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Current Radio Rules Mean Sinclair ZX Spectrum Wouldn't Fly Today
First time accepted submitter wisewellies writes "Ben clearly has way too much spare time on his hands, but he decided to see just how well an antiquated ZX Spectrum would hold up to modern EMC requirements. His blog is a good read if you're looking for something to do while pretending to work! From the blog: 'This year is the 30th anniversary of one of my favourite inventions of all time, the Sinclair ZX Spectrum. A few weeks ago, I finally bought one: a non-working one on eBay that I nursed back to health. Fortunately there was very little wrong with it. Unfortunately it's a 16K model, and a fairly early one at that, which won't run much software in its native state. This probably accounts for its unusually pristine condition. We took half an hour in the chamber to perform an approximate series of EN55022 measurements, to check its radiated emissions against today's standard. The question is, what have we learned as an industry since 1982?'"
"It’s not just a failure; it’s an abject one" Really? Now I admit the situation could be a ALOT worse with the accessories and cables, and until you've ran the test you don't know. But it's only about 6dB above the line, I've seen a lot worse problems [try 20dB!]. There is a good chance this would be a relatively easy fix when you start looking at the problem.
A ferrite bead on the power supply cable would probably fix the "bad power" supply if indeed that's what it is. And some judicious copper taping would likely fix the other problems. Worse case you do a board spin and add ferrite beads to the I/O and possibly move suspect traces into internal layers. Worse WORSE case you change the clocking to use spread spectrum which would likely not require any changes except in the clocking circuits. None of those would prevent a "modern" version of the product from going to market.. And a good engineer could probably implement them in less than 6 weeks in a production environment...
Plus it doesn't even manner, if you were going to bring a sinclair back to market it would draw about 20mA, run on USB power and be completely implemented on a single chip.... Because it has roughly the same processing power as a PIC uC.
The ZX didn't fly back in the day either. /rimshot
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
I have a ZX Spectrum in the loft I often see when I go up there. As far as RFI is concerned our regulations back then were non-existent. I once saw a BBC Micro for the German market, it was encased in metal and built like a tank. The ones on the UK market were plastic and caused havoc with my Amateur Radio gear until I quietened it a fair bit by coating the inside of the case with graphite spray and grounding it. TV's were another problem as they were susceptible to interference from Amateur radio transmissions operating within the legal limits and specifications and we had inspectors who audited our stations for compliance. It was all down to the manufacturers saving may be a penny or 2 by using a cheaper front-end transistor for TV's sold into the UK.
I wrote my first real program on a Sinclair. It was for TV troubleshooting and it took you down to the section. Storage was a cassette tape and the output was composite video for black & white TV.
Then I bought the memory expansion, took it to work and made a program for it to do cost estimate calculations. It was the 2nd computer anywhere in the company. I got promoted from cost estimating to Systems Administrator all in one go. I stayed with that company almost 30 years, then I left to start my own software company.
A few years ago I was telling that story to a client. He pulled a mint condition Sinclair -- still in the original box -- out of his desk and gave it to me. He said it bought it to learn computers and never used it. It was like giving me the keys to my first car.
The original TRS-80 was a wideband RF jammer. Cheap PCB design, plastic (unshielded) case, lots of ribbon cable external interconnects operating at megahertz frequencies.
One of the better ways to see whether the machine was frozen or just processing a long-running (but productive) internal loop was turn on an AM radio in the same room. Within about 3 feet, the RF noise would override all but the strongest stations and allow you to monitor the CPU's execution by the hums and burbles of the RF noise.
It's why the original TRS-80 became the Model I, rapidly superseded by the all-in-one Model III (with lots of internal shielding).
Welcome to the Panopticon. Used to be a prison, now it's your home.
Here's the actual blog instead of some stupid Register article: http://focusritedevelopmentteam.wordpress.com/
We're really lucky that the FCC clamped down on RF emissions from electronics. Otherwise, we'd all be looking at big electromagnetic compatibility charts before buying anything, trying to find combinations known to work well together. Offices would need RF spectrum analyzers to figure out who brought in something that was messing up other gear. I mentioned in another post that you couldn't operate a Milton Bradley Big Trak and an TRS-80 near each other. The other side of stopping RF emissions is that the shielding makes electronics much less sensitive to RF interference.
The development of really good RF noise management technology made modern cell phones possible. The concept of a handheld device with four radios (GSM, WiFi, GPS, and Bluetooth), all operating simultaneously within a few inches of each other, was totally beyond the RF technology of a generation ago. Two generations ago, it was so bad that marine radio stations had miles of separation between the receivers and the transmitters.