Wireless Waffle - A whole spectrum of radio related rubbish
Noisy Neighbourssignal strength
Thursday 30 October, 2008, 22:23 - Amateur Radio
Posted by Administrator
It may appear to have been quiet here at Wireless Waffle over the past couple of months, but that's because a number of things have piqued the interest and we've been doing a bit of experimentation and investigation. The first of them is the issue of Power Line Telecommunications (PLT) also known as Broadband over Power Line (BPL) and in particular the problems being experienced by many UK short-wave radio listeners with it. One of these devices could recently be heard, albeit quietly, across the HF spectrum (oddly it has since disappeared) at Waffle HQ but it raised the question as to how many more there were in the area. To find out, I fitted and HF antenna to my car and connected it to an HF receiver and then drove around a nearby housing estate to see what could be heard.

The antenna used resonated in the 18 MHz (17 metre) amateur band but received perfectly well in the 17 MHz (16 metre) broadcast band. Tuned to a clear channel around 17460 kHz, the car was driven around the area under test. Over the area covered by a small local estate, three devices were detected. Two were almost certainly the 'Comtrend' device, sounding just as the ones that UKQRM has demonstrated on YouTube. The third (shown in red on the map) emitted a more continuous tone, interrupted by occasional blips; the range of this device was somewhat less than the other two. Their range at other frequencies was not tested but anecdotal evidence driving round the area using other antennas and the same receiver suggests that the coverage on frequencies around 27 MHz is similar.

plt bpl interference rangeI've plotted the approximate location of the three devices identified together with the area over which they were clearly receiveable on the map on the right (the map covers approximately a 500 metre by 500 metre area). The blue device had the largest interference range and within the areas marked it is unlikely that any short-wave reception would be possible.

The density of these devices means that over the whole estate, short-wave reception would be virtually impossible. A cursory glance around the area indicated no amateur radio antennas so it is likely the devices are going undetected (or just unreported!) Not a positive result and unless the powers that be do something to halt the spread of these devices, it would be easy to foresee a situation where HF reception could be pretty much impossible over whole towns and cities, in residential areas for certain.

One piece of positive news is that Ofcom have set up a special team to deal with PLT interference and appear to have begun taking the problem seriously. Let's hope that this is more than just paying lip service to the problem before the whole HF spectrum is lost to the laziness of those who can't be bothered to use WiFi or put a piece of wire between various bits of equipment in their home. These devices are a disgrace and a menace and before they wipe out all short-wave reception and neighbour-on-neighbour war breaks out, serious action by the authorities is absolutely necessary.
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