On checking into the MP SDRs on Friday night 25th Oct, there was considerable interference evident at the lower HF frequencies. Starting at around 2.5 MHz, the noise extended up through the 80 and 40m bands. As no one was reporting the noise elsewhere, it appeared the the source was at MP.
Previously, Dave ZL1DL had noticed the “always on” light in the stairwell at MP was flickering slightly, so Saturday morning he tried turning off the light, but no change to the noise. Likewise with the external security lights; no change to the noise when they were turned off. So Sunday the 27th would be the great fox hunt.
Sunday at MP started early with ZL1BK setting up portable at a park bench. Harry set up a 9m extendable carbon fibre pole and even though the top section was little more than a mm in diameter, it happily supported a light wire as a vertical. Very soon there was quite a gathering. Although we could have happily spent the day outside, there was serious fox hunting required.
Charles ZL1RKO and Nikki ZL1PKL dropped in with biscuits and given the turnout, we literally ran out of room around the tearoom table. Dave ZL1DL brought cake; rumour has it he was close to a birthday that ends in 0. Still, we couldn’t just sit around and drink coffee – there was noise to flush out…
A couple of old school transistor radios, with ferrite rod antennas – ideal for direction finding, were produced. Very quickly it was established that the noise we were chasing was ubiquitous; it was apparent to some degree on most cables in the building…, and was, unsurprisingly, evident on all HF receivers inside the clubrooms. Outside and away from the building, the interference diminished, in the main, as one moved further away from the building, suggesting the source of interference was from within. The exception to this observation was from Dave ZL1DL, who managed to find a strong indication of interference no matter where he went. Even more puzzling was Dave’s inability to find a reliable direction null with his radio – the null moved as he turned. After a time of wonder – all was revealed; cellphone in pocket was producing QRM on HF. Of course, that wasn’t the QRM we were seeking. Powering off several items proved fruitless. In fact, fruitless aptly describes the level of success we had in pursuit of the interference source. Perhaps another day.
So our attention turned to installing the replacement batteries for the 5775 repeater; something that wasn’t so difficult to succeed with. Batteries installed and the repeater was reconnected to the battery backed supply and we called it a day. Fox 1, MPRG 0.