EB5AGV's Workbench: building my VNWA Kit

A pretty cool and handy gadget for RF work

VNWA 2.6

This page is devoted to the construction of my VNWA 2.6 Kit designed by Tom DG8SAQ and distributed by SDR-kits

These are some of the characteristics of this VNA:

I got it at the end of 2010 from the last batch of kits available. Now you can only buy the unit assembled... I am not sure of the reason but, trust me, assembling this kit is not for the faint of heart!. Read on to know why...


Assembling the USB interface PCB

The original VNWA was interfaced via a PC parallel (LPT) port. That port is obsolete now so the designer decided to add a plug-in PCB to control the VNWA by a more common nowadays USB port.
So the first thing I did was to build the USB interface plug-in board. It has some SMD ICs but lots easier to deal with than the VNA PCB ones. All in all, here you have some pictures of the process.

The kit is beatifully packaged, as you can see here:

VNWA 2.6

VNWA 2.6

VNWA 2.6

VNWA 2.6

This is one of the SMD ICs being positioned prior to solder it

VNWA 2.6

And this is the unit soldered... it is not as difficult as it may seem.
Hint: use soldering flux

VNWA 2.6

This is the other SMD IC, already soldered:

VNWA 2.6

A general view of the PCB:

VNWA 2.6

And now more populated:

VNWA 2.6

The rear side, with the interconnecting plugs:

VNWA 2.6

Voila!

VNWA 2.6


Assembling the VNWA PCB

OK, now that I had the easy circuit, I went for the real one!

This part of the kit is even more carefully packaged

VNWA 2.6

VNWA 2.6

VNWA 2.6

This is the PCB with one of the SMA connectors temporarily placed

VNWA 2.6

You need to file a bit the PCB in order to properly fit the connector

VNWA 2.6

Assembly manual is nicely written and provides an step-by-step approach so you build a part, check it and then go for the next one.
This is first part, the main power supply

VNWA 2.6

Then you add some more components and check they are OK

VNWA 2.6

So far, so good... now, let's start with the dreaded DDSs!. No, my finger is not unusually large ;-). You can see how tiny these items are. And how many pins they have!

VNWA 2.6

After some work, here you have first DDS placed

VNWA 2.6

But... would it be soldered OK?. Let's use a magnifier...

VNWA 2.6

VNWA 2.6

It seems so!. OK, let's do the second one

VNWA 2.6

I checked the DDSs, using the VNWA software and, yes, they worked fine!!!
So let's continue with next step, the output section

VNWA 2.6

Once basically checked (only voltages and consumption), let's go with the input section:

VNWA 2.6

So we are almost done!!!. And this is the result

VNWA 2.6

Perhaps looking at the pictures it could seem a couple hours work... no, it took me lots more, because there are plenty of 0603 SMD components. And they are really small.
I wanted to do a good work, even with all SMD labels in same orientation and all soldering as nice as I was able to do. Here you have some detailed pictures

VNWA 2.6

VNWA 2.6

VNWA 2.6

VNWA 2.6

There is a semi-rigid coax which should be placed on the rear side

VNWA 2.6

VNWA 2.6

And then the SMA connectors... and this PCB is done!

VNWA 2.6


Final assembling of the VNWA

Once I checked the unit, it was time to put it inside its casing

VNWA 2.6

VNWA 2.6

VNWA 2.6

And this is the result of all the work, a little RF jewel!!!

VNWA 2.6

VNWA 2.6

VNWA 2.6


Some measurement samples

Available soon... keep tuned!


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