开云体育

Well, I think for low-reflection DUTs the error might still be dominated by the residual directivity (and hence the return loss of the calibration load). But I agree that while the discussion about the loads is interesting, it will generally not be the limiting factor with the NanoVNA.

For the NanoVNA-V2 in particular, with frequencies of 3GHz and beyond, the firmware calibration routine and the included open and short standards are somewhat inadequate. By comparison, the load is fine... Apparently, there are plans for a 6GHz version, but unless calibration is sorted out, I'm not sure there is much of a point.

Not all is lost, with a PC connected you have a lot more options (of course for portable use that will not do you much good). NanoVNA-QT can use arbitrary touchstone files for the standards and NanoVNA-Saver can use a polynomial model. I usually use scikit-rf with Python instead, because it is more flexible for 2-port calibration. QT only does simple normalization for transmission and I suspect 2-port calibration in Saver is essentially broken.

Even if this is fixed, there doesn't seem to be a suitable low-cost option for a calkit at the moment (low-cost relative to the NanoVNA, I am aware of your products). At a minimum, it would need characterized offset delays. As you illustrate so nicely, the phase error can become signifcant and at some point you might be better off without a full SOL calibration.

The SDR-Kits calkits try to fill this gap, but beyond 1.5GHz the performance doesn't seem to be too great (at least for the female one). This is maybe not surprising, as they are aimed primarily at the 1.5 GHz VNWA. I suspect that the issue is mainly with the open and could be solved if the fringing capacitance were included in the model. If anyone has measured the SDR-Kits parts with a properly calibrated analyzer up to at least 3GHz, I would be very interested in the touchstone files.

Concerning zero-delay/flush shorts, I think this is not really the issue. For 3.5mm it is quite possible to make male and female flush shorts (at least you can order them from Maury Microwave). However, I expect it will be much harder to make a flush open with low capacitance. And I suspect this is the reason why you usually don't find a flush short in a calkit. If the difference in delay between the short and open is too large, the phase will eventually cross-over and the calibration equation becomes singular.

David,

Good stuff, thanks for posting.

Assuming the connectors physically stout enough to give repeatable results,
would it be possible to calibrate out most of the errors encountered in a cheap or homebrew calibration set?
Is this something that could be done through post-processing in nanovna-saver?

FYI, the two images in your "not-see-a-dot" FAQ don't show up
in either my Chrome browser or in Firefox.

Jerry, KE7ER

With the recent discussion about high return loss loads, I made the point
that it is a bit pointless worrying about it unless there’s firmware
support for calibration kits in NanoVNA, which as far as I am aware there’s
not.

The following is the the phase of a *female N calibration standard* from an
HP 85054B calibration kit, costing more than $20,000



The photographs show the VNA calibrated to 6 GHz - I happened to VNA warmed
up and calibrated up to 6 GHz.

On the far left of the Smith chart is the theoretically ideal short. On the
right is the theoretical ideal open.

This VNA covers 50 MHz to 20 MHz, so with a minimum frequency of 50 MHz,
the phase would not be the idealised 180 degrees, but it would be quite
close to 180 degrees. Hence the trace starts not quite on the far left.

At 6 GHz the phase has changed from 180 to 59.34 degrees. For simplicity,
assume that the phase is 60 degrees. So the phase has changed 180-60=120
degrees over 6 GHz. Assuming a linear phase change with frequency, which is
approximately true, that’s a phase shift of 120/6= 20 degrees per GHz.

So if this $20,000 kit was used to calibrate a NanoVNA using the NanoVNA
firmware, a 20 degree phase error would exist at 1 GHz. With such a large
phase error, it would be pointless worrying about the loads.

I would add it is possible to make an N female short with virtually no
delay, but HP chose not to do it.

When it comes to a male N calibration standard, it is technically
impossible to make it with zero offset.

This link might help an understanding of what is happening on those plots.




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

I shall contribute another nit:

it's not 377 ohms, 376.730... ohms (approximately 120*pi, but I think that's a coincidence) - and yes it's the ratio of E field (V/m) to H field (A/m) in a vacuum "far" from any other object that is not "a vacuum".

And that's only if you're using a measurement system that is Volts and Amps - It's also the square root of the ratio of the permeability (in H/m) and permittivity (in F/m), and it related to the speed of propagation as well.

E/H or mu0 * c or sqrt(mu0/epsilon0) or 1/(c0*epsilon0)

The *precise* (as in past the 4th decimal place) values depend on the current definition for things like the speed of light and the ampere, which does change over time.

Does it matter, most of the time? Nope..

Interesting concept.
Why does the impedance of the Universe change with distance???
If think you are confusing 'Far Field' with impedance.????? Kent




Just to clarify.? 377 ohms is? a physical constant relating the magnitudes of the electric and magnetic fields of electromagnetic radiation travelling through Free Space.? This only occurs when you are a considerable distance from the? transmitting antenna in the far field.

Perhaps you bought the wrong Harbor Freight DMM.

I compared my free-with-purchase HF 69096 against my very expensive $10 UT10A.
The UT10A shows 0.0 ohms with the probes touching almost immediately.
The HF shows 2.0 ohms with probes touching if you give it a few seconds.
Correcting for this, when measuring my 50 ohm standard from Hugen,
I see 49.6 on the HF and 49.7 on the UT10A.
Makes sense the standard would be a bit low at DC,
at 1GHz the skin effect will likely raise that some.
I'm left to wonder what sorts of compensation are necessary in
a really good 50 ohm standard.

It is easy to cripple a HF DMM, perhaps forget it's on ohms
and go to measure a voltage. They are not well protected.
But given the price, it's a good pair for my $40 VNA.
I've got a dozen of the HF DMM's around here: One in the pickup, one in the shop area,
one in the kitchen, one by the ham gear, one in the pumphouse, one probably left up on the roof,
one that the dog ran off with, ...

Jerry, KE7ER

These can of worms taste better with HOT Sauce and you get what you pay for !

On Mon, Aug 17, 2020 at 11:44 AM, KENT BRITAIN wrote:

Only on the input, the output is always 377 Ohm.
Example would be Yagi's with 50 or 75 ohm inputs.
Now, how well you match the 50/75 input to the 377 outputis determining Gain
and SWR.??? Kent

On Monday, August 17, 2020, 12:08:24 PM CDT, <namerati@...> wrote:

On Mon, Aug 17, 2020 at 12:34:21AM +0000, KENT BRITAIN wrote:

Takes a bit to think of your Yagi antenna as a 50 to 377 Ohm impedance

transformer.

And if you are building Stealth aircraft, you want them to look like 377, not

50 Ohm dummy loads!

So you are saying a Yagi is a transformer with multiple taps? :)

Just to clarify. 377 ohms is a physical constant relating the magnitudes of the electric and magnetic fields of electromagnetic radiation travelling through Free Space. This only occurs when you are a considerable distance from the transmitting antenna in the far field.

A thorough discussion of Electric, Magnetic and ElectroMagenetic fields and field impedance is written by W8JI, who has an extensive and well-researched web site.

Rog

On Mon, Aug 17, 2020 at 09:29 AM, David Eckhardt wrote:

The intention of the following:

1) ALL TRANSMISSION LINE(s): Fields close onto themselves. The system is
self contained as far as the fields are concerned.

This is only true if the current on the transmission line has the same magnitude (but opposite directions) on the two conductors. If not the transmission line will radiate.

Take the case of a dipole (or doublet) , connected to ladder-line transmission line, where the two elements do not have the same impedance due to being different lengths or affected by nearby objects. The current imbalance will cause the feed-line to radiate. The same thing happens with coax where radiation will take place from the outer surface of the shield.

Roger

Peter,

I have attached a measurement of port 2 return loss from my NanoVNA V2, bought from tindie. This one seems to be meet the specs (-20.3dB @1.5GHz and -15.5dB @3GHz).

There is also significant ripple on your measurement. It looks like your calibration is bad and you have significant residual source match error (or possibly your cable is bad, but less likely; since you are calibrating directly at the port 1 connector, you are measuring the cable as well). So I would take the results with a grain of salt. Mine is not perfect either, but it looks a lot less bad.

Only on the input, the output is always 377 Ohm.
Example would be Yagi's with 50 or 75 ohm inputs.
Now, how well you match the 50/75 input to the 377 outputis determining Gain and SWR.??? Kent

On 8/17/20 10:33 AM, John Baines via groups.io wrote:

For a 2:1 impedance transformer, 14:10 turns ratio gives 1.96:1 impedance ratio which may be close enough, or 17:12 turns ratio gives 2.007:1 impedance ratio (<0.35% error). A few minutes playing around with a calculator will probably find even better approximations.

yeah, I'd just go hunting through the Minicircuits or Johansen catalogs and look for something that does the function - I have no idea how they make them internally (well, I know it's some windings on a core) - but wideband transformer design is partly an art, partly engineering.

That would also solve a "unbalanced test equipment to balanced DUT" issue.

In the OP's case, measuring a filter, there's sort of two cases:
1) "what the heck is this unlabeled thing" and for that the "software correction in NanoVNA Saver" strikes me as the easy way
2) "adjusting a filter or doing manufacturing checkout" - it's over a narrow frequency range, so you can probably find a transformer that would work.


Minicircuits ADT2-1T+ goes 400kHz to 450 Mhz and 2:1 as an SMT device, for $3.85. Stick it on a board, solder it to the SMA connector, however you fixture it.

FOr a bit more ($5.85) you can get the T2-1-X65 in a 6 pin DIP, goes from 50kHz to 600 MHz.
Bigger pins to solder to if that matters - the pins are 0.1" apart (just like the SMT device) and on a standard "solder in" SMA, the center post is about 0.14" from the corner posts.

Minicircuits DOES sell a board for things

(with the fascinating note that you have to use your PNA's "impedance conversion function" ) - but they cost >$100.

73
John
M0JBA

On 17 Aug 2020, at 18:19, Jim Lux <jimlux@...> wrote:

On 8/17/20 7:36 AM, Stephen Laurence wrote:

I seem to recall from the distant past, reading instructions for one of the early hobby vna devices about this.
The software with the vna (mandatory pc to use it) could automatically readjust the response. The demonstration was an ssb sideband filter with input and output inpedance of several 100ohms. The initial result seemed to be a poor filter with maximum skirt attenuation of only 20db but after the corrections were applied, was the expected 80+ db. This was at hf of course.
What was going on? Can this sort of correction be applied. How do I assess a filter with several hundred ohm in and out impedance, or do I resort to a spectrum analyser with tracking generator ( do not have one) or noise source, which is what I have done in the past. I still have that kit ( does 0-120mhz using a scope for display) for posterity.
Is this an opportunity for a firmware ( or saver) addition?

There's a couple ways to approach this:
1) make a test fixture and cal kit that has 100 ohm loads - run the cal, and it should automatically fix everything - I would be concerned that various displays wouldn't "know" about 100 ohms, so displays of R and X would be wrong, even if S11, S21 are correctly displayed. The "center" of the Smith chart would be 100 ohms.

2) calibrate with 50 ohms, and post process to change to 100 ohms - one could implement such a thing in a program like NanoVNA-Saver, and that's probably the cleanest way.


Ultimately, though, for both of these the measurement uncertainty will maybe be slightly worse - the "bridge" in the NanoVNA is designed for 50 ohms, so you'll always get reflected power and the transmitted power will always be less - How that would quantitatively affect your results, I can't say.

3) build a test fixture that has a 2:1 impedance transformation (non trivial, since it's a transformer with a 1.414:1 turns ratio).
Now you're back to sort of a #1 scenario.


I note that this is of some interest to people making measurements on twisted pair cables (i.e. Cat 5), since they're 100 ohm nominal impedance balanced. And a TDR is a great thing for finding places where the installer bent the cable too tightly or some similar problem.


On a fancy analyzer, they'll provide software inside to change the reference impedance, so you can do a cal with 50, measure 100, display with 100, or any other combination. Here, I think NanoVNA-Saver is the right kind of place. Keep the inexpensive box with limited firmware space simple. Put the fancy features in software that can run on any platform.

Hmmmm,

I have a question.

The test/ education board available for about ?15 has simple loads, capacitors attenuators, etc with leads which have those inferal minute connectors to select which circuit you wish to play with. Each little circuit has the expected screen display overlaid on the circuit board. In my arrogance (ignorance) I have resisted buying one.

One of those little circuits is a ceramic filter. I presume its input and output impedance is anything but 50 ohm, more like 200-500 ohm. What happens there? Or is the filter especially selected for 50 ohm termination?

Steve L. G7PSZ

For a 2:1 impedance transformer, 14:10 turns ratio gives 1.96:1 impedance ratio which may be close enough, or 17:12 turns ratio gives 2.007:1 impedance ratio (<0.35% error). A few minutes playing around with a calculator will probably find even better approximations.

73
John
M0JBA

I have N, SMA, and OSM series precision cal. kits from HP. I made a DC
measurement of the 50-ohm standard loads for these three connector series
from these kits using the following instruments (what I have).

1) Bench DMM: HP 3478A
2) Hand-Held DMM from Harbor Freight: P37772
3) Hand-Held DMM from Sperry: DM6400

*Results follow:*

*HP** Harbour Freight Sperry*

50.375 45.50 50.20 Type-N
(HP 909C)

50.179 45.50 50.10 SMA
(HP 909D)

50.330 47.00 50.10 OSM
Connector (the expensive ones from HP)

AVERAGE OF ALL READINGS: 48.801 Ω Clearly the Harbour Freight unit
is dragging down the average.

AVERAGE OF ALL READINGS (excluding the Harbour Freight measurements):
50.214 Ω (0.43 % error against 50.0000 Ω)

These are precision HP cal. standards. Sure, they are better than what
comes with the NANOVNA's. But consider the cost!!!!!! Is it worth arguing
and expecting something less than 2.26 % error when the load reads 51.13
ohms? Really, now?

This is a hobby, not a metrology lab!!!!!!

Dave - W?LEV

On Mon, Aug 17, 2020 at 4:20 PM Wolfgang Wilde via groups.io <wwilde69=
[email protected]> wrote:

Fully agree with Dave. Are you not awaiting a little bit to much from
the NanoVNA? What precision can be expected regarding impedance, levels,
noise figures and so on? The FR4 material may not be precise enough to
guarantee 100% precise 50 Ohms impedance for the input/ output lines of
the NanoVNA itself!

Can it really work that precise? Over what frequency range? And in what
impedance range will it show the right numbers?

Would you really expect similar figures and precision from it than you
would expect from HP/Agilent/Keysight/Tektronix/Rohde&Schwarz labor
grade measurement equipment that costs 100 times as much or more? Don't
get me wrong, it is really a brilliant DIY project that helps me a lot
and is very handy tool for me to get a rough idea of what is going on.
But I would never expect the NanoVNA being absolute precise as I think
it never was target on that and I doubt it could deliver that precise
results. It already does almost magic, so let's adjust expectations a
little bit for reality.

vy 73,
Wolfgang, (DG7NEF)




Am 17.08.20 um 17:33 schrieb Dr. David Kirkby, Kirkby Microwave Ltd:

On Fri, 14 Aug 2020 at 01:52, Glen Jenkins WB4KTF <wb4ktf@...>
wrote:

The 50 OHM load (SMA-Male) that came with my nanoVNA-H4 measures 51.13+
ohms. Not a good start for calibration. Where is a good source for

GOOD

loads that are accurate?

--

-----

Glen Jenkins, WB4KTF, Austin, TX

Do you have a specification in mind? DC resistance doesn’t tell you much,
other than it puts an *upper* limit on return loss. As soon as you go up
in frequency, the return loss will most probably decrease.

If you measure up to 3 GHz, it gives you no idea what it will be like at

6

GHz. Sometimes loads worsen dramatically with frequency, but others, from
the same batch will get better.

The last I looked, there was nothing in the NanoVNA firmware that

properly

accounted for the open or short calibration standards. So there are

limits

to what you accuracy you are going to achieve if you had a really

expensive

load, as the phase errors will kill you.

Dave

--
Mit freundlichen Gruessen,
------------------------------------------------------------
Wolfgang Wilde, -o) Email: wwilde@...
Nuernberg /\\ wwilde@...
_\_v

------------------------------------------------------------
Diskutiere nie mit einem Irren -
er zieht dich auf sein Niveau
und schl?gt dich mit seiner Erfahrung.


Shit happens -
... manchmal bist du Taube, manchmal Denkmal.


Das Software Business ist binaer.
Du bist eine 1 oder eine 0,
lebendig oder tot.
Wer nicht innovativ sein will ist t o t.
Startup (von Peter Howitts)


Das Wissen der Menschheit geh?rt der Welt.
So wie Shakespeare oder Aspirin...
Startup (von Peter Howitts)


Es gibt keine Hindernisse, keine Grenzen.
ueberrascht mich, zeigt es mir, bertrefft mich,
bertrefft euch selbst.
Startup (von Peter Howitts)



Fürchtet euch nicht,
die Welt wird heute nicht untergehen.
Es ist n?mlich schon morgen - in Australien!
Eckart von Hirschhausen




"Was ist das?"
"Das ist blaues Licht."
"Und was macht das?"
"Es leuchtet blau."
RAMBO III



"Gott muss lieben Verrückte Menschen"
"Warum?"
"Er macht so viele Davon!"
RAMBO III



FIAT:
F uer
I talianer
A usreichende
T echnik


mail is sent from F. U. C. K. U. P.
First Universal Cybernetic Kinetic Ultramicro Program


Man muss die Welt nicht verstehen,
man muss sich nur in ihr zurechtfinden!
Albert Einstein


Phantasie ist wichtiger als Wissen
denn Wissen ist begrenzt.
Albert Einstein


Die gr??ten Wolht?ter der Welt sind Faulenzer.
Denken Sie mal daran
wieviel Unheil dadurch vermieden wurde
da? man einfach nichts getan hat!


Alle sagten: Das geht nicht.
Dann kam einer, der wu?te das nicht und hat's gemacht.
(Unbekannt)


Stop wasting entropy - start using predictable tempfile names today!


RFC1925:
(3) With sufficient thrust, pigs fly just fine. However, this is
not necessarily a good idea. It is hard to be sure where they
are going to land, and it could be dangerous sitting under them
as they fly overhead.
(6a) (corollary). It is always possible to add another level of
indirection.
(8) It is more complicated than you think.


Mike Cox, I've got a new angle for ya. (BTW- Long-time fan!) Start doing
the total sarcasm posts like normal, but change them a bit so you sound
like the Iraqi Information Minister. (I miss him.)
"There IS no Linux within a hundred miles of any PC!"


I just found out that the brain is like a computer.
If that's true, then there really aren't any stupid people.
Just people running Windows.


Sie sind nicht berechtigt,
unrechtm??ige Kopien dieser Mail
anzufertigen oder zu vertreiben.


This software is an abomination in every sense of the word!
Run it! Hug it! Feel the power of the Dark Side!
[ MGM, (C) by Xiphophorus, see ]


-- 21 ist nur die halbe Wahrheit --


Aus einem Mailwechsel zum Thema Unterbrechungsfreie Stromversorgung:

Es gibt immer einen, der den Stecker ziehen kann.

Apple arbeitet schon an dem Problem... ;-)

Sie wollen die USV erfinden?

Nein, Stecker, die man zum Entfernen in den Papierkorb legen mu?.


Muphy's Naturgesetze:
4.) Jedes Programm, das gut beginnt, endet schlecht.
Alles, was schlecht beginnt, endet furchtbar.


Muphy's Naturgesetze:
21.) Die Vorarbeit wurde immer von Personen ausgeführt, die noch
dabei sind, ihre unterste Stufe der Unf?higkeit zu erreichen.


Wer eine Personal Firewall verwendet, k?nnte auch eine Einkaufstüte
als Kondom benutzen: Den Sicherheits- und Lustgewinn beider Methoden
halten wir für vergleichbar. ;-)
[T-Online-Team in t-online.talk.internet]


Linux is like a wigwam:
no gates, no windows, and an apache inside.


"Bunt ist das Dasein und granatenstark."


COMMAND.COM kann nicht angehalten werden - System halted


-------------------------------------------------------
Mind your head and keep it simple !
-------------------------------------------------------

H?flichkeit ist wie ein Luftkissen.
Es mag nichts drin sein, aber es mildert die St?sse des Lebens.


The light at the end of the tunnel might be an oncoming dragon


Wenn Personal Firewalls die L?sung sind,
will ich das verdammte Problem zurück. [Robin S. Socha]


Good, Fast, Cheap: Pick any two (you can't have all three). RFC 1925


Stay the patient course.
Of little worth is your ire.
The network is down.


It's not denial! I'm just very selective about the reality I accept.


Erst jetzt nachdem du gesehen hast was du geh?rt hast
kannst du m?glicherweise die Wahrheit akzeptieren....


Nichts
> Was h?ltst Du von Quotes am
Ende?


echo '@a=(A..Z,a..z," ");$t="a"x16;{for($x=0,$|=$n=30; $n--;){for($l=$t;
1<rand 7;) {substr$l,rand 16,1,$ a[rand@a]}$q=$_="zeluR xuniL
ESuS";for($a=$l;
$_;){s/.//;$q++ if chop$a eq$&}if($x<=$q){$e=$l;die$ e,$/if($x=$q)==16}}
print$t=$e,"\r";redo}'|perl


Thought is limitation. Free your mind.


--------------------------------------------------------------------
Verglichen mit jedem x-beliebigen Redmonder Betriebssystem-Clone
ist Linux geradezu eine leuchtende Perle der Datensicherheit.
------ Frank Rennemann () -----


Trouble springs from idleness, and grievous toil from needless ease.
--Benjamin Franklin


-----------------------------------------------------------------
"Na sch?n, was sollen wir also tun, wenn wir von irgendwas
Lebensgef?hrlichem gebissen werden?" fragte ich.
Er sah mich an, als sei ich bescheuert.
"Na, was machen Sie dann wohl" sagte er. "Sie sterben.
Was denn sonst? Deshalb hei?t es ja lebensgef?hrlich."
------------- Douglas Adams: Die Letzten ihrer Art --------------


"355/113 -- Not the famous irrational number PI, but an incredible
simulation!"


Was auch immer geschieht:
Nie dürft ihr so tief sinken,
von dem Kakao, durch den man euch zieht,
auch noch zu trinken!
- E. Kaestner


In a free world without walls and fences, who needs windows and gates?


"Reality is always controlled by the people who are most insane" Dogbert


Ich bin vorwiegend mit unterbrechungsintoleranten Arbeiten besch?ftigt und
bevorzuge daher email gegenüber Telefonanrufen.


wonder why did i even answer to that user, i shouldn't do so, just flame
him to the hell as usual. Probably i was drunk then... -- [A'rpi]

ich denke, ich kann Dir für jede PHP-Dummheit eine Java-Dummheit
pr?sentieren. Schei?e wird nicht kleiner, wenn man ein UML-Diagramm
für den Darm malt, der sie produziert hat. -- [Kristian K?hntopp]

"Never underestimate the bandwidth of a station wagon full of
tapes hurtling down the highway" -- [Andrew S. Tanenbaum]

Wenn Personal Firewalls die L?sung sind,
will ich das verdammte Problem zurück. [Robin S. Socha]

While the IBM 650 was not a super-hot machine, it did have one feature that
made it sell [...] lots of blinking lights. [...] Some authors attribute
the
success of IBM to these blinking lights [...]
-- [
]

Whoever said, "Hire the handicapped; it's fun to watch 'em," never had to
work
in IT holding the hands of morons.
[

]

7. Mitarbeiter (...) Jeder Mitarbeiter sollte stolz darauf sein, bei SuSE
zu
arbeiten und sollte sich mit den betrieblichen Grunds?tzen
(Professionalit?t,
Kundenorientierung und eine offene und transparente Kommunikation gem?? den
Betriebsleitlinien) identifizieren. (...)
[
]

It's astounding, time is fleeting, madness takes its toll.

+--------------------+
| DAS IST KEIN HAUS! |
+--------------------+

"Multiple exclamation marks," he went on, shaking his head,
"are a sure sign of a diseased mind." -- [Terry Pratchett]

"The people who created MIME not only should be convicted, they should
be shot on the spot." [Linus Torvalds on linux-kernel 1996/05/15]
<Pine.LNX.3.91.960515095405.27927F-100000@...>

"Gerade gestern habe ich mich bei Slashdot wieder gefragt, ob das nicht
schlimmer als die Todesstrafe ist, wenn man Informatik Prof in Utah ist
und ein Gericht einen als Experten benennt, der sich den Windoze Quell-
code anschauen mu?." [Felix von Leitner in dasr 2002/02/23]

"Everybody knows you've been discreet,
but there were so many people you just had to meet
without your clothes
And everybody knows." [Leonard Cohen]

"Mit Verlaub Herr Pr?sident, Sie sind ein Arschloch!" -- [Josef Fischer]

Heute schon Deine IntEDV umarmt? Already hugged your Internal IT today?

Good, Fast, Cheap: Pick any two (you can't have all three). RFC 1925

Heckler & Koch: The original point?n?click interface.

S.E.I.F.E.: Synthetic Electronic Individual Fabricated for Exploration

MCSE: Microsoft-Compatible Spongiforme Encephalitis

Wenn ich eine SuSE-CD an ein Schwein binde und dieses trete, laufen
KDE & Co. auch ohne RAM recht schnell.
--Robin S. Socha in de.comp.os.unix.linux.newusers--

"Was meinen wir mit offener und transparenter Kommunikation?
Offenheit: Wir halten nicht unn?tigerweise Informationen zurück!
Transparenz: Wir legen unsere Entscheidungswege offen!
Ehrlichkeit und Verl??lichkeit: Wir sagen was wir meinen und stehen zu
dem
Gesagten!" <
>

"Q: Wie sind Deine ersten Eindrücke hier?
A: Zun?chst fühlt man sich etwas gehandicapped - Ich komme aus einer funk-
tionierenden und zuverl?ssigen Windows NT-Welt [...]"
<
>

"Q: Wie kommst Du mit der Software hier klar?
A: Ich benutze Excel bei der Arbeit. [...]"
<
>

If Java had true garbage collection, most programs would delete themselves
upon execution. [Robert Sewell]

Karneval ist die j?hrliche ?berdosis Abführmittel für Spie?er mit
chronischer Verstopfung. [Jens Grivolla]

Get back there in front of the computer NOW. Christmas can wait.
-- Linus "the Grinch" Torvalds, 24 Dec 2000 on linux-kernel

Yeah, yeah, it's 7PM Christmas Eve over there, and you're in the middle of
your Christmas dinner. You might feel that it's unreasonable of me to ask
you to test out my latest crazy idea. How selfish of you.
Get back there in front of the computer NOW. Christmas can wait.
-- Linus "the Grinch" Torvalds, 24 Dec 2000 on linux-kernel

Elektrosmog my ass. Wenn ich mal in's Keyboard beisse, dann wegen den
Unmengen an Kaffee, Zigaretten und dem ungesunden Essen, nicht wegen
diesem Esoterikschrott. [Jonas Luster]

"Du bist ein Dummer Haufen Luserscheisse. Deine Praesenz ekelt mich an,
ich muss mich uebergeben, wenn ich nur daran denken, dass Penner wie
Du auf das Netz, das ich liebe und heilige losgelassen werden."
[Jonas Luster zu Bernd Haug in dasr]

"Geh' fort. Geh' ganz weit fort. Paare Dich mit den anderen Wuersten in
microsoft.ALL und detebe, verschone mich, uns, diese Newsgruppe von
Deine Luserfresse, JETZT!" [Jonas Luster zu Bernd Haug in dasr]

"Du bist so scheisse, selbst das benutzerfreundlichste OS hasst Dich,
Mikrowellen schalten automatisch auf GRILL, wenn Du vorbeilaeufst,
denn selbst unanimierte Gegenstaende wuerden es hassen, wenn Du Dich
fortpflanzen koenntest." [Jonas Luster zu Bernd Haug in dasr]

BIND geh?rt genauso zum RL wie Fu?ballbundesliga.
Die einen haben Premiere abonniert, die anderen de.comp.security.firewall.
[Christoph von Nathusius in dasr]

"Ich muss weg!" [unbekannter Manager bei TV total]

"Es ist in Ordnung, wenn Du eine andere Meinung hast über das, was Du für
wichtig h?ltst. talk aber ist der einzige Platz dafür, die Meinung der
anderen darüber zu ignorieren." [Roman Drahtmüller am 10.4.2001 auf
talk]

"Das Neu starten eines Unix Rechners kann sehr schmerzhafte Folgen haben,
je nachdem wie schwer das naechste greifbare Buch ist, welches ihnen dann
an den Kopf fliegt." -- frei nach einer sehr alten c't

AOL-Kunden koennen keinen Videorecorder programmieren.
AOL-Kunden haben maximal 6 weitere Haushaltsangehoerige.
AOL-Kunden brauchen beide Haende, um 4 von 7 zu subtrahieren.
AOL-Kunden sind einfach drin. Hoffentlich bleiben sie da.

f u cn rd ths, u mst hv bn sng nx

"Da ich Pressemeldungen nur noch per Subject lese, l"auft mein Gehirn auch
nicht Gefahr, von meinem Dickdarm aus Verzweiflung erdrosselt zu werden"
-- [Daniel Bischof]

No matter how good she looks, someone else is sick and tired
of putting up with her shit.

I saw a woman wearing a sweatshirt with 'Guess' on it. I said, "Implants?"

Why is it that most nudists are people you don't want to see naked?


An expert is a person who avoids the small errors
as he sweeps on to the grand fallacy.
-- Benjamin Stolberg




Tech Support: "How may I help you?"
Customer: "I'm writing my first email."
Tech Support: "Ok, what seems to be the problem?"
Customer: "Well I can get the 'a'. But how do I put the circle around
it?"


All you have to decide
is what to do
with the time that is given to you
-- Gandalf at The Lord of the Rings


Yesterday,
All those backups seemed a waste of pay.
Now my database has gone away.
Oh I believe in yesterday.

Suddenly,
Tere's not half the files there used to be,
And there's a milestone hanging over me
The system crashed so suddenly.

I pushed something wrong
What it was I could not say.

Now all my data's gone
and I long for yesterday-ay-ay-ay.

Yesterday,
The need for backups seemed so far away.
I knew my data was all here to stay,
No I believe in yesterday.




Nuke Operator (16. Dezember 2003 23:22)

LE Big Macke schrieb am 16. Dezember 2003 20:12

> NCC-1701-A zum Bleistift?

Der Fileserver - unendliche Weiten...
Wir schreiben das Jahr 2004.
Dies sind die Abenteuer des Raumschiffs Nterprise,
Das mit seiner 400 Mann starken Besatzung fünf Jahre lang unterwegs
ist, um neue Software zu erforschen, neues Sourcen und neue Binaries.
Viele Kilobits vom User entfernt, dringt die Nterprise in
Verzeichnisse vor, die nie ein Mensch zuvor gesehen hat.




USB is for mice, FireWire is for men!


Boy, backups sure are a lot faster
since I linked /dev/st0 to /dev/null...


A computer is like an air conditioner.
It stops working when u open windows.


Was ist eine blondine mit gef?rbten Haaren?
Künstliche Intelligenz


An der Kinokasse h?ngt ein Schild:
Sonderpreis! Soldaten nur ein Euro!
Geht die blonde Susi hin, legt zehn Euro auf den Tisch und s?uselt
err?tend:
"Bitte zehn von der Marine ...!?"

--
*Dave - W?LEV*
*Just Let Darwin Work*

So - the Right-Hand-Rule applies to antennas as well....?

On 8/17/20 7:36 AM, Stephen Laurence wrote:

I seem to recall from the distant past, reading instructions for one of the early hobby vna devices about this.
The software with the vna (mandatory pc to use it) could automatically readjust the response. The demonstration was an ssb sideband filter with input and output inpedance of several 100ohms. The initial result seemed to be a poor filter with maximum skirt attenuation of only 20db but after the corrections were applied, was the expected 80+ db. This was at hf of course.
What was going on? Can this sort of correction be applied. How do I assess a filter with several hundred ohm in and out impedance, or do I resort to a spectrum analyser with tracking generator ( do not have one) or noise source, which is what I have done in the past. I still have that kit ( does 0-120mhz using a scope for display) for posterity.
Is this an opportunity for a firmware ( or saver) addition?

There's a couple ways to approach this:
1) make a test fixture and cal kit that has 100 ohm loads - run the cal, and it should automatically fix everything - I would be concerned that various displays wouldn't "know" about 100 ohms, so displays of R and X would be wrong, even if S11, S21 are correctly displayed. The "center" of the Smith chart would be 100 ohms.

2) calibrate with 50 ohms, and post process to change to 100 ohms - one could implement such a thing in a program like NanoVNA-Saver, and that's probably the cleanest way.


Ultimately, though, for both of these the measurement uncertainty will maybe be slightly worse - the "bridge" in the NanoVNA is designed for 50 ohms, so you'll always get reflected power and the transmitted power will always be less - How that would quantitatively affect your results, I can't say.

3) build a test fixture that has a 2:1 impedance transformation (non trivial, since it's a transformer with a 1.414:1 turns ratio).
Now you're back to sort of a #1 scenario.


I note that this is of some interest to people making measurements on twisted pair cables (i.e. Cat 5), since they're 100 ohm nominal impedance balanced. And a TDR is a great thing for finding places where the installer bent the cable too tightly or some similar problem.


On a fancy analyzer, they'll provide software inside to change the reference impedance, so you can do a cal with 50, measure 100, display with 100, or any other combination. Here, I think NanoVNA-Saver is the right kind of place. Keep the inexpensive box with limited firmware space simple. Put the fancy features in software that can run on any platform.

Yes, I used to know that.
But having radiation described as the result of an accelerating charge
got me thinking about it in a new way.
I guess that creates a magnetic field around the dipole wires,
which then begets an electric field when it collapses and off it goes.

Jerry, KE7ER

On Mon, Aug 17, 2020 at 12:34:21AM +0000, KENT BRITAIN wrote:

Takes a bit to think of your Yagi antenna as a 50 to 377 Ohm impedance transformer.
And if you are building Stealth aircraft, you want them to look like 377, not 50 Ohm dummy loads!

So you are saying a Yagi is a transformer with multiple taps? :)

The intention of the following:

1) ALL TRANSMISSION LINE(s): Fields close onto themselves. The system is
self contained as far as the fields are concerned.

2) ANTENNA(s): Fields open onto space (hopefully free space). The system
is open and not self contained regarding generated fields.

Dave - W?LEV

On Mon, Aug 17, 2020 at 1:48 AM Jerry Gaffke via groups.io <jgaffke=
[email protected]> wrote:

Roger and Jim.

I looked at Roger's png first, and that does explain why a dipole radiates
and a transmission line does not.
Will dig into Jim's antenna book when I have a chance.

Many thanks for the quick answers to a complicated question.

Jim wrote:

You would have problems in other senses, some of which manifest in what

you might call efficiency.

The radiation resistance gets very low, so the current, for a given

radiated power, gets very high.

So, for a "real antenna" that has ohmic loss, that becomes a big

fraction of the "power at the terminals"

A transmission line with an open at the end has zero current and maximum
voltage there.
A very short dipole would be a minor step away from that case,
Seems the impedance into such a short dipole should be very high and the
antenna current thus very low.
Though Jim used the phrase "for a given radiated power", which complicates
things some.

Guess I better read that book.

Jerry, KE7ER

--
*Dave - W?LEV*
*Just Let Darwin Work*