A two valve regenerative receiver for 40m from Stephen, VK2BLQ

Home brew master, Stephen, VK2BLQ has been at it again and has created a two valve regen a la 1967 All Wave Two, using two 6BL8 or 6U8 triode pentodes (heaters in series), and it still works with a 12 V HT supply instead of the 90 V used previously:

Stephen writes: 

"The receiver sort of works, but the 12 V supply limits the audio output, so is only good for headphones or feeding to an external amplifier. The stability on 40 m is Ok but overloads on strong signals, so I think an antenna pot might be better than the volume control, doing double duty, but it does combine the glamour of thermotron technology with the safety of low voltage.

For the makeshift vernier dial I used an old audio CD , which as fortune would permit, possesses the magic of Soldersmoke so is destined for greatness. Hacking an old variable pot and two grommets seems to function as a vernier drive.

Audio quality on the 39 m AM shortwave band seems to me more pleasant than one of the superhets and 40 m SSB and CW sounds "mellow". (Click to enlarge image).

I did make some circuit changes to suit the lower voltage: I changed the pot and resistors for the Regen control and I did use a 230v to 6v mains transformer for the speaker. Valves are great, the 6U8 worked with the same components even though I didn't have a 6GW8.

Next version gets the upgrades and a heterodyne converter, and if I can quote a line from the TV series "The Nevers":

"It's a prototype". 

If anyone actually has questions, I'm happy to help."

Here it is in action:

-- It's a fine looking prototype if you ask me. Thanks Bill for the link from Soldersmoke!

Raising an antenna support with a drone

This week I had visits from several hams including Dave, VK3ASE, who brought a long squid pole and an offer to help with antenna raising. Dallas, VK3EB, helped with the off centre fed dipole. 

I decided to try raising a line over a nice clear tree branch with a drone rather than the squid pole. The drone could lift the line without problem, the issue (which I anticipated), was landing again on the other side with the line now trailing above the drone.

Despite my best efforts to keep the line between the rotors eventually it tangled and the drone struggled for a while before I shut it off. This left the drone hanging from the line but undamaged. Dave recorded some video of the enterprise:

The supports for the ends of the dipole were in trees with substantial leaf cover so we used the squid pole for those.

My antenna tree supports an Off Centre Fed Dipole cut for 80m that does very well on 40 and 20m. Now it has a second support that currently has a dipole cut for 30m. The branch is nice and clear so the drone was easy to fly over it.

ABC Digital Radio Mondiale transmission on medium wave

The Bendigo Amateur Radio Club held a meeting where Brad Geier, VK3VLK, spoke about the great future of Digital Radio Mondiale (DRM) transmission. I didn't realise that the ABC has been running a transmitter on 747kHz from Wangaratta.

I can see the transmission quite clearly here at Drummond and also on the PkLoops SDR at Croydon.

In the past I've been able to receive DRM transmissions from Radio New Zealand International and they can sound very similar to FM quality despite weak signals and band noise.

The software needed to decode DRM is Dream. I couldn't get the latest version, 2.2 working but version 2.1.1 does work under windows. Another interesting lead is swradio-8 which I was able to build but not quite get going on Linux.

I'm using the IC-7300 as receiver by switching USB audio output to IF, choosing AM and winding the bandwidth out as much as possible.

My antenna is not very well suited to 747kHz so I'm not decoding audio just yet:

Appeared as a panelist on ABC Download This Show

This week I was invited to be a guest on Marc Fennell's Download This Show. Marc must be the busiest person in media but he still has time to put together a very professional radio/podcast show every week.

In the old (pre-COVID) days we used to go to ABC studios but these days we're well practiced in recording from home. Even Marc was at his home.

My internet here at Drummond is NBN fixed wireless and unfortunately upload speed isn't reliable enough for my taste so I travelled to Melbourne for the recording.

If you're interested you can get more info and listen here.

QJ-PS30SWI low noise switching power supply with "noise offset" feature

In my pursuit of low receive noise I've been using a linear power supply but the one I have makes a loud audio hum sound that is a bit annoying. Searching for low noise switching power supplies I stumbled across the QJ-PS30SWI which I purchased for AU$120 from AliExpress.

The supply is quite low noise, but there are lines visible on the waterfall about every 2kHz if I turn the preamp on.

Unlike switching supplies I've used with HF receivers in the past, where there are broad bands of noise that drift up and down, in this case they are narrow and the "noise offset" control lets me move them away from the frequency I'm listening to.

The supply is very compact and has a fan that doesn't seem to run, presumably it does when it gets hot.

Command line WSPR receive with weakmon

Work to reduce noise here at Drummond has been going well and,  yesterday during a voice contact with WSPR reception leader, Phil VK7JJ, he alerted me to the fact that I was on top of the leaderboard by distance. By a fair margin too.

My iOS app, WSPR Watch, displays WSPR spots pulled from WSPRnet.org and features a very simple transmit capability. People often ask if I could make it receive WSPR as well.

The obvious approach would be to port the decoding code from wsjtx but that source base is pretty daunting and includes several languages including Fortran. 

I went looking for other implementations and stumbled across rtmrtmrtmrtm's weakmon which is an almost pure python implementation (there's a few bits of c). The project hasn't been updated for some time and I ran in to a few issues running under python 3 on Ubuntu linux.

Weakmon directly reads audio from an input (including things like the IC-7300 I'm using) and can use serial CAT control to hop bands so it's very functional.

I found the most recent fork by kholia and forked that to create my version here.

My focus is on WSPR and running under python3. Other modes may not be working.

Changes I've made

• Updated the README.md to explain what my fork is about
• Running under Python 3.9.7 I struck a number of exceptions during decode all complaining about things that should be integers but instead were floats. I've fixed these as I've seen them but there may be more. (All in wspr.py)
• Phil, VK7JJ, pointed out that transmit maidenhead locators were incorrect. I've included a fix by Ross, EX0AA.

Since moving out of the city and receiving WSPR I've had some wonderful emails from people astonished that I was able to pick up their 200mW beacons from 16,000km away. They ask what magic I'm using - the answer is a quiet location and hunting down every bit of noise.

Set up OpenWebRX at Drummond

My low noise reception seems worth sharing with a few friends so I set up OpenWebRX. I initially tried on an Ubuntu 21.10 laptop but for some reason couldn't get the AirSpy HF+ to work with it even though SoapySDR said all was well. 

In the end I gave up and tried the easy option with was a pre-made image for Raspberry Pi. This worked well right out of the box.

This is a very low noise location but do you see that big band of interference down the left side? It seems to be from the Raspberry Pi or it's USB power supply. Very distressing. The lowest noise USB power supply I have is a battery pack with USB output. I've ordered a metal case for the Pi and some clip on ferrite chokes for cables and will be interested to see if things can be improved.

Despite my reservations, the 31m shortwave broadcast band comes alive in the evening here:

I first set this up on a Pi 3B which worked but struggled a bit. The Pi 4 is a very capable computer and handles the load with ease even with some background decoding of WSPR and FT8. 

To answer Paul, and other's question - no it's not publicly listed as my IP isn't fixed and it will be frequently off line.

Great work by the OpenWebRX developers!

Using an IC-705 remotely from macOS using SDR-Control

It is hot in my shack here at the moment and I can't stand it in the shed for more than a few minutes so I decided to buy a new macOS app called SDR-Control and try the IC-705 remote feature.

Set up was easy but you do need to note the IP address given to the radio over Wifi (it would be lovely if the software could find radios on the network).

My shack is a fair way from the house and the two are linked with a Google Wifi mesh network. Despite the multiple hops control, audio and the waterfall all work well.

Sound on the Mac laptop sounds excellent and the waterfall is quick to update. Note that you can't show the whole band, only the centre mode works. Like on the radio, you can click on a signal to tune to it.

I'm still learning how to use the software, parts of it are not quite what I expect, the user manual is here.

My only complaint so far is the difficulty of tuning. It looks like it supports the mouse wheel but I'm on a laptop. I wish there were a set of keyboard tuning up down step commands. I asked the author Marcus about this and he said it was not possible directly but you can make keyboard commands to step up and down and another to set the step size.

Some of the user interface is not very "Mac like":

Some of these squares are on/off buttons, others, (like band and mode) are drop down menus. Right clicking on many of these squares does other functions.

I hope Icom releases an update to the IC-7300 with network access (both Ethernet and Wifi please).

My congratulations to the author Marcus for an good piece of Mac software. It looks like a version of the software for Flex radios.

An off centre fed dipole antenna for more bands

It's been great having a dipole up high in the trees but I wanted to be able to use more bands so I made an off centre fed dipole, cut for 80, fed with a 4:1 balun. This gives me a number of bands with a low enough reactance that the IC-7300's tuner can match it. Here's a plot using AntScope2 on macOS.

The grey bars are ham bands. I'm sweeping from 3MHz to 30Mhz. As you can see I get low SWR on 80m, 40m, 20m, and 11m. With a manual tuner I've been able to use 30m but it's quite a stretch.

Speaking of stretch... The antenna wire is half of a figure-8 speaker wire and I think it is slowly stretching. I had a doublet for 160m up but the wire broke.

I did notice that 40m on the OCFD was not as good as it was on the dipole cut for 40m but the extra bands and convenience make it worth while.

The shack is improving! I ordered a 2m bench, a gas chair, and a 4 draw unit from Ikea. Delivery cost almost as much as the furniture. 

The afternoon sun hits the other side of the corrugated iron in front and it gets very hot. Next step is to insulate and line that wall at least. 

Update: Winning at WSPR reception

It's a combination of height, antenna and of course the low noise location. I'm pleased to see that after 24 hours of WSPR reception on 40m I'm at the top of the global chart by accumulated distance.

The WSPR challenge is a wonderful idea. I love the concept of competing by reception rather than transmission.

(Of course it's a bit unfair as we VKs are very distant from most stations so we have an advantage).

Another antenna improvement - more height

At my new location I was able to throw a line up a tree to support the balun for a 40m dipole. Dallas, VK3EB, kindly visited with an 18m squid pole and was able to get a line over a much higher branch. 

With extra height, reception, as measured with WSPR, is visibly improved.

Sincere thanks to Dallas for visiting and helping to improve the antenna.

Further improved antenna in country Victoria and noise fighting

I've continued to work on the 40m dipole here at Drummond and, despite an arm in a sling, managed to throw a line with a rock attached over the branch of a tree and hoist the balun up about 6m above ground. I've also got the dipole to be resonant within the band for a change.

All was going well until a very regular interference pattern appeared across the band. It didn't look like a switch mode power supply as the carriers are quite narrow and didn't drift. Very annoying as some were dead on popular frequencies like 7100kHz.

My first theory was that it was from the micro-inverters in the solar system here. They have a bad reputation and the sun was strong. I isolated the inverters and it stayed. In the end it turned out to be a switching wall power supply for a Synology NAS that I had recently installed. Now the band looks clear:

At 6:30pm local time I had a contact with stations VK2ASU at Maitland and VK2KB at Emu Plains. I could hear them both perfectly but due to the short distance they struggled to hear each other. Here's a video of just tuning around 40m. Hugely different to the experience in the city.

I normally look for good times to talk with John, VK2ASU by watching my WSPR reception of his club station VK2ATZ. Here's a signal to noise plot from the WSPR Watch App. Times are local. (There's a gap when we had our voice contact).

So, very happy with 40m operation now, the next step is more bands and general coverage reception.

Shack in shed and improved antenna

I've moved my shack into a shed and strung up a better dipole in some trees but away from everything electrical. Signal reception is improved and I heard Mark, VK3MJ, calling CQ and had my first voice contact from Drummond. The band looks great with very little noise at the moment.

It was great to meet Mark, who's in Geelong - so just 150km away. He recognised me from a recent video where I tuned across his transmission! An amazing coincidence. For him, I was just above the noise, for me he's clear as can be. Here's a bit of a recording of today's conversation.

The hum you can hear is a linear power supply sitting on the bench which unfortunately hums loudly. I'm not sure what to do about that.

I left WSPR receiving on 40m over night and got very good results, (not quite up to VK7JJ's fantastic reception performance though).

I even received Ross, EX0AA, from Kyrgyzstan, many times at up to -13dB SNR. These screen shots are from the WSPR Watch app.

Hearing the FreeDV 700e beacon on 7177kHz

With my new low noise QTH I'm able to hear Alan, VK2ZIW's FreeDV 700e beacon on 7177kHz.

He's running 20W from Emu Heights in NSW. The beacon transmits every 10 minutes.

Normally I use Linux but the version of FreeDV in the Debian library is too old for 700e so I used the macOS version. 

At Alan's prompting, I grabbed the freeDV GUI software and built it on Ubuntu 21.10 with no problem. There's a build_linux shell script that does all the hard work.

Alan's beacon has a feature where if you put your callsign in the text message it will replay your transmission back to you. 

Unfortunately the macOS build seems to have a bug where the message field isn't editable. UPDATE: I found the message field in the "options" dialog. My mistake.

I'm looking forward to some FreeDV contacts in the future!

How much better is HF reception outside of cities?

It's long been a dream of mine to have a location for HF reception in a quiet place outside of the city. Since we moved to Thornbury about two years ago I've been plagued with high levels of broadband noise which has left the HF spectrum, particularly on 40m, at often S9 +20 DB. 

That's the worst example. Amazingly even through high-level noise like this digital modes such as WSPR can still receive a few signals and I'm able to copy Steven VK2BLQ sometimes.

The dream of a second location has finally come true with the purchase of 5 acres north of Melbourne at a place called Drummond. 

40m looks completely different here:

Between signals it's S0 most of the time.

To measure the difference in signal-to-noise, Stephen transmitted five watts of WSPR from Sydney and I received simultaneously in both locations. The difference is huge. The largest difference I saw was 21dB better signal-to-noise at the country location!

Here is WSPR reception of stations more than 400km away:

For the initial setup, the antenna is far from optimum, it's just a wire dipole hanging up right next to the house with some coax going in through the kitchen window. This can be greatly improved in the future.

How much better is HF reception outside of the city I measured at up to 21dB.

PS: Unfortunately it's going to take me a while to improve antennas as during the initial move in I missed a step and fell heavily, breaking my left arm. This post has been written using the Apple built-in dictation system which I find to be excellent.

Why is every state's daily COVID report different?

We're not a big country really. It seems odd that each state has evolved a daily COVID report that broadly looks similar but has the various statistics in different orders.

I favour the South Australian approach which focusses on hospital patients and deaths.

I'm a panelist on ABC's Download This Show

Once again I was a guest on ABC RN's Download This Show presented by hard working and talented Marc Fennel.

"The Commonwealth Bank is adding cryptocurrencies to its banking app, becoming the first Australian bank to offer such a service.

Plus, Twitter launched its new subscription product, Twitter Blue, in the US this week but some experts are asking why some simple features are hiding behind the paywall.

And the US Justice Department is suing Uber over allegations it has been overcharging disabled people".

In the old days we used to go to an ABC studio to record shows like this. These days we're all remote. I've been working on improving my audio and the latest addition is a pop filter which lets me get closer to the mic without popping and I think my sound is comparable with Marc in the studio.

Listen on 300 big power AM stations on Thursday at 11:05 or you can listen on line here or via podcast.

Programming a Yaesu VX-6 with Chirp

I've moved to Melbourne, Victoria, and my 2m hand held radio didn't have any of the local frequencies in it. It's a real grind to program memories through the keyboard and, while I'd done a few, I'd also made mistakes along the way.

A serial cable was purchased from AliExpress and this morning I got it going.

The cable came with some software on a mini CD ROM but I don't have a way to read those so the next step was to get Chirp. I tried it on macOS, Linux and finally Windows, before the UI told me what I needed to do to get started..

Turns out, with a VX-6, you need to hold the F/W button down during power on and then press BAND to start the upload from radio to Chirp. (Those instructions weren't visible on macOS or Linux for some reason).

In the end, I threw away my own memories and grabbed the Chirp CSV file from the WIA which has all of the repeaters in it, with names showing the call signs. Great stuff WIA!

Uploading to the radio is similar, power on with F/W but then push V/M to start download. It took a few attempts to get all this to work, it seems timing sensitive.

Anyhow, now my radio is filled with repeaters and I was very happy to find that I could trigger the Macedon repeater, VK3RMM, from home for the first time. (Clearly I had something wrong with my manual configuration).

Note that the CSV file from the WIA which could be imported by Chirp was from the file titled "Example VBScript, Sorted Directory csv and CHIRP csv files and other csv formats WiaRep2 211009.zip" from this page.

My sincere thanks to whoever put this file together.

Response to attacks on the ABC by the Institute of Public Affairs

Last Monday the IPA published the first of five episodes in a new podcast series, “Their ABC”. Its preposterous proposition is that the ABC – in the words of the podcast’s anchor, the IPA’s Director of Communications, Evan Mulholland – is “a bloated, out-of-touch, biased broadcaster”.

The ABC Alumni, of which I'm a member, has published a video taking on the IPA’s “research”. It’s presented by our chair Jonathan Holmes, former presenter of the ABC’s Media Watch.

I realise that responding like this invites the Streisand effect but I think it's worth countering their misleading statements. 

Surface mount on home drawn circuit board

I've been slow to adopt surface mount components for home construction but watching Paul, VK3HN's, technique has convinced me it's the way to go. The way he lays components on a board, draws the tracks with a pen, then simply solders components on to the surface seems particularly elegant.

As a test I've built a simple emitter follower audio stage with a 3904 small signal NPN transistor. The transistor is tiny but able to be soldered. I've used a normal Sharpie pen in the past but recently picked up some Staedtler permanent markers which are often recommended. Here's the resist and you can see the transistor top right:

I etch with ferric chloride in a small plastic container.

This small amount has done a few boards already. It would last longer if I coloured in more of the copper area. Paul tells me that warming the solution will keep it going even longer if desired.

This board wasn't great but worked well enough to solder components in place.

A wonderful benefit of surface mount components is that you can buy these books containing all common values for not much money. I bought the large 1206 sized components to make it easier for me to work with them. It's great to have plenty of every value resistor and capacitor at hand in a compact book. The result, on my first attempt, is a bit rough:

Working with surface mount is not hard if you have good light, a magnified headset, tweezers, and something to hold down the part while you solder the first connection to a component.

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.