Thursday, December 30, 2021

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.

Thursday, December 16, 2021

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.

Wednesday, December 15, 2021

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!

Monday, December 13, 2021

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.

Sunday, December 05, 2021

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.