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Db range


johnjgormley 2021/12/21 11:40

Hello. I have used my nano VNA on mobile duplexers and it works great. I bought an external duplexer  that isolates up to 90 DB. I see that the specs only show the nano VNA going to 60 to 70 negative Db gain. When I hook the external duplexer up I can only get it down to just above -30 DB. Is that adding the -60 max +30? so does that mean I have 90 DB of isolation?  How does that work? Thank you

John Gord 2021/12/21 22:36

John,
Assuming you have calibrated your NanoVNA (short, open, load, and through), It probably means you only have about 30 dB of isolation in your setup.  Beware that you need to be very careful in setting up the test of a duplexer.  Poor cables and connectors can easily ruin otherwise good isolation.
The NanoVNA can't directly provide a measurement to -90dB, but it should be able to at show the response down to -60dB or better.
Do a search on "NanoVNA duplexer" to get some ideas on how to do your setup.
--John Gord

On Tue, Dec 21, 2021 at 07:57 PM, <johnjgormley@yahoo.com> wrote:

johnjgormley 2021/12/22 07:59

Hello. Thanks for your reply. No, I don’t believe the -30db is accurate. I can hook up a mobile duplexer and it gets down to -51. Also, since I sent this out yesterday, I tested another external duplexer and it shows the approximate same results. Right around -30. I doubt that both external duplexes are only getting down to 30 DB of isolation. It must be adding the max (60) plus what is displayed.
thanks
john

W0LEV 2021/12/22 17:51

No, John, you do not add the -60 dB to your reading of -30 dB to get -90 dB
of isolation. You have -30 dB of isolation. If your noise floor is -60
dB, that is the bottom of your dynamic range. You can not "squeeze"
another 30 dB below that.

Are you measuring in the transmission mode: Port 00 to duplexer to Port
01?

After a complete cal and storage of that cal (properly executed and stored
cal), what do you measure on the through configuration without the duplexer
using the same cables you use to measure the duplexer?

Disconnect the through cable. What do you measure for the noise floor in
this configuration?

Dave - WØLEV

On Wed, Dec 22, 2021 at 5:35 PM johnjgormley via groups.io <johnjgormley=
yahoo.com@groups.io> wrote:

> Hello. Thanks for your reply. No, I don’t believe the -30db is accurate. I
> can hook up a mobile duplexer and it gets down to -51. Also, since I sent
> this out yesterday, I tested another external duplexer and it shows the
> approximate same results. Right around -30. I doubt that both external
> duplexes are only getting down to 30 DB of isolation. It must be adding the
> max (60) plus what is displayed.
> thanks
> john
>
>
>

--
*Dave - WØLEV*
*Just Let Darwin Work*

Siegfried Jackstien 2021/12/22 20:15

To say in short.. You can not tune a duplexer to 90 or 100db isolation with
that device.. Impossible!!

A kc901 can be used for that but that is way more expensive...

If you use the software satsagen

And TWO plutos.. Both mounted in its own metal case... And with good shielded
cables... You maybe get enough isolation... But the dynamic range is limited..
Means its not easy to setup right..

Getting to over 100db isolation and similar high dynamic range is tricky

Dg9bfc sigi



Am 22.12.2021 18:51 schrieb W0LEV <davearea51a@gmail.com>:

> No, John, you do not add the -60 dB to your reading of -30 dB to get -90 dB
of isolation. You have -30 dB of isolation. If your noise floor is -60 dB,
that is the bottom of your dynamic range. You can not "squeeze" another 30 dB
below that.
>

>

>
>

>

> Are you measuring in the transmission mode: Port 00 to duplexer to Port 01?
>

>

>
>

>

> After a complete cal and storage of that cal (properly executed and stored
cal), what do you measure on the through configuration without the duplexer
using the same cables you use to measure the duplexer?
>

>

>
>

>

> Disconnect the through cable. What do you measure for the noise floor in
this configuration?

>

>
>

>

> Dave - WØLEV
>

>

>
>

>

> On Wed, Dec 22, 2021 at 5:35 PM johnjgormley via
[groups.io](http://groups.io)
<johnjgormley=[yahoo.com@groups.io](mailto:yahoo.com@groups.io)> wrote:
>

>

>> Hello. Thanks for your reply. No, I don’t believe the -30db is accurate. I
can hook up a mobile duplexer and it gets down to -51. Also, since I sent this
out yesterday, I tested another external duplexer and it shows the approximate
same results. Right around -30. I doubt that both external duplexes are only
getting down to 30 DB of isolation. It must be adding the max (60) plus what
is displayed.
> thanks
> john

>

>
>
> \--
>

>

> **Dave - WØLEV**
>

>

> _ **Just Let Darwin Work**_

>

>
>



_._,_._,_

* * *

OwO 2021/12/23 04:49

V2 Plus4 can tune duplexers to -90dB with the appropriate settings.
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