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An
Introduction:
Long Distance
Medium Wave Listening
by Steve
Whitt
1. Introduction
This
booklet is a guide to long distance listening (DXing) on the Medium
Wave (MW) band. If you've never tried listening to anything other
than your local radio station on MW then this booklet is intended
as a "road-map" to this uncharted area of the radio hobby. It
will give you an insight into the stations you could hear and
how to identify them. Also covered are the types of receivers
and aerials you should use and an introduction to signal propagation.
Of course once you've caught an interesting station you will probably
want a QSL card, so this booklet also includes information that
should make this task easier. Naturally a guide like this can
only scratch the surface of MW DXing so it needs to act as a pointer
towards more information and indeed you'll find up to date listings
of suitable books, clubs and sources of specialist equipment.
MW DXing
opens up another dimension not covered by most of the shortwave
(SW) bands. Although a few MW broadcasts are also available on
SW the vast majority are unlikely to be heard on SW frequencies.
Indeed many countries (mostly island nations) have no SW operations
and only broadcast on MW which means that MW DXing is the only
way of logging these elusive parts of the world. Furthermore most
MW stations are local in nature and thus can give an interesting
insight into what is going on locally; one can hear farm news
from the US mid-west, obituaries on Jamaican radio; war reports
from the former Yugoslavia, religious salvation from many stations
and adventures from ship borne broadcasters on the high seas.
The choice is yours!
Good listening.
2 Who goes
there?
2.1 Medium
Wave Stations
The Medium
Wave (MW) band is an internationally agreed band of frequencies
primarily set aside for the purpose of broadcasting. It is also
known as the AM or MF band or the Broadcast Band (BCB) in various
parts of the world. Indeed there are stations using this band
in every continent (except Antarctica) and to appreciate the sheer
numbers of broadcasters just consider that in the USA alone there
are about 5300 stations on 106 channels in the AM band. For many
years the MW band has stopped at approximately 1610kHz but it
is gradually being extended to 1705kHz in North America. What
sorts of signals can you hear on the MW band?
International
Broadcasters:
Mostly found
in Europe and South East Asia, these stations are designed to
target audiences in countries distant from the transmitter and
studios. Good examples are high power (500kW and upwards) transmitters
operated by the Voice of America, BBC and Radio Moscow. Over the
years these stations have been joined by a selection of religious
broadcasters such as Vatican Radio, PJB in Bonaire, TWR in Monaco
and HLAZ in Korea.
Regional
Broadcasters:
These are
best exemplified by the Clear Channel stations in North America.
These 50000 Watt stations have the exceptional privilege of having
a MW channel virtually to themselves. This is a deliberate move
to ensure that the vast rural interior can get good radio reception
at night when coverage of half the continental USA is typical.
Synchronised
Networks:
These are
networks of several stations all on one frequency carrying the
same programme set up specifically to provide national coverage.
Such networks need care in their design and operation to avoid
problems with carrier frequency synchronisation and variable delay
in the distribution of audio to each transmitter. The most notable
examples of synchronised networks are run by the BBC in the UK
for distribution of Radio 1 and the news and sports network. The
network operated by Virgin 1215, also in the UK, is less successful.
Local Broadcasters:
By far the
majority of stations on the MW band fall into this category, characterised
by the co-location of the station, its studios and transmitter
and its audience. Transmitter powers can range from as little
as 1W to 100kW or more, depending on the coverage area and the
degree of co-channel interference. Many local broadcasters in
North America operate only during daylight hours in order to avoid
problems with co-channel interference brought in by the night-time
sky-wave.
Navigational
Beacons:
Radio signals
are an essential means of navigating for most ships and aeroplanes
and the frequencies between the Long Wave band and the MW band
have been allocated for this purpose. More surprisingly, a sizeable
number of aeronautical beacons operate in the MW band interspersed
amongst the broadcasters. Over 100 beacons are known, of which
the majority are in the former Soviet Union. Beacons are usually
low power and intended to give accurate navigational information
over 50-100 nautical miles range, however long distancelisteners
(DXers) will be able to detect the repetitive Morse code identification
messages from beacons over much greater distances.
Clandestines,
Pirates and Jammers:
Most signals
described so far are more or less permanent features in the MW
landscape. However, there are several more transient types of
signals which can be heard, the most prominent of which are pirates
and clandestine operations. Pirates are stations operating openly
with out official licences from any country. They range from one
time hobby pirates operating from someone's bedroom to fully financed
operations broadcasting from ships at sea. The heyday of the seaborne
pirate seems to be gone since the likes of Radio Caroline, Voice
of Peace and R New York International have passed into the history
books. Just two radio ships are still operational, both in the
Mediterranean.
Clandestine
stations are usually politically motivated broadcasters often
supported by a covert government operation. Operations are complex
since stations can pretend to be what they are not and there is
always the possibility of the double bluff! These stations come
and go, reflecting political changes in their "host" country.
Currently the bulk of known clandestines are operating in the
Middle East. Long serving examples include National Radio of the
Saharan Democratic Republic (since 1975) and the Voice of Iraqi
Kurdistan (since 1965).
Clandestine
stations, as well as official broadcasters, are often the target
of jamming if the government in the area targeted by the broadcaster
feels threatened by the message being carried. Jamming usually
takes the form of a powerful transmitter broadcasting irritating
noise and interference on the same frequency as the station beaming
into the country. Jamming on MW has fallen dramatically since
the late 1980s and now is confined mainly to the Middle East and
the Korean peninsula.
2.2 Long
Wave Stations
Though the
Long Wave (LW) band (148.5 - 283.5kHz) is not strictly part of
the MW Band, many listeners have common interest in the two bands.
Long Wave is only used by broadcasters in Europe, North Africa,
Mongolia and the Asian part of the former Soviet Union. Elsewhere
in the world these frequencies are used mainly by navigational
beacons similar to those found between 283.5 and 525kHz. One exception
is in the USA where 160-190kHz is also used by experimenters who
are allowed just 1W of power to tiny antenna!
3 Getting
Started
Let's take
a brief look at what's needed to become a MW DXer and how you
get started. Firstly, it is important to realise that the MW DXer
can start listening with very cheap and simple equipment; any
domestic radio will tune the MW band and it is quite easy to hear
50 - 100 different stations at night using just an internal aerial.
However, it is probably preferable to use a better quality domestic
radio, or a good car radio to get started. With this type of equipment,
stations from up to 1500km away will be regularly heard at night.
If radio conditions are favourable and you listen at the right
time, reception of some stations over 3000km away should be possible.
In this way you can have a go at DXing the MW band before committing
yourself to any more sophisticated (or expensive) equipment. On
the other hand, if you are already an active short-wave listener,
all that is needed to get going on MW is a change of waveband.
Indeed many SW listeners tend to overlook the fact that their
radios can usually tune the MW band and that their outdoor aerials
are often effective in picking up distant MW signals. For the
SW listener who has grown tired of the mega-watt international
stations, a fresh challenge can be found on the MW band.
3.1 Round
The Clock
It is possible
to DX on the MW band 24hrs a day (provided you don't need to sleep!)
but the band has two distinctly different "personalities" according
to the time of day. During daylight hours MW radio signals are
absorbed in the lower layers of the ionosphere and only "ground-wave"
signals propagate; these signals radiate away from the transmitter
rather like ripples in a pond and allow reception at distances
up to about 500 km. Daytime is a good time to listen for low power
local radio stations since very few distant signals are audible
and therefore interference is at a minimum.
At night
the ionosphere tends to reflect, rather than absorb, MW signals
and thus energy radiated upwards from a transmitter is refracted
back down to earth at some point far away from the transmitter.
These are known as skywave signals. It is quite possible for night
time signals to under go multiple hops with alternate reflections
occurring in the ionosphere and off the earth's surface. This
mechanism allows reception to take place many thousands of km
away from a transmitter. For example Radio Globo in Rio de Janeiro,
Brazil is regularly heard in Europe, its signal having to cross
9500km of ocean on the way. You will of course notice that night
time sky-wave propagation fills your radio dial up with hundreds
of powerful signals, so how is it possible to hear the weak DX
signals?
Over the
years international broadcasting organisations have agreed a band
plan arrangement on the MW band which requires all stations in
an area to operate on fixed frequency channels. This has been
arranged to maximise the number of broadcasters who can operate
and to minimise the degree of interference affecting the listener.
Fortunately for the DXer, international agreement is not perfect
and as a result different MW band plans are operated in different
continents; most European, African and Asian stations use channels
that are exact multiples of 9kHz, whereas in the Americas channels
are assigned as multiples of 10kHz. This means that, in Europe
for instance, by tuning between the 9kHz channels reception of
trans-Atlantic stations becomes possible. For example;
1008kHz (112
x 9kHz) NOS Radio 5 Hilversum, Holland
1010kHz (101
x 10kHz) WINS New York, USA
1017kHz (113
x 9kHz) SWF Baden Baden, Germany
This particular
example also illustrates the value of knowing a station's timetable.
Although reception of WINS is technically possible as soon as
a path of darkness exists between New York and Europe, NOS is
a pretty powerful signal and will cause interference. However
NOS signs off for the night at the unusually early time of 2200hrs
(GMT) and knowing this it is possible to tune a virtually interference
free signal from WINS before midnight.
Stations
on split frequencies are usually the easiest to hear over long
distances since they suffer less co-channel interference. Obviously
in any part of the world reception conditions vary and different
stations are heard. In order to gauge what you are likely to hear
or what you are going to have real difficulty catching it is worth
joining a local club that includes MW in its remit; even better
would be joining a specialist MW club [see Section 6.1] since
you will have access to lots of information on MW listening and
in particular you'll be able to see what other enthusiasts are
hearing.
3.2 Confirming
Your Reception & Getting a QSL
These three
letters, QSL, are probably a bit of a mystery to the newcomer,
so what do they mean? Let us suppose you've just heard Radio Fiji
on your pocket transistor radio how are you going to convince
everyone that you weren't just dreaming? Wouldn't it be good to
have something from the radio station confirming that you really
did hear them? Well this is where QSL cards come into the picture;
a QSL card is usually a picture postcard (although it can also
take the form of a letter, a certificate, or a folder) sent to
a radio listener by a radio station confirming that reception
actually took place.
In order
to get a QSL card from a station there are several things you
need to do, but firstly remember that you have to hear the station
and then convince station staff that you did hear their signal.
Normally one is obtained by sending a station a reception report
giving details of how well their signal was received and of the
programme material heard, as proof of reception. Naturally you
need to say when you were listening (date and times should be
in GMT/UTC or in the stations own local time).
Historically,
the QSL originated in the days when stations relied entirely on
reports from listeners to determine their coverage area. In fact
the letters "Q-S-L" are based upon a radio operators shorthand
code (Q code) system that evolved during the early days of radio.
Nowadays, however, many stations use reports from professional
monitoring stations and have more accurate coverage predictions
available, and consequently the QSL survives largely as a service,
from the station's point of view. Additionally there is a significant
difference in QSL policy between the international short-wave
broadcaster, which issues QSL cards to maintain contact with and
to gauge the size of its audience, and the local medium wave station
being heard outside its usual coverage area. At best, the latter
will treat a far off reception report with curiosity and will
send out a QSL as a public relations exercise. At worst, to a
station with few staff and a limited budget, reception reports
from DXers can be a downright waste of time. It is therefore vital
that MW DXers follow some simple guidelines when sending out reception
reports to stations.
Firstly I
would suggest a personal letter to the engineer or manager together
with a detailed report of reception conditions (was the signal
strong? what was interfering?) and adequate programme details
to prove that you really heard the station ("music and talking"
is not good enough) are the basic requirements. Additionally make
a polite request - not a demand - for a QSL card or a letter confirming
reception, and remembering that most MW stations are local operations
run on limited budgets it is wise to write to them in their own
language (or that used in the programme) and to enclose return
postage in the form of an International Reply Coupon (available
at Post Offices), or appropriate mints stamps.
This may
all seem a complicated procedure but if you follow these tips
not only should you receive more QSL cards for your own collection,
but you will help maintain good relations between radio stations
and the DX fraternity in general.
3.3 The
Identification Question
If you tune
in to your local radio station it soon reveals it identity through
a number of clues; its strength, frequency, programme style and
most importantly its on air ID (callsign, jingle etc.) which is
easily heard since there is no interference. We now need to ask
what happens when you are trying to decipher a weak, fading signal
from a distant station that may well be using an unfamiliar language.
The fundamental question is, at what point is a station identified
and how should a station that is not fully identified be described.
The process
of identifying stations should be viewed as a broad spectrum of
probability. At one end is the completely unidentified station,
an example of which is the open or blank carrier with no modulation
- although you may have quite a good idea about its identity such
a signal really is unidentified. At the other end of the spectrum
is the positively (100% probability) identified (e.g. "...the
powerful missionary outreach station, the Atlantic Beacon 50000
Watts at 15-70, broadcasting from the beautiful Turks and Caicos
Islands in the West Indies..." leaves little doubt about this
station's identity!).
Many DX stations
fall somewhere between these two extremes; for example you may
hear only part of a callsign perhaps in a poorly understood language,
or maybe in the midst of heavy interference or jamming. Or perhaps
no identification is heard but certain characteristics of the
signal or programme content point in the direction of one particular
station. Generally speaking, the longer you listen to a station,
on one date or over many days, the more clues there are to help
achieve successful identification. If you can't ID a station keep
listening!
The factors
which contribute to the identification of a station are almost
without limit. Among them are time of reception, frequency, quality
of signal, and programming style. The latter is usually one of
the most important clues since valuable information can be gleaned
from the languages used and music played, as well as from advertising,
weather reports, time checks and so on. It should be appreciated
that one's ability to identify a station depends mostly on the
ability to interpret what is being heard. And, rather like a detective
investigating a crime, it takes experience as a DXer to reach
a correct conclusion based upon the limited clues available. Even
the most experienced DXer will not be able to identify everything
heard, so there needs to be some way of indicating how certain
(or uncertain) a particular identification is. Hence the following
shorthand expressions have developed as a solution to this problem.
Identified:
Implies that the listener is 100% certain of a station's identity
since a full announcement by the station was clearly heard.
Presumed:
When a station is listed as presumed it means that the listener
has had sufficient clues to the station's identity to be almost
(90-99% probability) certain of its true identity. About all that
is missing is a formal ID announcement.
Tentative:
This term usually describes a situation where the listener is
fairly certain that a particular station is being heard - indeed
that the probability is substantially greater than 50%, typically
from 75%-90%. It is important, however, to note that a tentative
logging is not just a pure guess since there still have to be
a number of clues pointing in the right direction.
Unidentified:
Anything short of tentative is called "unidentified" and the DXer
should resist the temptation to classify loggings as tentative
if there is insufficient evidence. When there is any doubt about
a logging, it is wise to err on the side of caution and list it
as unidentified; however it may be worth indicating which station
you think it might have been if you have an idea.
At this point
a word of caution is probably in order with regards to station
listings. All DXers use lists of one sort or another to help them
in their hobby (e.g. WRTH, club bulletins etc.) but it is dangerous
to rely on a list (even the most up to date) as the sole means
of identifying a station. That is not to say that lists should
not be part of a DXers "tools of the trade", but just that caution
should be exercised in their use.
Lists are
invaluable to help narrow down the range of possibilities when
it comes to indentifying a mystery station; they can also guide
a listener to the right place on the dial to possibly hear a particular
station, but they cannot actually identify a station - only the
station itself can do that.
Over reliance
on lists and a bit of related "wishful thinking" results in the
practice known as "list logging" which can be sometimes observed
as anomalous loggings reported in the DX logs of some magazines
and club bulletins.
3.4 DXing
in Your Sleep!
The easiest
way to identify a MW DXer is if they fall asleep during the day.
Since the fundamental characteristics of the ionosphere favour
long distance MW radio reception at night this hobby will be the
province of the shift worker, the insomniac or the outright fanatic.
There is one solution and that is to DX in your sleep!
All you need
apart from the standard aerial and receiver is a tape recorder
and a timer and a fairly methodical approach to listening. Neither
the tape recorder nor timer should be expensive and indeed I don't
know any serious DXer (SW or MW) who doesn't already use a recorder.
Depending on your selection of equipment there are two ways of
DXing in your sleep.
If you have
an ordinary radio and a separate cassette recorder you'll need
to buy a mains timer unit (get one with a digital display since
these can be set precisely to the minute) which will cost about
£15 - £20 (US$20-40). With such a timer connected in
series with the mains lead of the recorder you are able to make
a recording at any time of the day or night when you're not around.
Just make sure that your radio is tuned to the frequency of the
station you want to hear. Unfortunately such remote control is
trickier for really tough DXing since in these circumstance you
will want to be making continuous adjustments to your receiver
or aerials to improve reception. However, for less marginal conditions
this technique is very valuable particularly for night after night
monitoring of one frequency. I use it, for example, for monitoring
1440kHz after R. Luxembourg closes down. In this case it would
be impossible for me to be awake every night and I soon would
get put off by the DX-less nights. Indeed taping for an hour each
night allows me to quickly find the nights that are particularly
good for DX (just 5-10% say) and to then examine the tape more
closely for DX signals. In this way on 1440kHz I've heard several
North American and a couple of Latin American stations that I
would not have otherwise heard.
If you have
a receiver with a built in programmable timer (e.g. SONY 2001D)
you do not necessarily need a separate mains timer. It might be
possible to activate the cassette recorder from the radio or if
this is not directly practical an external unit called a VOX or
voice activated switch might be the answer. This piece of equipment
connects in the audio lead from radio to cassette and detects
when audio starts i.e. when the internal timer has turned on the
radio. It then switches on the recorder for as long as sound is
present. So if you have the equipment but have not tried this
before why not give it a go.
3.5 Interference
Interference
is a topic that affects not just the MW DXer but just about every
radio listener. In fact it is usually the level of interference
rather than any other factor that limits the reception of weak
and distant stations on the MW band.
Interference
is usually taken to mean any unwanted signal (or noise) that,
by adding to the desired signal, degrades reception of the wanted
information. It is usually the case that the interference most
often encountered on MW is man-made in origin. Whereas there is
very little one can do about naturally occurring interference,
it is possible, theoretically at least, to eliminate man-made
sources of interference. The first step to suppressing interference
is in fact recognising it and identifying its origin. Having identified
a source of interference it is an unfortunate fact of life that
it may prove impossible to do anything about it. The following
are the most common forms of man-made interference to affect MW
reception:
Co-channel
interference:
Since the
MW band is operated in a channelised manner and because there
is only 1080kHz of available MW spectrum, there are inevitably
several stations transmitting simultaneously on each channel.
Normally the powers and locations of stations allocated to a particular
frequency are chosen to ensure that a low level of co-channel
interference occurs within the target area of each transmitter.
However,
listeners outside the target area will experience this form of
interference which generally gets worse at night as interfering
signals propagate further via the "sky wave". In fact it is the
acceptable limit of co-channel interference (also known as the
protection ratio) that defines the target area boundary for a
particular transmitter.
Modulation
Splatter:
Splatter
or adjacent channel interference can be recognised as unintelligible
modulation or programmes heard mixed with the desired programme
with the interfering signal originating from a station transmitting
on a channel adjacent to that of the desired station. Given that
stations are adhering to their local channel bandplan, there are
two main causes of modulation splash. Firstly, splash can be the
result of a station not limiting the bandwidth of its transmitted
audio which results in components of the transmitted sidebands
interfering with signals on adjacent channels; this form of splash
can also result from a poorly maintained or over-modulated transmitter.
Secondly a form of adjacent channel interference can be generated
within a receiver with insufficient selectivity when receiving
very strong signals. To test if adjacent channel interference
is in fact receiver generated an aerial attenuator should be used
to reduce the strength of the incoming signal; if the relative
degree of interference reduces, a receiver effect should be suspected
but if no change is observed then it is possible that the interference
is actually being transmitted.
Heterodyne
Interference:
A heterodyne
is an audible beat note or whistle that is generated in a receiver
when two signals on slightly different frequencies are received
simultaneously. In a perfect world where all MW stations operated
exactly on their allocated channels, heterodyne interference would
not be a problem. However since different channel plans are used
in different parts of the world it is possible to hear heterodynes
on the MW band. Occasionally, within one radio planning region
it is possible to find off channel stations either because the
station has failed to conform with planning guidelines or a technical
problem has arisen in the transmitter. In 1978 the frequencies
of the European Asian and African channels were aligned to all
be exact multiples of 9kHz, and every station was expected to
retune their transmitter to the new channels. However quite a
few African stations did not make the move and even today a number
of off channel stations are audible. Their presence can cause
heterodyne interference to other stations but the keen DXer can
use the presence of a heterodyne tone as a good guide to a weak
distant station. For example 1395kHz is an official channel used
in Europe and Africa but Radio LomŽ in Togo never moved from
the old frequency of 1394kHz. So if the listener is hunting LomŽ
the presence of a strong heterodyne interfering with stations
on 1395kHz indicates that the path to West Africa is open.
Unwanted
heterodynes are annoying but fortunately they are easily removed
with an audio notch filter. DXers often purchase such an accessory
[see Section 6.2] since it improves reception and reduces listener
fatigue.
Electrical
Interference:
This title
covers a multitude of interference sources which will tend to
affect listeners living in built up areas, particularly near industrial
zones. Man-made electrical interference comes in all shapes and
sizes but can be classified as intermittent or long term. It can
be difficult to track down intermittent sources of interference
but fortunately their nuisance value is not long lasting.
Common examples
are engine interference from the poorly suppressed spark plugs
of passing cars, and arcing of electrical contacts in thermostats
and switches. If the source is identified it is generally not
too difficult to suppress this sort of interference. Other examples
are caused by faulty street lights and faulty insulators on overhead
power lines and in both these cases the solution is to inform
the relevant authority. The longer lasting variety is commonly
due to harmonic radiation from television (TV) and visual display
unit (VDU) timebases. TV interference is audible as a rough buzzing
located at precise intervals across the MW band of 15.625kHz (in
Europe) or 15.750kHz (in N. America). VDU interference can appear
with a frequency separation in the range of 14-18kHz. Unfortunately
this form of interference often restricts any serious DXing to
outside TV hours. Generally as more and more electrical equipment
enters the home and office the greater the level of interference
and the less chance there is of suppressing it. Among the more
recent sources of (very potent) interference are computers and
electronic telephones and office exchanges. Regrettably there
is usually little a DXer can do cure this affliction unless they
own the offending piece of equipment.
Jamming:
This is a
deliberate attempt to interfere with reception and is usually
a transmission of man-made noise intended to blanket another programme
to make it unintelligible. The amount of jamming present tends
to reflect the degree of political unrest in the world and today
there is relatively little to bother the MW listener. The extensive
jamming associated with Eastern Europe and the former USSR is
now consigned to history, but jammers are still active in the
Middle East and Korea.
Even if one
lived in a world without any man-made interference, one would
still notice a whole range of noises that limit reception of very
weak signals. Of these the least significant (for the MW listener)
is the thermal noise and other electrical noise components actually
generated within the components of the receiver. This is because
the level of other naturally occurring noise sources picked up
by the receiver's aerial is many times greater. Common examples
of these types of interference are atmospheric static, which manifests
itself as a continuous crackling noise and lightning discharges
which are heard as a loud crashing noise. The distinguishing feature
of these signals is their broadband nature; namely the noise will
be heard at all frequencies in the MW band although the intensity
will decrease at higher frequencies. It is interesting to note
that the radio wave emitted by a lightning flash behaves as any
other radio wave and therefore can propagate over considerable
distance; in fact one of the great sources of interference worldwide
is the noise generated by the large numbers of daytime tropical
thunderstorms. It is for this reason that many broadcasters in
the tropics choose frequencies between 3 and 6MHz for local broadcasting
where the effect of thunderstorms is much reduced.
4 The Next
Step
4.1 Receivers
The choice
of a receiver for MW use is nearly always a compromise between
performance and price. Even if money were no object, finding a
truly "no compromises" MW tuner is probably the "Holy Grail" of
the hobby. Nowadays, however, there are some extremely good value
for money receivers available that leave earlier generation units
in the shade when it comes to features and price. That is not
to say that a thirty year old valve receiver is no use, but older
receivers lack some of the convenience features like digital frequency
readout and memories.
For the DXer
there has never been a better time to buy a new receiver than
today since, like all things electronic, prices have fallen dramatically
in real terms over the years. If we take stroll down memory lane
to look at what a typical basic DXers receiver would have cost
in Europe, as an example, we find;
1953 Eddystone 750; Eleven valves £68 (US$100)
R1155 ex Air Ministry; Ten valves £12 (US$18)
1964 Codar CR66; Six valves £24 (US436)
HE30; Eight valves £41 (US$60)
1968 Trio 9R59DE; Eight valves £39 (US$60)
1971 Eddystone EB35; transistors £99 (US$150)
Eddystone EC10; transistors £75 (US$110)
1980 Yaesu FRG7; transistors £199 (US$300)
In 1994 the
choice of receivers has never been wider and the DXer could pay
anything up to a couple of thousand dollars (!) for a semi-professional
unit. If sheer value for money is top of your list then there
is probably not much around that will beat the Sangean ATS803A
which isold by a number of dealers under different model numbers:
e.g. as the Matsui MR4099 in the UK for under £100. This
receiver is a portable with digital readout, synthesised tuning,
no gaps tuning from 150-30000kHz, selectable bandwidth, BFO and
signal meter. Actually the ATS803A, which was based on the more
expensive Sony ICF2001, is built in Taiwan by Sangean. In the
14th edition of Radio Netherlands Receiver Shopping List, the
radio was awarded ****, the joint highest rating awarded to a
portable receiver.
What is
a Communications Receiver?
Many listeners
ask "what is a communications receiver and how do I chose one?".
There is no simple definition of a communication receiver but
often what sets such a device apart from an ordinary radio is
its need for an external aerial as opposed to the internal ferrite
rod or whip fitted to the majority of domestic units. For virtually
all other forms of DX listening (such as short-wave or VHF) a
specialised receiver will be needed, but fortunately for the MW
enthusiast it is possible to get started with even the most basic
of domestic receivers since they all tune the frequencies of interest
i.e. 520kHz - 1605kHz. Using this sort of equipment it is possible
to look for the weak signals that are found all the way down the
dial between the strong locals, but after a while the newcomer
to the MW band will start to appreciate the limitations of a basic
domestic receiver and want something better. That is not to say
that under the right conditions real DX cannot be heard on a simple
receiver, but a communications receiver will make it a lot easier
to hear. Why? Well there are several areas in which such a receiver
is superior to its domestic cousin.
In the main
a communications receiver is distinguished by its sensitivity,
its selectivity and the accuracy of its frequency readout. Sensitivity
is the measure of a receiver's ability to pickup and render audible
weak signals. This is not so much a problem on MW since many stations
use such vast transmitter powers. Furthermore the limit to weak
signal reception is rarely the receiver itself since the background
noise on the MW band due to atmospheric static and man-made electrical
interference is so high. A good receiver will be sensitive but
not overly so, since excessive sensitivity is often accompanied
by the unwanted tendency to overload on strong signals.
The ability
of a receiver to separate two radio signals on two different,
but closely spaced, frequencies is termed its selectivity. This
is a vital parameter if good MW performance is to be had from
a receiver (domestic radios are usually very weak in this area)
since the keen DXer will be trying to separate stations that may
be as little as one or two kHz apart on the dial. This is very
much the case if you are hunting transatlantic DX on split channel
frequencies. A good communications receiver will have several
different switch-selectable bandwidths ranging typically from
2 to 10kHz.
It is pointless
for a receiver to be able to separate closely spaced signals unless
the user is able to identify which frequency is being resolved.
This is why most communications receivers will have accurate dials
or frequency readouts; either mechanical scales or dials or the
more modern digital frequency readout. Readout to 1kHz accuracy
or better is highly desirable on MW.
To get started
on the MW band with a communications receiver could set you back
anywhere from £50 to £5000 depending on the sort of
equipment chosen. Over the years hundreds of different receivers
have been made, all with their pros and cons and to do them all
justice would soon fill a book with detail. There are some general
tips worth bearing in mind when choosing a receiver. Broadly speaking
communications receivers have gone through three phases, namely
the valve based units of the 1950s and 60s, the early solid state
receivers of the 60s and early 70s and finally the transistorised
receivers developed since about 1975. For the DXer on a budget
the best bet is one of the receivers in the first category, some
of which have justifiably become quite famous such as the RCA
AR88D, Murphy B40, Marconi R1155 or the Eddystone, Hallicrafters
or Hammarlund range of receivers. In general one can expect these
units to be heavy and robust with good dials and very good reception
on MW. If they have one limitation it is that they tend to run
out of steam above 20MHz but this is of little concern to the
MW DXer. Typically receivers of this class can be bought quite
cheaply second-hand but you may end up paying more if you purchase
'professional' receivers from this era such as the Collins R390A,
Drake R4, or the Racal RA17.
Quite often
you will see receivers such as the Eddystone EB35 or EC10 or the
Realistic DX-300 advertised quite cheaply second hand - steer
clear of these as they represent the second category. A problem
that afflicted the vast majority of early transistorised receivers
was their susceptibility to overload. By the mid- seventies transistorised
receiver designs were beginning to match the performance of the
valved receivers of the fifties. OK they had all the extras such
as digital readout, frequency synthesis and many other facilities
to make the DXers life easier but in terms of true DX hunting
ability they were still no better. The latest developments, since
1980 say, have almost entirely been driven by the Japanese companies
(except for recent military equipment which probably won't be
surplus for at least another decade!). Some of these receivers
are ideal for the serious MW DXer (e.g. Icom R71 or NRD525) but
be prepared to part with the sort of cash that would buy a second
hand car!
One parameter
which has often been overlooked in the design of receivers for
the hobby market is their strong signal handling characteristics.
This single characteristic actually is an amalgam of several underlying
parameters such as reciprocal mixing due to oscillator noise,
mixer intercept point and r.f and i.f filter performance. For
the MW DXer good strong signal performance is probably the most
important feature to look for when choosing a receiver.
Once you
have a good receiver, you may well be tempted to improve it some
way or other. Most commercial receivers are designed to a target
price rather than an specification and often surprising improvements
in performance can be realised for very little cost. The trick
is knowing what to do and a good starting point is the experiences
of other users of the same receiver. Many tips and enhancements
have been published by DX clubs [see Section 6.1] in their journals.
Since 1985,
when Sony introduced their ICF2001D/2010, there has been a growth
in the number of communications receivers offering synchronous
detection of AM signals. Simultaneously synchronous detectors
as add-on modules have also proliferated. Conventional diode detectors
used for AM reception for the best part of 70 years have several
limitations. In particular they cannot handle signals suffering
from the selective fading associated with signals arriving via
sky-wave propagation paths. Synchronous detectors perform much
better in this respect and therefore can produce much better quality
audio. Certain designs of synchronous detector also allow the
user to independently chose to listen to either the upper sideband
or the lower sideband. Since both sidebands in an AM signal contain
the same information they should both sound the same, however
one sideband is usually less affected by interference than the
other and so selectable sideband can be very valuable.
4.2 Antennas
DIY MW Loop
Aerial
This is the
commonest "specialist" antenna used by listeners to MW frequencies
because it is usable indoors, readily home-built and low cost.
The loop possesses a very predictable directional receiving pattern
which allows signals from different transmitter locations to be
selected by carfully rotating the antenna about its vertical axis.
In addition most loops are designed to be resonant on MW frequencies
and therefore are tunable. This is often a very valuable introduction
of selectivity before signals even reach the receiver. A good
loop tuned to 1MHz will easily reject most signals more than +
or - 50kHz away from the desired frequency, thus virtually eliminating
any images or 2nd order intermodulation products generated within
the receiver.
There are
numerous designs for loops. Some are tuned, others are broadband;
some are compact indoor models, others are massive outdoor devices,
but the commonest design is based on a 1m square wooden frame
on which 7 turns of wire have been wound. This inductance is then
parallel tuned by a variable capacitor with a maximum value of
about 400-500pF. The loop is mounted on a base supported by a
wooden broom handle which acts as its axis of rotation. For full
constructional details of loops it is best to seek out some of
the specialist publications listed in Section 5 since there is
not enough room here to cover the construction in detail.
Figure 1
illustrates the all important directional pattern of the loop,
which clearly exhibits two symmetrical nulls and peaks which can
be directed to undesired or desired stations by physical rotation.
In this way the loop is very capable of separating two or more
co-frequency stations provided the signals are not arriving from
the same (or directly opposite) directions. If the direction of
arrival of two signals is separated by 60¡- 120¡ then
the loop really excels.
DIY Beverage
Aerials
The second
key aerial, and probably the best, for MW listeners is the Beverage.
This aerial is one of the simplest and oldest designs around,
having been developed by Harold Beverage in the 1920s. In fact
an aerial of this type, 12km long, was used by Beverage in 1922
for the reception in the USA of some of the first low frequency
(approx 1.2 MHz) transmissions from Europe.
Figure
1: Directional properties of a Loop Antenna
For a Beverage
to be reasonably effective it needs to be between 1 and 10 wavelengths
long, which on the MW band implies lengths between 200 and 5000
metres. The longer it is relative to the wavelength of interest,
the more directional the aerial becomes. Remember that a Beverage
has its maximum signal pick-up along its length and that the aerial
should point along the great circle path towards the desired reception
area (Figure 2). The Beverage is even cheaper than the loop to
build. It is a broadband antenna (i.e untuned) and so effective
over the whole MW band, but by virtue of its size it always points
in one direction. This means that its reception nulls cannot be
easily targetted on unwanted signals. Professional receiving installations
(with bigger budgets than DXers) often construct whole arrays
of Beverage antennas radiating out like spokes on a wheel from
the listening site. The radio monitor of course is able to chose
the antenna which gives best quality reception.
Figure
2: Directional properties of a Beverage Antenna
Over the
last half century considerable research into the Beverage has
been conducted and detailed design rules exist but for the radio
enthusiast this is one aerial design that is very tolerant of
design imperfections. Here's what you need to do to put your own
Beverage aerial together and to have a go:
Location:
Unfortunately the Beverage is a large aerial but it doesn't really
need much space and it can often be a "secret" aerial erected
unobtrusively. Ideally you need to have a large field or woodland
at the back of your house but a long straight fence can be used
to support the wire. If you have lots of space you have the freedom
to chose the beam direction but if you are just taking advantage
of local geography then you may have to accept the limitations
imposed on you. If you lack any significant space at home a good
alternative is to find some open land nearby.
Wire: Hard-drawn
copper wire is best for a permanent aerial since it won't break,
but it is not cheap and is quite heavy. I tend to use 7/0.2mm
multi-stranded insulated wire for temporary DX-pedition type aerials.
A continuous barbed wire fence (galvanised steel) is OK also as
long as it's not too rusty to make good electrical connections.
If you want to put up a cheap and disguised aerial use thin transformer
wire (eg 40 guage); you can lay this along a hedge row. Whatever
wire you chose you'll need to be prepared for breaks and repairs;
"chocolate block" connectors are very useful accessories when
working with Beverages.
Supports:
Gardeners-style bamboo canes (4-6 feet tall) are cheap and good
for the job. Just cut a slit at one end with a penknife or junior
hacksaw to hold the wire. Lightweight wire (eg 7/0.2mm) needs
a support every 15metres or so. If a straight hedge-row or fence
runs in the desired direction you can dispense with the bamboo
canes; likewise it is possible to support wire in trees or bushes
as long as a reasonably constant height (between 4 and 10 feet)
above ground can be maintained.
Earth stake
and terminating resistor: If a Beverage is operated just as a
long wire it will be directional but will pick up signals from
both ends of the wire but if the end of the wire furthest from
the receiver and nearest the target reception area is terminated
with a non-inductive (eg carbon) resistor equal in value to the
aerial's characteristic impedance (usually about 500 - 600 ohms)
the aerial becomes unidirectional. For best results it's good
idea to experiment with the resistor value but even a fixed resistor
of, say 560 ohms, connected between the aerial and the ground
stake will do the job. One good way to produce the terminating
resistor is to solder in series a dozen 1watt 47ohm resistorswhich
are then encased in either heat-shrink plastic tubing or self-amalgamating
tape. The use of many low value resistors makes the whole combination
less prone to moisture affecting the total resistance value. Do
not forget that for best results a good earth stake is needed
at both ends of the aerial, one for the terminating resistor and
the other for the receiver.
Receiver:
If you aren't operating from a permanent home installation, or
planning a full scale DX-pedition from, for example, a farmhouse,
you'll need portable equipment. One good portable receiver that
performs very well on the MW band is the Sony ICF2001D. This radio
can run off its internal batteries but alternatively a communications
receiver that runs off 12V could be used. To make the most of
the 2001D (and many other receivers) it is usually essential to
place an aerial tuning unit between the Beverage and the radio
to avoid overload problems caused by strong local signals. Just
imagine the simplicity of driving up to your aerial, parking in
a lay-by off the road, and then all that you need to do is pass
the aerial wire through the car window, connect it to the receiver
and you are ready to go! With a bit of ingenuity you could be
DXing with your very own Beverage aerial; you certainly don't
need to own several acres of land.
In fact recently
I erected a Beverage on a piece of waste land not far from my
home. To find the location I did a little browsing of local maps
and then surveyed the sites by driving around the neighbourhood.
I guess I was lucky but I only had to visit four locations before
I found an almost ideal site. Furthermore the site was derelict
and deserted so I put up a 330metre run of wire through the bushes.
The receiver end terminates on a fence post with some large nails
to which I simply connect the receiver with crocodile clips. whilst
at the other end I installed the terminating resistor between
the aerial wire and a copper earth stake driven deep into soft
earth in a ditch. In my case a good ATU is essential since I have
a local MW transmitter on 1170kHz.
4.3 Propagation
Normal Propagation
of MW signals
To make the
most of MW listening you'll need to have a basic understanding
of how a radio signal arrives at the receiver from a distant transmitter.
A great deal of scientific work has been under-taken investigating
the propagation of radio waves, but fortunately for the MW DXer
things can be greatly simplified by considering just two dominant
propagation modes. MW propagation takes place by means of two
different and distinct mechanisms, namely groundwaves and skywaves.
GROUNDWAVES:
The groundwave, as its name implies, travels along a path close
to the earth's surface. How far such a signal goes is dependent
on a number of factors, principally transmitter power, operating
frequency and earth conductivity. Groundwave propagation is heavily
dependent on the frequency, with low frequency signals travelling
greater distances. In fact, every thing else being equal, groundwave
signals from a station on 550kHz will travel twice as far over
land as those radiated by a station on 1500kHz. The earth conductivity
is also a very significant factor and it is found that the better
the conductivity the further the signal travels. Sandy or rocky
soil is the worst terrain whilst sea water is best and in regions
such as the Caribbean, where the sea is particularly saline (and
therefore more conductive), groundwave reception of stations up
to 1000 miles distant is possible. In contrast, a similar signal
travelling over rocky terrain would carry only about one quarter
of this distance. Groundwave propagation is very stable resulting
in consistent reception conditions. It is, however, usually only
associated with daytime (although equally present at night) since
at night long distant reception is predominantly via the sky wave.
Because of its stable daytime behaviour, radio stations usually
optimise their aerials to radiate as much of their signal as possible
via the groundwave in order to improve coverage.
SKYWAVES:
There exists a rarefied region of the earth's upper atmosphere
that absorbs the intense solar ultra-violet radiation thereby
protecting life on the earth's surface. This radiation results
in a region of ionised gases known as the ionosphere, which, depending
on diurnal and seasonal variations, consists of several fairly
distinct layers of high ionisation (Fig. 1). These layers have
a profound effect upon radio waves approaching them from transmitters
on the ground below. Under certain conditions refraction of waves
occurs, resulting in the "reflection" of signals back down to
the earth, whilst at other times signals can be totally absorbed
by the ionised gases. During daylight hours solar radiation penetrates
the atmosphere far enough to form the lowest layer of ionisation,
the 'D' layer roughly 60km above ground. The 'D' layer so completely
absorbs signals on MW frequencies that any radio signals radiated
by a station other than those parallel to the earth's surface
are completely lost.
With the
approach of sunset, however, the 'D' layer absorption decreases
rapidly and within a few hours MW signals are being reflected
back to the ground from higher regions of the ionosphere; depending
on circumstances reflection occurs in the E region (about 100-120km
up) or in the 'F' layer (225-300km).
Figure 3
& 4 illustrate this process and shows the skip distance which
for MW frequencies turns out to be about 100 to 500 miles. Longer
distance reception is possible when multiple reflections occur
between the ionosphere and the earth's surface. This occurs with
least signal loss over ocean paths hence the possibility of good
reception of Brazilian stations here in Europe.
Figure
3: The Ionosphere and MW Propagation
Whilst the
skywave enables good MW DX at night, it also leads to a deterioration
in reception quality for the normal broadcast listener. Firstly
there is a region about 50-100 miles from a transmitter (Figure
4) where the groundwave and the skywave signals are received with
roughly equal (but varying) strength, leading to severe distortion.
Additionally all skywave signals are affected by fading as a result
of the continually changing characteristics of the ionosphere.
Figure
4: Skywave / Groundwave Interference
Anomalous
Propagation
A previous
section examined some of the basic factors governing MW (and LW)
reception, in particular the effect of the ionosphere and the
influence of solar radiation and ground effects. We deliberately
restricted the subject to effects of a regular or predictable
nature; the sort of parameters that a planner takes into account
when planning the reception area for a new station.
There are
however many other occurances that have a bearing on radio propagation
at these frequencies; each with a greater or lesser degree of
unpredictibility. Although it is nice to be able to predict when
good DX will be heard on the MW band, it is the possibility of
the unusual occurring that adds a touch of excitement to the DXing
hobby. One of the overriding features of MW propagation is the
effect of solar radiation on the upper regions of the earth's
atmosphere. Predictable effects of solar radiation can be seen
as diurnal and seasonal variations in MW propagation as well as
in the influence of the 11 year sunspot cycle.
Less predictable
events include ionosperic storms, shortwave fadeouts and polar
disturbances. These somewhat esoteric events result from disturbances
occurring in the sun, which is, under such circumstances, referred
to as 'active'. The mechanisms behind such events are both complex
and in some instances not yet fully understood but fortunately
the average DXer is likely to be more interested in knowing the
effect rather than the cause. In addition it could be very helpful
to know when such an event was in progress and to be able to gauge
its possible effect on DXing. A number of institutes around the
world keep a watch on the sun and the ionosphere but the DXer
is faced with the problem of obtaining (and interpreting) this
extensive scientific information.
Fortunately
the American National Bureau of Standards provides this information
via the standard time and frequency broadcasts of station WWV.
This station, which is most likely to be heard on 5.0, 10.0 or
15.0 MHz, transmits regularly up-dated radio propagation data
during the 18th minute past every hour. It is also possible to
obtain the same message by phoning a pre-recorded announcement:
the US phone number is +1-303-497-3235.
One piece
of information transmitted via WWV that is particularly interesting,
is the Fredericksburg 'A' Index (more properly called the Fredericksburg
Index of Geomagnetic Activity in the Earth's Magnetic Field) which
can be used as a simple guide to propagation on the MW band. It
is a simple matter to construct a daily graph of the A indices
from which basic propagation predictions can be made. High values
(above 20) indicate that MW signals in high latitude paths are
likely to be absorbed, leaving signals propagating via paths closer
to the equator to dominate. Low values over a period of time indicate
a likelyhood of improved reception via higher latitude paths.
Long periods of very low (6 or less) values are needed to raise
the possibility of good high latitude reception throughout the
entire MW band.
4.4 Make
Reception Reports Really Work
If you are
one of the many MW DXers who not only likes to hear a station
but wants to collect a verification or QSL to "prove" that reception
actually took place, then you'll appreciate that hearing the station
in the first place is only half the problem. I'm sure that you've
wondered why not every station replies to your letters or reception
reports. Perhaps only around 50% of MW stations reply; what can
be done to increase this ratio? Many MW broadcasters (in contrast
to their SW counterparts) are not interested in audiences in far
flung places since their double glazing advertiser is unlikely
to extend his sales overseas!
Firstly imagine
yourself in the position of the station engineer and then imagine
you received a letter from a faraway listener asking for a QSL
card. Could you be bothered to reply if you've already received
a hundred similar items in your in-tray that week? I know of station
engineers that have commented "... some of the reports we get
are terrible..", "... we only now reply to reports containing
IRCs as the postage was getting rather expensive..", and "...
I always reply to DX reports but never know if my letters are
received.."
What a listener
needs to do is to convince the station that reception really took
place and that the report is not just being made up. In addition
you need to make the station's task in replying as simple as possible
and it always helps to make your reception report stand out from
the crowd so that perhaps it won't end up in the "round file".
Try these 10 steps to good reception reports:
1) Convince
the station: Include full details of commercials and public service
announcements that you heard since virtually all stations record
these details in their logs. Station slogans won't on their own
convince anyone since they are often well-known and widely reported
and also lists of records heard are not always very useful since
details aren't always kept in station logs. Worst of all is something
like "man talking.." or "music" which won't help convince anyone!
The golden rule is the more detail the better.
2) Make their
job easier: Use the station's local time in reception reports
so that they don't have any tricky time zone conversions to do.
The only exception is if the station is an international broadcaster
that has been announcing a different time zone (e.g GMT or UTC)
on air. It is often wise to note down the actual time announced
in time checks rather than what your watch says since many stations
have somewhat inaccurate studio clocks!
3) Make their
job easier: Send return postage with your letter. Best of all
include mint stamps from the station's country but since this
is easier said than done you could send International Reply Coupons
which are obtainable from the Post Office. Unfortunately some
countries do not accept IRCs for exchange into local postage stamps.
For the USA and many other countries you can instead send a US$1
bill since hard currency is often appreciated.
4) Make their
job easier: Enclose a prepared sticky label with your return address
already on it.
5) Make their
job easier: Write in the station's natural language unless it
is a big international broadcaster with various language departments.
The natural language may not be the main language of the country
they are in (e.g. Spanish speaking stations located in the USA).
6) Help the
station: local MW stations don't need listeners thousands of miles
away; certainly they don't attract more advertising because of
this. So if you can help the station with constructive comment
on programmes (what you liked and disliked) and on technical quality
(eg modulation, audio quality or frequency stability) or by identifying
interference, so much the better.
7) Make your
letter stand out: BE POLITE and request a QSL card - never demand
one.
8) Make your
letter stand out: Introduce yourself and your location; maybe
include a local picture postcard or some stickers from your local
radio stations.
9) Make your
letter stand out: use commemorative or unusual stamps on the envelope;
there maybe a philatelist at the station. Unfortunately in some
parts of the world this might also make your letter attractive
to thieving hands in the postal system.
10) Make
your letter stand out: Give a realistic and detailed decription
of reception conditions in words that are not too technical (remember
it's not always the engineer reading your letter). Never use SINPO
style codes on their own.
If you follow
some or all of these tips you should not only increase your chances
of getting a reply from a station but you will help contribute
to good relations between DXers and broadcasters. Finally, if
you receive a reply from a station it is an often over-looked
basic courtesy to thank them. It is simple and quick (and not
too expensive) to send a postcard direct to whoever wrote from
the station letting them know that their letter arrived safely
and thanking them for their trouble. Research during a Radio Netherlands
Media Network edition revealed that very few bother to say "thanks",
and yet it makes all the difference.
5 Moving
On
5.1 Specialist
Clubs for MW/LW DXers
N America Publication Contact Point
National Radio Club DX News; 30 times per DX News Subscription Centre,
year Ron Musco, PO Box 118,
Poquonock, CT 06064-0118,
USA
International Radio DX Monitor; 34 times per 11300 Magnolia #43,
Club of America year Riverside, CA 92505, USA
Europe
MW Circle MW News; 10 times a year Club Secretary, Harold
Emblem, 137A Hampton Road,
Southport, Lancs., PR8 5DY,
England
Arctic Radio Club mv-eko; 12(??) issues per Box 5050, 350 05 Vaxjo,
year Sweden
UmeΠKortvaggskubb Distance; 16 issues per Box 117, 90103 Umea, Sweden
year
Oceania
Australian Radio DX Australian DX News Box 227, Box Hill, Victoria
Club (monthly) 3128, Australia
Most other
radio clubs that concentrate on shortwave radio also include sections
on Medium and Longwave listening. However not being specialists
their coverage of this topic is generally not as comprehensive.
A good list
of clubs can be found in the World Radio TV Handbook (pages 59-62
in the 1995 Edition). The following are only a small selection
of established clubs with regular publications containing good
MW/LW columns:
Europe:
- British
DX Club;126 Bargery Rd, Catford London SE6 2LR, England
- World
DX Club; 17 Motspur Drive, Northampton NN2 6LY, England
- Play DX;
via Davanzati 8, 20158 Milano, Italy
N America:
- Ontario
DX Association; Box 161, station A, Willowdale, Ontario M2N
5S8, Canada
S America:
- Conexion;
Casilla de Correo 465, 1900 La Plata, Argentina
- The Radio
News; PO Box 3551, El Trigal, Valencia 2002, Edo. Carabobo,
Venezuela
Africa:
S African
DX Club; PO Box 72620, Lynnwood Ridge, Transvaal 0040, S. Africa
5.2 Sources
of Equipment
Audio Accessories
Datong Switched capacitor Clayton Wood Close, +44-532-744822
Electronics Ltd. noise and tone West Park, Leeds LS16
filters 6QE, UK
JSP DSP noise and tone Box 97757, Rayleigh, NC +1-919790-1011
Communications filters 27624-7757, USA
Inc
I-Com. DSP noise and tone 793 Canning Parkway, +1-716-924-0422
filters Victor, NY 14564, USA
Antennas
Kiwa Electronics large air cored 612 South 14th Avenue, +1-509-453-5492
loops Yakima WA 98902, USA or 1-800-398-1146
free
Graham Maynard large air cored 16 Woodford Avenue,
loops, outdoor Newtownabbey, N Ireland
designs and BT36 6TL, UK
phasing units
Palomar Engineers ferrite cored PO Box 462222, +1-619-747-3343
small loops Escondido CA92046, USA
Receivers
Hundreds
of models are widely available new and secondhand so I will only
list receiver types that are particularly popular with top MW
DXers, selected primarily for good performance with MW AM signals.
- Collins
(or Motorola) R390A/URR (only second-hand, ex-military; rare;
valves, heavy)
- Lowe HF225
Europa (upgraded basic HF225, current product) [optional synchronous
AM]
- Sony ICF2001D/2010
(current product) [synchronous AM is standard]
- JRC NRD535
(current product) [phase locked ECSS fitted]
- JRC NRD525
(second-hand) [synchronous AM accessory needed]
- Drake
R7A (second-hand) [synchronous AM accessory needed]
5.3 Bibliography
Books you must have Author Publisher, date; Notes
ISBN
World Radio TV Editor: A.G. Billboard Good for MW but limited
Handbook Sennitt Books.1995 49th USA coverage; 600+pages
edition. annual
ISBN 0-8230-5926-X
Recommended Books
MW; A Practical Graham MW Circle 1988 22pp
Approach Maynard
Getting Started in National Radio
MW DX-ing Club 1987
Antenna File Vol. 1 various MW Circle 1993 26pp
Receiver Shopping Jonathan Radio Netherlands Regular publication;
List Marks et al. back issues also very
useful
The Wave Antenna for Walter J Wilhelm Herbst 36pp
Reception of Medium Schulz Verlag, Kšln. 1985
and Long Wave ISBN 3-923 925
10-7
WRTH Equipment Jonathan ISBN 0-8230-5949-9 Receivers, antennas,
Buyers Guide 1993 Marks Willem (new edition due software etc.
edition Bos mid-1995)
The Beverage Antenna Victor A Misek; Hudson NH 39 pages very good,
Handbook Misek 03051, USA 1977 maybe out of print
Receiver File Vol.1 various MW Circle 1993 Modifications & tips by
experts
Proceedings various Fine Tuning, c/o Excellent compedium of
John Bryant, RRT#5 articles on receivers,
Box 14, antennas, and features
Stillwater, OK written by experts; each
74074, USA issue is completely
different (biennial)
DXers Technical IRCA; 2nd Edition 120pp
Guide 1983
Recommended but with regional bias
NRC AM Radio Log NRC (annual) 15th Most comprehensive list
Edition in 1994 of all US & Canada MW
stations; annually
updated 440pages
99 Nights on MW Wilhelm Wilhelm Herbst European
Herbst Verlag Verlag Good introduction to MW
ISBN 3-923 DXing
925-04-2
Dial-Search 1992/94 George Wilcox G. Wilcox, 9 UK/Europe (biennial)
Thurrock Close, 48pp + maps
Eastbourne, BN20 ISBN 0-9508575-5-6
9NF, England
7th Edition; 1992
MW Guide to Asia, Australian Radio Oceania
Australia & the DX Club
Pacific
IRCA AM-FM Almanac IRCA 5th Edition General station/network
1991 data; USA + some Canada
200+ pages
Books to Avoid
Whites Radio Log Worldwide 136 page three way list
Publications In., of all MW, FM and TV
P.O Box 5206, stations in Canada &
North Branch NJ USA; BADLY OUT OF DATE
08876 USA
NB: There
are many books that contain listings and information about stations,
their frequencies and programme schedules. Although the rate of
change of MW stations is less than on shortwave (where frequencies
are often changed several times a year) books can rapidly become
out of date. Those published annually are the best and even these
rely on quarterly update bulletins to maintain a reasonable degree
of accuracy.
Copyright
notice: This publication is copyright and may not be copied without
permission. Publications wishing to reproduce sections of this
medium wave guide should contact us at
Radio Netherlands
attn: Jonathan
Marks
P.O. Box
222,
1200 JG Hilversum,
The Netherlands
.
FAX: +31
35 724352
© April
1994 Steve Whitt 4 Radio Netherlands. Updated April 1995
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