Tuesday, October 12, 2021

On ABC RN's Download This Show

This week I'm a guest on Marc Fennell's ABC RN "Download This Show".

"We’ll soon be walking around with them and flashing them to wine, dine and travel – but how easy will it be to spot a legitimate vaccine passport compared to a fake one? We discuss what could have prevented a security flaw and what’s being done about fake vaccine passports.  

Meanwhile, the Commonwealth Bank of Australia will be using an artificial intelligence tool to stem abusive messages being sent on electronic payments.

Plus, Facebook and Instagram introduce new features in an effort to protect young users from harmful content.

And would you wear a smart headband that claims to make you calmer?"

Marc was in the studio, I'm at home using an Audio-Technica USB microphone and I think it sounds as good as the studio.

uSDX tiny multi-band transceiver

The uSDX is not a great receiver or transmitter but it is usable and amazingly small. I bought mine through AliExpress. "uSDR uSDX 10/15/17/20/30/40/60/80m 8 Band SDR All Mode HF SSB QRP Transceiver Compatible with uSDX QCX-SSB".

Here's a recording of how a fairly week signal on 40m sounds:

The first unit I bought arrived with a broken screen. The AliExpress vendor provided free shipping for the return and refunded my payment.

I previously built the same circuit but this fully built version is more compact.

Manuel, DL2MAN who is the original designer of the uSDX sandwich contacted me with some comments about this (and similar) clone of his design. He has a video commentary and makes the following points:

  • His design is used but there is no credit to him at all
  • The license on the design was for non-commercial use only
  • He was never asked about a commercial license
  • The selling price is way above the actual cost (he thinks it would cost about US$40-$50) particularly as they are not supporting the developer
  • No effort was made with documentation, they've added no value for their margin
  • There are some changes to the schematic:
    • Output transistors have been changed but other parts of the circuit have not been adjusted
    • Harmonic suppression will be worse than the original design (and way below legal requirements)
    • Firmware upgrading is not easy as it was in the original design
    • The battery charging circuit is noisy
  • A physical design problem can short circuit the battery in the version with a battery
DL2MAN has now changed the license to Creative Commons but, of course, to comply manufacturers need to mention the source and re-publish their version under the same license.

So, all the materials are now available for legal manufacturing.

Manuel is clearly angry about the way he has been treated by the Chinese manufacturers who have stolen his work, without attribution and are profiting from it. There is an update of the design and Manuel feels it could be made for about $50 soon.

There's a video here that compares Manuel's latest version with one of the Chinese clones.

Friday, October 01, 2021

It's a good idea to update the Arduino IDE

There's some tribal knowledge around about Arduino IDE (and library) versions. I've heard from people that a certain version is the one that works and they don't want to update. Partly this is because they are using an old library and new code "breaks" the build.

Recently, I was talking with Paul, VK3HN, and he mentioned that he had a sketch that, when built for an Uno, was short of RAM.

Paul sent me the code, I compiled it, and didn't get the warning.

This was puzzling of course. I figured it could be one of two things:

  • One of the libraries had been improved to use less RAM
  • The gcc compiler bundled in the IDE had improved.
Here's the compile output from Paul:


Here's my output:


The figure is dynamic memory use:

Paul: 1539
Mine: 1132

Quite a big difference if you only have 2048 bytes of RAM.

It turned out that I was on a slightly later version of the IDE 1.8.15 (not even the latest) and Paul was on 1.8.12.

I tried the beta of Arduino IDE 2 and got the same memory use so I think the version of gcc bundled in it is the same. 

gcc has lots of options and, while I understand the Arduino IDE wants to keep thinks simple, it would be good if the compile options were exposed.

The lesson out of this is that the tools do get better and it's a good idea to upgrade.

Wednesday, September 29, 2021

Dallas, VK3EB's HF bush antenna

Dallas, like many of us, doesn't have much scope for a decent HF antenna at home so he has perfected the art of putting up antennas in trees. Check this out:


Excellent work!

Here's a previous video where I visited and you can hear some of the low noise reception available:



Tuesday, September 28, 2021

Facebook fake account scam promising "Mega Bonus"

This morning a friend said hello on Facebook messenger. The message said that we hadn't talked before - which was believable as we normally use other modes. I accepted the message and we were away:

"doing pretty good" was a red flag right away. "help the Old, Retired, Disable, " was another indicator. Why can't these people get basic grammar right? Or is it deliberate? I asked for more.


Of course I won't be making contact and I wonder what the next steps would be. Presumably this is a 419 scam where some fees need to be paid to clear the way for the $150,000 (which will never arrive).

Meanwhile, I viewed the account page and could see a fake Facebook account with Richard's profile picture on it and no other content.


I was really hoping the scammer would answer my video call but no such luck.

This happened to me a decade ago and I know Facebook has a mechanism to report fake accounts. You go to the profile page, click the "..." under the profile picture and choose "Find support or report profile". There is an item there for fake accounts.


The instant I reported the account I started getting "query error" on it so I suspect others had also reported it. Facebook did act quickly in this case.

To create the fake page they must have been able to see Richard's page and copy his profile image. The scammers must be able to see his friends list too - which is concerning.

I looked at my privacy settings but they seem to change frequently and I'm really not sure if I'm still vulnerable. There should be one big switch that defaults to private but there's not.

The Facebook platform seems to be a major location for scams including all the posts designed to go viral that gather engaged users or capture information that could be used for identity theft.

Tuesday, September 21, 2021

Resistive tap built with sharpie PCB etch

I'm keen not to burn out the input to the spectrum analyser. It's 50 ohms in with a maximum of +30dBm. The solution is to transmit into a dummy load and sample the signal with a resistive tap.

A good candidate for a simple PCB and I used Paul Taylor, VK3HN's, technique of drawing resist on the board with a sharpie. Components are all soldered on to the top of the board so laying them out to figure out where the tracks go is easy.

Here's the circuit and the components for the board:


I cleaned the board to remove fingerprints with Isopropyl Alcohol - is that the best thing to use? Using components to lay out the board, tracks were drawn with a standard sharpie. I didn't go to much trouble and could probably have filled in more of the board with earth plane to minimise the amount of copper to be etched.


In to a small bath of Ferric Chloride. While gently rocking we had a magnitude 6 earthquake which was fun. It took about 20 minutes to clear the copper.


After washing under water the etch looks great.


Steel wool was used to rub off the sharpie ink. 


Here's the completed board. 


I've got some more of the nice board edge mounting SMA sockets coming so had to make do with a panel mount for the tap output.

What should I use to protect the copper? I think Paul just tins the whole board but maybe there's a spray lacquer that would still allow solder modifications but prevent oxidation.

Sunday, September 12, 2021

An OWON XSA815-TG Spectrum Analyser for the bench

I've wanted to try a spectrum analyser for many years but they've been prohibitively expensive. Just as oscilloscopes have come down in price, spectrum analysers are also getting cheaper. I bought an OWON XSA815-TG Spectrum Analyser from Banggood for just under US$1,000.

This one is good to 1.5GHz which should be plenty for my use.

So far, I'm really impressed. It's very easy to use - easier than many CROs. Certainly easier than the TinySA. Here it is showing the local FM broadcast band:


Here is a signal from a 2m FM hand held (received off air):


Here is the tracking generator in operation showing a 9MHz low pass filter:

There is lots to learn but I feel that after a CRO, a spectrum analyser is a wonderful piece of test equipment that is now within financial range of some of us lucky hobbyists.

The terrible interference I often see on 40m has just returned. Here's how it looks on the IC-7300:


I tried plugging the antenna into the spectrum analyser in the hope of seeing the overall noise but I'm not:


I think I need to play with attenuation and gain to see what's going on. Much to learn!

Here's the output of my recent Si5351 WSPR transmitter with a fairly poor low pass filter after it. Those second and particularly third harmonics look pretty big.



Tuesday, September 07, 2021

Simple WSPR Beacon using Si5351 and ESP8266 NTP for time sync

Wanting to play with a simple WSPR Beacon in the house where I can't receive GPS for time synchronisation, I've hacked together a beacon using an Si5351 oscillator and an ESP8266 board that joins my Wifi and gets the time from an NTP server.

Here's the rig:


It starts off by joining Wifi, then requests the time from time.nist.gov. Next it figures out how many seconds to wait before the next 2 minute slot and delays that long. The WSPR signal is transmitted followed by a 10 second delay before requesting the time again. Assuming the NTP server replies, WSPR transmission is every second 2 minute slot.

The Si5351 generates a square wave into 5cm of wire and there's massive hum on the signal presumably due to the USB power. Here's how it looks decoding off air:

I got this going using a WeMos D1 R2 board which is basically an ESP8266 on an Arduino style board. I tried to use an ESP32 but for some reason (possibly power voltage) I couldn't get it to talk to the Si5351 although it could see it on the I2C bus.

Just a toy really but might be useful for something. The source code is here.

I'm using Arduino 1.8.15 and the following libraries are installed:

  • Etherkit JTEncode 1.3.1
  • Adafruit Si5351 1.2.1
  • Other libraries for UDP were bundled with the board, in my case LOLIN(WeMos) D1 R1

Wednesday, September 01, 2021

ZM-4 Z-match antenna tuner kit review

Years ago I built the AM-2 Z-Match antenna tuner and found that it could match pretty much any old bit of wire thrown outside. I melted the polyvaricons by running WSPR one day but they were easily replaced.

There's a German made evolution of this design with more robust variable capacitors and a larger toroid that claims to handle up to 15W.


The ZM-4 kit is available from QRP-Shop for 98 Euros. It came with an English manual but it helps to view it in colour here.

Nice spread out circuit board for easy construction.

Unfortunately a couple of component labels are missing from the board’s silk screening.


Instructions fairly clear but I started off reversing the direction of winding on the main toroid. 

It says wind to the right but neglected to say the winding should start on the bottom of the loop. At one point it says to wind over the red wire, but there’s no red wire. (I now see that it's red in the colour instruction manual).

The BNC connectors have substantial thermal mass and my little soldering iron struggled to heat the earth pins to melt temperature.

The metal case is great but it would be wonderful if the front and back panels were pre-drilled. My metal work skills are not great and I found the front and back plates to be quite hard aluminium to drill safely.


Great to see metric units with no comment.

When assembling the front and rear panels, have the circuit board close by as a guide. The instructions don’t suggest switches and plugs in the order they are on the panel and I ended up enlarging a hole that I shouldn’t have by mistake.

The kit comes with two banana sockets which I replaced with terminals so that a wire can be directly connected.

Some of the wiring, in particular the links from the panel switches down to the board is pretty tedious. I guess the solution would be a PCB behind the panel to handle that wiring but extra cost would be added by this.

Only after wiring up front and back panels did I realise that you need to slide the board in to the bottom of the case before connecting the panel wiring. I should have tried fitting the case before this but also the instructions should have mentioned it.

I unscrewed the BNC connectors and luckily had enough length of wire to the switches to be able to lift the panel out of the way and slide the board in to the lower part of the case which I had already lined with gaffer tape to try to minimise likelihood of shorts to the case as warned in the manual.

Hooked up to an end fed wire with a short counterpoise the Z-Match was able to get an excellent match by playing around with the additional capacitance switches and rocking back and forth between the variable capacitors.

Z-Matches are a versatile antenna tuner although I understand they can be lossy. This kit is well done but the switch wiring and panel metalwork takes some effort. When boxed up it's a compact and strong little tuner that will work well for portable QRP operation.

Wednesday, August 25, 2021

WSPR Watch app updated with better graphs

WSPR Watch is a free app for iOS that displays data pulled from WSPRnet.org. Originally I wrote my own code to draw charts of reception data but my clumsy attempts were pretty simple. Recently I started using the excellent Charts library and this has opened up all sorts of improvements. For a little while, the app lost features but now I think it's looking better than ever, particularly for stations that band hop.


There is a catalyst version of the app for macOS but it's not a great macOS app at this point. Thanks to everyone who has sent encouraging emails (you can do this through the app) and if you like it, please consider leaving a review. Latest version as I write is 3.29.

Friday, August 20, 2021

Digital modes with a Xiegu-G1M and DigiRig

Prompted by carrying too much equipment on a SOTA outing, I purchased a new low cost QRP transceiver from China. The Xiegu-G1M is very small and was dwarfed by the SignaLink USB I normally use for digital interfaces so I sent off for the new Digirig interface and have been working to get it going.


As there's no VOX I need to control PTT via CAT. The G1M manual is rather vague about CAT control and the radio doesn't appear in the Hamlib options yet. The user guide suggests using IC-7000 but that didn't work for me. IC-7300 worked to some extent but was very slow, including PTT on and off.

Examining the event log in Fldigi, I could seen loads of errors and timeouts which would explain the slow operation.

I took the RigCat IC-7300.xml and stripped out everything except frequency and PTT. Later I found the xml for the Xiegu-G90 and took the mode setting from that. Rig control works enough now for digital modes. I've put Xiegu-G1M.xml up on GitHub. (Download the raw file and configure Flgidi rigcat to use it). 

The serial connection on the DigiRig is 3V and this talks nicely to the G1M with a straight through 3.5mm stereo cable. Next step is to make up a cable for audio in and out.

One note on the Digirig... one of the 3.5mm sockets broke off after light usage. It looks like the connectors are surface mounted and there's not much solder there so I re-soldered them and hope they'll hold up to normal use now.

The Digirig interface is a very neat device containing a USB hub and both serial and audio interfaces working through a single USB-C cable. I feel the 3.5mm sockets are a weak point though.

I've made up an audio cable with a 100uF cap to block the DC bias on the mic. All seems to work fine with fldigi.


Listening off air, the transmit audio sounds a bit over-driven - I may need to add some gain reduction on both transmit and receive. A bit more feedback to the fine Digirig makers - the 3.5mm sockets are very close together and I hunt around to find plugs that were narrow enough to fit.

Sunday, August 08, 2021

New SDR++ software works well on Linux

I've been playing with SDR++ by Alexandre Rouma is available for macOS, Windows and Linux. Others, such as SDR#,  work well on Windows but mostly I run Linux for ham radio and it's great to find one that works as well on Linux as on Windows. Here it is on Windows:


Even on a low end laptop, the spectrum display updates fast and the receiver works well. (My reception here is terrible though). Here it is on Ubuntu 21.04:


I did run in to a common issue on Ubuntu 21.04. The app crashes on startup. If you run it in a terminal you see this alarming log message: 

"Hash collision!!! Fatal error!!"

Apparently it's due to multiple drivers in the soapysdr system. A workaround is to remove them all by running:

sudo apt remove soapysdr-module-*

It's mentioned in the troubleshooting section but I searched for the message with exclamation marks and so didn't find it.

Fantastic to see a high quality, high performance SDR client. I've used it with an Airspy HF+ and an SDRPlay. Others are using it with audio re-direction to receive digital modes.

Friday, July 23, 2021

The best digital mode for weak signal keyboard to keyboard QSOs?

Since moving from Sydney to Melbourne I've wanted to be able to chat with my Sydney friends but have wondered about the best mode to use for this from the huge list in fldigi.

Stephen, VK2BLQ, and I have been running WSPR and watching the signal to noise ratio for band openings on 40m. Today looked like this:

When WSPR shows an SNR of better than -10db we try for a contact. Until today I had thought that the best mode would be one of the wide modes such as Olivia 16/500 and we tried that for a while. We could hear each other but could not decode.

On a whim I suggested switching to good old BPSK31 and suddenly we were talking!

I find this rather puzzling and would welcome an explanation. Some commentators compare digital modes and rate BPSK31 very poorly compared to other modes. Local hero David Rowe has been doing some work on data modes for HF radio and I intend to try out what he's been working on.

K8JTK has quite a nice writeup of different modes here and we plan to test QPSK31 over BPSK31 soon.

The noise level here is distressingly high. A solid S9 of broadband noise. I've tried a loop antenna but it's similar.

Update: Good contact on Saturday

I received VK2BLQ at -10 on WSPR so we had a good contact using BPSK31 just now (local time 10:30).


For a while we had perfect copy (some errors are Stephen's typing) but then signals faded and I have a storm coming in.

We experimented with sending PSK carrier and measuring S/N and IMD. Stephen receives me with S/N 25db and IMD of -22dB which seems pretty good. I don't get him as well but we did determine that him reducing power a bit gave rise to a better IMD.

Noise levels for both of us are down today so that might be the explanation rather than just improved conditions on 40m.

Wednesday, July 21, 2021

Awesome Amateur Radio link list

Mirko Caserta has started a useful list of Amateur radio links. There's loads of these around the web but this one is on GitHub which means that contributors can fork and send pull requests to edit or add content. 

Mirko clearly favours alphabetical order.

The topic areas at the time of this blog post are:

  • Antenna
    • Analyzer
    • Balun
    • Tuner
  • Band Plan
    • CW
    • Digital Modes
    • Interface
    • Misc
    • Italy
  • Organizations
    • Global
    • by country
      • Australia
      • Canada
      • Germany
      • Italy
      • Japan
      • New Zealand
      • UK
      • USA
  • Propagation
  • Rig
  • Satellite
  • SDR
  • Shopping
So clearly there's lots more to add. I've contributed some Australian content and Mirko has granted me edit access so I'll keep going.

Sunday, July 11, 2021

Røde Wireless GO II microphone for iPhone review

Good audio with bad video is generally acceptable. Good video with bad audio is never OK.

In the past I’ve used the excellent Sennheiser radio mics but I’ve been tempted away by the prospect of digital output. My daughter uses the Røde Wireless Go kit and recently I purchased the Go II.

A third of the price of the Sennheiser but with superior features. Note that with the GO II you get two transmitters.

The GO II claims a range of 200m line of sight. I don't doubt this. Transmission is digital at 2.4GHz and seems highly resistant to interference. Compared to the analog Sennheiser system which needed an RF scan to avoid interference from other mics.

The GO transmitter and receiver are in a small 45.3mm square box with a clip that also conveniently slides in to a camera hot shoe.

The transmitter has a decent mic built in and comes with a fur wind shield. A lavaliere mic can also be used but is a separate product.

You can use just one transmitter and have it appear on both channels. Two transmitters can be used with one on left and the other on right (for later mixing). Transmitters can be muted.

Transmitters and receiver come paired although the instructions are rather brief.

Features I didn’t expect:

  • The two channels can be kept separate or mixed down to mono
  • The transmitters can record 40 hours of backup audio locally
  • You can record a second track at -20dB in case the level is so high that the main channel clips
  • The receiver has a USB-C port that, if plugged in to a computer, comes up as a sound card
  • Analog output from the receiver can be attenuated in three big steps or much smaller steps if desired.
  • There is an app, Rode Central, for iOS, macOS, Windows, & Android
  • When using digital output you can use a headphone to monitor reception

Connecting to an iPad pro is easy - a standard USB-C cable does the job and audio apps including Voice Memos and the Rode Reporter app switch input to use the device. Connecting to an iPhone does not work with standard USB-C to Lightning cables that you normally use to charge or sync. A special cable known as a Lightning Accessory cable is required and as far as I can find so far only Røde makes one called an SC15 cable.


Here's a little test recorded with an iPhone.


iOS is not great at showing use of external USB audio inputs. Generally, just plugging in an external audio device sets recording apps to use it but I read that in some cases you must launch the app first and then plug in the external audio input to get it to be used. I wish we could see all audio inputs and switch between them. In any case, test carefully before an important recording.

One small usability irritation is that the power on button, obtusely marked with a “Ø” symbol, is on the opposite side to the other two buttons on the receiver which makes it a bit difficult to press without pressing other buttons. The square form factor is a bit strange, particularly for the transmitter which clips on to a shirt with the mic pointing sideways. 

I can see the digital transmission at 2.4GHz:

I haven't pulled mine apart but the FCC listing shows a nicely made board:

Since Apple has started seriously messing with ad tracking I notice this rather weird targeted ad for dog food as a result of buying the Lightning accessory cable.


LOL. I really like this wireless kit and if you get the lightning accessory cable it makes a very compact video recording setup with excellent audio. The kit comes with a nice cloth pouch, two USB-C to USB-A cables, and three wind socks. There's not much documentation with the product but the online learning hub is pretty good.

Røde is an Australian company and from what I can see they've done fantastically well around the world. 

Friday, July 02, 2021

XIEGU G1M portable SDR HF Radio review and notes

After my recent SOTA experience I've become interested in more compact and portable QRP gear. A radio that's getting good reviews is the Xiegu G1M

As you can see it's almost dwarfed by the SignaLink adapter.

I bought via eBay and paid AU$354 plus shipping. (Prices vary a bit I notice).

The radio comes with a rather muffled microphone, a power cable (to open wire), a serial USB cable (for CAT and software updates).

A printed manual was included but it's not as up to date as the one available from the manufacturer.

The G1M puts out 5W sideband or CW and can also receive AM. It's general coverage receive and transmits on 4 bands: 80m, 40m, 20m and 15m.

It runs on 12-15V and works fine on a 3S LiPo battery from my drone days. Running on 13V it draws 400mA on receive with no audio and peaks at 2A on transmit.

Here's a backyard SOTA practice with a simple vertical on a squid pole matched with a Z-Match.


There is an active community discussing the radio on groups.io.

Mine came with firmware V1.06 but there is a new version 1.07 available. (For some reason it isn't yet on the Xiegu site here). Firmware is uploaded over a serial port using XModem. I used the go language uploader from Dale Farnsworth on macOS to upload the new firmware. 

You need to un-rar the file to get a .xgf file to upload.

The first two attempts stopped uploading before completion and I thought I might have bricked the radio but a third attempt worked.


As others have noted, the version still displays V1.06 Oct 22, 2019 but it's clear that the CW bandwidth is now narrower so it has changed.

There are several stickers to discourage disassembly but I couldn't resist. You need to take off the volume knob and remove the nut.


On the back, remove the nut from the BNC socket.



There are two thin co-ax links that need to be unplugged and two flat cables that can be released by flipping up the little plastic clip on the board end.



Interesting that there's space for another low pass filter on the board.



I've used the radio for WSPR reception and there is no reported drift. 


I'm quite impressed with this radio. It is an SDR and has a tiny little spectrum display that is actually handy for seeing signals. Reviews on eHam are generally good. There are a couple of reports of DOA units but mine works well and construction is of excellent quality.

To use CAT control with programs like fldigi, I have created a rigcat XML file for the G1M.