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Re: Is there an Android app for the NanoVNA - WebUSB
thank you for the advice. I do so.
Both WebSerial and WebUSB are available in Google Chrome. When accessing this page, the application uses WebSerial or WebUSB. It tries to use WebSerial with priority. However, WebSerial is more experimental than WebUSB. WebSerial currently has fewer issues than WebUSB, but the API is not stable. The following is a summary from my own perspective. WebSerial: pros: There is no need to replace the USB driver. There are few cross-platform issues. cons: The API is not stable. #enable-experimental-web-platform-features is required. WebUSB is the opposite of WebSerial. That is: pros: Enabled by default (# enable-experimental-web-platform-features is not required) cons: API is stable (almost libusb itself) There are cross-platform issues. |
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Re: Is there an Android app for the NanoVNA - WebUSB
In my experience, developing for a wide range of Android devices is painful,On my phone, 5 tablet computers did not work. Just a white screen.I'm using Huawei P20 (Android 9). I don't have an old Android anymore ... so now only iOS.. I suggest bumping minSdkVersion up to much newer, since somewhat older Androids should be still able to use webusb. I don't think that you will like Play Store feedback from failing Android users. By the way, I do not understand how to try webserial vs webusb. |
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Re: Is there an Android app for the NanoVNA - WebUSB
Can you please add an exit or quit command to the menu so we do not have toI will add. Also, is it possible to create a standalone Android app so there is no needThe resource is in the application and Internet access is not required. In fact, we have confirmed that the application works without a network connection. However, I still have permission for INTERNET access. |
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Re: [SimSmith] Fake physics ?
Hi Pete,
Hi Ward, Thanks so much for your replies. Yes, Pete - you are 'a body'. I thought that would come ... First I was intended to use different wording, But then I though no, let it be "Everybody agrees ..." Why? As this little 'provoking' statement (sorry for that) helps us to demonstrate that majority (or minority) opinions do not change facts or physics. ¡°Voting¡± percentages will never be a guarantee for truth. This is what I wanted to show. Thanks, Pete for your good assistance. Otherwise the sun would still truly circle around the earth - as that was the majority opinion, be it false or not. But Pete, you haven¡¯t told us why you disagree and how things are better explained by your way of seeing it. Where do you find a 180¡ã phase shift in a straight forward complex voltage division circuit? If you do: That would contradict Kirchhoff¡¯s law for the sum of all currents flowing from/into a point to be zero. Rather, in a voltage divider circuit the current at all places is identical. Only wave action can change things a bit, as another aspect comes into it that wasn¡¯t existing in the pure complex voltage divider circuit. Conditions change, if waves come into it. True facts can be challenged, but not proven to be false. Else they are no facts. More generally: In science we have two levels of knowledge: One is facts. These we can find by experiments, if the conditions truly describe the question. Results are repeatable. And physical facts can mathematically be derived, based on so far proven knowledge. Most scientific debates have no problem with that, even if there should be somebody who does ¡ But as I said, forget percentages, please. We will never be able to convince everybody, anyway. Some would not even listen or even attempt to prove or disprove. Their opinion is unalterable like a doctrine in spite of any facts given, whatsoever. But doctrines are not necessarily facts. The second level of knowledge is the interpretation of the facts found. In this level we find, however, much disagreement, as the interpretation leaves room for imagination. Thus the results of the second level are theories, not more than that, until the interpretation is proven. But by what? Often it is the easier, more straight forward formula, based on prior proven facts - but not always. Sometimes ¨C as when complex numbers were introduced ¨C even math needs to be updated. But in the easy case of a complex voltage divider we don¡¯t need further updating than just using complex math. See the attached Word document for derivation as a proof. Yes Ward: Your question "Why is ... a typical reflected wave 180 degrees out of phase?" is absolutely adequate. Good question! Again please note, that such question is a question of interpretation, that is second level of the above. That is, why we now only can talk about interpretation and theory. And that is where we can have opinions and disagreement as long as there still is room for better interpretation. A true theory only can be considered a fact, after the interpretation of the physical experiment is confirmed mathematically by derivation. Indeed, the fact "a typical reflected wave is 180 degrees out of phase" can be confirmed by experiments, if conditions truly describe the question. That fact indeed is repeatable. Never (if truely it is a fact) the contrary does happen. Doubt the fact? Then show an instance of the contrary occurring. If you can't, you better accept it. (But expansion is different to contradiction: Sometimes there are many possibilities of expansion.) There are several experiments that do have the proper conditions, where we can measure it: Empirically: Take a pingpong ball. It¡¯s ¡°towards the wall¡± direction changes when reflected: The reflected direction is "minus" (that is 180¡ã) of the original direction. (Any sideways component stays). Electromagnetic waves: The reflection of a wave of a Yagi reflector or metal wall Lambda/4 behind a radiating fed element will give 6 dB (thus double) signal in the main direction: 90¡ã from fed element to reflector, 180¡ã by the reflection phenomenon, and another 90¡ã back from reflector to the fed element's place. There the reflected wave in total is just in phase (360¡ã) with the wave sent by the fed element. And yes: we measure 6 dB forward signal increase. That confirms in this experiment the 180¡ãphase shift by reflection. If still in doubt: Try EZNEC for simulation. EZNEC makes Maxwell¡¯s equations easily understandable. Similarly we can also show 180¡ã phase shift with reflected water waves or sound wave experiments, where instead of free electrons, molecules move against some reflecting thing like a wall. You can measure the phase of the echo to show the 180¡ã phase shift of the component going against the wall. But let's stay at electromagnetic waves and let's come to line behaviour: We will measure what can be confirmed by experiment as well as by derivation. Please find the derivations for both: Gamma type (a) at a line (or by equivalence, also at a wave guide) end ¨C with kind permission or Prof. Dr. Reinhard Stolle of Fachhochschule Augsburg, Department RF Technics, who did that for me on request. Sorry, I have not yet transferred it yet into printable (word type) character format. Please note that in his derivation Z2 is load and Z1 is the characteristic wave impedance. In the drawing you can see ¨C just as with a pingpong ball ¨C that the reflected V and I waves have the minus (=180¡ã of incident) direction. (Here come two pics. Some email programs will not put it here but attach it. Please see and use it here.) In contrast to the above: Gamma type (b) at a complex voltage divider circuit: Please see attached (Word) draft version, where ¡°red letters¡± is my own addition and ¡°black¡± is Prof. Dr. Reinhard Stolle¡¯s original, put into printable characters already. Later all will be black, as this is just a draft. But as the red part additionally deals with angle of Gamma, it is helpful, too. For power transfer only, the |Gamma| without the angle is fully sufficient, however. That black part is from Stolle. Please also understand the preliminary nature of what I send here. Both, experiment (measured results) and derivation (attached) confirm the fact of 180¡ã phase shift for reflected waves. And there is also what first only was a theory, but what was confirmed by such (and other) experiments: Maxwell's Equations. They apply for waves. They are since long accepted as scientific fact - I think at least. Do we agree? At least I use EZNEC for getting the results, and EZNEC uses Maxwell¡¯s equations. Ward, there is more to it. You said: I also fail to understand why replacing an entire circuit by its lumped equivalent invalidates and entire design philosophy. I think alternative design methodologies are quickly adapted when they prove useful. To not get this even longer, I try to be short: You calculate in SimSmith at each component the impedance and make further use of it from there on. So from then on that equivalent is a ¡°given¡± impedance ¨C no matter whether or not before there were lines and waves involved or not. The Th¨¦venin equivalent at a point is the same, generator-ways. Thus at each point an equivalent complex load terminates an equivalent generator¡¯s complex Th¨¦venin equivalent impedance. This is why the conditions of (b) apply: A complex impedance (equivalent) generator, terminated with a complex (equivalent) impedance. Two impedances meet. No wave/reflection formula, but the two impedances formula (voltage divider) is applicable. All wave stuff was already dealt with before. Is that so? To my limited understanding: Yes. And as you said: ¡°Power matters¡±. For power considerations (b) is the answer, while (a) is good for reflection-less aim, avoiding distortions, or suppressing reflections (stealth anti-Radar paint layer applications, to name some). (a): Gamma = (Z1 ¨C Z2) / (Z1 + Z2) with Z2 being the characteristic wave impedance of the line. ¡°Wave reflection at line end¡° case. Good approach for calculation, before the equivalent Th¨¦venin generator impedance is even known, as it doesn¡¯t even use or need that and Z2 has different meaning than in (b). Typical at the antenna feedpoint. (b): Gamma = (Z1 ¨C Z2*) / (Z1 + Z2) with asterisk meaning conjugate complex and Z2 the Th¨¦venin equivalent impedance of the generator side. ¡°Two impedances meet¡± case. Good for power matching generalized calculation purposes (with ?generalized¡± meaning other than perfect conjugate complex match ¨C often a very realistic case) Not forgotten: Smith Chart conformal mapping between Z (or Y) plane and Gamma plane is ONLY by (a). That shall be and stay as it is. No doubt, no change, by no means! The answer to that dilemma is: (a) will become (b), when the reactance of the (serial) generator Th¨¦venin equivalent impedance is moved to the load side. If we would change the Smith chart fundamentals, the real axis of the Z and Y planes would no longer be straight, but deformed and the conformal mapping would become incorrect. 73, Hans DJ7BA -----Urspr¨¹ngliche Nachricht----- Von: [email protected] <[email protected]> Im Auftrag von ward harriman Gesendet: Samstag, 5. Oktober 2019 05:36 An: [email protected] Betreff: Re: [SimSmith] Fake physics ? I¡¯m a little lost. Why is a typical reflected wave 180 degrees out of phase? I also fail to understand why replacing an entire circuit by its lumped equivalent invalidates and entire design philosophy. I think alternative design methodologies are quickly adapted when they prove useful. Ward On Oct 4, 2019, at 3:55 PM, Pete Singleton via Groups.Io < <mailto:pete_singleton@...> pete_singleton@...> wrote: OOPS! I think I just fed a troll. Sorry! PeteS On 04/10/2019 22:55, DJ7BA wrote: Yes, "Return Loss" s o m e t i m e s is a misnomer: If used in context with simply two different impedances meeting at a connection. This can be understood as a complex generator's inner (serial) impedance Z2 being terminated with a (serial) complex load Z1 (parallel to be recalculated to serial equivalent). This can be built from lumped components. Everybody will agree, that there is absolutely no "returning" of a "wave", and no "reflection", in what is just a complex voltage divider. Physically it is a different (no wave) phenomenon. In such cases, all the following are "misnomers" I n t h e s t r i c t s e n s e of the wording: Standing "Wave" Ratio, "Reflection" Factor, "Return" Loss. Reflections will, however, appear on Lines: there is a forward wave and a reflected wave. There is a (wave typical) 180¡ã phase shift by reflection involved, that makes valid Gamma = (Z1 - Z2) / (Z1 + Z2) (a) But where there are no waves, there are also no reflections and thus no 180¡ã phase shift. This is why we get a different formula. Please note, that Z2 above is the line's w a v e impedance - that does not exist in lumped circuits. There we need to use a different Gamma: Gamma = (Z1 - Z2*) / (Z1 + Z2) (b) with the asterisk meaning conjugate complex. Z2 here now means generator's inner impedance (Some call it Th¨¦venin Impedance.) Unfortunately so many well established papers and publications do not care for that difference between (a) and (b) , just very few do. And the many careless publications are being quoted and repeated ever so often. That is the problem. (Just the same as with fake news ...) So - for complex voltage dividers - that is where there are simply no waves involved - but also if one had previously calculated equivalent impedances on places with waves, like at line ends - thus whenever we are using a load impedance Z1 and an (equivalent) generator impedance Z2, the above (b) is the correct formula. The problem with the Smith Chart is, that the Z (or Y) Plane is mapped to the Gamma plane only by formula (a). It would be extremely bad to "reinvent" the Smith Chart. So we must live with (a) - like it or not. I see no choice. The good thing is: The same (Smith chart type) mapping formula can stay, if both (serial) reactances are combined together at the load side. Then the (thus new) generator impedance is real without reactance and the (thus new) load includes the sum of the two (serial) reactances. Then the conformal mapping formula (a) can be applied again as usual in the Smith Chart. We need the voltage divider type formula (b) when dealing with power transfer. But when will that become common knowledge? Debating fake physics (calculating with wave formulas where there are no waves and thus no no phase shift) is like fighting against windmills ... 73, Hans DJ7BA -----Urspr¨¹ngliche Nachricht----- Von: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> Im Auftrag von Oristo Gesendet: Freitag, 4. Oktober 2019 17:32 An: <mailto:[email protected]> [email protected] Betreff: Re: [nanovna-users] Return Loss 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).. -- Diese E-Mail wurde von Avast Antivirus-Software auf Viren gepr¨¹ft. <> -- Diese E-Mail wurde von Avast Antivirus-Software auf Viren gepr¨¹ft. |
Oristo
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