Suppose I measure with a millivoltmeter the voltage across D2. Is it correct then to set the vbat_offset parameter to the value just read ?
TNX
Alberto
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Re: Wireless control of NanoVNA
So, the solution is an IR link?
Let's get designing folks!
On Sun, 26 Jan 2020 at 12:16 PM, David Eckhardt<davearea51a@...> wrote: With an RF instrument such as a VNA that measures down into the "noise", an
RF source in immediate proximity to low-level electronics is NOT a good
idea!!? Compression of linear devices in the instrument are a real
possibility.? IM with instrument-produced RF is also a distinct reality.
The input of the VNA is "wide open" with no 'filtering' to eliminate stray
RF energy.? 2.4 or 5 GHz WiFi at +10 dBm in close proximity to the
electronics will completely spoil the operation of the VNA.? NO!? Bad
idea!!
Calibrate the VNA, attach it to the feedpoint of the antenna, raise the
antenna, and, well......? Better yet, as has been previously suggested,
read the impedance at the shack end of the feedline and propagate that
reading back to the antenna using SimSmith.
Dave - W?LEV
toggle quoted message
Show quoted text
On Sun, Jan 26, 2020 at 3:39 AM gmendenh1947 <W8GNM@...> wrote: Here is a feature idea for the next? update of the NanoVNA design.? If the
NanoVNA had a WiFi transceiver on board in addition to the USB port, so it
could be controlled remotely by NanoVNA Sharp, NanoVNA Saver, or similar
applications.
This would allow the NanoVNA to be attached directly to the feedpoint of a
multiband antenna and hoisted with the antenna into the operating position,
thereby eliminating the complication of transmission line normalizations
over multiple frequency bands.? The unit could be programmed remotely and
the data could be captured remotely.
I would be willing to pay a significant premium for this capability.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
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Re: characteristic impedance
Halfway around the Smith chart isn't 1/8 wave; it's 1/4 wave.
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Re: characteristic impedance
Well there seems to be no consensus about this Using 1-900MHz device calibration from weeks ago, I followed Herb's steps /g/nanovna-users/message/10210for three generic CATV jumpers with F-connector barrels via RCA to BNC to SMA adapters on my worse clone which reported about 72 Ohms reactive and 1 Ohm resistive.
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Re: nanovna-users]NanoVNA-H4 2Port calibration problem
Hi Jos,
just one question, not related to the topic: why open 4 Topics with the same name? Why don't you continue the conversation in the first one by clicking Reply?
This breaks the thread. It seems like a new topic.
Thank you for your attention.
Gyula
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Dear Oristo, thank you so much. I have tried it and it works perfectly!! Bob Albert thanks also for your advice too.
It is really an amazing project and I am so happy to see such a strong & enthusiastic community behind it. Thanks you all and particularly to the developers/contributors,
°ä¨¦²õ²¹°ù.
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On Sun, Jan 26, 2020 at 11:54 AM, Oristo wrote:
communicated with nanoVNA's USB virtual COM port
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Re: Band pass and stop measurement
Could you please give us a picture of your filter response as you measure it? Is your BC band filter a passband, stop band, low pass, or high-pass filter? Typical use would be a stop band or high-pass filter to block the strong AM broadcasters. But we don't know with the information you've given us. Please fill in the blanks. Dave - W?LEV On Sun, Jan 26, 2020 at 5:59 PM sidebores via Groups.Io <sidebores= [email protected]> wrote: Hi all,
Could some give a rough guide in how to measure a filter. I have broadcast
band filter and when I measure it the signal looks upside down for the
bandblock. The only way I can make it look ok is by using the real seting?.
So when looking at a band pass/stop filter should the block be in the
trough and the pass in the peak.
Cheers Kev
-- *Dave - W?LEV* *Just Let Darwin Work* *Just Think*
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Band pass and stop measurement
Hi all,
Could some give a rough guide in how to measure a filter. I have broadcast band filter and when I measure it the signal looks upside down for the bandblock. The only way I can make it look ok is by using the real seting?. So when looking at a band pass/stop filter should the block be in the trough and the pass in the peak.
Cheers Kev
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Re: characteristic impedance
Use nanoVNA Partner v0.20 link:
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Re: Wireless control of NanoVNA
With an RF instrument such as a VNA that measures down into the "noise", an
RF source in immediate proximity to low-level electronics is NOT a good
idea!! Compression of linear devices in the instrument are a real
possibility. IM with instrument-produced RF is also a distinct reality.
The input of the VNA is "wide open" with no 'filtering' to eliminate stray
RF energy. 2.4 or 5 GHz WiFi at +10 dBm in close proximity to the
electronics will completely spoil the operation of the VNA. NO! Bad
idea!!
Calibrate the VNA, attach it to the feedpoint of the antenna, raise the
antenna, and, well...... Better yet, as has been previously suggested,
read the impedance at the shack end of the feedline and propagate that
reading back to the antenna using SimSmith.
Dave - W?LEV
toggle quoted message
Show quoted text
On Sun, Jan 26, 2020 at 3:39 AM gmendenh1947 <W8GNM@...> wrote: Here is a feature idea for the next update of the NanoVNA design. If the
NanoVNA had a WiFi transceiver on board in addition to the USB port, so it
could be controlled remotely by NanoVNA Sharp, NanoVNA Saver, or similar
applications.
This would allow the NanoVNA to be attached directly to the feedpoint of a
multiband antenna and hoisted with the antenna into the operating position,
thereby eliminating the complication of transmission line normalizations
over multiple frequency bands. The unit could be programmed remotely and
the data could be captured remotely.
I would be willing to pay a significant premium for this capability.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
|
Re: nanovna-users]NanoVNA-H4 2Port calibration problem
Herb,
After thinking having solved the previous problem with NanoVNA-H4 calibration I went on playing. :-D I did a 2port calibration 1MHz- 30MHz in NanoVNA-Saver with the '"S11 Phase"? chart shown and experienced the same problem as with the " S21 gain"? calibration , before calibration a decent display, after calibration no correction on it but all garbadge on the screen, see the picture before calibration attached. I did the measurement on the 50 Ohms standard I had used. Not that I was interested in the phase, but it shoiuld work correctly.
I think Oristo is right, about the communication from NanoVNA-Saver and the device.
Jos
Op 26-1-2020 om 01:24 schreef hwalker:
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Show quoted text
On Sat, Jan 25, 2020 at 03:58 PM, Jos Stevens wrote:
I did what you suggested , removed the portsavers re-calibrated the standalone VNA,the result was better then before 0.00 db, +0.12 and -0.25 at 50k, 750M and 1500M. Then I calibrated in Nanovna-Saver using 4 segs like you, Before was better, and After was an ideal straight line at 0 dB!
==============================================================================
Good job Jos. I initially had problems with Rune's calibration module but after he posted that you needed to start the module from a good calibration on the NanoVNA saved to "SAVE 0" it has always worked well for me. I still use the ideal models because I hate entering numbers that I don't fully understand.
Rune's NanoVNA-saver application has been working great with the NanoVNA-H4 thus far. The screen saver doesn't work because different code is required for the 4" display, and NanoVNA-saver reports the unit as a NanoVNA-H which may mean the hugen will need to change the -H4 identifier in firmware to help developers differentiate it.
- Herb
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Before calibrating, perform a reset.? Then select S0 reflection.
Bob
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On Sunday, January 26, 2020, 04:07:49 AM PST, Cesar <ea5ioq@...> wrote:
Oristo, thanks a lot! I will try and let you know, best,
°ä¨¦²õ²¹°ù.
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Re: characteristic impedance
Well there seems to be no concensus about this.? I have a couple of things more to try.
However, starting at the right edge, open circuit, and increasing frequency as the trace swings clockwise, at the 6 o'clock point there is one-eighth wave.? The reactance there, I thought, should be numerically the same as the characteristic impedance.? It's not; it seems to be 50 Ohms regardless (as one responder says).
Continuing clockwise the quarter wave point is reached at the left edge, where impedance becomes resistive and minimum.? So there is no information other than the line length (and attenuation).
Continuing clockwise we return to nearly open circuit at the right edge.? Again, it's resistive but now high impedance.? No information regarding Z.
Of course, terminating the line in a variable resistance shrinks the trace until it becomes a dot regardless of frequency; at that point it's easy enough to read the impedance.? This works (theoretically) for any length line at any frequency.? But it requires the user to adjust the termination.? I can do it that way but was hoping that the eighth wave method would work, eliminating a step that has some potential for error.
Bob
On Sunday, January 26, 2020, 08:50:13 AM PST, W5DXP <w5dxp@...> wrote:
> Bob Albert: When I measure 50 Ohm coaxial impedance with the 1/8 wave method, I always get 50 Ohms.? I tried some 75 Ohm cable and still get 50 Ohms!
Have you tried the 1/8WL open/short method? Where the two Zs cross is the Z0?
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Re: Wireless control of NanoVNA
Apple locks down the types of
communications that BT can handle to primarily audio-centric A programmable dongle could translate between USB virtual COM and a supported BLE profile. Android doesn't have this limitation My experience writing hardware-specific apps that worked well for many Android devices and generations was a much larger PITA than for iOS. My Android experience with nanoVNA reinforces that.. Most cross-platform solutions end up using WiFi. Stopping and resuming Wi-Fi to minimize interference with VNA measurements is liable to introduce more latencies than by BLE.
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Re: characteristic impedance
Bob Albert: When I measure 50 Ohm coaxial impedance with the 1/8 wave method, I always get 50 Ohms. I tried some 75 Ohm cable and still get 50 Ohms! Have you tried the 1/8WL open/short method? Where the two Zs cross is the Z0?
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Re: Wireless control of NanoVNA
iOS bluetooth control may be challenging, Apple locks down the types of communications that BT can handle to primarily audio-centric (with specific exceptions for handshaking apps and Apple's own hardware). To do data transmissions, you could write an audio codec. Since Android doesn't have this limitation, you'd want to have a separate data communication stack for Android. Overall, a big PITA.
Most cross-platform solutions end up using WiFi.
I'd say it'd still be worth it to implement the Android BT communication mode though. It's much easier to 'experiment' in the Android ecosystem.
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Re: characteristic impedance
On Sun, Jan 26, 2020 at 07:07 AM, Andy UA3RAW wrote:
As it was described by DJ7BA in #8655 message, you must find the lowest (=Lambda/4) resonance frequency. (Impedance there is about 0 Ohm.) One full revolution in the Smith diagram corresponds to a displacement along the line by a distance equal to half the wavelength in it.
So the half-way around, is equal to 1/4 wave length. This is a point of the lowest resonance and it is corresponding to the Marker 1 on your screenshot.
In order to find the characteristic wave resistance of a coax cable, you must find the point that is a half of 1/4 wave length, or 1/8 wave length, and read the reactance at this point. That's why it is called Lambda/8 method.
==============================================================
Andy,
Thanks so much for the clarification. Its something I'll definitely be adding to my engineering notes. Electronics has been both my vocation and avocation for the past 40 years. I still enjoy learning new things, however; few subjects make my eyes glass over as the smith chart does.
At the beginning of my career the company I worked for won a government contract to RF immunity test ignitors to ensure they didn't unintentionally misfire. I had to design rf matching networks for use between our power amplifiers and the ignitors at each test frequency. We brought in the great Christopher Bowick to teach a course on using the smith chart to design matching networks. After that project was completed I never had another practical application to apply what I had learned and as they say "if you don't use it you lose it".
The Lambda/8 method is the first real world application, other than verifying the quality of my solt calibrations or measuring components, that I have used in a while. I wish there was a way of automating the process.
Again, thanks for taking the time to reply. Perfect example of the members helping members format.
- Herb
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Re: Wireless control of NanoVNA
Bear in mind that WiFi and Bluetooth require a lot of real estate and impose a lot of restrictions on board layout. - Ed
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Re: available screens for the nanovna
3.2 inch is the biggest.?
Why not just replace the touchscreen?
Use an xacto knife to cut around the outside edge of the display to remove the old touch surface and just bond a new 3.2 inch touchscreen to the display.?
In fact, if you have an old junk Palm Pilot ot MP3 player that has a resistive touch surface, try that.
On Sun, 26 Jan 2020 at 10:02 AM, nanovnauser@...<nanovnauser@...> wrote: HI all,i have a nanovna that i replaced the screen on with a 3.2 inch version that i got from china,it worked fine untill i cracked the screen,now the touchscreen doesent work,i need to buy a replacement,whats the biggest i can get for this?,cheers in advance .73.
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Re: characteristic impedance
On Sun, Jan 26, 2020 at 04:50 PM, hwalker wrote: Since the actual method has always worked for me I didn't give it any
deeper thought. If the terminology I used needs correcting please add to the
discussion so I can correct my notes and not perpetuate incorrect information
(i.e. if that point is 1/4 wave length why is it called the 1/8th method).
- Herb
Ok Herb, I'll try. As it was described by DJ7BA in #8655 message, you must find the lowest (=Lambda/4) resonance frequency. (Impedance there is about 0 Ohm.) One full revolution in the Smith diagram corresponds to a displacement along the line by a distance equal to half the wavelength in it. So the half-way around, is equal to 1/4 wave length. This is a point of the lowest resonance and it is corresponding to the Marker 1 on your screenshot. In order to find the characteristic wave resistance of a coax cable, you must find the point that is a half of 1/4 wave length, or 1/8 wave length, and read the reactance at this point. That's why it is called Lambda/8 method.
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Alberto I2PHD
Oristo
Gyula Molnar
Cesar, EA5IOQ
Andy UA3RAW