Testing a link, on a band, at a time.

Foundations of Amateur Radio

The other day I wanted to know what kind of communication was possible between my station and the station of a friend of mine. We want to do some experiments and for that to be possible, we need to have a reliable communication channel.

Traditionally you would get in touch with each other and attempt to find a suitable frequency on a band to make a QSO or contact. That generally involves picking a band, then tuning around the band, finding a frequency that's not in use, then listening, asking if the frequency is in use, then telling your friend via an alternative method where you are, only to have them tell you that they have noise at that particular frequency. You go back and forth a couple of times, finally settle in on a mutually convenient frequency and have a contact whilst keeping note of the signal strength shown on your receiver.

On a good day that will take a few minutes, on a bad day that might take much longer or not work at all.

If you want to do this across multiple bands, you have the fun of doing this whole thing multiple times.

In case you're wondering, I've done this plenty of times and I will confess that it's an interesting combination of joy and frustration in attempting to get the answer to a pretty simple and common question: "Can I talk to my friend?"

In my shack there are plenty of tools, digital multimeters, LC meter, antenna analyser and the like. No doubt you have some or more of those. Perhaps you have an oscilloscope, a vector network analyser, or other gadgets.

None of those are particularly useful tools to solve this particular problem.

On the other hand, you are likely to have a receiver and probably a transmitter. If you're reading or listening to this, you're likely to have a computer as well.

Using a receiver and a computer as a tool to solve this problem might not have occurred to you. It hadn't occurred to me until recently that these are ideally suited for this particular repetitive task.

So, I fired up my copy of WSJT-X and set it to WSPR mode. Changed the band to 2m and set it up to transmit. The other station did the same. Within a couple of minutes the results were coming in. We could both see what the link quality was like between us. Then we changed to 70 cm and did it again. Rinse and repeat for 10m.

As it happens, the other station was receive only and they had to attend to some family activities and I was in my office earning a living, well actually, doing my bookkeeping, but you get the idea, you can do this test while you're doing something else.

I checked in a couple of times to see how it was going when he pointed out that I could see his actual results on the WSPRnet.org website.

I had been looking at the map with mixed results because it had been timing out for most of the day and when it did work, all I could see was that a message was decoded, not how well it was received. Randall VK6WR, the other station, then pointed me at the link to the database which I hadn't seen until then. If you're looking, it's at the top right.

Out pops a list of all the WSPR spots his station reported, and as a bonus, the spots reported by another local amateur.

If you know me at all it will come as no surprise that I used the opportunity to make a chart. Actually I made several, one showing the frequency drift between our stations, one showing the signal strength.

Between the three bands it looks like 2m gives us the best opportunity for experimentation, though 70cm does appear to have some possibilities. Sadly 10m isn't with the antennas currently in the air, but I saw an email the other day with reports of a new vertical at the other end, so we'll have a go at doing the 10m test again in the very near future, perhaps even today.

Right now from the WSPRnet.org website I'm downloading this month's WSPR reports from the Downloads section to see who else saw my signals. No doubt I'll make a chart or six. I'll keep you posted.

I must thank Randall VK6WR for pointing me at the database link on the WSPRnet.org website, because that made propagation and link testing so much more useful and repeatable.

Tools come in all shapes and sizes. What's one that unexpectedly helped you lately?

I'm Onno VK6FLAB