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Re: Increasing measurement range (ohms) ?

 

You are not going to be able to improved reading of high impedance very much as the primary limitation is the 50 ohm impedance bridge and signal level differences get very small at the higher load impedance.(refer to right hand, high Z side point of Smith chart. The difference in reflection coeff. is very small at higher Z).

Probably the best thing to improve unit's overall accuracy is the replacement of the cheap thick film 49.9 ohm chip resistors (EIA96 marking '68X') in the input bridge with 50.0 ohm 0.1% tolerance high frequency thin film resistors. They are about $1.50 each at Mouser Elect. for Vishay FC0603E50R0BTBST1 part number.

As for baluns, there are some good MiniCircuits baluns. TCM1-43X+ for 1:1. You will lose some low frequency operating range due the low end limit of the balun, down to about 10 MHz. The N1201SA UV RF Vector Impedance meter uses a similar balun from the impedance bridge to SA612 mixer with upper freq operation to 2700 MHz with fundamental Tx frequency and harmonic Rx down mixing. (uses a higher freq Analog Devices synthesizer).
Re: Reduce Frequency Range #hacking

 

Don't forget about the free Android audio spectrum analyzer apps you can run on your phone or tablet.?
They might even run on Chrome under arcwelder.?



On Fri, 13 Dec 2019 at 5:16 PM, Bob Albert via Groups.Io<bob91343@...> wrote: I will have to look around; do you have a link to a specific audio SA?? Basically I want it to measure distortion of an audtio oscillator.
Bob

On Friday, December 13, 2019, 01:52:57 PM PST, stone_ridge_road <xdavid@...> wrote:


There are various free PC applications that use the sound card for an
audio spectrum analyzer.? If you use a good quality sound card (flat
response, low noise level) I would think that the results would be
pretty good.? The sensitivity is typically good enough that there are
even VLF receiver applications out there.

73,
Dave?? AB7E



On 12/13/2019 12:56 PM, Bob Albert via Groups.Io wrote:
An audio VNA would be great, as would be an audio SA.? I have use for the latter but it's not a common item.
Bob K6DDX
Re: Reduce Frequency Range #hacking

 

The applications (I've used more than one) that I've used in the past are pretty old by now, so I found this supposedly more recent list of free applications:



However, this one looks pretty powerful and the standard version is only $30 US dollars if you buy it before December 15.



73,
Dave?? AB7E

On 12/13/2019 3:15 PM, Bob Albert via Groups.Io wrote:
I will have to look around; do you have a link to a specific audio SA?? Basically I want it to measure distortion of an audtio oscillator.
Bob
On Friday, December 13, 2019, 01:52:57 PM PST, stone_ridge_road <xdavid@...> wrote:
There are various free PC applications that use the sound card for an
audio spectrum analyzer.? If you use a good quality sound card (flat
response, low noise level) I would think that the results would be
pretty good.? The sensitivity is typically good enough that there are
even VLF receiver applications out there.

73,
Dave?? AB7E



On 12/13/2019 12:56 PM, Bob Albert via Groups.Io wrote:
An audio VNA would be great, as would be an audio SA.? I have use for the latter but it's not a common item.
Bob K6DDX
Re: Reduce Frequency Range #hacking

Bob Albert
 

I will have to look around; do you have a link to a specific audio SA?? Basically I want it to measure distortion of an audtio oscillator.
Bob

On Friday, December 13, 2019, 01:52:57 PM PST, stone_ridge_road <xdavid@...> wrote:


There are various free PC applications that use the sound card for an
audio spectrum analyzer.? If you use a good quality sound card (flat
response, low noise level) I would think that the results would be
pretty good.? The sensitivity is typically good enough that there are
even VLF receiver applications out there.

73,
Dave?? AB7E



On 12/13/2019 12:56 PM, Bob Albert via Groups.Io wrote:
An audio VNA would be great, as would be an audio SA.? I have use for the latter but it's not a common item.
Bob K6DDX
Re: Reduce Frequency Range #hacking

 

There are various free PC applications that use the sound card for an audio spectrum analyzer.? If you use a good quality sound card (flat response, low noise level) I would think that the results would be pretty good.? The sensitivity is typically good enough that there are even VLF receiver applications out there.

73,
Dave?? AB7E

On 12/13/2019 12:56 PM, Bob Albert via Groups.Io wrote:
An audio VNA would be great, as would be an audio SA.? I have use for the latter but it's not a common item.
Bob K6DDX
Re: Reduce Frequency Range #hacking

Bob Albert
 

It would be nice if someone would produce this unit for sale at a reasonable price.? An audio VNA would be great, as would be an audio SA.? I have use for the latter but it's not a common item.
Bob K6DDX

On Friday, December 13, 2019, 11:36:00 AM PST, Bob Larkin <bob@...> wrote:

It is a project, rather than an ebay buy, but

does a quality set of measurements from 10 Hz to 40 kHz.? It is all open
hardware and software.

Note that at lower frequencies one can find impedance by directly
measuring V and I (magnitude and phase) and calculating V/I.? That is
the usual method and is more accurate and simpler to do.

There are also some very simple implementations of the impedance
measurement part: G. R. Steber, WB9LVI, ¡°A Low Cost Automatic Impedance
Bridge,¡± QST Oct. 2005, pp. 36?39.? Also, ref 3 of the URL above.

A side note is that the AVNA in the URL above is programmable from a
serial link and prime for adaptation to the control software such as
wonderful nanoVNA-saver.? Anyone interested in doing that?? I would be
happy to support that with firmware changes to the AVNA, as needed.

Bob? W7PUA
Re: Reduce Frequency Range #hacking

 

A couple more notes. The reference 3 for Z measurement is in the QEX article


Also, there is a support group
/g/AVNA1

Bob W7PUA
Re: Reduce Frequency Range #hacking

 

It is a project, rather than an ebay buy, but

does a quality set of measurements from 10 Hz to 40 kHz. It is all open hardware and software.

Note that at lower frequencies one can find impedance by directly measuring V and I (magnitude and phase) and calculating V/I. That is the usual method and is more accurate and simpler to do.

There are also some very simple implementations of the impedance measurement part: G. R. Steber, WB9LVI, ¡°A Low Cost Automatic Impedance Bridge,¡± QST Oct. 2005, pp. 36?39. Also, ref 3 of the URL above.

A side note is that the AVNA in the URL above is programmable from a serial link and prime for adaptation to the control software such as wonderful nanoVNA-saver. Anyone interested in doing that? I would be happy to support that with firmware changes to the AVNA, as needed.

Bob W7PUA
Re: Increasing measurement range (ohms) ?

 

Larry,

Do we know if the clone bridges us the correct ferrites? I would stick with the transverters store version.

< >

Order and active probe or active while y=while you are there.

Mike N2MS

On December 12, 2019 at 8:44 PM Larry Rothman < nlroth@... mailto:nlroth@... > wrote:


On Sat, Nov 16, 2019 at 12:59 PM, Oristo wrote>

> > A green (not blue) ~US$10 reflection bridge
e.g. from eBay
with matched SMA references (want a matched pair to calibrate nanoVNA CH1)

> Oristo,
I picked up a bridge from the eBay link above. The build quality is poor and the 2, 100 ohm resistor pairs are each not in parallel. So even though the board is green, it's no better than one of those blue boards with the same issues.

At least it's fixable.
I've attached a couple of photos.
Re: Increasing measurement range (ohms) ?

KV5R
 

On Fri, Dec 13, 2019 at 09:01 AM, Dale Parfitt wrote:
I am not sure that makes it an effective balun. Or maybe at best a voltage balun, but not a current balun - which is what antennas require. As I recall, it is not possible to make a current balun, other than 1:1 ratio on a single core.
erik@ wrote: Its both - 1:9 transformer with the 9 side not connected to ground
Both Correct.
Per the Coilcraft datasheet, it's a regular transformer with primary and secondary windings, with high side isolated from ground. Nooelec calls it a "balun" (marketing?), but Coilcraft accurately calls it a "wideband transformer."
For Andy's stated application, it doesn't matter if it's a proper "balun" or not, just an impedance transformer with sufficient bandwidth. I proved it will transform 4500 to 500, with a flat response from 1-31MHz, so it should work to measure the feed-point impedance of an end-fed half-wave HF antenna.
As for common-mode rejection, it's likely very low for this device, but if it becomes a problem, is easily remedied by winding the li'l sma-sma cable a few times through a toroid, thus preceding the transformer with a CM choke.
73, --kv5r
Re: Increasing measurement range (ohms) ?

 

Please, guys, when you speak of a 1:n transformer. always specify whether n
represents voltage (turns ratio) or impedance. It is often not clear from context.

Thanks,

Dana
Re: Reduce Frequency Range #hacking

 

See msg #1252

Alan
Re: Reduce Frequency Range #hacking

 

You can homebrew a decent low frequency bridge and use a couple of opamps to accomplish the task. I posted the operation in another post message and with an LT Spice schematic. Will see if I can locate.

Alan
Re: Reduce Frequency Range #hacking

 

Probably, but you'd have to change the mixer coupling caps and the bridge circuit.? ?
??Here's your chance to play and let everyone know if it works!?
Also, the output is a square wave so you'd need to deal with all sorts of harmonics or, instead you could mod the output to only send pink noise to the speakers and mix the return with the internal Freq source.?

Sent from Rogers Yahoo Mail on Android

On Fri, 13 Dec 2019 at 10:55 am, Webb, William<billwebb12@...> wrote: Is there any possibility of customizing the NanoVNA software for a lower frequency range?

Yup, I wrote lower.? Aside from Ham radio HF applications, I would like to be able to characterize custom speaker crossovers.? The range would be, ideally, 20-20,000 Hz.? Can the hardware go that low?
Re: Reduce Frequency Range #hacking

 

On Fri, 13 Dec 2019 07:55:17 -0800, you wrote:

Is there any possibility of customizing the NanoVNA software for a lower frequency range?

Yup, I wrote lower. Aside from Ham radio HF applications, I would like to be able to characterize custom speaker crossovers. The range would be, ideally, 20-20,000 Hz. Can the hardware go that low?

Let me guess: no, it cannot be done.

Rather use MLS with your PC soundcard. (Maximum Length Sequence)


There are expensive commercial sytems like CLIO.



For a entry level system have a look here:


It starts with 50 euros.

OE8UWW
Reduce Frequency Range #hacking

 

Is there any possibility of customizing the NanoVNA software for a lower frequency range?

Yup, I wrote lower. Aside from Ham radio HF applications, I would like to be able to characterize custom speaker crossovers. The range would be, ideally, 20-20,000 Hz. Can the hardware go that low?
Re: F303 and 4" LCD for next generation NanoVNA #circuit #flash_size #improvement #enclosure #battery

 

At the moment ADC1 can't read VBAT data correctly, and I can't get into DFU
mode through the menu yet, I haven't found the cause of the problem yet
If MCU is changed from original nanoVNA, then I guess
also need change to NANOVNA_STM32_F072/board.h
for BOOT_FROM_SYTEM_MEMORY_MAGIC_ADDRESS

ADC1 address is buried in ChibiOS/os/common/ext/CMSIS/ST/*
Re: Increasing measurement range (ohms) ?

 

Yeah, there is flux all over and it looks like someone learning to solder assembled it. \_('_')_/

Sent from Rogers Yahoo Mail on Android

On Fri, 13 Dec 2019 at 9:51 am, Oristo<ormpoa@...> wrote: Hi Larry -

I picked up a bridge from the eBay link above.
The build quality is poor and the 2, 100 ohm resistor pairs are each not in parallel.
So even though the board is green,
it's no better than one of those blue boards with the same issues.
Sorry to learn that;? I suppose only ones from Ukraine are better.

At least it's fixable.
Leaving 100 Ohm resistors NOT connected in parallel improves sensitivity for differences at higher impedances,
but fixing coax terminations thru ferrite beads is necessary.
Re: Increasing measurement range (ohms) ?

 

I am not sure that makes it an effective balun. Or maybe at best a voltage balun, but not a current balun - which is what antennas require. As I recall, it is not possible to make a current balun, other than 1:1 ratio on a single core.

Dale W4OP

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of erik@...
Sent: Friday, December 13, 2019 9:40 AM
To: [email protected]
Subject: Re: [nanovna-users] Increasing measurement range (ohms) ?

Its both
1:9 transformer with the 9 side not connected to ground

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK
Re: Increasing measurement range (ohms) ?

 

Hi Larry -

I picked up a bridge from the eBay link above.
The build quality is poor and the 2, 100 ohm resistor pairs are each not in parallel.
So even though the board is green,
it's no better than one of those blue boards with the same issues.
Sorry to learn that; I suppose only ones from Ukraine are better.

At least it's fixable.
Leaving 100 Ohm resistors NOT connected in parallel improves sensitivity for differences at higher impedances,
but fixing coax terminations thru ferrite beads is necessary.
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