Foundations of Amateur Radio

The other day I was getting ready to go out when rain started pelting down. Not unexpected in this part of the world at this time of year but inconvenient for my plans.

I didn't particularly want to carry an umbrella and the thought of wearing a rain hood brought back memories of water trickling down my back. 

For reasons I'm not quite sure of, my eye fell on my hat on its hook at the door. The hat I wear in the heat of summer to keep my brain from frying, the hat I use whilst camping with my amateur radio friends, the hat I've worn whilst loading massive hay bales with a tractor and the hat I've worn swimming in the Ord River - well, a descendent, third generation if I remember correctly. I shook my head in disbelief, after donning my raincoat, put my trusty Akubra Territory on my head and stepped out into the rain. Perfect. Kept me dry, kept my glasses clear and no drips down my back.

You may well wonder what this has to do with radio and that's a fair question. I will preface this with a disclaimer that you might not have this set-up in your shack just now, but perhaps it will inspire you to get started.

I've been talking a lot about Software Defined Radio, and I do believe that it represents the future for our hobby, but that doesn't mean that my traditional radio, in my case a Yaesu FT-857d, is headed for the scrap heap just yet.

As you might know, with some preparation you can connect your radio to a computer and control it. You can also connect both the send and receive audio to a computer using a variety of techniques which I probably should get into at some point.

Assuming that you have, and I realise you might not yet have done this, but assuming for a moment that you have made this all work, you can use this to do things like JT65, FT8, PSK31, SSTV and hundreds of other modes.

One thing I did during the week was use this set-up to listen to noise. Seriously, that's what I did. I picked a spot on the band with nothing but noise. No discernible signal and fired up the application WSJT-X, it's the tool you use for many weak signal modes. As an aside, as a tool, it is also helpful in getting your digital mode levels set correctly.

One of the windows in WSJT-X is the waterfall and spectrum display. On it you can see the signal as it is right now and how it's been in the past.

If you turn on one of the filters on your radio, you can see the display change. You can literally see what gets filtered out. On my radio I've got the standard filter, as well as a 2 kHz and a 300 Hz Collins filter. Using this technique, you can specifically see what each filter does. If I turn on the built-in Digital Signal Processor, the DSP, I can see what the adjustments do, as well as the impact of the mode on the filter. And how the various settings interact.

For example, until I saw this display, I didn't know what the "DSP HPF CUTOFF" and "DSP LPF CUTOFF" specifically did and how they interacted with the other filters. Similarly what "DSP BPF WIDTH" did and how.

I also didn't know that even if you set both the high and low pass filter frequencies to the same value, you still have a usable filter, even if you might think that nothing could get through.

Now I do realise that your radio may not have those specific settings, but I am confident that if you pick a spot on the band, set up a frequency display and waterfall, you'll discover things about your radio that you hadn't before. I also realise that you can hear some of this by just playing with filters, but seeing it on the scope adds a whole other dimension to the experience. Just one example is to see how a narrow filter interacts with the in-built DSP, something that's difficult to hear, but easy to see.

If you have a Morse beacon to hand, you can also see how various frequency shifts work and the impact of selecting filters in relation to that signal. No need to just listen to the beacon with just CW mode either. Have a look at it using SSB.

Using something for an unexpected purpose can give you many great rewards. As for the hat, really, I hadn't used my hat to ward off the rain until then; you live and learn.

What have you discovered recently?

I'm Onno VK6FLAB