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I think that these new flat screen
TV sets and lots of other new electronic stuff need to have a
warning label along the lines "Danger- installation of this
equipment may result in damage to your mental health".
As electronic equipment has got newer the booklets accompanying
them have got more and more complicated, to the extent that not
one but two booklets are often issued. The second being a simpler
version.
Unfortunately the contents of most of these booklets leaves a
lot to be desired and the customer is usually left with something
that just doesn't work or at best works only minimally.
Take three examples I've encountered lately…
Case 1
A new flat screen TV replaced an old
CRT model that had expired. Switching on the new set and fiddling
with the remote control had resulted in absolutely nothing of
any consequence so I was called to assist.
The booklet was gibberish so, without its assistance, I managed
to find both analogue and digital set up. These were completely
independent and the former gave no inkling of the fact that the
TV was able to receive Freeview digital stations. In fact lots
of people are totally ignorant of the source of Freeview stations
even after several years of advertising their presence, and the
consequence of this is that many TV sets are never switched to
their digital setting.
I think the same goes for these new fangled DVD recorders. Most
of these are very coy about their ability to receive Freeview,
and in fact many currently sold models are still analogue only.
I sorted out this TV quite easily without the benefit of the
confusing booklet (page 65, it turned out had the setup information)
and left them to discover the intricacies of using their VCR
and to sort out the finer features of their new TV.
Case 2
This was initially a bit of a puzzle
as the TV was said to display a "NO SIGNAL" legend
when switched on. I trotted round to investigate, initially confirming
that the TV aerial was plugged in and the extremely long coax
feed did in fact end at an aerial, without losing in the process
any power to a masthead amplifier or a break in its length.
There seemed to be no amplifier fitted and the very long, rather
tatty, lead did in fact at least head off in the right direction.
I fiddled with the remote control after finding that the operation
booklet was useless, even to a seasoned repairer.
After poking around at several buttons on the remote control
I found the set had factory settings for "System BG"
and it wasn't looking at the UK UHF band when carrying out its
search for stations. It was also frozen at this point and totally
unresponsive to any buttons (something akin to Windows 98?).
After working out what buttons were supposed to do what on the
remote, I managed eventually to jog it out of its apparently
dead "NO SIGNAL" mode and to switch it to "PAL
I", and set in motion a search of the UK UHF band. This
was immediately successful, capturing around 80 odd stations,
despite the fact that the aerial was very old, had only half
a dozen elements, and pointing at a drunken angle towards a flat
roof instead of blue sky. This particular household had just
cancelled their Sky subscription and had hardly ever bothered
with their old aerial.
Case 3
An old friend had trouble after leaving
his house to the mercy of friends when they were on holiday.
There was only a poor Channel 4 picture on the TV. Nothing else
but noise. I'd recently helped out by setting everything up for
him, including new CRT TV, two Freeview boxes, a new DVD recorder
and a VCR, leaving him to grapple with five remote controls.
Over the phone and by email I tried to resolve the situation.
By the time we'd finished we had a good Channel 4 picture and
little else.
A house call was essential.
Findings were as follows…
(1) The TV had been inadvertently detuned
so that only Channel 4 was available. Maybe a scan of the cable
band had been done as Channel 4 here is on RF channel 21?
(2) The high gain aerial in the loft was mounted vertically instead
of horizontally. This accounted for the inclusion of a 34dB amplifier,
as this had been required to get a set of pictures from Rowridge.
I mentioned that even the Goonhilly engineers made this mistake
when trying to receive signals from Telstar... remember that?
(3) Next the coax. During my instructions I'd said to check that
no braid whiskers were touching the inners. Unfortunately this
request had resulted in three leads being cut back so that only
the inners were clamped in the two amplifier connections and
the aerial connection. The braid was an inch clear of the ground
clamp in every case.
Once the aerial had been twisted through
90 degrees, the coax had been sorted out, and the TV retuned,
the four local analogue pictures were completely noise free,
and both Freeview boxes were back in business.
Case 4
My own TV installation dates back some
years when Channel 5 was transmitted from a location some 40
degrees or so from the line to Rowridge, and to boot was very
very low power.
Once Freeview became available here
some changes became necessary.
Initially the digital transmissions
from Rowridge were made across the whole UHF band: that is to
say they were outside the passband of most local aerials which
were cut for the low end of the band, up to RF Channel 34 or
thereabouts.
The main analogue stations from Rowridge
utilise some 500kW of power but those for the digital transmissions
only 5kW. Putting some of these up at the top end of the band
resulted in most people not getting ITV and Channel 5 and necessitated
new aerials to be erected at great expense. For some inexplicable
reason these transmissions have now been relocated to the low
end of the band, causing extreme confusion as suddenly ITV disappeared.
"We just paid £120 for a new aerial and got a super
ITV picture but now it's gone", was the typical complaint.
Jolly good business for the aerial installers, fitting new broadband
aerials and swapping the LF boosters for new wideband types but
why, when only months later the stations were relocated and the
old aerials and booster would have been fine?
And where did it say that one had to
force a re-scan for ITV to be rediscovered? Well I got lots of
phone calls and it cost a lot of my time to put people right,
not to mention often stopping a tricky job and having to get
my feet back on the pedals after 20 minutes of explaining over
the phone about pressing the SETUP button etc and waiting while
they tried it…
Is all well now at my location?
No not really…
The choice of aerial and amplifier etc made when Freeview started
are no longer optimal.
What would you think when, on a warm
summer evening, all the digital signals break up and disappear?
Increase the amplifier gain.. Fit a better aerial… improve
the coax quality..?
I tried all this and got very confused as the better the installation
got the worse things became..
The penny dropped when I was just about to turn on a small distribution
amplifier which feeds two digiboxes and long feeds to different
rooms.
The pictures were perfect when the amplifier was OFF and disappeared
when the amplifier was turned ON.
The explanation... when 5kW digital
transmissions are sandwiched between 500kW analogue transmissions,
one can't go on amplifying the former without amplifying the
latter. There comes a point when the skirts of the analogue signals
swamp the tiny digital signals buried in between them.
Given a digital TV and a couple of digiboxes with different performances
it's tricky to get a good balance without expensive test equipment,
other than by using trial and error.
Not only that, but the plan I believe is to gradually change
the digital transmissions, increasing the power of these ad hoc
until analogue switch-off and then to switch to full power once
analogue is no more. All this will mean that redesign of aerial
systems and amplifier choice is not over by a long chalk…
Being on a hill we also get problems from ducting and peculiar
effects due to temperature inversion during summer months…
I wonder how this will affect digital? Sometimes our analogue
transmissions are even swamped by French TV from the Caen area..
Though not so much this summer as it's been mostly raining! |
