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Success! Removal of the FM9688 and adding the jumper did the trick. The nVNA starts up every time. I'm using an external battery pack with it. Thanks! --Al

You can try to remove the FM9688 first in order to confirm if it is caused by a fault in the FM9688.

Hugen, thank you for your reply. Do you think it's worth trying to replace the FM9688 IC? I have some experience and equipment to work on SMD and that chip has enough spacing of its leads to make it

Thanks for the suggestion. I tried it, but all I get is a more dramatic flickering of the display at a slower rate. --Al

It looks like the power IC is malfunctioning, so if you are willing to work without the battery, try removing the FM9688 and shorting pin4 and pin8 of the FM9688 location on the PCB.

Try disconnecting the battery, disconnecting the USB cable, powering it on to discharge any caps, and then boot it with just the USB as power supply? Battery might be getting soft... 73, Willie N1JBJ

Hello all, I'd had this nanoVNA-H for a few years, h/w v.3.4, and it's had this startup trouble for a long time. At power on, the screen lights up, a blank screen flickers as if trying to boot and

circle is the series circle" .... or is that back-to-front?? I've read it exactly this way in another article too. And in some other article I found it the other way around. IMHO I think it's just a

Hi, Re this article is Point 3, Page 3 correct ?? ie "The right/constant resistance circle is the shunt circle, and the left/constant conductance circle is the series circle" .... or is that

Hi Miro, Yes, you need 2 jumpers to engage a section, but only 1 to bypass it. It is more convenient to keep the 2 jumpers together, this way you switch the section with a single motion of turning the

SimSmith is a very powerful application. It's free and can be accessed at: http://www.ae6ty.com/smith_charts.html and an excellent tutorial specifically addressing SimSmith:

A nice document with a lot of good information.? The restrictions on impedance matching range in Figures 4 and 5 of the Abracon white paper are shown in more detail in Figures 5.57 and 5.58 of the

Nicely done Mike! Just a quick question - why do you need "dual" jumpers? Would it work if you have a single jumper per attenuator, so either you have attenuator engaged (jumper off) or shorted

And to answer to the google search string with another - "impedance matching lc calculator" :) Here are some https://leleivre.com/rf_lcmatch.html

I have read it and as a complete beginner to this it looks very useful. It's increased my understanding of the matching process. Intriguing that for a simple single frequency all that's involved is

ALL- I never saved the link and I looked at Banggood.com and do not see any like the ones I had. Frankly that purchase was pre-pandemic and Banggood is like Amazon.. A collaboration of individual

Yes and thank you for posting the link. At the time of my post I was on a computer interface that was very minimal!!! However, again thanks and that is the correct location. Enjoy.

I did not read it either, however here is the link: https://abracon.com/uploads/resources/Abracon-White-Paper-Antenna-Impedance-Matching.pdf John

Larry- No worries, I understand...

Plug in the search phrase: Antenna Impedance Matching Simplified authored by company Abracon It will get you there. Dave - W?LEV -- *Dave - W?LEV* *Just Let Darwin Work*