7 posts tagged with "radio"

The antenna from the previous note — two legs of twisted pair, about twenty metres each, six metres up — worked beautifully on receive. What did not work was the place where the wire meets the cable. To begin with there was a twisted joint and insulating tape: a solution that lasts until the first rain and does not hold electrically at all.

On 8 December 2023 I built a proper centre: a balun on a ferrite toroid inside a sealed box. And, more to the point of this note, I checked it with an analyser — and then worked out that I had checked something other than what I thought.

I wanted to hear the bands on a set I had first held in my hands in pieces. Not buy something finished and switch it on, but solder it, align it, get a wire six metres up and catch live voices. It happened on 80 metres, on a Sunday morning.

Every conversation about HF conditions comes down to four numbers: SFI, SSN, the K index and the A index. They get passed on the air, printed in forecasts and written in logs — but not everyone can read them.

In short: the first two say how much the Sun is giving out (and therefore how dense the ionosphere is), and the last two say how quiet the Earth's magnetic field is (and therefore whether a storm is choking that ionosphere).

Below is a full account of each index: what it means physically, how to read it, what it affects and when it is worth getting on the air. Beside each section there is a live gauge that pulls the current value from NOAA and shows where we stand.

Audio from the sound card turns into text, and all of it happens in the tab: nothing is uploaded to a server, nothing calls out to somebody else's API. A 14 MB neural network sits next to the page, the ONNX runtime is built into the same bundle, and after the first load the page works with no network at all.

The interesting part is not that it works. The interesting part is how many ways there are to get it wrong, none of which announce themselves with an error.

Morse code is usually presented as a table: a letter, and beside it the dots and dashes. In that form it looks like an arbitrary list, and all you can do with it is memorise it.

It is in fact a binary tree, and in that form you can see the engineering decision taken in the 1840s: the frequency of a letter sets its depth. E is one dot, T one dash, because those are the commonest letters in English. Q, J and Z sit all the way down on the fourth level. Alfred Vail arrived at this not by theory but by counting: he counted the letters in the type cases of a local newspaper.

A variable-length code, allocated by symbol frequency. A hundred-odd years before Shannon and Huffman explained why that works.

The idea for this platform is mine; I laid down the architecture back in 2025 and wrote it myself.

On 6 March 2026 I showed it running for the first time — from my own laptop, through ngrok, with a link that lived until midnight. Even then it kept a shared log, accepted contacts from WSJT-X over UDP, imported ADIF with duplicate checking, and had separate dashboards for hunters and for organisers. The next evening the bridge for digital modes appeared — for Windows, Linux and macOS.

In April, seven weeks after that demonstration, the special callsign EN40CNP was on the air for the 40th anniversary of Chornobyl. Two weeks, 1565 contacts, several operators — and the whole log was merged by hand: the platform was not yet ready for real use. Vitalii, UT0UI, put the experience most precisely: “merging logs after the fact by hand is a right pain”.

By August it was ready. What follows is what came of it: the platform uahamaward.com, on which the “35th anniversary of Ukraine's independence” award made 17,387 contacts in 31 days, and not one of them was merged by hand — neither during the month nor after it.

Throughout August 2026 the award “35th anniversary of Ukraine's independence” was on the air. Over 31 days the activators made 17,387 contacts with 8,226 different stations in 99 countries. Every line of the log carries a time, a frequency, a band, a mode, the other station's callsign, its locator and a report. Together they make a fairly rare thing: a month of continuous observation of the short waves, made not by an instrument but by people.

What follows is what can be seen in it. Not “the award was a success” but concrete numbers: when the bands opened, why Saturdays weigh more than the Sun, how far FT8 reaches compared with SSB, and why amateur radio remains a hobby of wealthy countries.