Re: Original NanoVNA a waste of money


geoffrey pike
 

THe SAA-2 is very different
Geoff
GI0GDP

On Sunday, 21 March 2021, 16:41:35 GMT, Andy G4JNT <andy.g4jnt@...> wrote:


I've had a DG8SAQ VWNA for a long time, now, which in terms of performance, quality of software, display capability and user interface knocks spots off these Chinese things.   Its a really professional quality bit of kit and would normally be the only one I'd ever use.   In use, it's as nice to use as the HP ones I used to use at work - just doesn't go nearly as high in frequency :-(

But it needs a PC attached, so when out in the garden or up a mast (!) a small self contained one has more than a few advantages.

These Chinese Mini VNWAs are a blatant rip-off of the DG8SAQ, that uses exactly the same hardware, NE602/612 mixers that conveniently have a differential input so perfect for taking the output from a resistive bridge right down to DC.  



On Sun, 21 Mar 2021 at 16:27, G8DQX list <list@...> wrote:

Andy,

the block diagram and circuit (schematic) diagram are at https://github.com/ttrftech/NanoVNA/blob/master/doc/nanovna-blockdiagram.png. What brings the machine alive, though, is the firmware, which has had considerable development over time.

There are occasional reports on the nanoVNA list (https://groups.io/g/nanovna-users) of touch screens failing due to cases fouling the surface. The usual solution seems to be to add washers or shims. One also has a vague recollection of solder splashes being a problem.

HTH, 73, Stay Safe,

Robin, G8DQX

On 21/03/2021 13:04, Andy G4JNT wrote:
Update.
I removed front ang back covers, and it started to - sort of - work.  The touch screen is a total failure, but I can drive it using the manual button thing.  replaced the covers and it stayed working.    SO I'm guessing an intermittent in a ribbon cable link on the touchscreen.
SO it has been saved from the sledgehammer for now.

Also took the opportunity to look inside, including lifting the covers over the RF portion. Pretty boring; three NE602 mixer chips, something that is obviously a soundcard type interface chip and one that is probably an Si family synth  - although the number was a bit meaningless.


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