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Hi Mike,

I agree totally ! It would be very useful in my case, waiting to
replace
the TCXO.

For the moment, i'm obliged to multiply the desired frequency by
1.0000855 to compensate

the too large error of the TCXO.

73 QRO,

Rudi, HB9ARI

Le 22.05.2020 à 17:38, vbifyz a écrit?:

It would be nice to have a menu option to calibrate the frequency. It

is easy to adjust the Si5351A output frequency, all libraries for it
include this function.

73, Mike AF7KR

It would be nice to have a menu option to calibrate the frequency. It is easy to adjust the Si5351A output frequency, all libraries for it include this function.

73, Mike AF7KR

I've been able to install the NanoVNA-Saver on Ubuntu 20.04 using the attached helper document. I regret to say that I forgot where I found it ... memory loss is the first sign of senility!

The nice thing about this approach is that it can be set up with a script, saved as a desktop icon and run easily. One caveat is that your username must be part of the"dialout" group on your Linux system so that access to the usb port will be allowed to connect the NanoVNA to your computer. As always, your mileage may vary if running other versions of Ubuntu or other distros.

73 Bob KC2JAV

Hi Ed
It is quite normal what you see. Please note that the number of point are
only 100 so for the span used 50MHz you have a point for each 0.5MHz.
Reduce the span to e.g. 140 to 150 MHz and see for every 100KHz the
impedance / SWR. The load are OK it is not what you concern should be, It
do not think you Ohm meter are accurate enough to determine the very exact
DC resistance and will only create a very little SWR contribution.
I would guess you antenna does not have 50ohm impedance on 145MHz. The
oscillation you see are natural for reflection from the antenna which is
wandering forth and back in the cable.
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af
ed@...
Sendt: 21. maj 2020 07:35
Til: [email protected]
Emne: [nanovna-users] Calibration issue causing ripples in SWR?
#calibration

After calibrating, I connected my nanovna to my VHF antenna via a brand
new 75 foot length of 50ohm DX400MAX coax. The SWR measurement oscillates
up and down every 4MHz or so (see attached). These correspond exactly to
the half-wavelength harmonics of the cable. Looking at the smith chart, it
is clear that the impedance is tracing a circle around about 45 ohms rather
than the constant-SWR circle centered at 50 ohms, resulting in a
frequency-dependent SWR.

Is there is a good way to determine whether this is a problem with my
nanovna, with the calibration standard, or with the cable?

One note: the calibration standard load measures 51 ohms DC resistance,
which seems like a problem to me. Should my standard be exactly 50 ohms dc
resistance?

Hi Geo,

In my two way wrist watch I have restricted the spell-checker to merely

suggesting by underline any words it thinks are wrong and it is not
allowed to "autocorrect". Sometimes it underlines correctly and other
times displays it's puny lexicon by underlining correctly spelled
words.

I mever nake big misteaks.

73,

Bill KU8H


On 5/21/20 3:37 PM, GEO BADGER via groups.io wrote:

Should NOT flake off. My droid won that battle. Ugh!

?___
Sent from my two way wrist watch
73 de W3AB/GEO?

--
bark less - wag more

Should NOT flake off. My droid won that battle. Ugh!
?___
Sent from my two way wrist watch
73 de W3AB/GEO?

Jason,

As an ex-employee of M/A-COM I can vouch for what you learned. We made
special connectors for the test equipment companies, HP, Wiltron and
such. The plating should flake off any OS connector.

BeCu is not necessarily dangerous with standard machining practices
because it produces large chips & not dust during the machining
process.

A couple of other companies I worked for used BeO. It an excellent
electrical insulator and possesses the highest thermal conductivity of
commercial ceramics. We needed that for the high power circuits we
designed. It was machined under water due the dust generated by
grinding & polishing.

IMHO, the frequencies that the NanoVNA operates at & the precision we
require are not compromised by good connectors & operating practices.
These devices should not be compared to a HP VNA. They are ideal for
amateur radio use.

I use push-SMA connector savers with excellent repeatability. I believe
they were made by Adams-Russell, another M/A-COM company.

?___
Sent from my two way wrist watch
73 de W3AB/GEO?

On May 21, 2020, 12:01, at 12:01, fishtronics <fishtronics@...>
wrote:

Using the SMA-M/SMA-F adapters as connector savers like I think you
show, Stan, is a very good idea. Even very high quality SMA connectors
(>$50 each) degrade in match very quickly. Cheap ones with only 2 jaws
on the center conductor are pretty much worthless for repetitive use.

I

was once told by the ME at Omni-Spectra their SMAs were rated to meet
spec for the initial connection only! I am getting a bunch and will
swap them out as soon as any gold flaking or wear is apparent under
magnification. Most of the cheaper SMA connectors from China look to

me

to have plain brass center contacts which will not apply any contact
pressure after the first mating. A capacitive gap results. The only
inexpensive SMA-M/SMA-F adapter I can find with a Beryllium center
conductor is the Cal Test CT3673. The only reason to use BeCu which
costs more and is poisonous to machine is if they heat treat it, to
make the jaws springy. I don't know whether there are more than 2 jaws
to the F pin. Better ones have more, but at < 1GHz it probably won't
make any difference untll the jaw loses its spring. I have a question
into the tech support to ask about it. Data sheet kere:
.
They are dirt cheap at
Amazon:.
Jason NJ7K

Using the SMA-M/SMA-F adapters as connector savers like I think you
show, Stan, is a very good idea. Even very high quality SMA connectors
(>$50 each) degrade in match very quickly. Cheap ones with only 2 jaws
on the center conductor are pretty much worthless for repetitive use. I
was once told by the ME at Omni-Spectra their SMAs were rated to meet
spec for the initial connection only! I am getting a bunch and will
swap them out as soon as any gold flaking or wear is apparent under
magnification. Most of the cheaper SMA connectors from China look to me
to have plain brass center contacts which will not apply any contact
pressure after the first mating. A capacitive gap results. The only
inexpensive SMA-M/SMA-F adapter I can find with a Beryllium center
conductor is the Cal Test CT3673. The only reason to use BeCu which
costs more and is poisonous to machine is if they heat treat it, to
make the jaws springy. I don't know whether there are more than 2 jaws
to the F pin. Better ones have more, but at < 1GHz it probably won't
make any difference untll the jaw loses its spring. I have a question
into the tech support to ask about it. Data sheet kere:
.
They are dirt cheap at
Amazon:.
Jason NJ7K

No it look like hardware problem (or measure frequency problem)

It possible fix by software need redefine

// XTAL frequency on si5351
#define XTALFREQ 26000000U

To current XTAL frequency and rebuild

Or replace XTAL

On Thu, May 21, 2020 at 09:06 AM, Rudolf Schaffer wrote:

As the TCXO frequency is out of tolerances, it's certainly a defect
component.

DiSlord suggested the error could be due to the firmware. What version are you running?

Roger