What did you hear last week?

Foundations of Amateur Radio

Last week I spent a little time talking about the Weak Signal Propagation Reporters network, or WSPR, pronounced Whisper. You might remember that I set up my radio to receive these signals to see what I could learn. Turns out, I learnt quite a bit.

I left the software running for a week. During that time my station reported 456 signals received with a total of 54 stations in 27 call areas.

The longest distance 14,000 km, PC1JB in Veenendaal in the Netherlands who was using 1 watt.

The best performance based on km per watt is R0AGL in Siberia, 10,000 km, with 2 milliwatt.

Highest power heard, one station with 100 watts, but from a performance perspective, only just squeaks into the top 10 contacts. Typically stations used 5 watt or less.

My 10m quarter-wave vertical antenna was pretty good in hearing things across all bands. I heard stations across the frequency range, from 160m through to 10m.

It heard 1 station on 160m, VK7MF, using 5 watts, 3,000km away.

The most prolific band was 40m, accounting for 41% of the signals, 30m was pretty close at 35% and even 10m was respectable with 5% of signals heard on that band. Which brings me to a comment about propagation. The Solar Flux Index this week was pretty abysmal. It's been the lowest it's ever been, 66 and still I was able to hear signals across all HF bands.

Just think about that for a moment.

All the solar numbers say the bands are dead, all the listening in the world says the bands are dead, but using WSPR reveals that this isn't true, it's not even close to being true.

My station in a very high noise environment still heard signals across all bands.

Based on a visual comparison with other stations, signals were generated in all directions, but for my station, I didn't hear anything coming from the North East Quadrant, that's between North and East. It could be that the signals are being suppressed by the distortion in my antenna pattern, which might be caused by a metal gutter in that direction, or it might be that signals coming from that direction, mainly Japan and the United States, are too weak to be heard above the noise level at my station. I'm investigating that further, but that's for another day.

Speaking of other stations, in total during the same period as my station listening, there was a total of 6.9 million reports, representing 2490 listeners and 4463 transmitters. That means that I heard just over 1% of stations on my radio. Not bad given my meagre set-up and minimal configuration and installation.

On to things that I was attempting to learn about the performance of my radio. Every WSPR transmission includes the frequency and location information, which allows you to determine what the difference is between what frequency the other station reports and what frequency your radio sees.

Of course, there can be variation across both radios and to make things more interesting, this changes over time. This drift is likely to be distributed pretty evenly across all stations, but then I didn't hear all of them, so my results are not completely definitive, but overall the drift reports show a frequency drift of minus 3 to plus 2 Hertz. Slightly skewed down. That's not yet conclusive proof that my station is slightly off frequency, but it seems to indicate that my new crystal is slightly low. I'll be investigating that further.

And that neatly brings me to why I have been doing this.

You might not be surprised to learn that many things inside your radio are frequency controlled. Those frequencies come from a single central location, a master oscillator that in my radio vibrates at 22.625000 MHz. The crystal that does this is affected by temperature. When you transmit, the radio heats up and the frequency of the crystal changes slightly. Normally this isn't an issue, but if you're working on being on a particular frequency, especially on the 2m or 70cm band, then this starts to matter. If you leave your radio running for a few hours, things are likely to be more stable, since the temperature in your radio becomes more stable.

Another way to do this is to control the crystal temperature directly. You can insulate it, or heat it in a little oven, or a combination of both. This is a so-called Temperature Controlled External Oscillator, a TCXO. It's more stable and thus over time the frequency shouldn't change much.

In my case, the range is 5 Hertz and as I said, it's slightly skewed down.

The next step is to measure the actual frequency that my radio is tuned to. This will require a little more effort. I'll talk about that next week.

In the mean time, I'm doing some more analytics to compare how my noise-floor affects my station, how it compares to other stations across the same time-range and how little changes in volume, antenna and the like affect what results I get.

There is lots of data to digest, lots of knowledge buried among the stats and I'll be spending the coming weeks seeing if there are things here of a wider interest.

One thing's for sure, this is the simplest way you can measure and compare your station against a whole globe of other stations. Of course it doesn't actually get you on air to make noise, and that is the ultimate test of the success of a station.

I'm Onno VK6FLAB