SAA-2N Vector Network Analyser made by Zeenko

I had been looking for a VNA which would work outdoors and which could optionally be connected to a PC with software for bench work indoors. The VNA is built in a nice metal box with N connector sockets. The label on the back says 50k-3GHz, H/W version V2_2.

It came in a nice protective case & included a calibration kit.

I loaded the VNA-QT software onto my Ubuntu Linux PC. This allowed me to upgrade the firmware on the VNA.

Updating the firmware

The VNA had version 202001117 on it when it arrived. This seemed to be a bit buggy, so I looked for the latest version. I found Unofficial Hardware Variants , “V2.74” from blackmagic 2020-10-13 firmware download worked OK. 106kB loaded.

Holding down the left-arrow button on the VNA (the button closest to PORT1) and switching on the VNA gave me a white, blank screen, indicating serial upgrade mode.

SAA2/NanoVNA V2/V2 Plus/V2 Plus4 user group forum

I have discovered today (2-April-2021) that the original developers have a dispute with Hugen/Zeenko. So having found what I took to be officially-supplied firmware for “Unofficial Hardware Variants”, I now see there may be really no support at all. This is a complicated world!

Portsdown + Langstone both using “3D Sound” USB audio dongle

I already had Langstone outputting sound via a “3D Sound” USB dongle. I wanted Portsdown sound to come out of the same dongle.

I referred back to Dave G8GKQ’s advice on the BATC forum.

I connected the Linux PC to the Portsdown‘s RasPi4 by ethernet, booted Portsdown & ran a putty session in a terminal, chose Hostname (or IP address) as (the address I’d specified in Portsdown), port 22 and then clicked Open.

In the putty window I logged in with:

User: pi
Password: raspberry

With the “3Dsound” dongle plugged in to the RasPi4 I checked the available devices by entering arecord -l. This produced the report as follows. Note the reference “Set“:

card1: Set [C-Media USB Headphone Set],device 0:USB Audio [USB Audio]
subdevices: 1/1
Subdevice #0: subdevice #0

I edited the file which specifies the audio output device for Portsdown:

cd ~/rpidatv/scripts

Line 57 was the then clause in a nested if statement:

if [ s? == 0]; then

I edited “headphones” to “Set” (for the “3D Sound” USB dongle) and saved the amended file. I left the Config setting Audio Out = RPiJack. On re-booting Langstone, I got sound through the USB dongle from LongMynd. So then both Langstone and Portsdown output sound via the “3D Sound” USBdongle.

RF power meter: HP363 Chinese board: 1 MHz to 10 GHz

I bought a power meter board over eBay. It has a plug-in display screen board which sits on top of it. It is rated up to 1mW, so needs good attenuators and/or a directional coupler. The soldered connections for the SMA connector needed re-soldering.

I cut a bit of polythene foam to support the floating edge of the display board:

I plugged the display board in:

I couldn’t find a source of ready-made extensions for the SMA buttons on the board, so I improvised by sticking a bit of plywood inside the lid and drilled holes in it for dowel pegs:

I had salvaged a button facia from an old mobile phone. I cut a piece of this for dowel covers & stuck it on with superglue:

It is a bit of a bodge, but it works! C toggles from add to subtract, CL toggles between Power Measurement and Attenuator Setting, OK alters the attenuator setting (adding or subtracting). Menu covers up a blemish on the case.

Ebay 1-Jan-2021: Changes to VAT treatment of imports into the UK

This is going to affect delivery of little packets of electronics from China and elsewhere:

  • The current VAT exemption for imports of goods in small consignment of a value of up to £15 into the UK will be abolished.
  • eBay will collect and remit VAT on consignments up to a value of £135 imported into the UK and sold to consumers.
  • In cases where the seller is a non-UK business and the goods are already in the UK, eBay will collect and remit VAT for supplies of goods sold to consumers within the UK.
  • If the buyer is a UK VAT registered business and provides their valid UK VAT registration number, the responsibility to account for VAT will switch to the UK VAT registered business customer.
  • All sellers will have to provide a gross price and separate VAT rate on their UK listings, so that eBay can determine the correct amount of VAT to collect from consumers.
  • All prices will be displayed inclusive of UK VAT.  Where eBay is responsible for collecting VAT, this amount will also be shown separately at checkout.

Connecting the ADALM-Pluto using Ethernet

I want to try controlling the Pluto from Portsdown4 via Ethernet rather than USB.

I obtained an Ethernet-to-USB 3.0 adapter and a short USB Micro male to USB female adapter lead. Here is the Ethernet-to-USB 3.0 adapter.

This is the USB Micro male to USB female adapter lead:

The USB Micro male plugs into the Pluto, the USB female connects to the Ethernet-to-USB 3.0 adapter.

With the Pluto connected to the Linux PC directly via the usual USB cable, I opened the Pluto mass storage “drive” on the PC. I edited the config.txt file with gedit.

I edited ipaddr_eth to be my chosen IP address for the Pluto and gateway_eth to the address of my router. Note: it is not advised to have the Pluto on the same sub-net as the internet connection, so I intend to change this later.

 ipaddr_eth =
 netmask_eth =
 gateway_eth =

I removed the USB cable and connected the Ethernet-to-USB 3.0 adapter USB to the Pluto. I connected the Ethernet-to-USB 3.0 adapter to the network with an Ethernet cable (the yellow cable in the picture) with RJ45 plugs. The Pluto also had a Power Supply feeding it.

I was then able to ping and also browse the Pluto at, so the Pluto’s Ethernet connection seemed to be working.

On the Linux PC, putty connected to the Pluto fine.

Portsdown4 + Langstone video

I moved the new Raspberry Pi 4 into the Portsdown box and used the Portsdown functions to upgrade both Portsdown and Langstone software versions to their latest versions. Via putty, I ran set_sound to select my “3D Sound” audio dongle. I fed the output to the speakers in the box via a little audio amplifier.

Here is a video of switching from Portsdown to Langstone and back. Langstone was still tuned to the GB3KEU beacon on 6cm or thereabouts, but there was no RF input to the Pluto.

LED lighting: RF quiet and RF interference from SMPs

I already knew that some Refrakta LED “bulbs” I had bought from Maplin years ago generated a lot of RF. I used a cluster of 3 bulbs with GU10 connectors in the kitchen light fitting. Each bulb had 4 super-bright LEDs so must have had built-in switch-mode power supplies (SMPs) to produce the low DC voltage, SMPs which generated RF. I fitted ceramic 1nF 1kV capacitors (Line-to-Earth and Neutral-to-Earth) and replaced the bulbs with LEDs with longer LED chains 31 LEDs per bulb. This much reduced the problem at VHF.

I did a contest on Top Band (160m) recently and this prompted me to look at my high noise level and start hunting for noise sources.

Disappointingly, the kitchen lights were still a problem, adding about 30dB of noise on Top Band. I tried increasing the suppression capacitors to 100nF 1kV, but this didn’t help much. The bulbs look like this:

Inside there is a little SMP which generates the RF. The LEDs may last for a decade, but the SMPs are unreliable and may fail much earlier. In one bulb I bought recently, it failed within seconds with an audible pop.

I found that the living-room cluster of 4 LED bulbs was RF quiet. They have 80 LEDs on each face.

Looking inside, they seem to have no SMP, just a series capacitor, a rectifier a smoothing capacitor and a few other chip devices.

These RF-quiet bulbs came from zf304160642-1 on eBay.