nanovna-users@groups.io

Re: New NanoVNA possibly malfunctioning?

Thanks, Larry.? I did go through the steps you described.? (You can even see in the screenshot from before that I had recalled settings 6.)? After dinner, to be sure, though, I ran through the steps again and suddenly there are no traces at all.? All 4 are turned on and Stimulus -> Pause Sweep is not on.? I reloaded firmware (Dislord v0.69) that the unit came with but no change.? I'm thinking at this point that the unit is at fault and will send it back for a new one.? For the day or so that it worked, I love it and look forward to a replacement to put it to real use.

Thanks again,

Mike

Show quoted text

On 1/9/22 5:47 PM, Larry Rothman wrote:


Mike,
When you calibrated the unit, did you hit the Reset softkey
immediately before pressing the Calibrate softkey and then save to a
specific memory slot?
If you saved to a mem slot other than 0, did you
recall that slot after you turned on the unit? All Nanos default to mem
slot 0 at power up.?
Can you check that the Apply box in the Calibrate
menu is checked?
If everything seems ok. Redo the complete calibration
again. I've seen this happen once in a while and recalibration usually
fixes it.?
Cheers
Larry
 
 
  On Sun., 9 Jan. 2022 at 4:41 p.m., Mike
Markowski <mike.ab3ap@...> ( mike.ab3ap@... ) wrote:   There
is a better than even chance that my NanoVNA is fine and I'm the issue.?
However, I started playing with my new unit this weekend and did some
basic things, swept a little telescoping antenna and measured cable
length.

Today, however, the measurements (pic attached, hopefully not
stripped) were from a freshly calibrated NanoVNA running Dislord v1.1.00.?
After a full range cal, then with 50 ohm terminator attached, vswr is
bouncing all over the place.? If I try to calibrate ranges for 140-148 MHz
or 420-450 MHz, vswr shows infinity.

I've handled the vna carefully and
haven't yet tried characterizing filters or anything where'd I'd transmit
into the NanoVNA, so there's no chance of exceeding input limits.? Can
more experienced users say if it sounds there a chance I have a bad unit?
Have I overlooked something beyond reset and re-cal?

Thanks very much,

Mike ab3ap





  

Re: Using NanoVNA to measure receive antenna port impedance #measurement

#26495

On 1/9/22 2:40 PM, Jeff Green wrote:
Thank you, I was afraid of that.
-------------------
From:


On page 61: "Splitting up the winding into two rings suitably spaced provided a reasonable compromise between simplicity of construction and constancy of antenna input impedance. However, instead of 125 ohm ±15% the impedance actually varies from 50 - 300 ohms."
-------------------
So, Any idea how the input impedance is measured and how did Collins verify the above data?

Thank you.
You'd measure it (today) with a VNA, making sure that you pick a drive level that's reasonable for the receiver (i.e. if your receiver input can only tolerate -50dBm, then better not put -10 dBm in).

The trick is that active devices often have impedances that vary with operating point.

Let's assume you know the gain of your receiver very accurately. That is, you've turned off any AGC, and you can measure the output for a given input level.? Then, you can put known impedances in series with the input, forming a voltage divider (Zrcv/(Zrcv + Zseries)), and from a set of measurements, you can determine what Zrcv is. You will need both resistive and reactive series Z, because typically, you can only measure the magnitude of the signal, not the phase.

Re: Using NanoVNA to measure receive antenna port impedance #measurement

#26494

On Sun, Jan  9, 2022 at 01:30 PM, Jeff Green wrote:


Goal:
Given my hardware, software, and less then stellar knowledge and skill set, is
it practical to measure the actual antenna input port impedance of several
general coverage receivers?
Jeff,

Yes you can measure the input impedance of an HF receiver with your NanoVNA but you need to be careful you do not overload the front end.   The output of the NanoVNA is around 0 dBm which is too high.

The trick is to lower the NanoVNA output power as much as possible.  If you have recent firmware by DiSlord you can set the power level to 2 ma. (which is the lowest possible) but still too high.  The next step is to add a 20 dB attenuator to the S11 port and then calibrate with the attenuator in place.  The attenuator will lower the signal into the receiver and reduce the dynamic range but you can still  get reasonable SWR and RL measurements.  The impedance measurement will be reasonable as well if close to 50 ohms.  The further away from 50 ohms the worse the accuracy.

You will notice that the impedance will change rapidly when you are outside the passband of the receiver front end filters.  

Roger

Re: Using NanoVNA to measure receive antenna port impedance #measurement

#26493

On 1/9/22 12:51 PM, Jeff Green wrote:
The Backstory:
The company I work for has been merged via hostile takeover with a nother company and most of the employees are being laid off or offered early retirement. A coworker is relocating to a company in Texas, cleaning out and gave me a year old, unused, Nooelec NanoVNA - Open Hardware Vector Network Analyzer Kit.
The Analyzer kit included SOLT calibration kit.

I downloaded NanoVNASaver.x64 from


I've played with the hardware and software enough to be passably familiar with the process, I used a 75 ohm CATV terminator to produce a 1.5:1 mismatch and the results were what I expected.

Goal:
Given my hardware, software, and less then stellar knowledge and skill set, is it practical to measure the actual antenna input port impedance of several general coverage receivers?It should work ok, but make sure your receiver can tolerate the input power? from CH0.

Re: Using NanoVNA to measure receive antenna port impedance #measurement

#26492

Check out W2AEW testing the input of an amp. with a nano:


Hope this helps.
Richard,  K8CYK



On Sun, Jan 9, 2022, 3:41 PM Jeff Green <Jeff.L.Green1970@...>
wrote:

Thank you, I was afraid of that.
-------------------
From:



On page 61: "Splitting up the winding into two rings suitably spaced
provided a reasonable compromise between simplicity of construction and
constancy of antenna input impedance. However, instead of 125 ohm ±15% the
impedance actually varies from 50 - 300 ohms."
-------------------
So, Any idea how the input impedance is measured and how did Collins
verify the above data?

Thank you.

Re: Upcoming payment for this group - Response about a Donation

#26491

Thanks for letting me know David,?
I have cleaned a lot from here so only right I give something back. Only to happy for next year.?
Regards Dennis G6YBC

Show quoted text

On Sunday, January 9, 2022, 8:39 pm, Martin Glazer <mglazer2014@...> wrote:

I can help with a donation.

On Sun, Jan 9, 2022, 11:34 AM Dave Daniel <kc0wjn@...> wrote:

Tominaz,

We have received pledges for funds sufficient to cover the expense for
2022. I have put your name on the list of people who have offered to
donate.

We will be doing this every year going forward.

Thank you.

Dave

On 1/9/2022 1:20 PM, Tominaz wrote:
Tominaz $5.00 will be best $5.00 I ever spent

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Re: New NanoVNA possibly malfunctioning?

#26490

Mike,
When you calibrated the unit, did you hit the Reset softkey immediately before pressing the Calibrate softkey and then save to a specific memory slot?
If you saved to a mem slot other than 0, did you recall that slot after you turned on the unit? All Nanos default to mem slot 0 at power up.?
Can you check that the Apply box in the Calibrate menu is checked?
If everything seems ok. Redo the complete calibration again. I've seen this happen once in a while and recalibration usually fixes it.?
Cheers
Larry
 
 
  On Sun., 9 Jan. 2022 at 4:41 p.m., Mike Markowski<mike.ab3ap@...> wrote:   There is a better than even chance that my NanoVNA is fine and I'm the issue.? However, I started playing with my new unit this weekend and did some basic things, swept a little telescoping antenna and measured cable length.

Today, however, the measurements (pic attached, hopefully not stripped) were from a freshly calibrated NanoVNA running Dislord v1.1.00.? After a full range cal, then with 50 ohm terminator attached, vswr is bouncing all over the place.? If I try to calibrate ranges for 140-148 MHz or 420-450 MHz, vswr shows infinity.

I've handled the vna carefully and haven't yet tried characterizing filters or anything where'd I'd transmit into the NanoVNA, so there's no chance of exceeding input limits.? Can more experienced users say if it sounds there a chance I have a bad unit? Have I overlooked something beyond reset and re-cal?

Thanks very much,

Mike ab3ap

Re: Using NanoVNA to measure receive antenna port impedance #measurement

#26488

I doubt it, since measuring at the equipment’s antenna port you’re measuring the circuitry inside and there’s no telling what the ‘results’ will be.  But you’ve nailed down how to test measuring for a specific impedance; any simple non-inductive resistance will work.  Same principle for testing ununs / baluns / any impedance matching network. 

Have fun!!!

"Silence is golden. Duct tape is silver."

Show quoted text

On Jan 9, 2022, at 16:30, Jeff Green <Jeff.L.Green1970@...> wrote:

?The Backstory:
The company I work for has been merged via hostile takeover with a nother company and most of the employees are being laid off or offered early retirement. A coworker is relocating to a company in Texas, cleaning out and gave me a year old, unused, Nooelec NanoVNA - Open Hardware Vector Network Analyzer Kit.
The Analyzer kit included SOLT calibration kit.

I downloaded NanoVNASaver.x64 from 


I've played with the hardware and software enough to be passably familiar with the process, I used a 75 ohm CATV terminator to produce a 1.5:1 mismatch and the results were what I expected.

Goal:
Given my hardware, software, and less then stellar knowledge and skill set, is it practical to measure the actual antenna input port impedance of several general coverage receivers?

I tried using the search function to see if anyone has already tried this.

Thank you
Jeff

New NanoVNA possibly malfunctioning?

#26487

There is a better than even chance that my NanoVNA is fine and I'm the issue.? However, I started playing with my new unit this weekend and did some basic things, swept a little telescoping antenna and measured cable length.

Today, however, the measurements (pic attached, hopefully not stripped) were from a freshly calibrated NanoVNA running Dislord v1.1.00.? After a full range cal, then with 50 ohm terminator attached, vswr is bouncing all over the place.? If I try to calibrate ranges for 140-148 MHz or 420-450 MHz, vswr shows infinity.

I've handled the vna carefully and haven't yet tried characterizing filters or anything where'd I'd transmit into the NanoVNA, so there's no chance of exceeding input limits.? Can more experienced users say if it sounds there a chance I have a bad unit? Have I overlooked something beyond reset and re-cal?

Thanks very much,

Mike ab3ap

VNA_220109_160255.bmp

Funds for 2022 nanovna-users group annual fee

#26485

All,

As I posted yesterday, we have sufficient funds pledged to pay the groups.io fee for 2022.? The response, in under two days, has been overwhelming.

**Further pledges are not necessary**.

We will need to do this every year going forward, so there will be ample opportunity to contribute in the future.

Thanks to everyone who has pledged to support the group.

The next steps for collecting the pledged funds and paying the fee to groups.io will occur starting next week.

DaveD

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Re: Upcoming payment for this group

#26484

I have been a member of the group for a few months, and have derived significant knowledge and benefit. I would certainly be willing to do my part by making a similar contribution.
Thanks

Show quoted text

On Jan 9, 2022, at 14:28, Dave Daniel <kc0wjn@...> wrote:

?Pat,

No, there is not link. I was asking for pledges, not actual funds at this time, just so I could gauge whether we could meet the expense by small amounts of funding from various members.

Thanks.

Dave

On 1/9/2022 11:49 AM, lobos305 via groups.io wrote:
I'd be glad to help.  Is there a link?

Pat

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Re: Upcoming payment for this group - Response about a Donation

#26483

I can help with a donation.

Show quoted text

On Sun, Jan 9, 2022, 11:34 AM Dave Daniel <kc0wjn@...> wrote:

Tominaz,

We have received pledges for funds sufficient to cover the expense for
2022. I have put your name on the list of people who have offered to
donate.

We will be doing this every year going forward.

Thank you.

Dave

On 1/9/2022 1:20 PM, Tominaz wrote:
Tominaz $5.00 will be best $5.00 I ever spent

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Re: Upcoming payment for this group

#26482

I will pledge $5 toward the fee.  Raymond Lewis, AA4EZ

Bi direction amp

#26481

I have a small bidirectional amp, I'm using a 20db attenuator.  The way I have setup to measure TX gain:

S11 to amp input
S21 to 20db atten then connected to amp output.  

I'm see the gain of TX, How do I check RX gain?

Re: Upcoming payment for this group - Response about a Donation

#26480

Tominaz,

We have received pledges for funds sufficient to cover the expense for 2022. I have put your name on the list of people who have offered to donate.

We will be doing this every year going forward.

Thank you.

Dave

Show quoted text

On 1/9/2022 1:20 PM, Tominaz wrote:
Tominaz $5.00 will be best $5.00 I ever spent

-- 
This email has been checked for viruses by Avast antivirus software.

Re: Upcoming payment for this group

#26479

Pat,

No, there is not link. I was asking for pledges, not actual funds at this time, just so I could gauge whether we could meet the expense by small amounts of funding from various members.

Thanks.

Dave

Show quoted text

On 1/9/2022 11:49 AM, lobos305 via groups.io wrote:
I'd be glad to help.  Is there a link?

Pat

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Re: Upcoming payment for this group

#26478

I'll pledge $5, let us know if more is needed when the time comes.

-- 
Phil KE3FL

Re: Upcoming payment for this group - Response about a Donation

#26477

Tominaz $5.00 will be best $5.00 I ever spent

Re: Upcoming payment for this group

#26476

I'd be glad to help.  Is there a link?

Pat

Re: Upcoming payment for this group - Response about a Donation

#26475

Hi all,?
Not?sure what you actually still?need but can donate $10 US if still needed etc.?

Regards Dennis G6YBC

Show quoted text

On Sunday, January 9, 2022, 10:16 am, cosbug@... wrote:

Count me in for $5 as well.

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