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JT-65 and all that…
I’ve been playing a bit with JT over the last few weeks and found it quite enjoyable although since the tempo is not, shall we say, ‘dynamic’ it sometimes quite hard to keep track of whether I’ve saved the QSO or not. That aside, it’s quite fun! Thanks JT.
Now, I subscribe to the Elecraft reflector and a few days ago there was a discussion over whether JT was a weak signal mode or a low power mode. Apparently, there are stations running QRO levels of power in these modes in order to try and ‘force’ some distant wanted DXCC entity into answering them so they can get another tick in the box. Naturally the thread descended into disagreement and accusations of QRM etc.
Never having experienced this style of operating, I was a bit skeptical. However, this afternoon, I got more than I bargained for!
Here is a series of pictures that demonstrate what happens to QRP-level QSOs when the QRO stations ‘forget’ to turn the power down.
Now, someone is sure to say, I should have my AGC on. Well, yes, I tried that but the effect is that I can’t receive the weak signal that I was working half way round the world. What I can say is that I’m amazed at how robust JT 65 is being able to pick out the weak signal despite the overwhelming strength of signals over 1000 km away. Of course, after a while, it got a bit tiresome for both the DX and myself and we have up. After all extending a 7 minute QSO to something nearer 15 due to QRM is a bit ridiculous!
Most of these pictures were taken when the QSO seemed no longer viable or had been abandoned.
I guess the only guy with an excuse is the 9H station which is on a hilltop within about 8 miles of here – I would totally expect to see a strong signal from him.
In summary, I’m not a bit put off. I had a really nice run much of the morning and look forward to working a few more but I do wonder how workable the mode will be in the long run if people keep throwing power at the DX ‘problem’ rather than patience.
The Danfoss Compressor
Danfoss make an enormous number of compressors. They are everywhere in cooling machinery. They are especially prevalent in boats where they are by far the most common refrigerator compressor.
What the heck? So why is that of interest the average ham radio operator. Well the answer is simple, they’re also very well known as a significant source of QRM.
So why does that matter to me? I’m operating for part of my stay in the Bahamas at stocking island which forms the north east coast of Elizabeth Harbour. As the winter progresses, more and more boats arrive to pass a few weeks in the sun. These are cruising yachts and most have refrigerators. The west coast of Stocking island is where I have been operating and the bay with the dock seems to attract the boats.
This has been very convenient until recently but as more and more boats arrive the steady ‘chirp’ of the Danfoss compressor has become more and more problematic. When they all get going its a bit like a summers evening in the Mediterranean with cicadas. Although they are more noticeable on the lower bands, the QRM extends as far as 17m where it will change a quite workable QSO into a nightmare. Worse still, the fridges are thermostatically controlled so you might think you have found a quiet frequency only to get nicely settled into a pileup when Mr Danfoss decides it’s time to spoil your fun. I hope this explains why sometimes I give a 5/7 (just above the noise floor most of the time recently) and then sometimes struggle to work the station. It was particularly bad today working Europe and eventually I had to give up. So as more and more boats arrive, I am considering, in the interests of productivity, moving my QTH a little further away.
I have a new QTH scoped out but this one does not have a dock although the takeoff for Europe is slightly more favourable. Another downside is that there is no convenient tree within reach of the length of coax I have with me. That is somewhat offset by the fact that is on the local nudist beach so there may be some compensations. No – don’t ask I am not doing SSTV!
Itinerant Ham 