Re: What is the resonate frequency of this?
On Tue, Sep 8, 2020 at 06:41 AM, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
This will be difficult to draw in an email, so I will describe it, too
鈥斺�斺�� R 鈥斺�擟鈥斺��-
| |
X鈥斺��- 鈥斺�斺�� X
| |
鈥斺�斺�� R 鈥斺�� L 鈥�-
1) C in series with R
2) L in series with R
3) Networks 1 and 2 above are in parallel
R=sqrt(L/C)
What鈥檚 the resonant frequency measured between the two X鈥檚 ?
If the components were ideal components there would be no resonant frequency. The "equivalent parallel reactance" of C and L would be equal and opposite at all frequencies and the impedance would be a constant value equal to the SQRT (L/C) +j0. But with practical components R would not precisely be the SQRT of L/C and L and C would change with frequency and resonance would happen with very low Q. Roger
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Re: Definition of resonance
Can someone please shed some light on the definition of resonance in
conjunction with an antenna.
I'll make an attempt.
Let's agree that "resonance occurs when +/- jX is zero".
It does not take knowledge of x-degree differential equation , modelling ,
size of wire , moon phase etc.
It is applicable to ANY AC circuit, antenna included.
True. The definition of resonance requires the capacitive reactance equals
the inductive reactance or: -jX = +jX. Since the two cancel eachother,
only real resistance remains at resonance. For an antenna in free space,
that resistance amounts to the sum of the radiation resistance plus loss
resistance in the conducting structure. In practice, losses in the field
return structure ("ground" or earth losses required in some installations
as in a 1/4-wavelength vertical) also contribute to losses.
Let's also agree that dipole , by definition resonant radiator, exhibits
APPROXIMATELY 50 Ohms impedance
at the center feed point. For a sake of simplification let's also agree
that variation of the center point impedance with - insert your favorite
parameter here - is not fundamental to the discussion .
A dipole is understood to be a resonant radiator. A doublet is a dipole
configuration with resonance structure outside the frequencies of interest,
but still exhibits resonance(s).
At typical amateur heights above soil surface, not DX antennas and
installations which are far above the typical amateur budgets, yes, 50-ohms
feed or radiation resistance of a dipole is in order.
Now for the punch line
By definition , ANY length of transmission line of characteristic impedance
will transfer impedance at the load - AKA terminal impedance EQUAL of
transmission line characvteristric impedance TO the input of such
transmission line.
Absolutely true. That's what the Smith Chart is all about. A coaxial
transmission line of known length and characteristic Zo acts as an
impedance transformer. In reality, why is the *antenna* terminal
impedance so important when it must be connected to a transceiver through
that coaxial transmission line (or any other transmission line)? What
really counts is the terminal impedance at the *station end* of the
transmission line! It's academically interesting for the design engineer
(like myself) to know the antenna terminal impedance just to verify the
results of putting the whole system through the Smith Chart exercise, but
from a strictly practical viewpoint what's really important is what the end
of the feedline presents to our station inside where its climatically
controlled. So, measure at the station end of the transmission line and
forget about the transformative properties of the transmission line.
Others: please don't flame me for that statement, but from a practical
standpoint, that's all that is important.
Place note - I am still using general terms, adding SPECIFICS - such as
velocity factor of RG58 coax is immaterial - for the sake of this
discussion.
Described ideal system ,for purpose of staying with basic, not woo-doo
electronics , with "real data of 50 Ohms substituted " parameters of
source impedance of 50 Ohms ,
transmission line of characteristic impedance of 50 Ohms
and load / antenna impedance of 50 Ohms
will PRIMARILY exhibit FUNDAMENTAL resonance @ ONE frequency.
IF these parameters are SAME and EQUAL on harmonics , resonance @
harmonics will be observed.
Yes, resonances at harmonically related frequencies to the fundamental
1/2-wavelengths will be present. However, they likely will not exhibit
the same resistance as the intended resonant frequency. Again, decouple
the concept of SWR from resonance!
Hope this helps just a little.....
Dave - W脴LEV
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On Tue, Sep 8, 2020 at 5:17 PM Anne Ranch <anneranch2442@...> wrote: Can someone please shed some light on the definition of resonance in
conjunction with an antenna.
Let's agree that "resonance occurs when +/- jX is zero".
It does not take knowledge of x-degree differential equation , modelling ,
size of wire , moon phase etc.
It is applicable to ANY AC circuit, antenna included.
Let's also agree that dipole , by definition resonant radiator, exhibits
APPROXIMATELY 50 Ohms impedance
at the center feed point.
For a sake of simplification let's also agree that variation of the center
point impedance with - insert your favorite parameter here - is not
fundamental to the discussion .
Now for the punch line
By definition , ANY length of transmission line of characteristic
impedance will transfer impedance at the load - AKA terminal impedance
EQUAL of transmission line characvteristric impedance TO the input of such
transmission line.
Place note - I am still using general terms, adding SPECIFICS - such as
velocity factor of RG58 coax is immaterial - for the sake of this
discussion.
Described ideal system ,for purpose of staying with basic, not woo-doo
electronics , with "real data of 50 Ohms substituted " parameters of
source impedance of 50 Ohms ,
transmission line of characteristic impedance of 50 Ohms
and load / antenna impedance of 50 Ohms
will PRIMARILY exhibit FUNDAMENTAL resonance @ ONE frequency.
IF these parameters are SAME and EQUAL on harmonics , resonance @
harmonics will be observed.
So if the load (antenna) impedance at random frequency NO LONGER matches
the transmission line characteristic impedance - everything else staying
same , balum or no balum, you see the results.
.
--
*Dave - W脴LEV*
*Just Let Darwin Work*
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If the nano follows the HP network analyzers, it doesn't matter what the order is until after DONE is pushed...
..even if you did one of the conditions over again.
Does it matter with the nano? At least using 2019 nanoVNA firmware, order DOES matter: the device is making the "next" measurement until that expected button is pressed. If an unexpected button is pressed, current device data is for the expected button.
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Re: Definition of resonance
Anne,
I think your central point is that with a 50+j0 ohm load and a 50 ohm transmission line,
the transmitter sees a 50 ohm impedance looking into the coax regardless
of the length of the coax. That is correct.
The question is, what happens when the antenna itself is not being used at its
resonant frequency, so it has significant inductive or capacitive reactance?
In this case, a carefully chosen length of coax can rotate the antenna impedance
around the smith chart center point until the impedance seen by the transmitter
is purely resisitve. And thus the system of coax plus antenna is resonant.
However, the pure resistance seen by the transmitter is not likely to be 50 ohms.
Alternately, you can have whatever length of feedline is convenient,
and use an antenna tuner at the transmitter end to make the entire system
of antenna tuner plus feedline plus antenna be resonant, presenting the
transmitter with a pure 50 ohm resistance.
None of the above methods has an inherent inefficiency, it all comes down
to the quality of components.
A matching network placed at the antenna feedpoint to make the coax
see 50+0j ohms will have some losses, often mostly due to resistance in the inductor.
An antenna tuner at the transmitter end transforms the impedance in exactly the same way,
the only extra loss is that reflections may make several round trips through the coax before
going out the antenna, being attenuated with each trip.
Just a piece of coax also transforms the impedance, but in this case can only rotate it
around the center of the smith chart, so not as good a solution in the general case.
I'd say the system is resonant when the transmitter sees a pure resistance,
assuming resistive losses are not swamping out the complex impedance of the antenna.
And that the system is fully matched when the transmitter sees 50 ohms of pure resistance.
Jerry, KE7ER
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On Tue, Sep 8, 2020 at 10:17 AM, Anne Ranch wrote:
Can someone please shed some light on the definition of resonance in
conjunction with an antenna.
Let's agree that "resonance occurs when +/- jX is zero".
It does not take knowledge of x-degree differential equation , modelling ,
size of wire , moon phase etc.
It is applicable to ANY AC circuit, antenna included.
Let's also agree that dipole , by definition resonant radiator, exhibits
APPROXIMATELY 50 Ohms impedance
at the center feed point.
For a sake of simplification let's also agree that variation of the center
point impedance with - insert your favorite parameter here - is not
fundamental to the discussion .
Now for the punch line
By definition , ANY length of transmission line of characteristic impedance
will transfer impedance at the load - AKA terminal impedance EQUAL of
transmission line characvteristric impedance TO the input of such transmission
line.
Place note - I am still using general terms, adding SPECIFICS - such as
velocity factor of RG58 coax is immaterial - for the sake of this discussion.
Described ideal system ,for purpose of staying with basic, not woo-doo
electronics , with "real data of 50 Ohms substituted " parameters of
source impedance of 50 Ohms ,
transmission line of characteristic impedance of 50 Ohms
and load / antenna impedance of 50 Ohms
will PRIMARILY exhibit FUNDAMENTAL resonance @ ONE frequency.
IF these parameters are SAME and EQUAL on harmonics , resonance @ harmonics
will be observed.
So if the load (antenna) impedance at random frequency NO LONGER matches the
transmission line characteristic impedance - everything else staying same ,
balum or no balum, you see the results.
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Re: Has OneOfEleven gone again?
This is a very lame post.
Your behaviour is the reason devs like 1of11 are not fully sharing their
work.
I suggest you to have some respect.
A ter莽a, 8/09/2020, 14:22, <gary.sewell@...> escreveu:
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I just downloaded the latest build yesterday and today I get the Error 404
that page does not exist again.
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Re: Definition of resonance
Can someone please shed some light on the definition of resonance in conjunction with an antenna.
Let's agree that "resonance occurs when +/- jX is zero".
It does not take knowledge of x-degree differential equation , modelling , size of wire , moon phase etc.
It is applicable to ANY AC circuit, antenna included.
Let's also agree that dipole , by definition resonant radiator, exhibits APPROXIMATELY 50 Ohms impedance
at the center feed point.
For a sake of simplification let's also agree that variation of the center point impedance with - insert your favorite parameter here - is not fundamental to the discussion .
Now for the punch line
By definition , ANY length of transmission line of characteristic impedance will transfer impedance at the load - AKA terminal impedance EQUAL of transmission line characvteristric impedance TO the input of such transmission line.
Place note - I am still using general terms, adding SPECIFICS - such as velocity factor of RG58 coax is immaterial - for the sake of this discussion.
Described ideal system ,for purpose of staying with basic, not woo-doo electronics , with "real data of 50 Ohms substituted " parameters of
source impedance of 50 Ohms ,
transmission line of characteristic impedance of 50 Ohms
and load / antenna impedance of 50 Ohms
will PRIMARILY exhibit FUNDAMENTAL resonance @ ONE frequency.
IF these parameters are SAME and EQUAL on harmonics , resonance @ harmonics will be observed.
So if the load (antenna) impedance at random frequency NO LONGER matches the transmission line characteristic impedance - everything else staying same , balum or no balum, you see the results.
.
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Re: What is the resonate frequency of this?
Correction:
Inductive impedance is positive, capacitive impedance is negative.
So scanning through a quartz crystal from high frequencies to low,
the impedance is positive, then negative between series and
parallel resonance, then again positive.
(Though the current phase angle is negative, positive, negative.)
Jerry, KE7ER
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On Tue, Sep 8, 2020 at 07:56 AM, Jerry Gaffke wrote:
If you check the impedance on your nanovna you will see that it is inductive
at frequencies
above series resonance, so an impedance with a phase angle near -90 degrees.
The phase angle flips to +90 degrees (capacitive) between series and parallel
resonance
as you reduce the frequency.
Then flips back to -90 degrees below the parallel resonant frequency.
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Re: What is the resonate frequency of this?
On Tue, Sep 8, 2020 at 06:41 AM, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
This will be difficult to draw in an email, so I will describe it, too
鈥斺�斺�� R 鈥斺�擟鈥斺��-
| |
X鈥斺��- 鈥斺�斺�� X
| |
鈥斺�斺�� R 鈥斺�� L 鈥�-
1) C in series with R
2) L in series with R
3) Networks 1 and 2 above are in parallel
R=sqrt(L/C)
What鈥檚 the resonant frequency measured between the two X鈥檚 ?
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Re: Has OneOfEleven gone again?
Thanks. I just noticed site was back up.
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Re: What is the resonate frequency of this?
Regarding a quartz crystal, another puzzle is the characteristic impedance over frequency.
If you check the impedance on your nanovna you will see that it is inductive at frequencies
above series resonance, so an impedance with a phase angle near -90 degrees.
The phase angle flips to +90 degrees (capacitive) between series and parallel resonance
as you reduce the frequency.
Then flips back to -90 degrees below the parallel resonant frequency.
Very curious.
The solution to that conundrum has to do with the basic behavior
of L and C in series and in parallel.
In series at high frequencies the L dominates
because it is what mostly restricts any current.
At series resonance the circuit has a very low impedance, near zero ohms.
In parallel at high frequencies, the C dominates because all the current
goes through the C instead of the L.
At parallel resonance the circuit has a very high impedance.
I'm sure all the analog design folks here find this rather trivial.
But I had to sit and think about off-frequency phase angles
for longer than I'd care to admit.
Jerry, KE7ER
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On Tue, Sep 8, 2020 at 07:11 AM, Jerry Gaffke wrote:
More interesting is the model of the quartz crystal resonator,
consisting of a series R,Lm,Cm in parallel with a Cp
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Re: Has OneOfEleven gone again?
On Tue, 2020-09-08 at 06:09 -0700, gary.sewell@... wrote: I just downloaded the latest build yesterday and today I get the
Error 404 that page does not exist again.
There for me right now. New app build today.
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DiSlord,
After playing more with the interface I now see that you can select into the STOP frequency button to manually set this. Up to this point it was using the current marker location to create a new STOP point when I would select this. My assumption was that the NanoVNA starts off the interface at the maximum readable bandwidth and then you narrow it from there. My apologies for not investigating this button further, thanks for the suggestions all!
-River
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Re: What is the resonate frequency of this?
Yes, the R's have no effect on resonant frequency.
They do lower the Q.
More interesting is the model of the quartz crystal resonator,
consisting of a series R,Lm,Cm in parallel with a Cp
The R,Lm,Cm are due to the physical properties of the quartz,
with Lm being extremely huge, perhaps a Henry or so, and Cm being very small.
That is the primary series resonance of the quartz.
Cp is a few pF, due to the plates on each side of the quartz for the electrical connection,
plus any packaging and wiring and IO cells at any device IC it is hooked up to.
I recently spent half a day scratching my head figuring out why
the parallel resonance came about, and why it was so near the series resonant frequency.
When the frequency rises a little bit from series resonance, there's a uH or so
of Lm that does not get canceled out by Cm, and that uH becomes resonant
with Cp to create the parallel resonant frequency.
Jerry, KE7ER
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On Tue, Sep 8, 2020 at 06:55 AM, John Baines wrote:
My first guess was that the resonant frequency is unchanged by any value of R,
though Q is certainly changed.
A quick drawing of the vector diagram seems to agree with this.
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On Tue, Sep 8, 2020 at 06:24 AM, <river@...> wrote:
John,
Just installed the firmware version you recommended, but I still am seeing a
default stop frequency of 900MHz. Is there a setting I need to change so that
I can measure frequencies beyond 900MHz?
-River
Enter as stop frequency more bigger value?
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Re: What is the resonate frequency of this?
On 2020-09-08 14:41:+0100, you wrote: This will be difficult to draw in an email, so I will describe it, too Good question, David. Perhaps you could have typed it in using a fixed width font? My email does this. Perhaps not UTF8? I usually send plain text, but am sending this in hopes that it will come thru OK. It seems that you want (please view in fixed width font) 触枣搁枣颁枣颁枣触 X梶 |� X 触枣搁枣尝枣尝枣触 触枣搁枣颁枣颁枣触 X梶 |� X 触枣搁枣尝枣尝枣触 1) C in series with R 2) L in series with R 3) Networks 1 and 2 above are in parallel R=sqrt(L/C) What抯 the resonant frequency measured between the two X抯 ? Your email to me was a real disaster ;-) because of prop fonts and UTF... This still leaves the question... ;-) Kindly Rich -- 72/73 de Rich NE1EE On the banks of the Piscataqua
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Re: What is the resonate frequency of this?
My first guess was that the resonant frequency is unchanged by any value of R, though Q is certainly changed.
A quick drawing of the vector diagram seems to agree with this.
73
John
M0JBA
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On 8 Sep 2020, at 14:41, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:
This will be difficult to draw in an email, so I will describe it, too
鈥斺�斺�� R 鈥斺�擟鈥斺��-
| |
X鈥斺��- 鈥斺�斺�� X
| |
鈥斺�斺�� R 鈥斺�� L 鈥�-
1) C in series with R
2) L in series with R
3) Networks 1 and 2 above are in parallel
R=sqrt(L/C)
What鈥檚 the resonant frequency measured between the two X鈥檚 ?
--
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
|
What is the resonate frequency of this?
This will be difficult to draw in an email, so I will describe it, too
鈥斺�斺�� R 鈥斺�擟鈥斺��-
| |
X鈥斺��- 鈥斺�斺�� X
| |
鈥斺�斺�� R 鈥斺�� L 鈥�-
1) C in series with R
2) L in series with R
3) Networks 1 and 2 above are in parallel
R=sqrt(L/C)
What鈥檚 the resonant frequency measured between the two X鈥檚 ?
--
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
|
John,
Just installed the firmware version you recommended, but I still am seeing a default stop frequency of 900MHz. Is there a setting I need to change so that I can measure frequencies beyond 900MHz?
-River
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Francisco,
The ttrftech reop only contains H and earlier firmware so you have no issue with installing anything from there on to your Nanovna.
Hugen makes versions for H and H4 but they all have H or H4 in the filename.
If you want, you can carefully lift the LCD out of its frame and touch up the soldering of the ribbon cable under it as sometimes, the solder cracks.
good luck!
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On Monday, September 7, 2020, 11:58:22 p.m. EDT, Francisco Gonzalez <franciscoti5lx@...> wrote:
I try several firmware at but issue remains. Also I cant tell if those are for H or H4.
In other place I found one still old (0.4.5-4 ) with a clear indication for H version ( NanoVNA-H_AA_20200118 ) by聽 Hugen79 and ended with that one.
I come to the conclusion the touch is defective however I can still navigate with no issues from the knob.
Thanks a lot for the help. I learned a lot with this experience.
I will order an H4 version.
One last question how do you know if the ones at ttrftech are for H or H4 ?
Thanks
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Re: Definition of resonance
On 2020-09-08 02:08:-0700, Mike Brown wrote: There's also a question about height, at least for modelling. The antenna would have to be very, very tight or be supported along its length to remain 1m above ground. Is that the case or is it a V shape with higher ends? I have a spreadsheet that I use...developed after much research into the subject of sag and tension... I set it up for a nominal Synthetic Textiles support rope - 5mm and antenna for a support span of 20 m (the antenna is 16 m) and a sag of 0.2 m the tension is 1.2 kg. I used this when I installed my 40 m EF supported on 60 m of the same 5 mm. It correctly calculates that I needed ~2 kg for a 1 m sag. -- 72/73 de Rich NE1EE On the banks of the Piscataqua
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Roger Need
Oristo
CT2FZI
Rich NE1EE
Dr. David Kirkby, Kirkby Microwave Ltd