As of 2022 there are many badly performing clones on the market. V2/3GHz NanoVNA uses parts like ADF4350 and AD8342 which are costly and clones have been cutting costs by using salvaged or reject parts.
See official store and look for V2 Plus4/V2 Plus4 Pro versions only to avoid getting a bad clone. We have stopped selling V2.2 versions since October 2020, so all V2 hardware that are not Plus or Plus4 are not made by us and we can not guarantee performance.
I have some difficulties on understanding the design of the coupler in the NanoVNA v2. From what I understand is that this is a wheatstone bridge but I have some problems understanding the initial design process for that and where all the additional resistors are coming from. What was the initial design process to come up with 10dB transmission.
Hello,
It is not a pure Wheaston Bridge, but loaded resistive bridge. The main
difference is, that the diagonal (where you put the Galvanometer with
high impedance) is loaded with a 50 ohm too. In most cases of
reflectometric bridges there is a balun to get the diagonal output
asymetrical with one pin grounded. If you do the math (and do not forget
to use the 50 ohm generator - voltage source in series with 50 ohm
resistor), you should get the power getting from diagonal in proportion
to reflection coefficient.
Here is detailed description from the Rohde&Schwarz ZRB2 bridge manual.
http://ok1ufc.nagano.cz/radiotechnika/RF_Bridge_schema/SWR_Bridge.pdf
Dne 03.10.2021 v 18:31 spam@gamma-kappa.com napsal(a):
The last couple of messages in the below thread are also worth a read.
There is an article from the HP VNA guru Joel Dunsmore, and a newer article
from Brian (virtualparticles) who is an RF guru from Copper Mountain.
https://www.eevblog.com/forum/rf-microwave/can-a-siggensadirectional-coupler-be-used-as-a-poor-mans-scalar-analyzer/msg3631413/#msg3631413
On Mon, 4 Oct 2021 at 18:36, OK1VAW <ok1vaw@volny.cz> wrote:
To reply to this topic, join https://groups.io/g/NanoVNAV2
