Posts Tagged ‘EMC’

Speaker failure

Yesterday the Medion computer speakers that I used with my Elecraft K3, failed. I was WSPRing on 10m and had the speakers switched off at the time but I saw some unusual interference on the waterfall and switched them on to listen. Nothing happened. No audio, nor did the blue power LED light up.

I checked the obvious things such as the cables and that the power supply was delivering 14V DC. It was. I took the speaker containing the audio amp over to the workbench and tried it on the bench power supply. Although the speaker was behaving as if no power was being applied, 20mA was being consumed when the switch was on. I have no idea where it was going.

Without a schematic there isn’t much I can do but I doubt that the speakers are repairable anyway. There are no active components on the circuit board apart from one integrated module attached to a small aluminium heatsink. This has presumably let its smoke out. There are a number of capacitors on the board and the cable connections are extremely well filtered against RFI. I have never seen such attention paid to preventing RFI. I guess that this is because Medion is a German company and Germany seems to be the only country that takes compliance with EMC standards seriously. The speakers were almost completely immune even when I ran 100W. Having a tone control they produced very rich-sounding audio from the K3, unlike its internal speaker which is shrill to listen to and has very little bass response.

I’ve now replaced the Medions with a pair of passive speakers that I originally got for this task but with those the audio sounds boxy no matter how I fiddle with the K3’s RX EQ settings. The only benefit of them is that I’m using one less wall wart!

These Genius speakers look like they might be a good replacement but ordering a pair would be a lottery as I have no way of knowing if they are RF-proof enough. One pair of Logitech speakers I bought were a dead loss. They were handed to the local Oxfam shop within an hour of the postman delivering them as they were so sensitive to RF they were beyond hope.

Death of short wave imminent

Amateur radio as we know it could be extinct by the year 2020. That is the only possible conclusion to draw from an unpublished EU policy document that has been leaked to several ham radio bloggers including myself. The document proposes that existing RFI standards protecting the short wave frequencies be torn up as “preventing the use or increasing the cost of essential technology in order to protect the activities of a small number of hobbyists makes no political sense.” This policy has already been unofficially in place at the UK’s Ofcom, which was one of the major contributors to the report.

The report suggests that withdrawing the standards relating to short wave RFI would save significant costs by removing the need to deal with complaints about interference. It also suggests that the UK Telecommunications Act (and similar laws in other EU countries) be amended to remove any right to protection from interference of the broadcast, amateur or CB services.

To support its recommendations the report claims that “short wave broadcasting is in rapid decline, with most broadcasters moving to the internet” and that “the intended use of Citizens Band as a personal communications service has largely been replaced by cellphone usage.” Amateur radio, it says, carries “little communication of any importance that could not be made using the telephone, cellular network or the internet.” The main use of ham radio, it suggests, is “largely recreational” and could be replaced by “online simulations and VOIP chat services.” Hams could also make more use of the largely interference-free bands above 400MHz which otherwise could be sold to commercial users. Radio amateurs “could still experiment with radio in the time-honoured manner, they just should not expect to be able to enjoy interference-free reception on the short waves.”

The reason for the desire to remove the protection of our frequencies becomes clear when you read the part of the report that describes forthcoming technologies that are expected to cause problems with RFI compliance. In order to meet carbon emissions targets and deal with expected power shortages caused by the early closure of nuclear power plants in countries such as Germany, the EU plans to introduce smart grids in all European nations by 2020. These smart grids use BPL technology to communicate with smart meters in each individual home. The smart meters, in turn, use PLT technology to communicate with smart devices in order to regulate their use. When demand for electricity is high, power cuts or the switching on of expensive standby power stations can be avoided by shutting off inessential devices instead. Examples of inessential devices given in the report include amateur radio linear amplifiers – assuming it’s still possible to hear anything on short wave over the BPL and PLT QRM in the first place.

The EU is also proposing that 80% of properties in member states should be equipped with solar panels by 2020. To achieve this target, installation costs will be heavily subsidized by governments, which clearly want to cut costs as far as possible. Estimates produced by a Chinese manufacturer of solar power systems suggest the cost saving that would result from eliminating the need for RFI suppression circuits in the power converters would amount to 4 billion Euro for the whole of Europe.

The report concludes that “the cost of protecting the short wave spectrum from interference from technologies that are essential to be installed throughout Europe in the next decade to meet emissions targets and maintain the well-being of all European citizens is quite simply prohibitive” and urges that EU Commissioners pass the necessary laws by 1st April 2012.


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  • Matt W1MST, Managing Editor




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