Re: NanoVNA #calibration


Larry Rothman
 

Radu,
Please note there is a big difference between upper case C and lower case c as an indication of calibration. 
Refer to the User Guide in the Forum files section. I emphasized this in the section on calibration. 
If you see c0 instead of C0 then the unit is NOT calibrated. (The number can be 0 thru 4)
Remember to always press the Reset menu button before calibration and then Save to one of the memories ( 0 is the power-on recall default memory). 



On Sat, 23 May 2020 at 10:29 PM, Radu Bogdan Dicher<vondicher@gmail.com> wrote: Larry,
Thank you for your input. When I run the scan, I see "c1" on the top/left
side, and I'm always keeping it current.
That said, I just tried in both modes - RECALL 0, and RECALL 1 - and I
can't see a difference in the graph shape. Maybe my calibration hasn't been
successful?... Or, maybe this is a sign the device is defective?
Thank you,
Radu.


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On Sat, May 23, 2020 at 4:04 PM Larry Rothman <nlroth@rogers.com> wrote:

Please remember that if even if you've saved your new calibration to c1,
if you power cycle the Nano, it automatically recalls c0 and you need to
manually recall c1 every time you turn the unit ON

On top of that, many Nano units will power cycle when connected to USB
power.


  On Sat, 23 May 2020 at 6:56 PM, Radu Bogdan Dicher<vondicher@gmail.com>
wrote:  Just to document this a bit better - I placed my calibration data
on "c1,"
which I'm recalling (and I see on the left side of the screen, on top)
before running measurements. I calibrated for a CENTER of 10.7MHz, and a
SPAN of 1.4MHz. This was done with the cables in place, including the patch
extension (per guidelines), but my little kit that allows me to socket the
filters was not connected during calibration (I came to wonder if I should
do that).

To continue establishing the baseline of my setup, the kit has proper
termination for the filters (~330ohm) and cables (~50ohm), and also a 10pF
cap on the filters output (per Murata datasheet).


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On Sat, May 23, 2020 at 3:29 PM Radu Bogdan Dicher via groups.io
<vondicher=
gmail.com@groups.io> wrote:

Hi all,
Having some confidence I've completed calibration on the band of interest
to me (I think I did 10MHz to 11MHz), I am getting the same titled scan
of
pretty much any number of filters I threw at this (I enclose a sample). I
am not sure if I need to return this, or request a replacement some other
way.
I contacted the seller (R&L), but it doesn't look like they have stock at
all and they haven't had any in a while.
[image: image.png]
Thank you all for you input.
Radu.

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On Wed, May 6, 2020 at 8:23 PM Radu Bogdan Dicher via groups.io
<vondicher=
gmail.com@groups.io> wrote:

I think I figured it, a bit trial and error and such. The idea seems to
be
to turn off two traces out of four and make sure the two left follow
certain inputs (LOGMAG for each CH). Past this step, it's a bit weird
how
the calibration menu steps one ahead on you, making it a bit confusing
as
to whether it completed the previous step or not. But it seems the
traces
settle in a way that tells me the device read "itself" and calibrated
accordingly.

I'm repeating the procedure, as my 10.7MHz filters plots still lean
lower
on the left side. This is across multiple filters, can't be due to
them,
still think it's the device.

On Wed, May 6, 2020 at 7:41 PM Radu Bogdan Dicher via groups.io
<vondicher=
gmail.com@groups.io> wrote:

I'm at the start of the calibration procedure, and I've connected
both
cables on CH0 and CH1, while using the pass-through attachment ("F-F
SMA"
in the v1.1 guidelines, in my interpretation) on the other end of the
SMA
cable coming from CH0.

The menu steps are clear until step 4, which calls for a "4. SINGLE."
I'm
not sure what this is. I don't see it anywhere following/around
TRACE 0
(which is there). I wonder if this is due to recent changes in the
menu
structure. Or maybe I am just missing something...

Thank you all for your help.
Radu.

On Tue, May 5, 2020 at 7:14 PM Radu Bogdan Dicher via groups.io
<vondicher=
gmail.com@groups.io> wrote:

Thank you all.

Firstly - on the attachments. Paul: I guess by elimination works
great!
;)
In fact, makes complete sense and thank you.

Secondly - on the filters. Jim: yes, I am terminating the measuring
rig
properly by impedance matching (closest possible to 330ohm to
filters
and
50ohm to the NanoVNA). Even after eliminating unnecessary
complications (50ohm BNC cables, SMA adapters, etc.), the filters
response
is still screwy (though much improved), and this is across multiple
filters. I assume next step on this pursuit is to recalibrate. I
assume
this is probably about as good as factory calibration, so there's
not
much
to loose there.

Thirdly - on the manuals/files: Thank you for that repository, I
wasn't
aware of it!

Radu.

On Tue, May 5, 2020 at 6:37 PM Jim Allyn - N7JA <
jim@allynelectronics.com>
wrote:

If the filters are not properly impedance matched, they will not
be
symmetrical.  In fact, the passband may be horribly distorted
compared
to
what you expect.  Further, the group delay of the filter will be
screwy,
which is important to those going for minimum distortion in their
FM
receivers.









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