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Saturday, 27 June 2020

NanoVNA V2

(my own V1 next to a V2)

First a tiny bit of history. The original nanoVNA that originated with a japanese engineer has seen a lot of interest, eddy555's original NanoVNA design has already been released for several years prior to the current NanoVNA popularity boom, but during those years eddy555 was only selling the product in small quantities as a DIY kitset.
The current low cost NanoVNA's available on the market now are mostly the "hugen" version known as the NanoVNA-H. Hugen is a ham who innovated on eddy555's original open source design, adding features like battery management, improved PCB layout, PC software and extending the frequency range from 300 MHz to 900 MHz. Then a group HCXQS put together and redesigned the low cost VNA and called it V2.

From the product pages:
"S-A-A-2 NanoVNA V2
3GHz vector network analyzer, designed in collaboration with OwOComm. Under the LGPL license agreement, it is completely manufactured according to the v2_2 files issued by OwOComm at Development Department, in line with the original technical specifications designed by OwOComm.
The S-A-A-2/NanoVNA_V2 uses a similar user interface to the NanoVNA, but with a different technical architecture, the S-A-A-2/NanoVNA_V2 does not load the initial calibration data at startup, and does not automatically interpolate the calibration data after the user changes the frequency, and must recalibrate or call back the calibration data after each startup and frequency change. Please read the user manual carefully before use to avoid damaging the device.
User guide:

  • Frequency range: 50kHz - 3GHz
  • System dynamic range (calibrated): 70dB (up to 1.5GHz), 60dB (up to 3GHz)
  • S11 noise floor (calibrated): -50dB (up to 1.5GHz), -40dB (up to 3GHz)
  • Sweep rate: 100 points/s
  • Display: 2.8'', 320 x 240
  • USB interface: Micro USB
  • Power: USB, 300mA
  • Battery: not included. Includes charging circuitry. User can install a 1000mAh - 2000mAh lithium-ion battery with maximum dimensions 6 x 40 x 60 mm.
  • Battery connector: JST-XH 2.54mm
  • Maximum sweep points (on device): 201
  • Maximum sweep points (USB): 1024
  • Port 2 return loss (1.5GHz): 20dB typ
  • Port 2 return loss (3GHz): 13dB min
  • VNA-QT software supported platforms: Linux, Windows (7+), Mac OS planned
I would suggest that none of the original, later versions or even the V2 are what many might refer to as 'lab grade' equipment but they do provide a tool that will measure RF filters, tune antennas, measure coax cable loss, and find cable faults.

I have had a few of the original NanoVNA and now I have both an original of obtained from Tindie or
of the V2 and 'clone' from an alternate source (AliExpress) , all being in China, this blog post aims to show the similarity, or otherwise, of these two and what sort of measurements are possible.

I should point out that the design and all the supporting technical information on these is open source. So it is possible to clone them. That means that the original funds the designers the clones do not (not at this time anyway). The impact is that whilst the original might be properly supported the clones may not.

There have been other open source designs 'ripped off' in this manner and it is the responsibility of the purchaser to ensure that they are not unwityingly supporting piracy of this type.

My review of the devices will follow here.

Images of them as they arrived:
The original:

Side by side the clone (from AliExpress):

The clone had a small laser cut acrylic case (these photos are with the protective layer still in place), the pieces are clear.

I will test and compare mine briefly with current devices and the like. A review of this site might be useful.

I have that RF  board mentioned with unmodified U.FL connectors.

Tuesday, 19 May 2020


Just waiting for a couple of kits to come through to me a through hole and a SMD version. Both will have a 2x16 LCD and I suspect I will mount them like this.

I have some of the grey slope front meter boxes (from an Australian trip when bought some from Jaycar)

More details

More images... thanks to Dr Le Hung for permission.

the TH version single side PCB can be made with information found in the zip file download here:

Saturday, 18 January 2020

3D Print Stuff

Finally getting around to updating a few things on Creality Ender 3 printer, so going to donate some of the older bits to update an older K8200.

The older V 1.1.3 motherboard will replace the older board or Arduino & RAMPS board.

Will add raspberry Pi and Octoprint and Octoview to it.

New stepper motors for all the axis and extruders. Will add some stepper dampers as well.

The old bed and thermstor will replace with a new one and add the glass Ender 3 bed I had used.

As using TCM2208 steppers on the Ender 3 so will add the TL smoothers to the K8200 instead which will use the original Ender 3 stepper drivers.

Have a couple 1.75 mm filament extruders and a dual head so will make it dual filament, PVA for one. The 3mm (2.85mm) extruder and original nozzle will be put to one side.

Spare BLT V2 so will add auto bed leveling.

Meanwell 24V PSU

Will add LED strip (separate 12V 3A supply).

This will then be used to create test enclosures.

Thursday, 12 December 2019

Measuring harmonics when main RF at 400W

No photos of the setup just yet.

This is probably easy for those that might have done it. Maybe?

Got an RF output at 7Mhz c400W using one of those broadband dual SSPA LDMOS things, NXP sent me some nice samples even though explained I was qrp, anyway pretty sure there might be some mixing product output at 3.5Mz and 14Mhz as well as higher (no surprises really) before necessary filtering. Exciter sending either single carrier or 2 tone stuff (I have something was from Far Circuits that can send a matrix of up to 8 different tones in pairs). So just to see how effective different filtering options were as I originally though the extra signals/ 'problem' was due to a cheap audio amp 65V SMPS being used but it wasn't as I borrowed an expensive supply and saw the same issues.

I was messing about with use of various filters between the exciter c1Watt and different 1st stage transformers into the amp the later seemed to make a huge difference as do coax stubs (not terribly practical in a PA even if just a coil of RG174) but pretty sure even though well down the mixing product signals are just detectable at the output. Definitely well down on the primary and pretty sure they comply (c-50dB) but trying to work out exactly how far 'down' they are and any other mixing products as working out RF budgets. Having been qrp for years you don't really want a readable signal either.


I first noticed I could detect 'something' on a PHSNA (see this blog, or Google for it, another ARCI/GQRP homebrew thing) so decided I had to to see what it was and where.

So how:
Not having a £££ HP spectrum analyser to hand I decided to use an RSP1 (original version), with the latest spectrum analyser code, and sampling the output using, originally the head from a homebrew LP100A watt meter but found the signals seem better (and I can muck about with it without worrying too much about the commercial head) with a simple T68-2 transformer (about 30-40 turns of 18-22SWG c90% of the core is filled when turns spaced out) with the primary the center of a length of RG213 all on some PCB in a dicast box. This feed goes to a nice 5 chip resistor dummy load suspended in an olive oil can. All in all it looks just like one half of your typical vswr meter. I used my old 500Khz NoV current and phase meter on the feed in and out more for curiosity to see if I had attenuated any of the output signal before and after (no surprise no noticable effect). The max signal off the transformer based on a 400W RF carrier is about 5mV give or take, I might remake it to lower this but need to be sure the harmonics are still readable (if there). The harmonic signals are several magnitudes lower in the uV range. You can still 'see' those signals on the RSP much clearer as the noise floor is much lower than the PHSNA (I noted the background noise floor was almost 10dB higher when up in Cambridge). The exact transformer ratio (or the maths calculations anyway) wasn't that important just as long as the voltage produced is well below what the RSP front end can reasonably handle. It didn't look like enough but I didn't want to attenuate ALL the signals so using some sample filters I had been thinking for a use for (just like those TOKO cans) I created a band stop that attenuated it further at 7Mhz, I wasn't worried by how exactly much as long as well well below the needs of the  RSP1 front end and the signal peak was well down. As the RSP and software combination was not really calibrated (I guess you could), I used a separate signal generator (a USB board with an Si5351 thing I think G0BBL gave me a few years back) to select the exact same frequency and match the amplitude on the SDR with an adjustable output (simple pot really) and then using a cheap chinese AD8137 RF detector (temporarily borrowed from the QO100 project!) and DVM (the AD amplifies the signal back up again by about 55dB) so you can roughly calculate the RF power levels. I hope that is simple enough explanation? The original voltages are down at the uV level I might rewind that transformer to increase it bearing in mind that the fundamental increases too.

I am sure lots have done something like this themselves which investigating HF amps and harmonics. I might be interesting to see any comments? Especially anyone that does this professionally.
I assume I might be able to work out some of the third order intercepts etc if I can crack this.
Not sure I'd ever use the finished PA as intended but this is an interesting albeit perhaps academic exercise all the same.

Monday, 16 September 2019

CNC2418 and TUX

TUX inspecting the led. Got a new switch box for the 12v LED and fan, along with some cable-chains and xyz stops.

What is TUX doing here? Apart from adding quality control, simple really the controller I rewrote with linux code so he is watching for bugs.. 

Tux had been in the shack hibernating amongst the bugs (spiders) but is now ready for more build projects.

EASY-100 PA options

The options for PA are multiple.

I have a couple of these which were said to not work too well but a mod was suggested and a couple in parallel 'should' be enough.

I also have an RF2126 which should be a bit better

and of course the EPAB


My Bodges.

Does it fit (trial)

The SMA are not always exactly straight :-) So GHz RF will have to go around corners.


The in and out will be via 2 N type chassis connectors I have used a couple RG316 pig tails for now.

The lid fits (yes the PA and the 2.4GHz LPF will go in another enclosure.