Hi Herb,
my code thus far does indeed try to extrapolate what the -60 dB point would
be. Only I'm nowhere near good enough at making calculations like this, so
I'm stumbling a little. I know what the -6 dB point is, and I know
(roughly) how many dB per octave or decade the filter drops by. I think I
then need to do something magic involving logarithms, probably something
really simple - but I haven't sat down and figured it out yet.
Suggestions welcome if it's obvious to you, the reader. :-)
--
Rune / 5Q5R
toggle quoted message
Show quoted text
On Fri, 4 Oct 2019 at 17:53, hwalker <herbwalker2476@...> wrote: [Edited Message Follows]
Mike,
Google on filter bandwidth and the majority of the results will come up as
the -3 dB point. Not saying the -6 dB and -60 db points are not useful
info, just that the -3dB point is the common reference.
One other point is that -60 dB is in the dirt for portions of the nanoVNA
measurement range. Rune would have to extrapolate the -60 dB point in that
range which lends itself to possible inaccurate assumptions of the filter's
behavior.
Herb
|
Dr. David Kirkby from Kirkby Microwave Ltd
On Fri, 4 Oct 2019 at 16:32, Oristo <ormpoa@...> wrote: its become the consensus that return loss is a negative number
IMO, "return loss" is a poor term. But one used very extensively. Personally, I don't have a problem with it. Arguably, >>any<< return is loss, when sending power is the goal. In which case,
"return loss" might be power sent (since lost from return)..
Not always. There are one-port amplifiers, such devices as Gunn diodes and IMPATT diodes, but they are quite rare. For them, the signal returned is greater than that sent to them. They work on the principle of negative dynamic resistance. That means increasing the voltage, decreases the current. They still have a positive resistance though. A device might draw 100 mA at 7 V, but 90 mA at 8 V. The voltage has increased, but the current goes down. I know what my opinion on the subject is (return loss is positive for any passive device), but I am not going to try to force it on anyone else. I'm an atheist, but I would never try to convince anyone of any religion that their belief is silly. It is a waste of my time. -- 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
|
Re: Accuracy of calculated values - Nano VNA and Saver
Hi Martin, thank you very much for your appreciation! :-) I don't know Owen, so I couldn't possibly comment on his experiences; nor will I speculate on where his heart is. I only know what impact comments like his can have on the motivation of a developer. David suggested a number of different readings in a separate post that I think one of his pieces of hardware shows. All those could be interesting to add, perhaps to a pop-out display in order to fit them all ;-) The user definable SWR markers have been a request, and I think I'll put them in for both Smith, SWR - and of course, "return loss" ;-) -- Rune / 5Q5R On Fri, 4 Oct 2019 at 15:11, Martin via Groups.Io <martin_ehrenfried= [email protected]> wrote: Hi Rune,
Understood. I really like Saver and very much appreciate what you have
achieved so far, especially in such a short space of time, and I'm very
grateful for your effort and dedication.
A lot of Owen's frustration is due to problems with other VNA's and
antenna analysers that have some serious issues with calculated values that
never seem to get fixed, and the negative response he has had from the
manufacturers when these have been flagged up, hence his reluctance to
engage directly.
I agree that amateur conventions often differ from those used in the
professional world, and that perhaps some of Owen's comments are merely a
reflection (no pun intended) of that conflict. However is heart is in the
right place when trying to point out these issues, even if perhaps his
methodology is not to your liking.
The AIM VNA shows both parallel and series values, so maybe it would be
useful to include those in addition to conductance & admittance and then
it's not necessary to resort to external calculators and spreadsheets ?
Finally - would it be possible to add some user definable SWR marker lines
to the Smith and SWR plots ?
Regards,
Martin - G8JNJ
|
Mike,
Google on filter bandwidth and the majority of the results will come up as the -3 dB point. Not saying the -6 dB and -60 db points are not useful info, just that the -3dB point is the common reference.
One other point is that -60 dB is in the dirt for portions of the nanoVNA measurement range. Rune would have to extrapolate the -60 dB point in that range which lends itself to possible inaccurate assumptions of the filter's behavior.
Herb
|
Lower frequency limit: will be unchanged because the si5351 is still present and is switched in below 140MHz.
Larger screen: we are going to use the plug-in style of ILI9341 display rather than the bare FPC version because this board has components on both sides, so the 3.5 inch ILI9341 display is drop in compatible (provided you buy one with the correct pinout). Size beyond 3.5inch is not currently doable because 3.5inch is the largest SPI LCD size available. Larger displays (for example on the NanoVNA-F) use a parallel interface with far more pins which will require a larger MCU, adding many dollars of cost.
MAX2871: unfortunately this costs about 30 times the ADF4350, so isn't doable for the base version.
IAM-81008: that's a nice part, cheaper than the AD8342 and less power consumption. We might evaluate it and see if it will give acceptable performance. The IIP3 is much lower though, which means it has to be operated at lower signal levels to avoid bad linearity.
Open source: the schematic will be posted as soon as the product is generally available.
In the longer term we may introduce a higher end VNA. However the bigger priority there is full two port support - measuring all 4 S parameters at once. This is more aimed at lab use, so we may just remove the screen altogether (it's a big cost adder and a nuisance for shipping and firmware development) and have only a USB and wireless user interface.
|
Re: Nano saver - Reading / Writing cal data
Martin,
You might also try using the console commands via a terminal to accomplish saving and loading configurations. If it can be done via a terminal, then you can provide that feedback to Rune and it will make it easier for him to incorporate that function into his application. Larry has just added an updated list of commands to the "Files" section.
Herb
|
its become the consensus that return loss is a negative number IMO, "return loss" is a poor term. Arguably, >>any<< return is loss, when sending power is the goal. In which case, "return loss" might be power sent (since lost from return)..
|
Re: How many hardware versions?
Perhaps the nanoVNA-F could be added? The document points to /g/nanovna-f
Thanks! Rather a pity that the two couldn't be combined. I appreciate that some folks here seem interested in both. Many messages with potentially useful content already here lack context and often stray far from nominal topic, requiring "reverse engineering" to exploit. I focus on sorting descriptions of function for only NanoVNA-H e.g. among firmware flavors. For other examples, Windows 7 and Windows 10 user experience differences are IMO poorly addressed by current documentation, and I feel badly about not updating interactive menu tree for newer firmware.. For my own relatively trivial few contributions, version control and documentation update coordination provoke quite a lot of what is described for ducks as "furiously paddling beneath the surface", but I am only a poor and slow typist.
|
I read a recent post that said that, among hams, its become the consensus that return loss is a negative number. I respectfully disagree.
Regarding return loss, I understand some think its a negative number, some a positive. I am in the later camp. Why? When I was a young engineer I had the great fortune, in the early 1980s, to work for HP. Arguably the premier test and measurement company of its time. And equally arguably a leading if not THE leading microwave and rf company.
As new sales people, we were sent to 3, 3 week training sessions to learn the technology and the products so we might interact with our engineering customers in a technically sound way.
One thing HP taught, as I've said in a much earlier post, was that return loss was always a positive number. As someone on this list pointed out, negative loss is gain. And we KNOW that no return loss measurement, of a passive device, can exhibit gain.?
With respect, there is no gray area here. Return loss, is always a positive (or, perhaps better said, a non- signed) number.?
Even if you are at a hobby level of involvement, why not use the proper, and correct, terminology? If you're a private pilot, you are expected/ required to use the proper terminology. Same if you are an amateur road racer. Or "fill in your favorite" hobby.?
Sent using
|
Re: Another push button mod
If you ever bought one of the popular starter kits for microcontrollers like Arduino, it probably contains some suitable switches.
I bought a bag of assorted varieties of these switches from Banggood so I could try out the various form factors, especially the length of the button: In that assortment they are about 3 cents per switch. If you need a bunch of a single type, you can buy bigger bags of them and they are even cheaper.
|
Method of equivalent circuit used on HP 4284A LCR meter
Dr. David Kirkby from Kirkby Microwave Ltd
There has been some discussion about the best way to represent data
measured as impedance, into an equivalent circuit. The most comprehensive
of these I have seen, which my company owns, is my obsolte HP 4284A
precision LCR meter.
which is *not* a VNA, but measures the impedance of a device using a 4-wire
Kelvin measurement. This means everything shown here could conceivably be
displayed.
Someone *might* want to implement all or a subset of these. *I'm not
suggesting they are all implemented - I am just listing them for possible
discussion. *I suspect my HP 4285A LCR meter (75 kHz to 30 MHz) does the
same, but I have not checked.
*HP 4284A 1 MHz LCR meter. *
Cp-D - a parallel capacitance Cp, with a dissipation fact D
Cp-Q - a parallel capacitance Cp, with a Q of Q
Cp-G - a parallel capacitance Cp, with a conductance G
Cp-B - a parallel capacitance Cp, with a susceptance B
Cp-Rp - a parallel combination of a capacitance Cp, and resistance Rp
Cs-D - a series capacitance Cs, with dissipation factor Q
Cs-Q - a series capacitance Cs, with a Q of Q
Cs-Rs - a series combination of capacitance Cs and resistance Rs
Lp-D - a parallel inductor, with a dissipation factor D
Lp-Q - a parallel inductor, with a Q of Q
Lp-G - a parallel inductor, with a conductance of G measured in siemens
Lp-Rp - a parallel combination of an inductance Lp and resistance Rp.
Ls-Q - a series inductor Ls, with a Q of Q
Ls-Rs - a series inductor Ls with resistance Rs
*R - X - I don't need to explain what that is. *
Z-theta (degrees) - The magnitude and phase of an impedance expressed in
degrees.
Z-theta (rad) - The magnitude and phase of an impedance expressed in
radians.
G-B - G is the conductance measured in siemens (admittance Y = G + j B)
Y-theta (degrees) the magnitude of the admittance Y, and phase angle
expressed in degrees
Y-theta (rad) the magnitude of the admittance Y, and phase angle expressed
in radians
--
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
|
On Sun, Sep 29, 2019 at 06:21 PM, Gabriel Tenma White wrote:
Price will be around the same as the existing NanoVNA.
That might be interesting option. I expect a bigger screen is not really needed as you should be able to run from PC/Laptop anyway. I know some might want /P but that use might be in the minority. The design (H/W) will be open source? Given the history and user community already I would have thought that makes sense. 72 Dom M1KTA
|
Re: How many hardware versions?
Reinier wrote:
The block diagram is missing the measurement of the reference signal?
----------------------------------------------------------------------------------------------------------------
Tidbits of info have been slow to trickle out. As Hugen's development team releases more details, you can be sure this group will get it out to its members.
Herb
|
Re: Which Firmware Version?
Larry,
Where cam I find the DFU File Manager to convert the bin or hex file to dfu?
Mike N2MS
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Larry Rothman Sent: Thursday, October 3, 2019 3:03 PM To: [email protected]Subject: Re: [nanovna-users] Which Firmware Version? No problem. There are many names around for the same file.That is why I uploaded them in the files section and dated each one. Forum member ORISTO has created a WIKI page that describes the various releases: Firmware Versions (with links) by Oristo Po
|
Rune,??
I checked with a friend who is very involved in such things.? I think 6db and 60 db are the normal points used for filter definitions.? For example, that is what Elecraft uses...
Mike WY6K
"... somewhere in the distance, there's a tower and a light, broadcastin' the resistance, through the rain and through the night..."
toggle quoted message
Show quoted text
On Thursday, October 3, 2019, 3:04:51 PM CDT, Rune Broberg <mihtjel@...> wrote: Mike, see attached for a first sneak peak of what I'm working on. I think I'm currently under-estimating the roll-off by measuring it from the -6dB point and to the end of the data. Is there a norm for how to do these measurements? Or should I just make it up as I go along? [image: image.png] -- Rune / 5Q5R On Thu, 3 Oct 2019 at 15:45, mike watts via Groups.Io <wy6k= [email protected]> wrote: Yes, all of those filter measurements would be useful for things I do.
Those functions would elevate you from "hero" to "demi-god" in my world.
:-)
Mike WY6K
"... somewhere in the distance, there's a tower and a light, broadcastin'
the resistance, through the rain and through the night..."
? ? On Thursday, October 3, 2019, 4:20:50 AM CDT, Rune Broberg <
mihtjel@...> wrote:
? Hi Norbert,
the application can run calibrations at far more than 401 points - I have
certainly done 5050 points at one point. ;-) But it does this in the
application, and not on the device, due to the hardware limitations.
I agree that a function to find cut-off frequencies for filters etc. would
be interesting, and I've put it on the list of features I would like to
implement for the next version, ie. for next week. I don't make any
promises though :-)
What measurements would be relevant to provide? Cut-off frequency, span for
band-pass, dB/octave and dB/decade fall-off, pass-band ripple?
--
Rune / 5Q5R
On Thu, 3 Oct 2019 at 11:12, <norbert.kohns@...> wrote:
Hi Rune,
thank you for fixing this issue!
I have a question for you in respect to the required number of data points
to measure a band pass filter. With 101 points it is most likely not
possible to find the -3 dB points because the sample point is way off from
-3 dB on both sides of the band pass. With 401 points it would work. An
automatic feature of measuring the bandwidth would be absolutely cool! The
TAPR software is able to perform a calibration at 401 points or even more
than that, so I am certain that you could do that as well.? I have no glue
on how difficult that would be, but more data points for calibration would
be a huge improvement.
Kind regards
Norbert, DG1KPN
|
Size matters - with consumer electronics especially. It's just the old aged who have trouble with small screens (me included). The solution is simple, design it to be compatible with both small and large screens of the same number of pixels, or wear stronger glasses.
Mike
|
Re: New mode R / L / C display
Agree this would be very helpful feature, particularly (asking for too much?) if it can support open or short zeroing to compensate for attachment mechanism (like the AADE LC measurement meter.)
|
Really? Its length been frustrating me for a long time. I don't see other people putting it in and I don't think it's doing you any favours but you could at least try to get it on one line!
|
Re: How many hardware versions?
From: Oristo Wiki now has a "Hardware Versions" link:
/g/nanovna-users/wiki
Perhaps the nanoVNA-F could be added? The document points to /g/nanovna-f================================ Thanks! Rather a pity that the two couldn't be combined. David -- SatSignal Software - Quality software for you Web: Email: david-taylor@... Twitter: @gm8arv
|
Re: List of NanoVNA Console Commands
Nope - the WIKI page was created several weeks AFTER I created my document and it was out of date and lacking info when posted, so I added a link back to my document which I just updated today.
I don't know why the poster didn't just link to my document to begin with.
toggle quoted message
Show quoted text
On Friday, October 4, 2019, 5:23:21 a.m. GMT-4, hwalker <herbwalker2476@...> wrote: Jim, Larry pulled his original PDF document in favor of this link,? /g/nanovna-users/wiki/shellcommands . Herb
|
OwO
Oristo
Shirley Dulcey KE1L
WY6K Mike Watts
David J Taylor