Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
On Thu, Nov 19, 2020 at 02:40 PM, AllassoPraise wrote:
But I just checked
using only the nanovna with USB disconnected, and the SWR curves look
just about identical. I even connected up my USB cable, and observed
no difference in the sweep on the nanovna screen.
That's probably because your antenna is inherently balanced and the feed-line is adequately decoupled by means of a balun or similar. The main problem is with unbalanced antennas, that have a tendency to use the feed-line as part of the antenna, and often don't have adequate decoupling from the radio (and everything else it is connected to). But you should still try to replicate everything that is normally connected when making measurements, so that you get the best possible 'snapshot' of what is happening. If you notice a difference when the USB cable is connected (or disconnected), then ideally you should investigate why this is the case. ---- Regards, Martin - G8JNJ
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Re: Smith chart - admittance scale ?
NanoSaver already calculates serie and parallel impedances. That's not the issue.
Only thing the Smith chart display needs (for educational purpose) is this circle pattern of the standard chart flipped around in another color. We can already swith on and of SWR circles (which is great!)
I just hope that one of the hobby-programmers thinks it might come in handy so he or she would add this to nanoSaver. If not, I can live with that. Programmers have done so much already.
73
Arie PA3A
Op 19-11-2020 om 14:18 schreef W1RS:
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I would offer the idea of using a pre-calculated graphic overlay for the scales in the programs like NanoSaver. It seems a waste of processing to have to compute the chart impedance or admittance graphs every time the program is run. The fact is, they never change. I am not a programmer and don't know if there is support for this in QT, but I have made use of this method in Excel. Just use the saved picture of the chart as the "overlay" and all you need to compute / plot are the reflection coefficients. Again, not being a software type, I may be way off base here and would appreciate feedback on this.
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Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
Sorry Martin, I see you already made those points.
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On 11/19/20, AllassoPraise <allassopraise@...> wrote: Interesting, I've been making all my measurements using QT on my
laptop, then panicked a bit when I read this, as I have made many
tedious antenna[1] tweaks based on that data. But I just checked
using only the nanovna with USB disconnected, and the SWR curves look
just about identical. I even connected up my USB cable, and observed
no difference in the sweep on the nanovna screen.
I suppose that is because the laptop doesn't get ground through the
power adapter. But it appears like just the computer itself didn't
make any appreciable difference in the system either.
This thread does bring to mind what seem like important
considerations: If I'm tweaking an antenna which will be used on a
device which will be grounded, shouldn't I ground my nanovna as well?
And moreover, shouldn't I try to replicate the target setup as much as
possible?
[1] Antenna is a yagi uisng a folded dipole driving element, tuned to
achieve <2vswr from 814¨C894 MHz
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Re: 3D printed nanoVNA-H BNC holder and binding post DUT holder
VK7AM
email me
--
73
Bob? KD8CGH
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NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
Interesting, I've been making all my measurements using QT on my
laptop, then panicked a bit when I read this, as I have made many
tedious antenna[1] tweaks based on that data. But I just checked
using only the nanovna with USB disconnected, and the SWR curves look
just about identical. I even connected up my USB cable, and observed
no difference in the sweep on the nanovna screen.
I suppose that is because the laptop doesn't get ground through the
power adapter. But it appears like just the computer itself didn't
make any appreciable difference in the system either.
This thread does bring to mind what seem like important
considerations: If I'm tweaking an antenna which will be used on a
device which will be grounded, shouldn't I ground my nanovna as well?
And moreover, shouldn't I try to replicate the target setup as much as
possible?
[1] Antenna is a yagi uisng a folded dipole driving element, tuned to
achieve <2vswr from 814¨C894 MHz
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Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
On Thu, Nov 19, 2020 at 06:31 AM, Martin wrote:
If the NanoVNA is in turn connected to a computer, that also forms part of the
antenna system, so it is always best to use a 'floating' laptop (or Bluetooth
adaptor) in order to minimise such problems.
Ok, Bluetooth SPP NanoVNA piqued my interest. :) I'm going to look into that since I plan on using the 250m of antenna wire I just bought from SOTAbeams. :)
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Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
You might try running the calibration with whatever cable you're using to
connect things to PC connected to device.
The only other thing I've noticed occasionally is that if I sweep too wide
a range of frequencies on the device, the 101 points becomes the limiting
factor, and I may miss the absolute min/max of a peak or valley in the
graph, or occasionally a very sharp dip may get missed entirely.
The Saver app overcomes that by graphing shorter frequency spans at a time.
If you adjust your Start/Stop frequencies to just a few hundred kHz apart,
you should see similar numbers.
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NanoVNA, SAAV2+4, RigExpert
Hello All,
I have a classic white gecko clone nano with the Sept firmware, and have been following its evolution here since last year. Also have been following all the progress with the V2 which has its own issues much to my dismay. There is also apparently a V3 in development but there has been no info on it available on its forum other than its possibly in the works.
My question is, has anyone compared the performance to a RigExpert. The latter costs substantially more and has a following. I was wondering how much they can pack into that small device that makes it cost substantially more than a nano. When you look at professional devices like HP, Anritsu etc the are substantially larger and can cost 10s of thousands. What I don¡¯t like about the RigExpert is that it looks like it only has a reflective connector as well (one). I don¡¯t really know if functionality can be switched in the software. The yellow models seem to be a better build than the blue which have higher frequency. Given all the experience here with VNAs in general, professional and others, what would you consider for a second unit?
Just looking for opinions.
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Yes, and this person also posted the exact same question on the Softrock and FT-817 forums, too. Makes me curious ... 73, Zack W9SZ On Thu, Nov 19, 2020 at 3:38 AM Brian Duerr/WB2JIX <brian@...> wrote: This is the exact same question on the IC-7300 Forum. I asked the person
to clarify.
Pardon me if it's not legit but seems odd to see the same, exact question
on other forums.............
Brian/WB2JIX
<> Virus-free. www.avast.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: Smith chart - admittance scale ?
I would offer the idea of using a pre-calculated graphic overlay for the scales in the programs like NanoSaver. It seems a waste of processing to have to compute the chart impedance or admittance graphs every time the program is run. The fact is, they never change. I am not a programmer and don't know if there is support for this in QT, but I have made use of this method in Excel. Just use the saved picture of the chart as the "overlay" and all you need to compute / plot are the reflection coefficients. Again, not being a software type, I may be way off base here and would appreciate feedback on this.
On of my favorite tools for building and visualizing matching networks with the Smith Chart is at:
You can input s-parameters or use the keyboard or mouse to enter points and toggle impedance or admittance graphs on or off.
It allows elements to be cascaded between source and load. The demoversion is limited to 5 datapoints and 5 elements.
- Fritz Dellsperger was a Professor for RF and Microwave Engineering
at Bern University of Applied Sciences from 1992 to 2012, now retired.
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Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
On Thu, Nov 19, 2020 at 10:42 AM, Arie Kleingeld PA3A wrote:
Yes, the grounding effect is definitely there.
Remember that anything connected to the antenna system becomes part of it. For example if you disconnect the radio in order to connect the NanoVNA, you change the antenna system. If you change a cable length, you change the antenna system. If you connect a mains power supply, you change the antenna system, and so on. When you connect the NanoVNA you need to keep everything as close to the exact operating configuration as possible. If you disconnect the radio, then try to make as short a connection as possible between the screen of the coaxial cable where it connects to the NanoVNA and the chassis of the radio. If you connect your NanoNVA directly to an antenna, then make sure the screen of the coax still makes contact with the screen of the NanoVNA connector. If the NanoVNA is in turn connected to a computer, that also forms part of the antenna system, so it is always best to use a 'floating' laptop (or Bluetooth adaptor) in order to minimise such problems. You can use a common mode choke, but..... yes you guessed it, that also becomes part of the antenna system :-) Antennas such as the end fed half wave and variants are particularly problematic, as the feed point is at a very high impedance node, and the feed line which forms part of the cannot easily be choked off. So anything that is connected to the feed line, or even comes within close proximity, can interact quite dramatically and change its electrical characteristics. Budget test equipment such as the NanoVNA is now allowing folks to see what is really going on with their antenna systems, and this can often lead to surprising revelations :-) --- Regards, Martin - G8JNJ
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There have been a couple of posts recently that have been questioned by the nanovna-user community. The moderators appreciate forum members voicing their concern and we continue to monitor those threads
DaveD
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On Nov 19, 2020, at 05:37, Alan G4ZFQ <alan4alan@...> wrote:
Brian,
This is the exact same question on the IC-7300 Forum. Well, some do post the same question on different forums all at the same time.
Drives me mad if I spend ages answering on one forum and find it has also been answered on another.
But quite a few forums are getting posts like this, a general question, maybe one that gets them unmoderated so loads of spam may be sent.?
73 Alan G4ZFQ
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Brian, This is the exact same question on the IC-7300 Forum. Well, some do post the same question on different forums all at the same time. Drives me mad if I spend ages answering on one forum and find it has also been answered on another. But quite a few forums are getting posts like this, a general question, maybe one that gets them unmoderated so loads of spam may be sent.? 73 Alan G4ZFQ
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Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
Yes, the grounding effect is definitely there.
I used a common mode choke on the usb cable, and that solved the problem. Since I use my nano mostly on HF, I took a combo of two 35mm cores: 3S4 and 43 material.
73
Arie PA3A
-----------------------------------------
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I have noticed the unit SWR changes from
Battery to USB power and in the car I noticed
Hand help changes it too. Some RF grounding effect??
----------------------------
I went out to a park today to tune my EFHW and it seems that the latest
NanoVNA saver shows a SWR that is significantly different than the device
shows. I almost wound up cutting the wire too short but I thought
something was off and went to check the graph on the LCD. It was around
1.7 where the Saver software was showing 2.4+. Has anyone else seen this
issue?
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Re: NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
I have noticed the unit SWR changes from
Battery to USB power and in the car I noticed
Hand help changes it too. Some RF grounding effect??
--
Sent from my Android phone with GMX Mail. Please excuse my brevity.
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On 11/19/20, 02:38 Richard <groups.io@...> wrote:
I went out to a park today to tune my EFHW and it seems that the latest
NanoVNA saver shows a SWR that is significantly different than the device
shows. I almost wound up cutting the wire too short but I thought
something was off and went to check the graph on the LCD. It was around
1.7 where the Saver software was showing 2.4+. Has anyone else seen this
issue?
|
NanoVNA Saver showing SWR radically different than the device
#nanovna-saver
I went out to a park today to tune my EFHW and it seems that the latest NanoVNA saver shows a SWR that is significantly different than the device shows. I almost wound up cutting the wire too short but I thought something was off and went to check the graph on the LCD. It was around 1.7 where the Saver software was showing 2.4+. Has anyone else seen this issue?
|
This is the exact same question on the IC-7300 Forum. I asked the person to clarify.
Pardon me if it's not legit but seems odd to see the same, exact question on other forums.............
Brian/WB2JIX
|
Re: 3D printed nanoVNA-H BNC holder and binding post DUT holder
whether nanovna H. Can I replace the LCD? because when exposed to the light it is not clear how it looks ... thank you Pada tanggal 19 Nov 2020 09:18, "Pierre Martel" <petem001@...> menulis:
if you are not too far from Hobart you have at least 2 places around.
And from those you will maybe find someone even closer.
Have some fun and meet some young hacker. You never know some might even
have some interest in the hobby!
Pierre
VE2PF
Le mer. 18 nov. 2020 ¨¤ 20:52, <vk7am@...> a ¨¦crit :
Thanks Bob. That technology isn't available down here in Tasmania. We
are 20 years behind! USPS small packet in my experience is quite cheap and
its fast as well... Again my thanks 73 Alan VK7AM
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Re: 3D printed nanoVNA-H BNC holder and binding post DUT holder
if you are not too far from Hobart you have at least 2 places around.
And from those you will maybe find someone even closer.
Have some fun and meet some young hacker. You never know some might even
have some interest in the hobby!
Pierre
VE2PF
toggle quoted message
Show quoted text
Le mer. 18 nov. 2020 ¨¤ 20:52, <vk7am@...> a ¨¦crit : Thanks Bob. That technology isn't available down here in Tasmania. We
are 20 years behind! USPS small packet in my experience is quite cheap and
its fast as well... Again my thanks 73 Alan VK7AM
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Re: 3D printed nanoVNA-H BNC holder and binding post DUT holder
Thanks Bob. That technology isn't available down here in Tasmania. We are 20 years behind! USPS small packet in my experience is quite cheap and its fast as well... Again my thanks 73 Alan VK7AM
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Arie Kleingeld PA3A
Bob Benedict, KD8CGH
BryonB
