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I tried the 1500 MHz firmware yesterday and was happy to see that nanoVNAsaver worked with the extended range. Of course, with the very weak signal levels above 900 Mhz the data plots are quite noisy. It would be wonderful if the software could be set to average multiple scans in order to increase the S/N ratio.

erik@, if you want to get deep measurement for S21, I suggest you to disconnect NanoVNA from PC and perform measurement from the battery. The result will be significantly better. I don't know what is the source of noise with connected USB cable, but USB cable connection has significant influence on measurement.

Interesting measurements!
On my own build VNA using exactly the same principles as the NanoVNA (SI5351 and 3*SA612) but using a PC audio input instead of an on board adc and a PC processor for the dsp work instead of the STM I observed the audio output of the transmission SA612 using a realtime 16k points FFT. This makes the noise versus the 5kHz signal very visible, it clearly shows the frequency dependent leakage where the real noise is independent from the LO signal to the SA612.
The pictures I get are similar to what you get but due to the much longer FFT and thus much smaller bucket size the noise is at -110dB and the leakage signal varies between below noise (sub -110dB) below 100MHz till -50dB when around 900MHz. A full thru signal is at -10dB.
Of course a dead bug style bridge will have lower performance compared to the well done PCB layout of the nanoVNA but the leakage amounts are very similar

On Wed, Sep 18, 2019 at 04:39 PM, Kurt Poulsen wrote:

It also depend what the NanoVNA user gets delivered or purchase later on. If
it is one with a disk, then throw it away

I got this open load with NanoVNA, is it bad?

I received my NanoVNA yesterday. I purchased from this ebay seller: Took about 3 weeks to receive the unit. A friend of mine ordered from the same seller and he got his in less than 2 weeks (he only lives about 50 miles from me) so shipping time varies.

Seems to work fine, as many have mentioned, the toggle switch is not the best but it does work OK. Here's a few pictures of the packaging and NanoVNA I received.

Steve_WB8GRS

On Wed, Sep 18, 2019 at 04:34 PM, Andy G0FTD wrote:

If we also consider a previous statement that the input amp is best measure
with the correct load,why was there no difference between
doing a calibration routine with a SHORT or an OPEN with regards to the noise
floor ?

Just performed test. I disconnected PC to avoid interference and performed measurement from the battery.

SHORT load on CH1: noise floor almost -50 dB above 600 MHz

OPEN load on CH1: noise floor -55..-60 dB

No load on CH1: almost the same as OPEN load

50 ohm load on CH1: noise floor below -70 dB up to 900 MHz

So, the SHORT terminator has most worse case
OPEN terminator is better than SHORT, but worse than 50 ohm.

The best result acheived with 50 ohm terminator on CH1.
It is 10 dB betten than OPEN load and 20 dB better than SHORT load.

I've been looking into what could be done to improve the nanovna's
dynamic range at the +900MHz frequencies, and so discussions about noise
and leakage are very relevant.

I've started my analysis as close as possible to the raw data. The nanovna
already gives the option to read the raw sampled data (command "dump 3"),
which replies with the "Reference" & either "Reflection" or "Through" ADC
signals for each of the 48000KHz samples in a 1 millisecond interval (i.e.
48 samples per channel).

I've temporarily tweaked my firmware for the dump command to instead give
96 consecutive "Through" samples. The following results use this modified
firmware.

*Graph 1 - 190MHz Thru with a cable connecting the 2 ports*
The results of the two sequential sets of 48 samples readings are overlaid,
together with a pure 5KHz signal regenerated from the FFT of the combined
96 samples. What I find astonishing is that the results of corresponding
readings 1 millisecond apart are with in 1 or 2 of each other - the codec
is giving very highly repeatable results. "Samp" and "Samp + 1ms"
completely overlay each other in the graph. The pure wave doesn't exactly
match because of the presence of the 3rd harmonic, which is more easily
seen in the PSD display. Ignoring the 2nd and 3rd harmonic peaks, the noise
floor is around -25dB.

*Graph 2 - 190MHz Thru with Port 2 terminated in 50 ohms*
As expected, the "Thru" input signal is virtually non-existent (although it
has a negative DC bias). The PSD shows no signal, apart from the DC
component. The noise floor is around -45dB

*Graph 3 1.3GHz Thru with a cable connecting the 2 ports*
At this frequency there is still a strong thru signal, but it is visibly
noisier. The PSD shows a noise floor at around -6dB, This is much higher
than at 190MHz, presumably because the codec has been programmed to give an
additional 47.5dB gain at this frequency.

*graph 4 1.3GHz Thru with Port 2 terminated in 50 ohms*
The raw data is showing considerable noise (particularly in comparison with
the equivalent measurement at 190MHz in graph 2), again likely because of
the additional gain. The PSD shows no evidence of any peaks at any
frequencies, although there is a gradual downward trend at higher
frequencies. The "pure" wave overlaid in the upper graph is the result of
the FFT & therefore just reflects the noise at 5KHz.

*graph 5 - as for graph 4, but with "offset 7000"*
The noise levels look very similar to graph 4.

I've included all these results to build some confidence in the approach.

I've only sampled a few frequencies, but cannot explain why I get different
results from Erik's. Further study required!

Rgds,
Dave
[image: 190MHz-Thru.png]
[image: 190MHz-Terminated.png]
[image: 1_3GHz-Thru.png]
[image: 1_3GHz-Terminated.png]
[image: 1_3GHz-Terminated_7KHz.png]

On Wed, Sep 18, 2019 at 02:43 PM, <erik@...> wrote:

Should you compare with isolation measured with 50ohm or isolation measured
far from 50ohm????

Don't confuse isolation with noise. Noise doesn't depends on a leak from the second channel. Noise is independent.

If you want to calibrate isolation, you're needs to reduce noise by terminating input with 50 ohm load.

If you want to cancel noise caused by high impedance on the input during measurement... I don't know if it's possible at all. Probably it is impossible :)

On Wed, 18 Sep 2019 at 16:39, John Baines via Groups.Io <jbaines=
[email protected]> wrote:

Checking with my ‘scope, at 7MHz I get 0.2V pk-pk which is -10dBm.

Passed through a 40m lpf it is still 0.2V pk-pk but the scope trace looks
a lot nicer!

Thanks for the help.

The filter will obviously chop off the harmonics,

The high-end VNAs, like the Keysight PNA-X, have the harmonics suppressed
by 60 dB or so. Obviously, they work a very different way to the NanoVNA,
but one could buy 10,000 NanoVNAs for the cost of even a modestly equipped
PNA-X,

73
John
M0JBA

On 18 Sep 2019, at 16:21, John Baines via Groups.Io <jbaines=

[email protected]> wrote:

Thanks Erik,

I’m in the right ballpark.

73
John
M0JBA

On 18 Sep 2019, at 16:19, erik@... wrote:

-10dBm

--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

Rune,
The new "Using the software" section on your GitHub page () is much appreciated! The new pip installation also is nice, although on Windows I prefer to just download your release and run the executable from my "C:\NanoVNA" directory.

Nice to see the output verification with an oscilloscope. I guess in theory, with a completely different firmware it could be re-purposed as an extremely low power WSPR mode transmitter (0.1 mW)....but the catch being that an external clock of some kind would be needed to keep the proper transmission cadence. In the past I've had some success running WSPR mode at 0.1 mW power output. But I digress...what an amazing thing the nanoVNA is.

Checking with my ‘scope, at 7MHz I get 0.2V pk-pk which is -10dBm.

Passed through a 40m lpf it is still 0.2V pk-pk but the scope trace looks a lot nicer!

Thanks for the help.

73
John
M0JBA

John,
From the specs below, expect -13 to -9 dBm. Since you are a ham, the power to voltage calculation should be trivial to you.

Basic Parameters:
- PCB: 54mm x 85.5mm x 11mm (without the size of connectors, switches)
- Measurement Frequency: 50KHz ~ 300MHz (50KHz -900MHz, enable extended firmware)
- RF Output: -13dbm (maximum -9dbm)
- Frequency Accuracy: ???0.5ppm
- Measurement Range: 70dB (50kHz-300MHz), 50dB (300M-600MHz), 40dB (600M-900MHz) enable extended firmware)
- Port SWR: < 1.1
- Display: 2.8 inch TFT (320 x240)
- USB Interface: USB Type-C; Communications Mode: CDC (Serial)
- Power Supply: USB 5V 120mA, built-in 400mAh electricity, maximum charging current 0.8A
- Number of Calibration Points: 101 (Fixed)
- Number of Scanning Points: 101 (Fixed)
- Display Tracking: 4, Marking: 4, Save Setting : 5
- Measuring S parameters, voltage standing wave ratio, phase, delay, Smith chart and the like

Thanks Erik,

I’m in the right ballpark.

73
John
M0JBA

-10dBm

Hello Erik
Super if that is so then no open adaptor should be used for minimum fringe C not encountered for
It seems sensible not to embed anything in the firmware
I suppose more comment on the topic so lets see how it evolves
I will demonstrate the NanoVNA to night in the local Hamclub ?
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af erik@...
Sendt: 18. september 2019 16:35
Til: [email protected]
Emne: Re: [nanovna-users] Filter measurement

On Wed, Sep 18, 2019 at 06:39 AM, Kurt Poulsen wrote:

All in all clarification of the (bloody) 50/60fF would be nice

@Kurt,

Are you referring to the "open_model" data in the firmware?
I could not find any reference to that model in the firmware so I guess it is not used.

Hi all,

What output voltage should I expect from the NanoVNA into a 50 ohm load with CW FREQ selected under the STIMULUS menu.

73
John
M0JBA

On Wed, Sep 18, 2019 at 06:39 AM, Kurt Poulsen wrote:

All in all clarification of the (bloody) 50/60fF would be nice

@Kurt,

Are you referring to the "open_model" data in the firmware?
I could not find any reference to that model in the firmware so I guess it is not used.

I started a separate topic on measuring the CH1 noise or leakage

There are many discussion on this forum around the "noise" on CH1 limiting the dynamic range and weather the noise is influenced by the termination of CH1 or by good or bad SA612
So I decided to measure.
First 3 measurements of the "noise floor" in CH1 with a load on CH0 and an open, load or 50ohm on CH1. These are 1001 point measurements with 1/8 exponential averaging
As you can see the phase at higher frequencies is much too consistent to be caused by noise and this suggest leake of the test signal from the SI5351 to be the problem.

So using the "sample ampl" command I disabled the reference signal impact and you can see the switching of the ADC sensitivity when measuring a thru signal
The same measurement without input signal on CH1 does show approx the same as the first three measurements.
The I disabled the impact of the CH0 output signal generation by using a little known command that you can use to set the offset between the CH0 output and the SA612 LO signal to something different from the 5000Hz as hard encoded in the dsp.c (co)sine table and I set "offset 7000" to move CH0 signal outside the dsp filter window and this delivers a somewhat different picture
Apart from the step up at 300MHz where the switch to overtone is made and you loose 17dB sensitivity and this is compensated in the amplification setting of the adc, the noise floor shows a very different pattern suggesting the biggest impact on the dynamic range of the NanoVNA is leakage and NOT noise on CH1.