¿ªÔÆÌåÓý

Don't forget to upgrade NanoVNASaver - that phase error was fixed in 0.0.9,
and 0.0.10 will be out "soon" :-)

--
Rune / 5Q5R

Glad to help Joe.
I recognise your callsign from the QRSS Grabber that I have monitored in the past.
I think it got zapped by a lightning strike ?

73 de Andy

Further thoughts.

Best evidence presented so far shows two plots, one with a noise floor of abut -80db,
the other with a load connected to Ch1 shows a -85db noise floor.

But that noise floor wobbles about by plus/minus 5db
Average of that is..zero.

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 ?

These are the two extremes that an input amp could have on Ch1.

And yet my own test (which I am still puzzled by) is WITH a 50R load.

Maybe the amp IS working properly when it sees it's designed load, because it's designed to amplify when terminated
correctly. As an amplifier, it's function is to amplify when terminated with the correct load. Well if that's the case then
this is the time when it's able to amplify any noise present most efficiently ;-)

That would correlate nicely with my increased noise observations, and the degradation of the noise floor.

Not arguing, just exploring and learning.

73 de Andy

Hi qrp.ddc and Rune
I think it is time to get this discussion straightened out..
Doing a simulation of an SMA female adaptor with e.g. the program FEMM and by basing the simulation on mechanical dimension/drawings from a well know manufacturer e.g. Rosenberger, the Fringe C of the female adaptor is 32.24fF equal to an one way offset of 1.612ps. If the designer of the NanoVNA is using the fringe C of 50fF as a delay=2x the Offset then it correspond to a Fringe C of 25fF = an offset of 1.25ps and not that bad
I have just measured these parameter using my HP85033C 3.5mm calibration kit and a good VNA and the SMA female had an one way offset of 1.03ps=20.6fF. Calibration is of course pending the state of the calibration kit which has served my for some years and provide superb calibration when doing T-Check and sweep of my APC7 airlines
Measuring the Open adaptor supplied with my NanoVNA (in the center of image) the one way offset was 1.45ps=29fF an increase of 0.42ps=8.4fF
Measuring an open adaptor from Fairview Microwave or Pasternak (lower part of Image) no increase registered compared to the female SMA left unterminated
Measuring 3 pc. Huber Suhner Open adaptors (top of the image), which has a disk fitted towards the calibration plane, had a one way offset as 2.16 +-0.1ps equal to 43.2fF average.
These Offset are pending the mechanical design as shown in attached image. The open adaptor supplied with the NanoVNA is in the center and as the cylinder mating the reference plane has same inner diameter as the inner diameter of the mating ring of the calibration plane. then it will interact with the field lines form the center conductor.
These field line does not range outside the end of the SMA female adaptor so that is why the Fairview Microwave /Pasternak Open adaptor/Dustcover has not influence. (I have tested to 8GHz and the impact is hard to detect)
An open adaptor from Amphenol RF having a disk (like the Huber Suhner) even caused a short when using my torque wrench.
So I plainly love to use nothing as Rune mention, but the big question is what the designer of the Firmware for NanoVNA has defined the referred 50fF (I have even seen 60fF mentioned) to be an offset = one way or a delay = 2x Offset.
It also depend what the NanoVNA user gets delivered or purchase later on. If it is one with a disk, then throw it away
Regarding the Short which is supposed to be 0ps delay/offset I measured the supplied short to be -0.65ps (yes negative) whereas my simular short from Farview Microwave measured -0.1ps. The reason being the insufficient thickness of the shorting disk and the turned center pin for the one delivered has a small chamfer.
All in all clarification of the (bloody) 50/60fF would be nice
That was my humble contribution
Kind regards
Kurt OZ7OU (calibration nerd)



-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af qrp.ddc@...
Sendt: 18. september 2019 12:11
Til: [email protected]
Emne: Re: [nanovna-users] Filter measurement

Rune Broberg, the problem with "nothing connected to CH0" case is that it has different geometry configuration than usual SMA connector. It leads to insufficient capacitance and different delay line, which leads to incorrect measurement. But it depends on what you needs. If you're work in 1-30 MHz range, you may keep "nothing connected to CH0" it will not affect result much. But if you want to use frequencies above 30 MHz, you're needs to use proper open terminator.

Goddammit...

Have I waste $1 / 1€ / ?1 on these now ;-)



Please, no (mass) debates ;-)

For info only.


73 de Andy

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

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.

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.

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, 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.

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?

On Wed, Sep 18, 2019 at 07:35 AM, <erik@...> wrote:

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.

Erik, I'm not sure if the NanoVNA-H code at
is the firmware you are referring to, but there is a 50 femtofarad capacitor in
the eterm_calc_es() routine in main.c.

I've attempted to hightlight (sort of) the specific line, below:

- Jeff, k6jca

eterm_calc_es(void)
{
int i;
for (i = 0; i < sweep_points; i++) {
// z=1/(jwc*z0) = 1/(2*pi*f*c*z0) Note: normalized with Z0
// s11ao = (z-1)/(z+1) = (1-1/z)/(1+1/z) = (1-jwcz0)/(1+jwcz0)
// prepare 1/s11ao for effeiciency
float c = 50e-15; <<<<<< 50 femtoFarad capacitance
//float c = 1.707e-12;
float z0 = 50;
float z = 6.2832 * frequencies[i] * c * z0;
float sq = 1 + z*z;
float s11aor = (1 - z*z) / sq;
float s11aoi = 2*z / sq;

// S11mo�= S11mo - Ed
// S11ms�= S11ms - Ed
float s11or = cal_data[CAL_OPEN][i][0] - cal_data[ETERM_ED][i][0];
float s11oi = cal_data[CAL_OPEN][i][1] - cal_data[ETERM_ED][i][1];
float s11sr = cal_data[CAL_SHORT][i][0] - cal_data[ETERM_ED][i][0];
float s11si = cal_data[CAL_SHORT][i][1] - cal_data[ETERM_ED][i][1];
// Es = (S11mo'/s11ao + S11ms�)/(S11mo' - S11ms�)
float numr = s11sr + s11or * s11aor - s11oi * s11aoi;
float numi = s11si + s11oi * s11aor + s11or * s11aoi;
float denomr = s11or - s11sr;
float denomi = s11oi - s11si;
sq = denomr*denomr+denomi*denomi;
cal_data[ETERM_ES][i][0] = (numr*denomr + numi*denomi)/sq;
cal_data[ETERM_ES][i][1] = (numi*denomr - numr*denomi)/sq;
}
cal_status &= ~CALSTAT_OPEN;
cal_status |= CALSTAT_ES;
}

Ah. Correct. He did not refer to the model structure but used direct numbers in the code.

On Wed, 18 Sep 2019 at 19:54, <erik@...> wrote:

Ah. Correct. He did not refer to the model structure but used direct
numbers in the code.

That

c = 50e-15;

needs to be replaced by a function

C(f)=C0 e-15 + C1 e-27 f + C2 e-36 f^2 + C3 e-45 f^3

where C is in farads, and f in Hz.

That's the format used by all HP/Agilent cal kits, which are by far the
most common on the market. Copper Mountain use the same, and others use
something similar.

where for a constant 50 fF, it would be

C0=50, C1=C2=C3=0.

The values of all the Keysight cal kits can be found at



Many kits have different values for male and female parts.

The very common 85033D or 85033E (3.5 mm kits) have identical values for
male and female, but the common 85032B N cal kit does not, and neither does
my 85054B N cal kit. Obviously for APC7 kits it is irrelevant.

It would be good if the user could define a few cal kits, and name them.
For example, the kits I have are

* 85050B (APC7)
* 85052B (3.5 mm)
* 85054B (N)
* 85038A (7-16)
* 85039B (F)

None of those kits are going to be common on the use market at a price hams
are likely to be able to afford, although the 85052B does share the same
coefficients as the 85033D and 85033E, which are quite common. The 85050B
(APC7) can often be found cheaply, but it is not a kit most people are
going to want.

I personally intend building cal kits for every connector I can think of
into a box that the NanoVNA fits in. That's partially out of the
practicalities of never have to carry a cal kit, but partly out of the fact
that I can do it.


--
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

Qrp.dd (whoever you are)
It seem like the distance from center conductor to flat part is as long as to the top of the female SMA so probable without any influence.
You can test it yourself by calibrating using nothing for the open and enable S11 phase trace with a resolution so you have a slanted line dropping down some half the screen at 900MHz. Then mount the open adaptor and see if the trace is changing at all. If a change used the Display/Scale/Electrical delay and adjust until the line is horizontal (50KHz to 500MHz as probably a straight line for that frequency range) and the remove the open adaptor and see the difference by repeating Electrical Delay setting until same trace and the difference between the two Electrical delay setting is the added delay for you open.
Remember to reset the Electrical delay to 0 after the test
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af qrp.ddc@...
Sendt: 18. september 2019 19:05
Til: [email protected]
Emne: Re: [nanovna-users] Filter measurement

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?

On Wed, 18 Sep 2019 at 22:35, Kurt Poulsen <kurt@...> wrote:

Qrp.dd (whoever you are)
It seem like the distance from center conductor to flat part is as long as
to the top of the female SMA so probable without any influence.
You can test it yourself ....

I don¡¯t know if all the NanoVNAs are being shipped with the same open, but
I tested the open shipped with my NanoVNA using an HP 8753ES VNA after
first calibrating with an HP 85052B cal kit. The open did make a *small*
difference - a bit under 1 degree of phase difference at 900 MHz.

It did however cross my mind later that I had a 3.5 mm test port, rather
than SMA, so it would be worth my while repeating with SMA. My own
experience with both 3.5 mm and *SMA* connectors indicates adding *any*
sort of open ended device on the end, does make a measurable difference to
the phase, but I would have thought it pretty insignificant at 900 MHz.

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

Hi Andy,

Hi, Andy,

but your call also seemed familiar to me ;o)
Yes, it's true, on 17.07.2017, in the morning at 04:30 I had a direct hit in my LF antenna. The antenna was disconnected but unfortunately not grounded. Because of this the flash could jump over to the VHF/UHF mast, 6m away. So it was in the shack and left a smoking ruin :o((
I found parts of the 4m transverter 15m away, around the corner, which must have flown like projectiles through the shack. All 3 main fuses (63A) it "atomized". All electronics in the house were destroyed, even sockets were blown out of the wall. I could repair a lot since then but a lot is lost.
In the meantime I have also changed the QTH and only very limited antenna possibilities. But this will change in spring, when we move to a farm at the Dutch border, with a lot of space.
Then the grabbers will go online again. At the moment I'm experimenting with a frame antenna on LF/MF incl. transmission attempts, but so far nobody has heard me in WSPR. The power from the Ultimate 3 is too low, but I'm working on a small 400 W PA, with 50 - 70 W in the frame I should be heard then, hopefully ;o)))
Information about the frame experiments can be found here:

73 Joe