开云体育

"Good" for me, might taste awful to you.
Not leaving the EFHW here. It works!



On Mon, Dec 20, 2021 at 5:05 PM Max via groups.io <kg4pid=
[email protected]> wrote:

Low SWR doesn't mean it's a good antenna !
On Monday, December 20, 2021, 03:23:01 PM CST, Bo W4GHV <
bobarr@...> wrote:

Will do. I just did a 80--10 meter sweep of my 80-10 EFHW with 12801

data

points on the PC app. Wow!
The Smith Chart and SWR show why the EFHW is so popular. SWR <= 2:1

over

the whole range!

On Mon, Dec 20, 2021 at 1:25 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

On Mon, Dec 20, 2021 at 09:50 AM, Bo W4GHV wrote:

I just obtained mine, so forgive my lack of knowledge.
I thought it only had 100 data points? How do you scan a wide range?
But, I just read you can do this if it is connected to a PC using the
software.

Bo W4GHV since '54

I suggest you read the Absolute Beginners Guide in the Files section of
this group. Also check out the group Wiki.

Roger

On Mon, Dec 20, 2021 at 09:50 AM, Bo W4GHV wrote:

I just obtained mine, so forgive my lack of knowledge.
I thought it only had 100 data points? How do you scan a wide range?
But, I just read you can do this if it is connected to a PC using the
software.

Bo W4GHV since '54

I suggest you read the Absolute Beginners Guide in the Files section of
this group.? Also check out the group Wiki.

Roger

Think of it in golfing terms. It's like trying to putt with a 'mashie'.
(personally I prefer a #2 wood to putt)

Mike C.

On 12/20/2021 1:48 PM, Dave Daniel wrote:

Remember, the difference between “accuracy” and “precision” is important.

Accuracy has to do with the degree to which an instrument can determine

a measured value compared to the actual value, independent of the method of
measurement.

Precision is the degree to which an instrument can display the actual

value.

For precision, think about measuring a length; does the scale read in

10ths of an inch, 100ths of an inch? And how accurate are those markings on
the scale?

DaveD

On Dec 20, 2021, at 13:18, Earle Wilkinson <earle.wilkinson@...>

wrote:

?Thanks for the response will let you know the outcome


Earle D Wilkinson
(6Y5EW)

Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA

On Mon, Dec 20, 2021, 10:21 AM Jim Lux <jim@...> wrote:

On 12/20/21 12:27 AM, Earle Wilkinson wrote:
Earle D Wilkinson
(6Y5EW)

Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA

On Mon, Dec 20, 2021, 3:18 AM Earle Wilkinson <

earle.wilkinson@...

wrote:

New at this.

I got myself an NanoVNA 2 version 4.
Everyone says best thing ever happened.

Better than sliced cheese.

My problem is that I a sticular when it comes to accuracy.

I would like to check my club stations duplexer accuracy on 147.960

high

pass filter with 147.360 as the split on the low pass filter, that is

minus

600 kc split.

Now her is my problem I can only set my markers at 147.300 and

147.900.

Not the exact repeater frequency.

Will the difference of 60 hz make a difference in the accuracy of the
tuning insertion loss etc.

I realise that I need to be accurate at least with the 50 ohms

impedance.

Thanks for your response.
Earle D Wilkinson
(6Y5EW)

Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA

Two issues that arise:

#1 The NanoVNA only has a limited number of frequency steps
(101,201,401, depending on which firmware and model) unless you're

using

software on an external computer that does multiple scans. So, if you
set your span to, say, 147 to 148 MHz, then you'll get a measurement
every 10 kHz (with 101 points). Solution here is to use one of the

many

software packages that will talk to the NanoVNA and make multiple scans
and combine them.

#2 The 28 MHz oscillator in the NanoVNA isn't necessarily accurate
enough. I don't recall the spec, but let's say it's on the order of 10
ppm (good for a TCXO) - at 147 MHz, that means it could be off by 1470

Hz.

I had something similar happen... Once windows decides the type of device (right or wrong), it assigns a driver. Often, when you try to load the correct driver, windows will insist it already has the "best" driver.
Perhaps the Nano had been connected, before the required driver was loaded first, that can cause windows to load the incorrect driver.
I used a program called Zadig Available here ===> Select show all devices, find the one in question, then load the generic usb driver
Next load the correct ST Microdevices driver.

Remember, the difference between “accuracy” and “precision” is important.

Accuracy has to do with the degree to which an instrument can determine a measured value compared to the actual value, independent of the method of measurement.

Precision is the degree to which an instrument can display the actual value.
For precision, think about measuring a length; does the scale read in 10ths of an inch, 100ths of an inch? And how accurate are those markings on the scale?

DaveD

On Dec 20, 2021, at 13:18, Earle Wilkinson <earle.wilkinson@...> wrote:

?Thanks for the response will let you know the outcome


Earle D Wilkinson
(6Y5EW)

Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA

On Mon, Dec 20, 2021, 10:21 AM Jim Lux <jim@...> wrote:

On 12/20/21 12:27 AM, Earle Wilkinson wrote:
Earle D Wilkinson
(6Y5EW)

Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA

On Mon, Dec 20, 2021, 3:18 AM Earle Wilkinson <earle.wilkinson@...

wrote:

New at this.

I got myself an NanoVNA 2 version 4.
Everyone says best thing ever happened.

Better than sliced cheese.

My problem is that I a sticular when it comes to accuracy.

I would like to check my club stations duplexer accuracy on 147.960 high
pass filter with 147.360 as the split on the low pass filter, that is

minus

600 kc split.

Now her is my problem I can only set my markers at 147.300 and 147.900.
Not the exact repeater frequency.

Will the difference of 60 hz make a difference in the accuracy of the
tuning insertion loss etc.

I realise that I need to be accurate at least with the 50 ohms

impedance.

Thanks for your response.
Earle D Wilkinson
(6Y5EW)

Home page:
Email address: earle.wilkinson@...
Echolink: 6Y5RA

Two issues that arise:

#1 The NanoVNA only has a limited number of frequency steps
(101,201,401, depending on which firmware and model) unless you're using
software on an external computer that does multiple scans. So, if you
set your span to, say, 147 to 148 MHz, then you'll get a measurement
every 10 kHz (with 101 points). Solution here is to use one of the many
software packages that will talk to the NanoVNA and make multiple scans
and combine them.

#2 The 28 MHz oscillator in the NanoVNA isn't necessarily accurate
enough. I don't recall the spec, but let's say it's on the order of 10
ppm (good for a TCXO) - at 147 MHz, that means it could be off by 1470 Hz.

Robin:

Rather insensitive terminology here!
"1) there is the odd Doll on this group as well as [far too many, /pro rata/] Guys”

Chuck Young

On Dec 20, 2021, at 6:56 AM, G8DQX list <list@...> wrote:

Jens,

1) there is the odd Doll on this group as well as [far too many, /pro rata/] Guys

2) for the technical question, imagine that there are *2* oscillators active, one at f?, one at f?+IF, where IF is an intermediate frequency and f? is the measurement frequency. Then, as square waves, the measurement oscillator will produce frequencies f?, 3f?…, and the local oscillator will produce frequencies f?+IF, 3f?+3IF… Then at the fundamental frequency, the difference frequency is IF, but when the third harmonic products mix, the difference frequency is 3IF. The products at 3IF will be rejected by the post mixer bandpass filter.

3) similar arguments apply when harmonic mixing is employed, such as for the 300?MHz - 900?MHz range. Note in this case, that there will be an unwanted product from the fundamental frequencies at ?IF (hence the use of a bandpass, rather than lowpass, filter) and the 5^th harmonic at 1?IF.

Also note the reducing power in the harmonics, thus doubly reducing the mixer products to be measured. The fact that any of this works is a triumph of human ingenuity and DSP.

4) Identifying all the frequencies and corresponding mixing products for n^th harmonic operation is left as an exercise for the interested reader!

HTH, 73, Stay Safe,

Robin, G8DQX

PS: For this sort of hybrid analogue & digital machine, often the block diagram is more informative than the circuit (schematic) diagram. The actions of the software are also key components.

On 20/12/2021 11:11, Jens M?ller wrote:

Hello Guys,

I've one question which puzzles me, and was unable to find information neihter in the forum nor in the Wiki.
Since the NanoVNA outputs a rectagular signal which's harmonics are not neglectable and has no selective input (what I can see from the schematic is broadband), how can the S12 and S21 measurements be accurate as all the harmonics of the output will go into the mesurement at the input.

What do I have overseen?

Thanks for bringing me on the right track

Jens DF9HJ