Hello;
New here. I am trying to tune a duplexer. I am using the NanoVNA saver software on my laptop. I wanted to test a duplexer that I know is tuned correctly before I tune another one.  The Nano VNA was off by about 1500 Hz. No problem. Just need to calibrate it right? I've gone through all the steps calibrating both ports by following the instructions. Tried both with and without the cables I am using to tune the duplexer. Tested 2 known good duplexers. Same thing. Way off.  Am I missing something? Thanks
John

I am quite curious what is the frequency of the diplexer, that 1500Hz does matter. The other thing is, if the discrete pll step is not greater than 1,5kHz on nominal frequency during the sweep, you can see the used step on the screen. There is no special stable XO inside, so an error over 10ppm is quite probable, I suppose something between 10 to 100ppm. Owo can give a specification.

On Thu, Sep 17, 2020 at 12:14 AM, <johnjgormley@yahoo.com> wrote:

.. I am trying to tune a duplexer. I am using the NanoVNA saver software on my laptop. I wanted to test a duplexer that I know is tuned correctly before I tune another one.  The Nano VNA was off by about 1500 Hz. No problem. Just need to calibrate it right? I've gone through all the steps calibrating both ports by following the instructions. Tried both with and without the cables I am using to tune the duplexer. Tested 2 known good duplexers. Same thing. Way off.  Am I missing something?

John,
Gabriel responded the following in a previous post,  when asked about the frequency step-size of the SAA-2:

"I think the minimum doable step size is 6kHz, limited by the maximum modulus of the adf4350 fractional synthesizer which is 4096. The reference clock is 24MHz, and 24MHz / 4000 = 6kHz. I see that it's set to 12kHz step-size in the code; I'll try 6kHz tomorrow and see if there are any problems."

At that time the minimum step-size of the SAA-2 was 12kHz above140 MHz. I haven't checked if the change to 6kHz was ever implemented, but neither step-size would allow the tuning resolution you are trying to achieve - if the duplexer frequency is above 140 MHz.

- Herb

452 &457 MHz. Thank you

452 - 457 MHz

John,
If you want finer frequency steps above 140MHz, you can try the firmware at:
https://ojisankoubou.web.fc2.com/nanovna/nanovnav2.html#document
In the vicinity of 457 MHz, it gives a minimum step of about 750Hz.
--John Gord

and if that fw from that japanes hp would have the bigger buttons it
would be superb ;-)

typing in numbers with the smaller buttons is not easy (depending how
good your touch screen works)

but overall that fw works fine ...

cause i have two devices i have one with this and one wth that fw...
still figuring out what works best hi hi

greetz sigi dg9bfc

Am 17.09.2020 um 20:53 schrieb John Gord via groups.io:

> John,
> If you want finer frequency steps above 140MHz, you can try the
> firmware at:
> https://ojisankoubou.web.fc2.com/nanovna/nanovnav2.html#document
> In the vicinity of 457 MHz, it gives a minimum step of about 750Hz.
> --John Gord
>

At this frequency range 1500Hz are nothing to care about.

Also if this are antenna duplexers, you can't tune them with the
nanovna. The filter points change with load and source complex impedance.

So you need to do the fine tuning with the antenna, cables, transceiver
and receiver in place.

You need to couple the measurement signals with directional couplers to
minimize the influence to the setup.

you can pretune a diplexer with a VNA, but the finetuning can only be
done with real loads, sources and cables.

On transceiver side put a power meter between transceiver and diplexer,
also between diplexer and antenna.

Use only high quality power meters with perfect rf shielding and very
low SWR.

Also use only double shielded cables between diplexer and rx / tx.

Also separate the two cables to reduce coupling.

Also inject via a directional coupler and some attenuators a signal
generator to the diplexte rtransmitter input at the receive rfrequency.

So you can tune for low loss on you tx frequency and good rejection on
rx frequency.

Also use a directional coupler or pick off in front of the rx input for
a spectrum analyzer. With the SA you can adjust fro tx frequecy
rejection and rx frequency pass.

The rejection of tx frequency at the receiver input is mor important
then the damping of the rx frequency, because most receivers are very
sensitive to rf blocking.


If done right it is possible to have only 1 to 2 dB receiver side
damping and some percent loss of tx power.


Have done such setups for mobile LMR basestations a lot of times. No
chance to have a good setup without finetuning of the individual setup,
but then there was allways a very good and reliable performace over many
years.

Also please use a antenna with low sensitivity to environmental changes
like temetature, snow, etc.



Isidro

DB1SBI


Am 17.09.2020 um 16:53 schrieb johnjgormley via groups.io:

> 452 - 457 MHz
>