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it works, not very good, but at least you can use it to see overall performance your antenna or filter.

When you have choice to use up to 1500 MHz with limited dynamic range, this is definitely better than no choice at all :)

My understanding is that hugen pulled the initial firmware that allowed operation up to 1500 MHz because performance was so poor (probably especially true for those NanoVNA with oscillator chips that have trouble operating to 300 MHz). Subsequent firmware developers found they could get useable range extension by a change of mixer stimulus.

I have two NanoVNA's and have updated both of them to 1500 MHz operation. Above 900 MHz most of my measurements are s21 thru-loss. Between 900 MHz and 1 GHz I have about 30 dB of useable s21 measurement range on both NanoVNA's. Above 900 MHz increasing to 1.5 GHz the s21 measurement range gradually falls off to 20 dB on both units.

On each of my NanoVNA's, S11 measurements are acceptable up to 1 GHz but start to become suspect >1.2 GHz.

I consider the firmware upgrades (currently using hugen's 0.2.3 version) to be worthwhile for my two units. I might also add the new NanoVNA-H that hugen is marketing has the 1500 MHz firmware installed. So he must believe it is stable enough to use in his commercial product. The last thing he would want is bad marketing by including firmware that doesn't perform well.

- Herb

Hi Andy,
Well it can be used more or less up to about 1200 MHz, but the returnloss dynamic range from 900MHz to 1500Hz decreases from 30 dB to 8 dB.
Jos

yes, duplexer design is sensitive to termination Z.

Toss out some vna dynamic range for a second and pad the ch0 and ch1 ports with 10 db and try a retune. Cal with pads in place.

Alan

On Sun, Nov 10, 2019 at 05:42 AM, Kurt Poulsen wrote:

Understood, so it is without use of inline attenuators in TX and RX as the
noise was normal.

Nope. I did use a 10dB attenuator after the Tee, so before port 2, otherwise it would be much worse

--
Erik, PD0EK

--
Erik, PD0EK

The short answer is: It depends.

Tuning the S21 of a filter: yes, but not the stop band as there is very little dynamic range. There is a trick to gain 20dB. Tuning a filter has been demonstrated up to 2.1GHz
Measuring the impedance of an antenna: Doubtful. The nanoVNA measurement bridge loses directivity quickly above 800MHz. I could not tune an antenna at 886MHz
You may have luck when running on battery. Connecting to a PC during measurement makes performance above 600MHz worse.
--
Erik, PD0EK

I joined the group too late to catch this: What is a "T-check"?

Thanks,

Dana K8YUM

Hi,Where can I get this software nanovna partner, pls?
Trimis din Yahoo Mail pe Android

Pe Du, nov. 10, 2019 la 7:59, neb40gsm via Groups.Io<neb40gsm@...> a scris: Hi Roland,

Below are the tuning readings of my home UHF repeater system using nanoVNA. The repeater uses a notch-type duplexer and a
band-pass filter on its receiver. As Alan said don’t forget to terminate with 50 ohms dummy load the unused port during tuning.
Hopefully, the readings can serve as your reference.

Capture1 is taken when CHO is connected to the ANT port and CH1 is connected to the Low port while High port is terminated.
Capture2 is taken when CHO is connected to the Low port and CH1 is connected to the ANT port while High port is terminated.

But personally, I prefer to use my old HP8591E spectrum analyzer with TG? instead of nanoVNA when tuning duplexers and filters
because of the inhirent slow refresh rate of the nanoVNA.

neb

That is a good questiion. So much happens between 900-1000 MHz. I use LoRa in home automation and could make good use of that range. The 900 MHz just missed.

--
*Doug Basberg, N8VY*

On Sun, Nov 10, 2019 at 05:25 AM, Oristo wrote:

CH1 has worse impedance, it's about 45 Ohm

Should adding e.g. 4.7 Ohms in series with CH1 center pin on PCB
overall improve nanoVNA?

----------------------------------------------------------------------------------------------

I use a HP, 18 GHz, 3 dB sma attenuator on CH1. It increases the return loss of CH1 by about 6 dB and also acts as a port saver. The sma attenuator's profile is slightly longer than a normal port saver. Of course the trade off is that I lose 3 dB of through signal when using the attenuator.

- Herb

OK, so I see quite a lot of firmware updates appear to include 1500Mhz now.

Is it really usable ?

About 6 weeks ago or whatever when I last read about the trials, the trials of the Nano VNA's useablity
really appeared to be about 900Mhz, and attempting anything higher was a step too far.

Has something changed, or is 1500Mhz just appealing to vanity ?

Honest question, because if it is usable then I may revisit the idea of a firmware upgrade.

73 de Andy

Hi Roland,

One thing a very smart radio guy taught me is that tuning a duplexer using
test equipment is only going to get you 'close'.

Once you get close you should connect the duplexer in the field and use an
external rf generator to generate a signal to peak up the final tuning
'over the air'.

This is because duplexer tuning is impacted by the equipment and cable
impedances, which will not be the same as the impedances of the test
equipment used to do the initial tuning.

I can not do a good job of explaining exactly the steps to take to
accomplish this but just know that you will want to do some final tuning of
the duplexer once it is connected to your repeater/cabling/antenna
combination.

there is a good web site called 'repeaterbuilder' that you can search for.

73
dwight
n7kbc


--
dwight

Hi Erik
Understood, so it is without use of inline attenuators in TX and RX as the noise was normal.
I forgot to mention I had to edit the s2p file as the line telling if the frequency sweep is lin or log was missing
I attach the modified file
Kind regards
Kurt


-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af erik@...
Sendt: 10. november 2019 13:48
Til: [email protected]
Emne: Re: [nanovna-users] T-Check for my nanoVNA - Results look excellent below 150 MHz and acceptable up to 300 MHz

On Sat, Nov 9, 2019 at 02:31 PM, Kurt Poulsen wrote:

How did you obtain this fine result ? introducing error corrections ??

I'm using a firmware with some experimental features.
The most important change is fixing the SI5351 output power on level 1 You can do this with the "power" console command:
power 1
Normally power is set to -1 to tell the nanoVNA to automatically adjust the power but this introduces non-linearities so it is better to have constant power.
You have to recalibrate after setting the power to 1, this demonstrates the substantial impact of the nonlinearity


--
Erik, PD0EK

CH1 has worse impedance, it's about 45 Ohm

Should adding e.g. 4.7 Ohms in series with CH1 center pin on PCB
overall improve nanoVNA?

I still have extra diodes

You're needs to take into account that CH1 has worse impedance, it's about 45 Ohm on 500 MHz, so it may affect your measurments

Well... I now know what I can do today! :)
Many thanks for the links!

#76: The Big Three Free Software Tools Supporting The Independent Research
-
@Gary O'Neil, N3GO - 10 November 2019 :
/g/nanovna-users/message/6711

Dear Gary,

Thank you, since you are giving us the very rare chance nowadays to revise
all that 10+ years old work, to see its weaknesses, to try once again to fill its
gaps, to express new, improved, ideas
-
always facupov, about fundamental, considered as "well-known" concepts,
because, the Most Difficult Thing to Finally See is the Simplest One Standing
in Front of You
-
and to improve further our skills regarding:

The Big Three Free Software Tools Supporting The Independent Research

we are still using by combining their Symbolical, Numerical, and Graphical
abilities, that is respectively of:

[Maxima], [Open Watcom], and [GnuPlot].

Thank you very much, indeed.

Sincerely,

gin&pez@arg

:76#

Can anybody tell me what the right setting is for tuning a duplexfilter

This will not ALWAYS work, because e.g. "duplex" fails, but:
* go to /g/nanovna-users/wiki/home
* enter duplexer in Search box

In particular, there is quite a lot of duplexer stuff at