Groundhog Day?
Techno Talk
Mark Nelson
Déjà vu? That feeling you’ve already experienced something that is actually happening for the first time.
Two of this month’s topics may look familiar, but they are actually follow-ons, not repetition, and the rest
is entirely new. It’s easy to work out which is which!
B
ack in the early 1970s, there
was a trendy shop in London’s
Tottenham Court Road going
by the exciting name of ‘Cassette
Revolution’. Plenty of record shops
were selling albums as pre-recorded
‘musicassettes’, but the shop named
above was brave enough to sell no vinyl
at all, which was pretty revolutionary
at the time. Subsequently, CDs virtually killed off compact cassettes, with
CDs in turn giving way to downloads
and streaming for many folk. Two disruptive trends then followed: the vinyl
revival and the cassette comeback.
Generation Z has rediscovered tape,
although bizarrely, some buyers don’t
even own tape players. Instead, they
use the tape as a form of memorabilia!
Data tape is back too
Even more surprising, tape is making a
comeback among professional users too.
A report in The Economist last December
made the remarkable statement that despite its archaic image, magnetic tape
has a surprisingly promising future in
data storage. The simple truth is, hard
drives are costlier than tape, have shorter
lifespans and the amount of heat that
they generate makes hard disc storage
undesirable for universal use. So-called
‘cold’ storage of data that requires only
occasional access can be handled more
economically on tape. Even better, the
report continues, the storage density
of magnetic tape has been increasing
steadily, by 34% a year for nearly three
decades, meaning that tape may catch
up with hard drives within five years.
All this makes perfect sense, if you
have mission-critical data that requires
unconditionally reliable, long-term
storage and you have the space and
climate-controlled premises. No other
data storage medium that I’m aware of
can beat tape in that scenario. Flash
drives and other solid-state media are
for short-term storage only. And as victims know, hard drives are vulnerable
to head crashes and DVD-Rs can lose
their data in five years or less (I have
learnt bitter lessons in both respects).
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Unfortunately, the vulnerability of unwise data storage does not get through to
consumers or companies which are not
tech-savvy. When I worked at a wellknown car manufacturer’s HQ in the late
1970s, they lost a whole month’s worth
of accounts data when their preferred
data storage medium failed. The accounts
staff had to recompile everything from
scratch (and benefitted from unlimited
overtime for the next four weeks!). And
what was that preferred data storage medium? Compact cassettes! No, not the sort
used in your Walkman but the data-storage type that had a large identification
notch in the cassette housing. These
tapes were not optimised for audio use;
but they did, nevertheless, fit in a normal cassette machine’s tape deck, which
is why some office thief nicked them.
Openreach still on the
learning curve!
Way back last December, we chastised BT
Openreach when it took 18 months to sort
out poor broadband connectivity and slow
speeds in north Wales. It blamed these
issues on an unsuppressed old television
receiver instead of inadequate filtering
and screening of its network hardware.
Any lessons learnt in Wales appear not
to have filtered down to other parts of
this Sceptred Isle, as this report from
our West Country correspondent proves.
He writes: ‘I previously mentioned a
colleague and his neighbours who are
blighted by an RFI/EMI fault that crashes
their broadband regularly. Sounds like
a mains PME fault to me. Had it myself
when I worked for BT Openreach, but
they have not handled this properly or
effectively. Why? BT sent him a new hub,
as if a new hub would solve the problem!’
PME is ‘protective multiple earthing’, and
if a fault occurs on the combined protective earth and neutral conductor, then the
neutral conductor of your mains wiring
may not be properly earthed. There’s a
technical discussion on these problems
at: http://bit.ly/pe-may21-tt
The ‘colleague’ bought a mains EMI
filter and says it has reduced the frequency of crashes and the broadband now
recovers more quickly after a crash. On
the other hand, his neighbour has fallen
out with his service provider entirely because of the unresolved fault. Instead,
he ditched the landline altogether and
is now using 4G cellular for both voice
and broadband.
Mucky mains again
The March edition of this column recalled the problems that plagued Gerry
Wells of the Vintage Wireless Museum
in London, which he had put down to
what he called ‘dirty electricity’. He died
in 2014 and never accessed the Internet
and Amazon’s emporium. Had he lived
another seven years, he could have bought
an AlphaLabs Dirty Electricity Meter, a
natty-looking power line monitor that
displays noise on a colour screen, calibrated in mV peak-to-peak. Even better,
a built-in loudspeaker plays the alleged
sound of the electromagnetic interference, amplitude demodulated, in order
to identify the EMI source (such as an
AM or shortwave radio station vs. a motor vs. an electric arc).
Only Gerry wouldn’t have bought it
at the £161.99 price asked, because he
didn’t spend money like water. That said,
the gadget is quite neatly turned out (see
https://amzn.to/3cWr4LZ). On its own, the
meter/detector is exactly that and only
indicates how ‘dirty’ your mains supply
is. To resolve the problem, you need to
buy also the DE2 Dirty Electricity Mains
Filter, costing £45.60. This will filter out
the EMI interference and ‘reduce’ the
dirty electricity in your house. Probably.
More free electricity!
Researchers at the University of Colorado
have demonstrated eco-friendly thermoelectric generators that convert your body
heat into elelctricity that will power bodyworn devices. The 12.5µW delivered at 5V
can drive most low-power sensor nodes
with radio-frequency communication.
Internal wiring of the devices uses liquid
metal, resulting in self-healing properties, Lego-like reconfiguration and good
recyclability. Best of all, the devices cost
$10 to make. More details at doi.org/fvdv
Practical Electronics | May | 2021
