AOR AR7030m Operation Information Manual

							AR7030 OPERATING MANUAL          PAGE 31
11 Aerials (Antennas) and earth systems
The subject of aerial choice (and earth) can be quite
complex. There are many advantages and disadvantages
of each aerial type to consider before connecting an
external aerial to your receiver.
One interesting phenomenon is that aerial theory and
practice can be surprisingly different. Within common
sense bounds, aerial construction is one of the few
remaining areas for listeners to easily experiment and often
achieve fantastic results.
Whip aerial: Whip aerials can give fair results for casual
listening. For best results external aerials in clear space
are recommended.
Location: It is important to mount any external aerial
as high as possible and in clear space. If possible the
aerial should have a clear path to the horizon.
Results are usually disappointing when an installation
is in a loft space.
Long wire aerials: For short wave reception a
random length of long wire approximately 10 to 20
metres in length forms a good compromise. The wire
should be connected to the WIRE input of the AR7030.
If possible try to locate the receiver close to a window
so that the wire has the shortest and most direct run
from the rear of the receiver to the outside world.
Never attach the wire aerial directly to a support or wall.
Instead attach a short length (about one metre) of
insulating cord (such as nylon) to each support (house or
tree for example) and then onto the aerial wire. Allow the
wire aerial to drop diagonally into the window and receiver
rather than straight down, close to the wall. Keeping the
aerial away from supports and buildings will reduce the
loss of signal from the wire aerial and prevent unwanted
noise from entering the aerial system.
Transformer coupled long wire aerials are becoming very
popular as they allow coaxial cable to be used as the
down-lead from the wire aerial into the receiver. The
transformer converts the medium impedance at the end
of the wire to a lower value, suitable for 50ohm coaxial
cable. In this instance the path of feeder is unimportant
and chances of noise entering the aerial system reduced.
The 50ohm aerial input of the AR7030 is ideally suited for
such an aerial system.
Dipoles: For the very best results you should consider a
dedicated aerial such as a single or multi-band dipole or
similar aerial. It is quite easy to make a dipole for short
wave. Short wave are usually mounted horizontally. It isworth noting that dipoles are also quite effective on two
and three times their design frequency so you can cover
a few bands at once. Reception using a half-wave dipole
is best at right angles to the direction of the aerial, however
if used at two or three times it’s fundamental frequency,
reception is best along the direction of the aerial.
A dipole has two legs running in opposite directions. One
leg is connected to the centre conductor of the coaxial
feeder cable while the other leg is connected to the outer
screen of the coax. A simple formula can be used to
calculate the required length of each leg for a half wave
dipole:-
Length of each leg in metres = 75
 / 
Frequency in MHz
For example, a half-wave dipole resonant at 14.2MHz
would have each leg 5.3 metres long. The total length of
the aerial would be 10.6m plus the supporting cords.
Coaxial cables: When connecting dipole aerials to
receivers 50ohm coaxial cable should be used. For short
wave URM43, URM76 or RG58U is ideal.
Aerial Tuning Units (ATUs) and Preselectors: An ATU
can improve the selectivity of any receiver when listening
to short wave and connected to a long wire aerial (other
than a very short wire of just a few metres). Preselectors
will normally work with 50ohm aerial systems although
they may include matching for long wires. This valuable
extra selectivity is created by the ATU or preselector
rejecting out of band signals enabling the receiver to single
out one band of frequencies while rejecting potentially
strong unwanted transmissions. One disadvantage,
however, is the need to constantly re-tune the ATU or
preselector when changing receiver frequency.
Passive devices, which contain no active circuitry and
generally do not need power, will not normally degrade
the performance of the AR7030. Users should be aware
that devices with pre-amplifiers or active matching units
are unlikely to have such a high dynamic range as
the AR7030 so the receivers performance will be
degraded by the device.
Earth systems: A separate connection from the
receiver to earth may improve aerial efficiency and
reduce noise. Suitable earth points include
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) 
						

							PAGE  32          AR7030 OPERATING MANUAL
system. If in doubt consult an experienced electrician.
Connecting an external earth wire may greatly reduce the
local noise encountered when listening on the short wave
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 not if the receiver must be distant from
the rod -  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 50 ohm coaxial cable
with the centre and screen shorted at the earth rod end
and only the centre connected to the GND connection of
the AR7030, the outer screen braid being cut back and
insulated.
12 Propagation - short wave bands
Unlike VHF and UHF transmissions which generally
propagate only short distances (to the horizon plus a small
amount), short wave 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.
Luckily the frequency spectrum of short wave is often
reflected back down to the 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. Often
they will be reflected back by the ionosphere yet again
providing reception into another and possibly more distant
location. The ionosphere is constructed of many layers of
ionised gas. Of particular interest to short wave listeners’
are the lower E and upper F1 and 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 layer
tends to absorb low frequencies reducing the distance
covered by medium wave transmissions. At night time
when the D layer dissipates, medium and low frequency
transmissions may propagate over much greater distances
because they can reflect from the higher layers.
If the transmitted frequency is too high to be reflected by
an ionospheric layer or the wave meets the layer at too
steep an angle, transmissions will pass straight though
without being reflected and will travel upward to the next
ionospheric 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 reflects 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 propagationresults from dense pockets of E layer ionosphere,
reflecting 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.
F1 and 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 the F layer that is largely responsible for short
wave propagation over great distances. The density of
the ionospheric layers vary depending upon season, time
of day and sunspot activity (which is believed to follow an
eleven year cycle of good and bad propagation conditions).
Often large areas of the earth’s surface lie between the
point of transmission and the region were the transmission
is reflected down to - in this area there will be little or no
reception. For this reason F layer propagation is often
referred to as skip propagation 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 continue outwards
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 short wave broadcasters and oceanic air traffic control.
For instance the MUF (maximum usable frequency) is
often stated for a path between two locations at a particular
time. 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 short wave listeners’ representatives. Various
publications are produced giving transmission and contact
details for world-wide reception. These titles include:-
Passport To World Band Radio, IBS North America,
Box 300, Penn’s Park PA 18943, USA.
World Radio TV Handbook (WRTH), PO Box 9027,
1006 AA Amsterdam, The Netherlands
or BPI Communications, 1515 Broadway, New York
10036, NY USA. 
						

							AR7030 OPERATING MANUAL          PAGE 33
13 Technical specification
Performance figures relate to a typical production receiver and are not guaranteed levels.
Test signals:- AM mode : Modulated to 70% depth at 1kHz
FM mode : Deviated by 1.5kHz at 1kHz
SSB  mode  : Unmodulated carrier, resolved at 1kHz
1. Receiver system
Dual conversion super heterodyne system with intermediate frequencies of 45MHz and 455kHz.
High dynamic range mixer using a DMOS lateral FET quad.
Tuning by single loop PLL / DDS system from a TCXO reference.
All receiver functions under microprocessor control.
2. Reception and Tuning
Tuning continuous from 0 to 32MHz in 2.655Hz steps (10.62Hz in AM and NFM modes).
Frequency settability from keypad to ± 1.4Hz.
Tuning rate from spin-wheel 1kHz per rev (4kHz in AM and NFM modes), increasing with rapid rotation.
Fast tuning mode increases rate by 256 times.
Reception modes : AM Envelope detector and PLL synchronous detector.
SSB Upper and Lower sideband.
NFM Narrow band FM.
Other CW and Data.
3. Display and Controls
All receiver states displayed on back-lit, liquid crystal, character / graphic display.
Display is 2 lines of 24 characters, S-meter graphic is 70 segments form S1 to S9+50dB.
Frequency display to 10Hz resolution.
Rotary controls : Volume spin-wheel (with detent).
General spin-wheel (with detent) used with the menu system.
Tuning spin-wheel (free running).
Display viewing angle / contrast (on rear panel).
Push buttons: Power on / off and setup menu.
Menu select (1 button) and menu choice (4 buttons).
Mode select (2 buttons).
Fast tune.
Remote keypad : 32-key infra-red remote control
Numeric keypad.
Volume and tone.
Filter select and passband shift.
Tuning and memory operations.
Computer remote control of all functions via 1200 baud, RS232 type interface.
4. Memories
100 frequency memories contain :
Tuned frequency, mode, I F bandwidth and passband shift.
Squelch setting for AM, NFM and SSB modes.
BFO setting for CW and DATA modes.
Scan include / exclude.
Three setup memories contain :
I F bandwidth, passband shift, BFO, squelch and AGC speed settings for each mode.
Treble and bass settings, aux output levels and aux relay operation, squelch muting and
  scan hold.
R F gain, auto / manual switching and Sync detector auto / manual mode and bandwidth.
Remote keypad tuning step size. 
						

							PAGE  34          AR7030 OPERATING MANUAL
 5. R F Input
Three antenna inputs (selected by rear-panel switch) :
50ohm unbalanced via SO-239 connector.
600ohm unbalanced via wire grip connector.
Hi-Z whip input (on SO-239) with reduced R F performance.
R F band split at 1.7MHz with high-pass and low-pass filters.
R F pre-amplifier and attenuators give +10 / 0 / -10 / -20 / -30 / -40dB R F Gain.
  Switching is automatic with manual override.
6. I F System
Four I F filters fitted as standard, nominal bandwidths :
2.2 kHz (default for SSB, CW and Data modes)
5.5 kHz (default for AM and Sync modes)
7.0 kHz
10 kHz (default for NFM mode)
Provision for two more optional filters (at 455kHz) of any bandwidth from 250Hz to 10kHz.
Passband frequency adjustable by ± 4.2kHz for all filters.
Resolved audio frequency is adjustable by ± 4.2kHz in CW and Data modes.
AGC is carrier derived with peak detector in SSB modes and mean detector in AM modes.
AGC release speed selectable : Fast / Medium / Slow. AGC can be switched off.
Manual I F gain control operates as maximum gain limit.
Squelch operation is derived from AGC level, with optional audio muting and aux relay operation.
455kHz I F output available from the AUX connector at about -20dBm / 50ohms.
7. Audio System
Entire audio path is two-channel (stereo) with mono loudspeaker output.
External LS output (disconnects internal LS) via 3.5mm mono jack : 2.2W into 8ohms.
Headphone output (disconnects internal LS) via 3.5mm stereo jack (mono compatible) : 2.5V from 100ohms.
Aux outputs (independently adjustable levels) via 8-pin DIN connector : 0 to 800mV from 1kohm.
Treble tone control : 8dB at 2kHz in 2dB steps.
Bass tone control : 9dB at 200Hz in 1dB steps.
8. Power supply
15V from external a.c adapter, current 300 to 500mA typical, 1A max. 30mA on standby.
Will operate on 12 to 15V d.c with degraded performance at 12V.
EMC compliance is not guaranteed with all types of power supply.
9. Dimensions
Case : 238 x 77 x 191mm (W.H.D)
Overall : 238 x 93 x 227mm (W.H.D)
Weight : 2.2kg.
10. Sensitivity
All measurements are p.d. at 50ohm input. Figures in brackets indicate R F preamp switched on.
SSB and AM values are for 10dB S+N/N, NFM value for 12dB SINAD.
Frequency USB (2.2kHz filter) AM (5.5kHz filter)           NFM (10kHz filter)
20 kHz 1.9uV (1.4uV) - -
100kHz 0.73uV (0.34uV) - -
500kHz 0.50uV (0.18uV) 0.85uV (0.33uV) -
1.0MHz 0.52uV (0.19uV) 0.88uV (0.36uV) -
1.8MHz 0.56uV (0.21uV) 0.95uV (0.38uV) -
5MHz 0.50uV (0.19uV) 0.86uV (0.35uV) -
14MHz 0.58uV (0.23uV) 1.0uV (0.42uV) -
28MHz 0.60uV (0.23uV) 1.0uV (0.40uV) 1.2uV (0.48uV)
32MHz 0.68uV (0.24uV) 1.1uV (0.43uV) - 
						

							AR7030 OPERATING MANUAL          PAGE 35
11. Selectivity
The following data is taken from measured performance of the 455kHz I F system and ignores effects of the
45MHz roofing filter and any audio frequency response tailoring. AGC was switched off.
Filter stop-band attenuation : All filters > 110dB
2.2kHz filter characteristics : -6dB bandwidth : 2.29kHz
-60dB bandwidth : 3.34kHz
-80dB bandwidth : 4.98kHz
6/60 shape factor : 1 : 1.46
5.5kHz filter characteristics : -6dB bandwidth : 5.54kHz
-60dB bandwidth : 9.11kHz
-90dB bandwidth : 10.75kHz
6/60 shape factor : 1 : 1.64
7kHz filter characteristics : -6dB bandwidth : 6.90kHz
-60dB bandwidth : 11.60kHz
-90dB bandwidth : 13.36kHz
6/60 shape factor : 1 : 1.68
12. Dynamic range
Reciprocal mixing effects : Quoted figure is unwanted signal strength, relative to noise floor, that decreases
wanted signal S+N/N ratio by 3dB.
Tested at 12.75MHz in USB mode with 2.2kHz filter. Wanted and unwanted signals both unmodulated.
Noise floor : -123dBm
    Signal separation    Signal rejection Local osc SSB phase noise
5kHz 90dB -123dBc/Hz
10kHz 99dB -132dBc/Hz
20kHz 109dB -142dBc/Hz
50kHz 119dB -152dBc/Hz
100kHz > 125dB < -158dBc/Hz
Blocking effects : Quoted figure is unwanted signal strength that reduces wanted signal level by 1dB
(with no AGC action). Tested in USB mode with R F pre-amp switched off.
Wanted signal at 20MHz, unwanted signal at 10.7MHz, both unmodulated.
Blocking signal strength : +14dBm (1.12V) Blocking dynamic range : 137dB
Intermodulation effects : Quoted dynamic range figure is the difference between the receiver nose floor and
the level of two equal unwanted signals required to produce an intermodulation
product at the noise floor level. The IFDR figure here is calculated from measuring
the intermodulation level produced by two signals at 0dBm, and verified by
re-calculation at -5dBm.
Tested at around 12.7MHz in USB mode with 2.2kHz filter and R F pre-amp switched off.
Noise floor : -123dBm
           Signal separation Intermodulation-free dynamic range 3rd order intercept point (IP
3)
5 / 10kHz 92dB +15dBm
10 / 20kHz 100dB +27dBm
20 / 40kHz 104dB +32dBm
50 / 100kHz 104dB +33dBm
100 / 200kHz 105dB +34.5dBm
Switching in the R F pre-amp reduces IP
3 by about 10dB, and IFDR by about 2dB. 
						

							PAGE  36          AR7030 OPERATING MANUAL
Second order intermodulation effects : Measured as above with two signals of 0dBm at around 12.7MHz,
resolving the SUM frequency at 25.5MHz.
Intermodulation-free dynamic range : 104dB 2nd order intercept point : +85dBm
13. Spurious responses
Unwanted signal rejection : Quoted figures are the levels of unwanted signal, relative to wanted, required to
produce a similar S+N/N ratio. Many figures vary depending on the frequency the
receiver is tuned to, so ranges of values are given.
    Spurious response Frequency Rejection
1st I F 45MHz 85 to > 100dB
2nd I F 455kHz > 100dB
1st I F image Fr + 90MHz 85 to > 100dB
2nd I F image Fr + 910kHz > 95dB
Others Fr ± >10kHz > 85dB
14. AGC characteristics
Dynamic characteristics quoted for a 30dB change in input level between -90dBm and -60dBm.
Output range (AM mode) : 19dB
Attack time (to within 2dB of final level) : 4ms (SSB modes) 8ms (AM and Sync modes)
Holdoff time (for first 2dB change) : 250ms (fast) 450ms (med) 1.0s (slow)
Decay time (to within 2dB of final level) : 700ms (fast) 1.15s (med) 2.0s (slow)
15. Audio quality
In-band intermodulation : For 2 signals more than 200Hz apart, all intermodulation products < -37dB.
Harmonic distortion : SSB modes, input signal at S9, THD < 0.2%.
AM modes, input signal at S9, THD < 1.3%.
Noise : AM mode ultimate S/N ratio 52dB (unweighted).
16. Frequency stability
The receiver uses a single frequency reference which is a temperature compensated crystal oscillator. TCXO
specification is ±2.5 ppm from -30°C to +75°C, and will typically give a receiver stability better than ±1ppm from
10°C to 40°C.
Specification subject to change due to continuous development of the receiver. E&OE.
© AOR Manufacturing Ltd 1995, 1996.