开云体育

Hello Team,

Did anyone sucessfully inserted the nanovna inside a metal enclosure? Will that improve any accuracy and/or stability?

How to overcome the need to turn off/on every time we plug the USB cable to PC?

May I see some examples?

Cheers and thanks in advance!

Luis, CT2FZI

How to overcome the need to turn off/on every time we plug the USB cable to PC?

Use QRP firmware:

Based on my own trivial experiments, metal enclosure for worse unshielded clone
makes things somewhat worse above 600MHz.
Otherwise, limitations appear to be from internal crosstalk and e.g. mixers' nonlinearity.

On Mon, Nov 11, 2019 at 01:09 PM, SPACE OPQA wrote:

How to overcome the need to turn off/on every time we plug the USB cable to
PC?

With NanoVNA-Q firmware there is no needs to power off/on after USB connection. It allows to read paused sweep.

Regarding to USB disconnection, the reset happens due to hardware issue. IP5303 just remove power for some short period of time. So, this doesn't depends on firmware. You can keep NanoVNA alive with no reset at USB disconnect by applying external 3.3V power on the SWD connector at the right side of NanoVNA board.

May be adding some capacitor on power line will help to keep it alive with no reset. Needs to try.

I have boxed my NanoVNA in an aluminium box, no problems.

For the power switch, I simply connect a switch across the original switch, because you must keep the power connected
to the charger controller / original power to work properly.

For USB connection, I use magnetic USB connector.

73 de Andy

Also I do not use the "jog" switch.
I drag and drop the markers / and use all menu's by the touch screen.
I also use a simple and very cheap PDA stylus.
It makes life very easy and simple.

73 de Andy

Ugg. You used UHF connectors. They are not very good impedance above HF..... You should use N style connectors.

yes, UHF connectors have terrible performance even on HF

Golden rule of reducing uncertainty, use the connector type that you will be using to connect directly to
the equipment / antenna that you test.

Otherwise, I'd need more adapters to connect to a different type calibration kit that introduces just as
much uncertainty as the original UHF style connector.

I calculated that even at 500Mhz, my quick bodge PL259 cal kit would introduce 0..2 ohms on the 50R
load and a phase error of 3 degrees, and that's what I see.

So for those of us that are really 0-50Mhz users it's more than good enough, and certainly accurate enough
as a daily driver even at UHF.

Heck, I've relied upon no more than 2 x 1N4148's and an LED to tune my HF stuff up -



Even my HF amp uses one (see attached). (And that uses audio style push connectors for the antenna output) ;-)))
So using a vna like this is overkill for some of us.

The nice thing is, if at anytime my requirements change, then I just change the bulkhead connectors to suit



The larger box also allows me to introduce a larger battery if I need it.

At some time in the next few years that tiny Li-Ion is gonna fail and I may have difficulty replacing it.

With the extra space in the box, I could go for a a bunch of AA's, or even just a single 2000mah 18650 cell.

It works, it's future proof, no messy switch extensions, it KISS.

Time to think about an external component test fixture next to keep me amused.

Ideas anyone ?

73 de Andy