Re: VNArduino project

DuWayne Schmidlkofer

Here is another 1 port VNA you might be interested in

DuWayne KV4QB

On 11/30/2017 12:27 AM, Vaclav vaclav_sal@... [PHSNA] wrote:
Clifford thanks,
I'll take a closer look at the datasheet...
As far as using AD8302 module - this is my fist real SMT project and I decided 
NOT to solder SMT IC's especially  when someone already done that.

But you make a good point - there are few copies of the original design with not much circuit description.
Most of the "description " is how wonderfully  it works in different "mode" and with cool display(s) - CD, TFT etc.
Just a note - I dropped the "Arduino"  - I have "just " HF VNA.
I used VNArduino in my post becuse that is whan is "on the market".
And for other reasons...


On Wednesday, November 29, 2017, 9:51:09 PM CST, Clifford Heath clifford.heath@... [PHSNA] wrote:



Read the data sheet for the AD8302. The module just puts it on a board.

There are two independent multi-stage log detectors, and a mixer that
multiplies the two signals. The phase detection relies on the two signals
being close in amplitude (within 30dB, which limits the depth of a null
you can detect). There is no filtering at all, so whatever comes out of
the mixer gets detected as phase, even if the two signals are on
completely different frequencies. Same deal with the relative amplitude;
it's only *relative* amplitude of the transmitted vs *all* received signals.

It was designed to recover a video signal from a clean filtered IF.
I.e. it works ok if you have clean signals and no interference. When
probing an antenna, that pretty often just isn't the case; especially
up on a roof where other antennae are transmitting. A real VNA is
immune to off-channel interference.

Clifford Heath.

> On 30 Nov 2017, at 2:40 PM, Vaclav vaclav_sal@... [PHSNA] wrote:
> I have not really look at the schematic / concept details of VNArduino.
> The AD8302 module is coming without much doc ( as expected from e-bay) , but from the looks of it the output has some componets , perhaps filter? I will do some "reverse enginnering " when the module arrives.
> I am in hardware stage and as much as I appreciate your comments I'll use AD8302 alone for now.
> I need to clean up my spec , I keep a log of "progress" and it is getting little cluttered.
> Give me couple of days.
> On Wednesday, November 29, 2017, 7:49:38 PM CST, Clifford Heath clifford.heath@... [PHSNA] wrote:
> On 30 Nov 2017, at 12:21 PM, vaclav_sal@... [PHSNA] wrote:
> > I am repackaging VNArduino VNA.
> > This is just an amateur project, not an attempt to reinvent the wheel.
> > I am using the original VNArduino as base - changing some hardware and controller / processor.
> > This is strictly a fun amateur project NOT intended to be mass for profit production.
> >
> > I welcome anybody who wants to participate.
> I'm doing a similar project at the moment, and also wanted to
> use the AD8302... until I decided that I didn't.
> The problem with the VNArduino is the very limited rejection of
> spurious signals of they AD8302, which picks up *everything*.
> If you want to analyse an antenna, you need a more selective
> front-end because you're often in a high-RF environment.
> The same problem exists with the PHSNA, of course.
> The current plan is a bit more sophisticated and *much* more
> capable. It uses a mixer and a dual-channel DDS (AD9959)
> that's good to 200MHz. The LPF after the mixer allows rejection
> of anything more than 10KHz away from the transmitted signal.
> There's another cunning aspect regarding phase detection that
> I won't go into here. It involves digitising the audio off the mixer.
> If you're interested in using the AD9959, I wrote a library for it:
> .
> In any case, I'd like to see your spec please.
> PS
> I did look at github and have to say I am impress with readme.
> It actually contains useful info instead of usual copies of "open source" legals.
> Clifford Heath.
> > At preset I am collecting necessary hardware and laying out PCB.
> > I envision to have ability to use any suitable controller / processor and associated hardware.
> > I have written short specification to keep the project from wondering of the track.
> > If anybody is interested I can share the spec, but NOT in public.
> >
> > Vaclav
> >
> > 73 AA7EJ
> >
> >

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