practical experience of the elevated noise floor,

up and down the h.f. bands, that such an arrangement produces will be a
hard sell but the mixing effect is no less real.

John

at radio station VE7AOV? ?

On 2019-09-20 4:35 a.m., erik@... wrote:

slide 11

Simple and cheap: Back to back diodes
? Protection not dependent upon configuration
? Diode type is not critical (except, don’t use PIN diodes)
? Limited to low input power levels => receive only applications
? +30 dBm = 1 watt max (when using ? watt diodes)
? If either diode fails open => receiver front end not protected
? Spurious signals in receiver can be a problem
? Some mfgs offer choices on spurious levels (DX Engineering RG-5000 series)

--