AOR AR3030 Receiver Operating Manual

							AR3030 operating manual
51
coverage.  Due to their necessary construction discone aerials are a little prone
to “wind noise” due to vibration and possible damage in severe gales.
Earth systems
The AR3030 power supply has no EARTH connection to the mains plug.
However a separate earth point is provided on the rear panel of the AR3030 for
connection to a water pipe, central heating radiator or external earth rod.  If
fitting a separate external earth rod,  consider the implications carefully if your
mains supply uses Protective Multiple Earth (PME) system.  If in doubt consult
an experienced electrician.
Connecting an external earth wire may greatly reduce the local noise
encountered when listening on the shortwave bands.  It is very important to
provide a good earth should you use an aerial tuning unit.
A short length of thick gauge earth wire may be connected to a nearby central
heating radiator or water pipe but never use a gas pipe for earthing.  Ideally a
separate earth rod should be used but the length between the receiver and rod
becomes restrictive,  if too long the earth system may well “pick up” noise
rather than remove it.
If a long run of earth wire is necessary,  it may be worth considering a
“screened earth system”.  This simply comprises a coaxial cable (such as
URM43, URM76 for short runs or URM67 or RG213 for longer runs) shorted
inner to outer at the earth rod end with only the centre core connected to the
AR3030 earth point,  the outer braid being cut back and insulated.
This provides a screen for potential incoming interference and passes any
noise down the cable away from the receiver and toward the earth rod.
(11)   Propagation - shortwave bands
Unlike VHF and UHF transmissions which generally propagate only on a
localised basis (to the horizon plus a small amount),  shortwave transmissions
may travel for many thousands of kilometres.  Depending upon the frequency
in use, time of day, season of the year and sun spot activity,  transmissions
may propagate completely around the World.
Radio signals are electromagnetic waves very similar to light beams.  As such
they do not readily follow the curvature of the Earth but attempt to travel out
into space.
The ionosphere
Luckily the frequency spectrum of shortwave is often reflected back down to
Earth by the upper layer of the Earth’s atmosphere called the ionosphere.
When the reflected signals reach the Earth again they may either be
received or reflected back up into space.  If lucky, they will be reflected by the
ionosphere yet again down toward the Earth providing reception into another 
						

							AR3030 operating manual
52
and possibly more distant location.
The ionosphere is constructed of many layers of ionised gas.  Of particular
interest to shortwave listeners’ are the lower “E” and upper “F1” & “F2” layers
although a lower “D” layer exists during day time.
“D” layer
During day time the lower “D” layer 
forms around 60 to 80 kilometres above
the Earth’s surface.  This “D” layer tends to absorb low frequencies reducing
the distance covered by medium wave transmissions.  In the night time when
the “D” layer dissipates,  medium and low frequency transmissions may
propagate over much greater distances.
If the transmitted frequency is too high for to be reflected by the ionosphere,
or the angle too steep,  transmissions will simply pass straight though the
ionosphere without being reflected and will travel upward to the next
ionosphere layer.
“E” layer
Above the “D” layer is the “E” layer located at a height of about 100
kilometres.  The “E” layer tends not to absorb signals as much as the “D” layer
but refracts some signal back to Earth where it may be received some distance
from the original point of transmission.
Usually in Autumn and Spring “SPORADIC E” propagation consisting of dense
pockets of “E” layer ionosphere, reflect even the higher VHF and UHF
transmissions causing patterning on television sets.  This is to the delight of
Radio Amateurs who are then able to communicate for many hundreds and
even thousands of kilometres on frequency bands usually capable of only local
reception.
Occasionally a similar effect can be caused by temperature inversion layers
creating “tropospheric propagation” selectively “ducting” transmissions
between two points.  Tropospheric propagation is usually applicable to the 
						

							AR3030 operating manual
53
higher VHF and UHF bands.
“F1” & “F2” layers
During the day time there are two upper layers of the ionosphere,  these being
the “F1” layer at about 200 kilometres and the “F2” layer at about 400
kilometres.  As evening falls,  these layers combine to form a single “F” layer.
It is “F” layer propagation that is largely responsible for shortwave propagation
over great distances.
The density of the ionosphere layers varies depending upon season, time of
day and sunspot activity which is believed to follow an eleven year cycle of
good and bad propagation conditions.
You will note that large areas of the Earth’s surface lays between the point of
transmission and reflection,  in this area there will be little or no reception.  For
this reason “F” layer propagation is often referred to a “SKIP” and the reflected
signal as “SKY WAVE”.
Generally speaking only frequencies below 30MHz are reflected by the
ionosphere.  Higher frequencies pass straight through even the “F” layers and
will continue outward into space for ever.
Choice of frequency
Depending upon the time of day and desired skip distance,  different
frequencies will be selected by Radio Amateurs and commercial users such
as Oceanic Air Traffic.
For instance the “MUF” (Maximum Usable Frequency) is often stated for a path
between two locations.  Choosing a frequency above the “MUF” will not
produce results as transmissions will pass straight into space.
Many propagation predictions and statistics are published and usually
available from most country’s National Amateur Radio and Shortwave
Listeners representatives.
Various publications are produced giving transmission and contact details for
World wide reception.  These titles include:
World Radio TV Handbook (WRTH), BPI Communications, 1515 Broadway,
New York 10036, NY USA.
Passport To World Band Radio, IBS North America, Box 300, Penn’s Park PA
18943, USA.
Listings for utility services are also widely published and available.
For a list of Shortwave and Amateur Band allocations refer to the table in
section 6-12 of this manual.
(12)   Specification 
						

							AR3030 operating manual
54
Model... AR3030
Receiver coverage... 30 kHz ~ 30MHz
Tuning selection...MHz, kHz, 100Hz, 10Hz
(5Hz minimum step)
Receiving modes... AM, S.AM, USB, LSB, CW,
FAX & NFM
Frequency stability... 5 ppm -10 to +50 degrees C
Number of memory channels... 100 total (00 - 99)
Receiver sensitivity...SSB, FAX, CW (10dB S+N/N)
1uV   30 -50 kHz
5uV   540 - 1800 kHz
0.5uV   1.8 - 30 MHz
AM (10dB S+N/N)
3uV   30 - 50 kHz
15uV   540 - 1800 kHz
1.5uV   1.8 - 30 MHz Narrow
FM (12dB SINAD)
0.5uV   1.8 - 30 MHz
Selectivity... SSB/FAX2.4 kHz -6dB
AM 6.0 kHz -3dB
AM narrow 2.4 kHz -6dB
C W 500 Hz -3dB *
(* with optional filter)
FM 15 kHz -6dB
Image / spurious rejection...70dB
Dynamic range... 100dB @ 25kHz spacing with
500Hz CW filter fitted
Aerial connection... LW - HF 50 OHMS nominal BNC
LW - HF 450 OHMS for wire terminals
LW - HF High impedance whip on BNC
(slide switch selection)
VHF 50 OHM nominal BNC for
optional VHF adaptor installation
Audio output... 1.8 WATTS 8 OHM load @ 10%
distortion
Power requirement...Internal dry batteries (8 x AA) or
external 12V DC @ 0.8A (nominal
13.8V)  negative ground
Size...250mm (W) x 88mm (H) x 240mm
(D)Approx excluding projections
Weight... 2.2kgs without batteries fitted *
Specifications subject to change without notice due to continuous
development of the receiver. E&OE.
Manual V1.01