GM4ULS ham radio station

a QRM-free zone!

Niggles and nuggets

Posted by gm4uls on October 28, 2012

Of late 10m has been very lively. I have been back on AM and also on FM on the KQ2H repeater where, for the first time since last winter, I met up with Ian M1OOO and Hans PD0AC for a three-way. Maybe this is the start of a period of fine propagation, as at this time last year.

However, I have been plagued with a niggle on 10m, namely an occasional burst of what I can only call ‘rude noise’, as though someone is blowing a rather tuneful raspberry at me in short bursts. One of my 10m AM contacts, Tom W0TDH, identified it as ‘TWI’ or ‘Travelling Wave Interference’, and sent a large image of it showing up on an analyser (sorry the reproduction is so small here – email me [gm4uls{a}] and I’ll send you a larger version).

Meanwhile I was convinced that the noise was local. There were blokes working with machinery nearby which could have explained it. But just a couple of days ago it occurred to me to wonder whether I was having trouble with the RM KL 203-P linear amplifier again. So when the phenomenon recurred I simply switched off the amplifier and – voila – it disappeared. The noise, not the amp! I should point out that the pre-amp was not switched on at the time, by the way. Anyhow, I have taken it out of line, and as long as the propagation is good it doesn’t matter much, because the 12W AM out of the AT-5555 is quite enough to take advantage of it.

But if anyone has a clue to what is making the fault happen – if it sounds familiar to you – I’m open to approaches on the subject.

This weekend the CQ WW SSB contest has been on, and the bands have been packed, as you would expect. This included every spare KHz of 10m, where there appeared to be more SSB signals than you could shake the proverbial stick at. Having spent a great deal of Saturday on 10m and 15m (less on 20m), I decided to get up early this morning and try 40m. Just to remind you, on 40m I used a 1982-vintage Yaesu FT-101ZD barefoot into a doublet. The antenna is mounted just above roof height, is fed by a dog-leg of twin feeder, and is itself not particularly straight. However, with the help of an MFJ-993B ‘IntelliTuner’, it served as my principal HF antenna until I got my MA5B, and it still functions as my 40m antenna. It’s far from ideal, but having had QSOs with ZL using it I’m not complaining too much.

This morning I managed no contacts at all on 40m, even though there were loud signals from, in particular, CR3L and various USA stations. This was unusual, because I do not tend to have any trouble on 40m if I can hear the station at the other side. Now, I know it’s not as simple as that. I know the principle of ‘if I can hear him he can hear me’ is unreliable. But I did notice that the tuner was acting a little strangely. Below is a picture of the display, taken when I was transmitting on 7.132MHz. As you can see it’s registering 6.385MHz with an SWR of ‘>25’. Indeed, when I whistled into the mic the tuner shut down and gave it’s ‘QRP’ morse alert.

So far I have physically checked everything I can think of. All connections seem to be tight and sound. It sits right next to the 10m linear. Maybe there’s a flu virus going round…

Back to the CQ WW contest. At 06:24UTC this morning, well before daylight, I had a contest QSO with VK7ZX on 14.266MHz. It was via long path. I checked the direct beam heading and it was about 4 S-points down on the long-path heading. I had to call him several times before I got in over the scramble. Interestingly, on the majority of the occasions when I called, as soon as I dropped PTT I heard my own voice giving the last letter of my call sign. I can only conclude that my signal had carried all the way round the globe and back to me. That is the furthest I have ever known my signal to travel, and if I could award myself a QSL card I would!

I don’t enter contests myself, but I do ‘take a wee dander’ through the bands to see what’s worth getting in my log. Here are a few of what turned up so far.

10m: PJ2T, HK1NA, ZD8O, V26B

15m: UP2L, VP5T, 5X5P, VP2MDG, PJ4X, C5A, 8P5A, 6V7S, FY5KE, KP2MM

20m (early morning): C5A, P40L, PJ2T, VK7ZX

None of this is world-beating stuff and everyone out there worked these guys, but it was nice to get some new prefixes in the log. Incidentally, 5X5P is a bit of a puzzle – he doesn’t turn up on If anyone has his details, please let me know.


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