Re: At which point do we take the value of impedance to tune an antenna?
For a parallel resonant circuit there are three different definition of resonance (Nelson
M. Cooke, "Mathematics for Electricians and Radiomen," McGraw-Hill, 1942, page 478):
1. The frequency at which the parallel circuit acts as a pure resistance;
2. The frequency at which the line current becomes minimum;
3. The frequency at which the inductive reactance equals the capacitive reactance.
For a high-Q circuit, the differences may be negligible, but for a low-Q circuit, they
may be of sufficient value to be important.
For a series circuit all three values are coincident in frequency.
73,
Maynard
W6PAP
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On Sunday, August 14, 2022 07:46:28 PM Jerry Stuckle wrote: Sorry for the late reply but I've been away.
There is only one definition of resonance - that where the reactive
component of the impedance is zero. That is true for ANY AC circuit -
including antennas.
But you're correct in that it might not matter much. While a 3:1 SWR will
cause transmitters to cut back, it's only a 25% power loss or about 1.25db.
When you consider 1 S-Unit is 6db (ideally), that's about the width of the
needle on many S-meters. Nothing noticeable except in the most extreme
conditions.
No, a 1:1 SWR may not occur and won't in most antennas. But don't count on
the lowest SWR being at resonance - in fact, very few antennas will have a
50 ohm impedance at resonance without some type of matching network.
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Re: At which point do we take the value of impedance to tune an antenna?
Sorry for the late reply but I've been away.
There is only one definition of resonance - that where the reactive component of the impedance is zero. That is true for ANY AC circuit - including antennas.
But you're correct in that it might not matter much. While a 3:1 SWR will cause transmitters to cut back, it's only a 25% power loss or about 1.25db. When you consider 1 S-Unit is 6db (ideally), that's about the width of the needle on many S-meters. Nothing noticeable except in the most extreme conditions.
No, a 1:1 SWR may not occur and won't in most antennas. But don't count on the lowest SWR being at resonance - in fact, very few antennas will have a 50 ohm impedance at resonance without some type of matching network.
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I recently purchased an SV4401A from Aliexpress for $299. As a lab instrument, it is very nice, a giant step up from the F-V2. With up to 1001 data points, the sweep resolution is great. The N connectors are nice too, though a cal set of N types would have topped it off. It has mass and is ruggedly built, inside and out. The batteries are replaceable without soldering.
My unit has two serious issues, which I am trying to work through with the tech guy at Sysjojnt, who also developed the V2. The software nanovna-saver is picky about which Win10 pcs it'll run on. I get a failed to execute script msg. Strangely it runs on my cheap tablet and a desktop at work. Three others will not work. I am not a pc or Windows expert. Maybe there is a setting that will let it run? The other issue I have is that, when left off for a while unplugged, it will not boot. Instead, it cycles through a power on sequence indefinitely. The batteries are fully charged. So to take it outside I must bring a 5VDC power source with type C USB connector. Whether these problems are design flaws or just with my unit remains to be seen.
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Re: look what I found at Goodwill
When I was in high school, one of my buddies ordered the brand new Texas Instruments SR-50 scientific calculator. $150 back in 1974.
I saw a calculator with the same capabilities, plus the ability to do calculations in binary, octal, and hexadecimal (like the TI Programmer) in a dollar store calculator.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Maynard Wright, P. E., W6PAP via groups.io Sent: Sunday, August 14, 2022 1:46 PM To: [email protected]Subject: Re: [nanovna-users] look what I found at Goodwill My first scientific calculator, a CompuCorp 324G (which still works fine) was not an RPN device. When I bought my first RPN calculator, an HP-21, I was doing some assembly programming, and RPN seemed to fit right in with that, pushing and popping the stack, so I was pretty happy with RPN and my usual calculator today is an HP 32S II. But I haven't abandoned slide rules. I have about 75, including an Emeloid Smith Chart slide rule which is pretty handy. 73, Maynard W6PAP On Sunday, August 14, 2022 09:44:18 AM John Stewart, wa3jrs via groups.io wrote: I always felt a little smug using RPN on the HP¡¯s (mine was the HP 41cv) - like I was inputting data and commands the way the processor was seeing it. John, wa3jrs On Aug 14, 2022, at 9:20 AM, PhilKE3FL via groups.io
<sweepspk@...<mailto:sweepspk@...>> wrote:
?You and me both Stan, as soon as programmable calculators came out
I got my first HP calculator, I still have the last one I bought, an
HP48, and I now have an HP41 emulator on my smart phone, one of the
best HP calculators, IMHO, except for the crummy case, which is not
a problem with an emulator ;-) The only problem is that I can't save
the programs to phone memory so I'm stuck with what is in the calculator's memory.
The HP67 calculator emulator does have a way to save & recall
programs from phone memory. A very nice touch. But, the HP67 doesn't
have alpha for prompting or for output IDing. So I have to document
that in a text file for when I forget.
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Re: look what I found at Goodwill
My first scientific calculator, a CompuCorp 324G (which still works fine) was not an RPN
device. When I bought my first RPN calculator, an HP-21, I was doing some assembly
programming, and RPN seemed to fit right in with that, pushing and popping the
stack, so I was pretty happy with RPN and my usual calculator today is an HP 32S II.
But I haven't abandoned slide rules. I have about 75, including an Emeloid Smith Chart
slide rule which is pretty handy.
73,
Maynard
W6PAP
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On Sunday, August 14, 2022 09:44:18 AM John Stewart, wa3jrs via groups.io wrote: I always felt a little smug using RPN on the HP¡¯s (mine was the HP 41cv) -
like I was inputting data and commands the way the processor was seeing it.
John, wa3jrs
On Aug 14, 2022, at 9:20 AM, PhilKE3FL via groups.io
<sweepspk@...> wrote:
?You and me both Stan, as soon as programmable calculators came out I got
my first HP calculator, I still have the last one I bought, an HP48, and
I now have an HP41 emulator on my smart phone, one of the best HP
calculators, IMHO, except for the crummy case, which is not a problem
with an emulator ;-) The only problem is that I can't save the programs
to phone memory so I'm stuck with what is in the calculator's memory.
The HP67 calculator emulator does have a way to save & recall programs
from phone memory. A very nice touch. But, the HP67 doesn't have alpha
for prompting or for output IDing. So I have to document that in a text
file for when I forget.
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Re: Pitfalls of measuring components with the NanoVNA
#measurement
On Sat, Aug 13, 2022 at 04:07 PM, AG6CX wrote:
Roger-
I¡¯m looking at an older post concerning S phase and Impedance phase, where
you plot the graph and note that they are zero at an identical frequency, but
different otherwise.
I have been looking for a reference on that very topic, and wonder if you have
one?
I do not have a specific reference on this topic. I wrote something on this subject a while ago and have attached it to this post.
Was that condition unique to that particular just experiment? Or is a
generalization that true resonance, as implied by the frequency at which
impedance crosses from negative to post Is also defined by the frequency at
which S phase crosses zero?
Whenever the reactance (X) becomes 0 the S11 phase angle will be 0 degrees or 180 degrees (depending on the value of R). Take a look at the horizontal axis of the Smith chart for a 50 ohm reference impedance. For R<50 and X=0 the S11 phase angle will be 180 degrees and for R>50 and X=0 it will be 0 degrees. For example a dipole greater than .18 wavelengths above ground will have R > 50 at resonance (X=0) so the S11 phase angle will be 0 degrees. Lower than .18 wavelengths R is less than 50 so at resonance S11 phase angle will be 180 degrees. The impedance angle, which is not plotted on the NanoVNA, is the arctangent (X/R) will require some additional calculation in another program (like a spreadsheet). Attached is a measurement of an inductor before and after resonance. The S11 phase angle and impedance phase angle are on one plot for comparison. Note that R in this case is >50 so S11 will be 0 at resonance
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Re: This thread should be a whitepaper in downloads when closed.
Hi Folks,
Every time you change any information on an existing Subject line, it becomes a new topic.
(Even adding a space between words.)
If you want to address the contents of an existing thread, you need to do it as a ¡°reply¡± within the original thread, otherwise a new ¡°orphan¡± thread will be created.
Larry
AC9OX
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Re: This thread should be a whitepaper in downloads when closed.
Which thread is that?
--
VY 73,
Wes WB7BR
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Re: look what I found at Goodwill
I always felt a little smug using RPN on the HP¡¯s (mine was the HP 41cv) - like I was inputting data and commands the way the processor was seeing it.
John, wa3jrs
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Show quoted text
On Aug 14, 2022, at 9:20 AM, PhilKE3FL via groups.io <sweepspk@...> wrote:
?You and me both Stan, as soon as programmable calculators came out I got my first HP calculator, I still have the last one I bought, an HP48, and I now have an HP41 emulator on my smart phone, one of the best HP calculators, IMHO, except for the crummy case, which is not a problem with an emulator ;-) The only problem is that I can't save the programs to phone memory so I'm stuck with what is in the calculator's memory.
The HP67 calculator emulator does have a way to save & recall programs from phone memory. A very nice touch. But, the HP67 doesn't have alpha for prompting or for output IDing. So I have to document that in a text file for when I forget.
--
Phil KE3FL
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Re: look what I found at Goodwill
You and me both Stan, as soon as programmable calculators came out I got my first HP calculator, I still have the last one I bought, an HP48, and I now have an HP41 emulator on my smart phone, one of the best HP calculators, IMHO, except for the crummy case, which is not a problem with an emulator ;-) The only problem is that I can't save the programs to phone memory so I'm stuck with what is in the calculator's memory.
The HP67 calculator emulator does have a way to save & recall programs from phone memory. A very nice touch. But, the HP67 doesn't have alpha for prompting or for output IDing. So I have to document that in a text file for when I forget.
--
Phil KE3FL
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Firmware to 1500 MHz Wich one ?
Hi,
Wich version is safe to update this item to 1500 MHz?
I know above 1100 MHz the measure is shit , but hey better something than nothing
Attachment of my nanovna here : (it's from AliExpress)
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This thread should be a whitepaper in downloads when closed.
Wow, this thread needs to be turned into a PDF. There is a lot of useful information on the offer. Thank you everyone!
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Correct. The Smith chart provides a very clear visualization of impedance transformations which are rotations in Argand space. Well worth learning to use it.
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Re: NanoVNA_H4 4.3_MS schematics
I reworked the NanoVNA-H4 Rev4.3 schematic to remove R44 from the NanoVNA-H4 Rev4.3. This resistor may damage U2 and the battery if the NanoVNA-H4 is not used for a long time and the battery is low. A similar problem was first seen with earlier versions of LiteVNA, newer versions of NanoVNA-H4 are sold with this resistor removed, if your NanoVNA-H4 Rev4.3 has this resistor installed, it is recommended to remove it.
In addition, using a ferrite bead or inductor instead of R93 can improve SD compatibility, you can also try to short-circuit R93, but need to be careful not to hot-swap the SD card in the power-on state after making these changes.
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Re: Pitfalls of measuring components with the NanoVNA
#measurement
Roger-
I¡¯m looking at an older post concerning S phase and Impedance phase, where you plot the graph and note that they are zero at an identical frequency, but different otherwise.
I have been looking for a reference on that very topic, and wonder if you have one?
Was that condition unique to that particular just experiment? Or is a generalization that true resonance, as implied by the frequency at which impedance crosses from negative to post Is also defined by the frequency at which S phase crosses zero?
I have found limited references to the use of true resonances and antiresonances in antennas in the literature. If you have some links or articles or sources I¡¯d be most interested in reading up on them.
Thanks,
Ed McCann
AG6CX
Thanks
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Re: look what I found at Goodwill
your welcome. I have happy memories looking my sliderule too. On Sat, Aug 13, 2022 at 8:32 AM Steven LeBlanc <steven.leblanc@...> wrote: Dad had the same one. By the time I got to that point in school it was all
scientific calculators. But I would see dad at the dinning table hunched
over doing what he loved to do. I would crawl up on a chair beside him and
watch.I do believe Dad should be up for a Saint Hood. Working on something
important and having a 4 - 5 year old questioning everything I saw him do.
But he would pull my chair in close and try to explain this kind of stuff
to me. I'm sure in that time he taught me to use one but in all those
intervening years with Beer, Drugs, Beer, doing stupid crap and more beer I
forgot most of what I learned if not all of it. But this has brought back
some warm and fuzzy memories of the late 60's. Thanks for posting.
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Re: look what I found at Goodwill
Dad had the same one. By the time I got to that point in school it was all scientific calculators. But I would see dad at the dinning table hunched over doing what he loved to do. I would crawl up on a chair beside him and watch.I do believe Dad should be up for a Saint Hood. Working on something important and having a 4 - 5 year old questioning everything I saw him do. But he would pull my chair in close and try to explain this kind of stuff to me. I'm sure in that time he taught me to use one but in all those intervening years with Beer, Drugs, Beer, doing stupid crap and more beer I forgot most of what I learned if not all of it. But this has brought back some warm and fuzzy memories of the late 60's. Thanks for posting.
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Re: look what I found at Goodwill
I still have mine from 1971.
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I used one in college..45 years ago :-)
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Re: look what I found at Goodwill
Real nice. I wish I knew where mine disappeared to. Had a cheap plastic one and a good one (Pickett Brand??)
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vh2
Roger Need
Larry McElhiney
Wes WB7BR
F4WCV
Martin Glazer