The
Hi-Fi Section
- DX-ing
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In the
days before DAB (Digital Audio Broadcasting) Radio, when listeners were still
striving for "Quality" rather than
"Quantity", DX-ing was a popular pastime
of many Hi-Fi enthusiasts.
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Back
in the early / mid' 1970's,
"Stereo" radio was still not available in every
"Nook and Corner" of Great Britain. This
was especially true, here in "Rural"
Norfolk, being one of the last areas in Great
Britain to have Stereo radio coverage. If you
wanted to enjoy the pleasure of such broadcasts,
then you would need to receive a signal
from a distant (DX) "Stereo" transmitter,
rather than that provided by your local "Mono" only
transmitter i.e Tacolneston.
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This
would normally require the use of a "High
Gain" FM
aerial, consisting of at least four elements,
coupled to the obligatory "Aerial
Rotator". The fragile signal being fed
through a "Low Loss" Co-ax cable, into
the FM tuner of your dreams. This sort of
equipment did not come cheap, and for me, like
many others, much DIY was required
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"The
Map" and Pioneer TX-9100 Tuner - Cira 1977
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VHF 88-108
MHz
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During
this time, "Local Radio" was only in its
infancy, and the VHF 88-108 MHz scale (Band II) was far less
cluttered than it is today. The only FM broadcasts to be found, were those from BBC i.e. Radio 2 (Light),
3 (Third), 4 (Home) and maybe a "Local
Radio" station. Additionally, if your tuner
had poor AM rejection, than you would probably
find the local police, transmitting somewhere
towards the higher end of the VHF scale, in AM..
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Very occasionally,
during favorable weather conditions, you might be
lucky to find a "Handful" of Western European
stations scattered across the scale of your tuner.
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Note
- The first "Local Radio" station, in
Great Britain, was "BBC Radio
Leicester". Broadcasting commenced in
November 1967, via a 50 Watt "Valve" VHF
transmitter. This was replaced, in 1971, by a 300
Watt "Transistorized" VHF transmitter.
Now 50 years old in November 2017.
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BBC
"Test Tone Transmissions" and Multiplex
Stereo Radio
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During the early
1970's, and very late in the evenings, the BBC
transmitted a series of "Test Tones" on
Radio 3. These transmissions were designed to help / aid, in the
"Setting-up / Alignment" of stereo decoders e.g. Cross-talk
adjustment, and for Channel Identification
purpose's etc. Information, about these
transmissions, was freely available from the
"BBC
Engineering Information Service" at that time i.e.
"Information
Sheet 1605(5)"
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For
more information on how FM Multiplex Stereo radio
works, please see the excellent article by "Harry
Leeming".
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Various
Aerials .....
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There
were many
commercially manufactured Band II aerials
available in the 1970's, but the larger
arrays were somewhat out of my price range. Therefore, after having
read many books and papers on aerial design, I set
out to have a go at designing and building my own.
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The
British government was then starting to "Shut Down" the
old VHF, 405 Line
"Black & White" television
transmitters, broadcasting on Band's I and III (See
Map and Information). Moving up to the
newly allocated UHF channels, for 625 Line "Colour"
television broadcasts, on Band's IV and V.
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Therefore,
there would be plenty of material,
from the copious amount of old redundant aerials, available for DIY Band
II aerial construction.
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See
"Various
Aerial's" used for Band I, through to
Band V, Television and Radio reception. Together
with an
"Old Advert" dating back from 1957.
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A "Selection" of Band I and III
aerials
(Larger
View)
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Yet
Again !
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Whilst
on the subject of television broadcasting .....
as of
the old VHF, 405 Line
"Black & White" television
broadcasts, then the current UHF, 625 Line "Colour"
television broadcasts are due to be
"Phased Out". With the first
transmissions "Shutting Down" in 2008,
with completion by 2012. The old UHF service will
be replaced with, wait for it ..... DTV
(Digital TeleVision). This time making
all of the "Older", pre SCART connector,
Band IV / V Television receivers and Video
recorders redundant ..... !
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Provided
that the signal strength was adequate, then the
picture quality obtained "Off Air" via
UHF broadcasts, was very good indeed. Without any
of the problems that we find with Digital
Broadcasts.
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I sometimes wonder if change is really necessary ?
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My
apologies for deviating from Hi-Fi / Band II
aerials.
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"High Gain" Band V aerial and Rotator (Larger
View)
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DIY
"Band II" Aerial's
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DIY designs were
normally constructed from the "Recovered"
elements, obtained from old "Band I" television
aerials i.e. due to their larger physical
dimensions. With the Boom / Spine of the old
"Band III" aerials, being used to
support the "New" elements. All the old
material being
cleaned and cut to size, then used in the
construction of Band II aerial designs.
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Starting
with a very simple 2-element i.e. Dipole and
Reflector design, mounted on
the chimney bracket together with existing VHF and
UHF television aerials.
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Finally
building a 6-element Band II aerial i.e. Dipole,
Reflector and Four Director elements, for
"Extra Gain". The DIY 6-element aerial was
fitted in the loft space.
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Much better ..... I now required a suitable rotator
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DIY 2-element "Band II"
aerial, below TV aerials
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Austin
Cambridge A55, Connection
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I used
a suitably geared, electric motor for the aerial
rotator. Being that of a "Window
Wiper" motor assembly, recovered from my late fathers
old "Austin
Cambridge A55" motor car.
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The
"Series" connected wiper motor, would only run in one
direction i.e. "Clockwise", irrespective
of the polarity of the DC power supply
(12 Volts, at 2 Amps "Full Load"). However,
after fitting a bridge rectifier
"Around" the field winding, the motor
would run both "Clockwise" and
"Anti-clockwise", as
required.
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The
output speed was still quite fast, so the unit was
feed on "Pulsed DC", thus slowing the
unit down considerably. High value capacitors were
fitted across the armature and field windings, to help reduce
the vibration problems that are associated with
such a supply.
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A
suitable section of "Short Pole", was
welded to the output drive of the motors gearbox.
Thus allowing the aerial to be physically attached
to the "Rotator".
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Electrical
"End Stops" were fitted to the
"Rotator", in the form of
"Micro" switches wired in series with
the motor. To allow the motor to be reversed, a
"By-pass" diode was fitted in parallel with each of the two
"End Stop" switches.
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Original sketch of DIY "Aerial Rotator"
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"The
Map"
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The
aerial and rotator combination worked very well.
However, I was totally oblivious to what direction the aerial
was pointing. Some form of direction indicator
would be required !
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I
found a map of Europe and glued it to a suitably
sized piece of Hardboard. The map was to become a
suitable "Feature" on the wall above the
Hi-Fi. Then, by using a piece of copper clad PCB,
I constructed a rotary switch. This would be fixed
around the output shaft of the rotator. My own
physical location on the map, being the centre
axis of the switch, and the contacts, being the
direction of the desired transmitter stations.
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Each
transmitter station being represented by a
"Bi-coloured" lamp on the map i.e.
"White" state, to indicate the location
of all the transmitter stations, changing to a "Red" state, to
indicate the aerial was pointing towards that
particular transmitter station. An
adjustable "Wiper" contact, being fitted
to the output shaft of the rotator, allowing for
system calibration.
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Using
a "Duplicate" switch on the rotator
controller, and a few relays, the system was
"Automated". Whereby, you simply selected the desired
transmitter station, via the rotary switch, and the
aerial would "Automatically" stop, when
it faced the selected transmitter station.
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"Transmitter Station"
site Map - Circ 1976
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From
DIY to the "Real Thing" !
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Alas, 100% success from my DIY aerial designs was rare,
and not so rewarding for all the effort involved.
However, having said that, the designs served me very well for the years that I
used / relied on them.
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To obtain better signals i.e. "More Strength", then I would need to purchase a
suitable aerial, built for the task.
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I
decided on a "Six" element aerial (JAYBEAM
"Stereobeam" SBM6). This had a good
"Forward Gain", 8.5dB, and not
physically too large. Initially,
the aerial was situated in
the excellent sized loft space available, together
with the "Home-made" rotator unit.
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At
a later date, the aerial taken out of the loft
space and mounted on the chimney stack. Alas, the
aerial would not be attached to the DIY Rotator
unit, as it was far too heavy and definitely not
weather proof !!!
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The
DIY aerial rotator, was eventually replaced with a
commercial unit i.e. "Stolle" 2010, which is
still in excellent working condition. The "Stolle"
2010 rotator, together with the associated remote
control unit, worked very well with the SBM6
and later with a "High Gain" Band
V UHF TV aerial.
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JAYBEAM "Stereobeam" SBM6
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Cira 1978
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Tuner
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My
original Tuner, being the excellent Armstrong 524
FM tuner, with the "Optional" M8 Stereo
decoder board fitted. This gave very good
service for many years, and is still in use
today, by it's current owner.
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The Armstrong
524 FM tuner was replaced by a
Pioneer TX-9100 unit. The later having excellent
"Sensitivity / Signal to noise ratio"
and ideal for the task of DX-ing.
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Many
happy hours were spent, searching out alternative
programme material etc, using the Pioneer TX-9100.
Indeed, there was precious little in the way of
Stereo broadcasts in the Norfolk area, at that
time, to listen to in any case.
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Looking
back, I always will remember
the Armstrong 524 sounding far better, more
natural, than the
Pioneer TX-9100.
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Armstrong 524, FM only tuner
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A
fellow local Hi-Fi enthusiast, circa late 1970's,
had a wonderful system for DX-ing. Consisting of a
"Nine" element aerial, with a "Stolle"
aerial rotator, coupled to a "State of the
Art" Trio KT-8005 tuner.
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I
had always been impressed with the Trio
KT-8005 tuner, both in terms of Audio Quality and
it's excellent RF Sensitivity, but I had never found one
suitably "Discounted". However, in the
middle of the 1980's I acquired a second-hand Trio
KT-8005 tuner, for just £15. It is still in
current daily use in my workshop.
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Trio KT-8005 tuner on workshop
shelf
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Being
a valve fanatic, the Leak "Stereo Trough
Line III" is probably one of the best designs
that I have ever had the pleasure of listening to
and owning. Alas, in the late 1980's, I swapped it
for a Pair of Leak TL12 plus valve power
amplifiers. A course of action, that I deeply
regret !
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What of the future ?
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Just like the
old VHF, 405 Line
"Black & White" television
broadcasts of the past, the "Great"
British
government is now preparing to "Shut Down"
the "Excellent" VHF FM Radio broadcasts
on Band II (Also shutting down AM broadcasts). Thus making all of our treasured Leak
/ Quad etc, AM/FM Radio equipment redundant (re UK
Broadcasts).
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So,
as
excellent as the VHF FM broadcasts are (2009), by
2015 they will
cease to be ..... Gone forever.
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Well thanks for
that ..... us Hi-Fi enthusiasts, and many
others, will find that really useful !
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As for the
future of "High Quality" Radio
Broadcasts ..... it would appear that DAB (Digital Audio
Broadcasting) is the only way ahead at present.
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Yes, I admit
that there are some advantages with DAB, but with the
"Current" audio quality being only slightly better than that
of MP3 ..... what can I say. As is so typical in
this "Digital Crazy" era, we appear to
be sliding backwards, rather than moving forwards
..... Oh lucky us !!!
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Up-date
- In 2016, British radio stations are still
broadcasting on VHF FM.
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Plus (or is it minus) ... Not Eco friendly etc .....
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In
the current way of thinking, this "Plan"
is far from being eco friendly, as ALL
perfectly good AM/FM radios/tuners will be redundant
i.e. USELESS. Therefore, they will most likely be "Bagged-up" and sent off to help fill-up
yet more landfill sites.
Such a waste of
equipment and money when the current broadcasting system is
a perfectly good one !
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Again,
I have the need to deviate here, as my own feelings on the matter
are so strong In
my opinion, the reasons for the "Shut
down" are more political ones, rather than
those due to improvements in technology. Alas,
the "Shut down" of AM/FM radio
broadcasting in Great Britain will certainly generate huge sales of DAB
radios/tuners, but in terms of business and trade,
I cannot see how this will financially help Great
Britain, as the majority of these units are
imported from overseas.
The
"Shut down", is yet again
something the people of Great Britain have not asked for,
but something they are forced to accept.
We
are suppose to be living in a democratic society
..... or are we ?
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