Sinclair ZX Spectrum FAILS latest radio noise rules SHOCK
A pal of mine suggested a short while back that it might be fun to obtain the blueprints for Sinclair Research’s ZX Spectrum and have a batch built up to sell to fans of retro computing. It’s a good job this plan never made it out of the pub: the dear old Speccy would have immediately fallen foul of modern electromagnetic …
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Caution: long. Contains facts, logic, and small amounts of technology.
" I mean, when these devices were being produced (literally in sheds and garages to begin with) and there wasn't huge amounts of regulation, I don't hear stories of how they destroyed TV and radio transmissions. "
You're utterly clueless on this subject aren't you (or you're trolling). It's OK to be clueless, it's not OK to make ignorant ill-informed comments based on that cluelessness.
When devices were being produced in sheds, there wasn't much RF spectrum in intensive use, there weren't that many electronic devices being made or in use (how many radios in a typical house back then?), and pretty much none of the electronic devices in widespread use were devices capable of wideband RF emissions (such as the switched mode power supply as found in every modern piece of consumer electronics and loads of other places too).
When devices were being produced in sheds, there were also no miraculous applications of modern technology such as the various flavours of DSL broadband, which is basically long, medium and short wave radio down phone lines rather than through the Ether. Phone lines never intended for that use, but which conveniently (a) happen to work well enoug for most folk to use (b) happen to work well enough without causing significant disruption to other simultaneous users of the same RF spectrum, in the same place or elsewhere.
By the miracle of DSL, every available station frequency is in use at the same time, not for voice or music over the Ether but down your telephone line to encode a few kbits per second (per station) of data, upstream or downstream. Telphone lines used this way can pick up RF noise from outside (though mostly they do OK at rejecting most of it). The cleaner the overall RF environment, the more station frequencies are usable and the better the data rate is for each station, so the faster the overall connection is. The dirtier the RF environment, the worse the DSL performance. [Apologies if anyone is offended by my gross oversimplification]
I have no idea how old you are, but I'm sure some readers here will remember how the arrival of increasing numbers of TVs in the UK rendered long wave broadcast reception useless across much of the UK. That would be an example of how unregulated devices destroyed the usability of radio transmissions, something which very definitely happened even if you didn't notice it.
The CE regulations, and EMC best practice in general, are supposed to (amongst other things) help avoid repeating such entirely avoidable disasters, so long as the 'light touch regulation' folk get a clue (or just shut up).
"a lighter set of regulatory requirements that allow inventors to come up with new products for minimal overheads, although perhaps only where these do not involve the use of Wireless RF components."
Show me a device that demonstrably cannot involve the production of significant RF emissions and I'll show you a device whis is ALREADY exempt from the RF parts of the CE regulations.
"electrocuting your customers or burning their houses down tends to be bad for business!"
And everything less serious than that is OK? Even if it stops other legitimate uses (TVs and long wave broadcast, for example?)
Thanks for reading, have a low-emission weekend
“rather fishy power supply and cable”
I may be mistaken, but I seem to recall that it was a bog standard iron core transformer and rectifier, with a linear reg inside the machine itself. Might be a bit crap, but not as noisy (rf-wise) as modern swicthers. (or was that the zx81?
probably both were like that.
Not the external PSU
The Spectrum is indeed powered by a traditional copper and steel transformer at mains frequency. But then on the motherboard, besides the dissipative regulator supplying +5V for the logic, there is a secondary switched-mode PSU producing +12V & -5V for the memory.
Fit a metal shield and it might be okay.
The Apple 2 was a bastard for giving off RF too, so much so that they sold it without the modulator. You don't tend to find much knowledge of this on the web as it doesn't fit in with the beautiful, magical history of Apple and the legendary genius of Woz (who was a poor engineer at first).
http://wikipcpedia.com/wiki/wait-for-ages-then-three-come-along/adding-colour-%E2%80%93-apple-ii/
I remember a program on my old Microtan 65 that produced 'sound' (well, a slightly less random noise) when you tuned in your radio to 750Khz (the clock frequency).
Pretty much any old computer churned out loads of interference.
That's not noisy
I'd love to see how bad my original Vectrex is. Now those things made some buzz!
I think if you built the ZX Spectrum there would be little reason to use the original circuits. Could probably emulate the lot on some cheap ARM chip and throw the whole design into a look-a-like box with 100 games flashed into it too.
Emulating the ZX Spectrum using MAME
Haven't looked in any detail, but there seem to be MAME-based emulators for the ZX Spectrum.
MAME: Multiple Aracde Machine Emulator
Runs on multiple platforms supporting gcc/qt/python.
Apparently available on Android (and therefore by implication on ARM/Linux?)
This isn't news.
When Timex were looking to sell a US version of the ZX Spectrum they put it through the FCC tests, which it failed in 1983. That's the main reason they ultimately came up with the TS2068.
Re: This isn't news.
IIRC correctly the Timex version had the internals of the casing painted with a metallised coating for this very reason.
throw a lumb of Lead in there surely that will sheidl the nastys enough?
"How do we know? Register reader and blogger Ben Supper recently put one of these early 1980s 8-bit micros into an EM test chamber..."
They're waiting for you, Gordon. In the test chamber.
Fond memories, I started coding on a zx81 back in the eighties, and after that had a spectrum. This article doesn't surprise me. As I was getting into computing, my sister was getting into CB radio. She couldn't use the CB when the Spectrum was on due to interference.
Not just the Spectrum?
I'd love to see also the results of testing the X-10 PWM aplifier ...
Far from an abject failure, OK it does not have cables connected and that could make a BIG difference but a failure at two frequencies by not too much should be easily fixed and would not be too unusual for a test run on a first prototype for a modern product. I have seen worse test results than this on CE marked equipment!
I get the impression the writer knew what story he wanted to writer and was going to write it whatever the test result unless it passed on everything.
My Amiga a500 ocs used to almost blanket the entire radio spectrum for about a foot around it with its interference . The ecs one I got later wasnt nearly as bad. I think the later Amiga had an rf shield encasing the top of the motherboard that the old one was missing.
Dont recall the speccy 48k chucking out much interference though.
EN55022
Conformance to EN55022 is non-mandatory. It just shows due diligence to the EMC regulations. In fact, conformance to the law seems to be non-mandatory if you have enough cash and can lobby hard enough.
A lot of LED lights that are on the market do not conform to EN55022 and have been seen to cause interference to DAB receivers...
Spectrum Cursor Keys
Notice how the Sinclair machines' cursor keys ((caps) shift + 5, 6, 7 and 8) went in the order left, down, up, right ..... based on which, I bet I know what software was used to write the manuals!
Modern computers lack charm
The buzz of the Spectrum as it calculated its moves in Chaos still haunts me to this day (will it dis-believe my Gold Dragon)......
Ve haff vays of making you ffail....
And VDE 0871!
Thia sort of stuff's been my living since 1983, though less now, semiretired. In the "good old days" clocks* ran in the SW spectrum, where we in the US could listen to the BBC,**. Or the neighbor's computer.
* Except cuckoo.
** No US broadcasts now.
Wasn't just emissions problem
I remember coding late into the night and being a bit disturbed when the machine spoke to me. (No, I was too young to drink then!). I looked out of the window to see a British Gas van in the street and all was clear- the Speccy was demodulating the van's radio set!
EMC issues
A new PCB layout with modern practices would solve that problem. Routing and bypassing was still pretty primitive in those days. I'm used to being almost unobservable for radiated emissions with only good routing and two layer boards in plastic enclosures.
Sensationalist title - we never had a problem with my Spectrum ...
...not once. I was using it for hours, my parents still listened to radio in the next room, I was also playing music from cassettes etc - and yet no problem, never.
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