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=
[email protected]> 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=
[email protected]> 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=
[email protected]> 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=
[email protected]> 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@...>
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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