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- From: fybush@world.std.com (Scott Fybush)
- Subject: Welcome to rec.radio.shortwave (AM/FM DXing)
- Expires: Tue, 3 May 1994 00:00:00 GMT
- Reply-To: fybush@world.std.com (Scott Fybush)
- Organization: Nancy Kerrigan Fan Club
- Date: Fri, 1 Apr 1994 04:27:49 GMT
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- Message-ID: <radio/monitoring/am-fm-dxing-1-765174447@cbnewsj.cb.att.com>
- Followup-To: rec.radio.shortwave
- Summary: Answers to Frequently Asked Questions about long-distance
- reception of local AM (medium wave) and FM stations.
- This article is posted monthly.
- References: <radio/monitoring/introduction-1-765174331@cbnewsj.cb.att.com>
- Sender: ralph@cbnewsj.cb.att.com (Ralph Brandi)
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- Posted-By: auto-faq script
- Archive-name: radio/monitoring/am-fm-dxing
-
- [Last revised: Oct 3 1993]
-
- AM/FM DXing
-
- By Scott Fybush and Earl Higgins
-
- One of the easiest parts of the radio spectrum to explore are the
- broadcast bands. This posting will attempt to offer some hints to make
- your exploration of the mediumwave and VHF-FM bands more enjoyable.
-
- I. WHAT ARE THE AM/FM BROADCAST BANDS?
-
- The mediumwave (commonly referred to as AM) broadcast band currently
- extends from 525 to 1605 kilohertz. Channels are spaced in even 10 kHz
- increments; i.e.: 530, 540, 550, ... , 1600 kHz in the United States and
- Canada. Elsewhere, channels are spaced in 9 kHz increments, i.e.: 531,
- 540, 549, etc.
-
- In the United States, the band is being expanded to 1700 kHz. Stations
- which are currently experiencing high levels of interference will begin
- appearing on the 1610-1700 kHz frequencies sometime in late 1993 or
- 1994. They will simulcast the new frequencies with the old for a period
- of a few years, eventually dropping the `old' frequency. This opening up
- of new channels presents some once-in a lifetime opportunities for the
- alert mediumwave DXer.
-
- The VHF-FM broadcast band in the United States extends from 88 to 108
- megahertz. Channels are assigned at 200 kHz increments; i.e.: 88.1,
- 88.3, 88.5, ... , 107.9. The channels from 88.1 to 91.9 are reserved
- for noncommercial educational stations. Outside the United States and
- Canada, the boundaries and channel spacing vary. In Japan, the band
- starts at 76 MHz. In Western Europe, the band generally runs from
- 88-108 MHz, but channels can be irregularly spaced, i.e.: 101.25 MHz.
-
- II. SIGNAL PROPAGATION
-
- The distant stations you are able to receive will depend largely upon
- signal propagation. This varies depending upon the time of day, the
- season, and other factors. For mediumwave, the single most important
- factor for good DX is the time of day. Mediumwave signals almost always
- get absorbed by the D Layer of the ionosphere during daylight hours. As
- a result, all mediumwave signals received during midday hours will
- arrive by ground wave, making reception of signals over a few hundred
- km/miles away unusual in daylight. At night, however, the ionosphere
- reflects mediumwave signals, making it possible for signals to be heard
- at much greater distances, up to a few thousand km/miles, via `skywave'.
- To a lesser extent, the period up to two hours after local sunrise, and
- two hours before local sunset, called "Critical Hours", have varying
- levels of skywave, and also can provide some very unusual reception
- opportunities for the mediumwave DXer. Reception also tends to be better
- in winter than in summer, due to lower levels of atmospheric noise and
- longer hours of darkness. In the United States, due to the large number
- of stations, many smaller mediumwave stations are required to sign off
- or reduce power sharply at sunset so as to reduce interference to
- distant stations.
-
- Whereas the mediumwave band can be counted on to provide distant
- reception with much dependability, this is not the case at all on the
- VHF-FM band. Under `normal' conditions, VHF-FM signals generally carry
- no more than 150-250 km (100-150 miles), or `line of sight', since the
- ionosphere generally does not reflect VHF-FM signals. VHF-FM
- transmitting antennas are thus usually located as high as possible. Tall
- towers, high buildings, and mountaintops are common VHF-FM transmitter
- sites.
-
- However, under certain rare conditions, the atmosphere will even reflect
- VHF-FM signals, thus making it possible to receive these stations at
- quite long distances. There are two major forms this distant reception
- can take; the most common is Tropospheric Ducting, or tropo for short.
- Typically, this occurs when a warm air mass forms on top of a cooler
- mass closer to the ground. The area between these masses acts like a
- pipe, `bending' the signals back to the earth well beyond the horizon.
- This reception is most common in local late spring and summer months, in
- the post-sunrise hours. It will enable the alert VHF-FM DXer to log
- stations up to 800 km (500 miles) away in optimum conditions.
-
- The other relatively widespread form of VHF-FM DX is called Sporadic E,
- or E-skip, because it is the E Layer of the ionosphere which reflects
- the signals. Like the name implies, this form of propogation is very
- sporadic, yet very intense. When it's in, it is VERY strong. Stations
- from a relatively limited geographic area 1300-2000 km (800 to 1200
- miles) away will suddenly boom in, strong, often in stereo but quite
- fadey, even overpowering semilocals in many cases. It will start at the
- bottom of the VHF-FM Band (actually TV channels 2-6 first) and work its
- way up in frequency. The highest frequency at which signals are
- reflected by the ionosphere is called the Maximum Usable Freqiuency
- (MUF), just as it is in shortwave, and it can occassionally surpass the
- top of the VHF-FM dial in an unusually good opening.
-
-
- III. RECEIVERS
-
- Almost any radio is capable of some broadcast-band DXing, especially
- long-distance mediumwave reception. However, most recent radios, even
- those designed for quality shortwave reception, do not have outstanding
- broadcast band reception. One exception is the General Electric
- Superadio III (Model 7-2887.) The SR III is designed for optimum AM/FM
- broadcast performance, incorporating:
-
- * RF amplifiers on both bands
- * Ceramic filters and Automatic Frequency Control on FM
- * No PLLs or digital displays for less electronic noise
- * A 2-way speaker system with 1 watt of audio power
-
- The SR III is a bulky (4" x 10" x 12") portable radio which can be run
- off 120V AC or 6 "D" batteries, providing over 400 hours of battery
- life. This radio has become popular among the DX community for its
- exceptional performance.
-
- It costs between thirty and sixty dollars in the US, and may be found at
- many discount outlets. It can be obtained from Bennett Brothers (Order
- #R3116) at 1-800-621-2626 or 1-800-631-3838, or from Best Products
- (Order # 140457) at 1-800-950-2398.
-
- If you don't have a Superadio, some important things to seek out in a
- receiver are:
-
- * External antenna connections. These make it easier to use a better
- antenna than the one supplied with the radio.
-
- * High selectivity. This refers to the receiver's ability to reject
- strong signals on adjacent frequencies, and is more important to good
- reception than is sensitivity, since a good antenna will provide
- more-than-adequate signal strengths.
-
- * Digital frequency display. While the circuitry involved can add to
- the level of internal electronic noise in the radio, digital display
- makes it possible to more easily determine what station is being heard.
-
- IV. ANTENNAS
-
- For mediumwave reception, most receivers have a short internal ferrite
- rod. This will provide acceptable signals for high-powered distant
- stations. Ferrite rods are quite directional, and the radio can thus be
- turned to null out strong interfering signals, or to improve reception
- of the desired signal.
-
- For more advanced DXing, external antennas offer certain advantages. The
- most common external antenna is a simple random wire, 15m (50 feet) or
- more run out the window and then as high as possible (up in a tree, for
- example). The wire can be connected to the external antenna terminal.
- If none exists, you can open up the radio and wrap the wire a few turns
- around the ferrite rod inside. It is also possible, although less
- desirable, to simply wrap the wire around the entire radio. If the
- radio has a terminal marked "ground" or "GND," another wire can be run
- from this terminal to a copper rod driven a meter/a few feet into the
- earth.
-
- One problem with a random wire antenna for mediumwave work is it's
- inability to reject strong local signals. Most receivers today lack the
- dynamic range to effectively deal with the extremely strong signals from
- a local mediumwave broadcaster as picked up by a random wire antenna.
- Thus, some sort of tuned antenna is best for all but the most isolated,
- rural locations.
-
- The most popular antenna for mediumwave DX today is called a `loop'
- antenna, and can be either of two types: ferrite rod or air-core wound
- wire loop. These antennas are small, 25-100 cm (1-3 feet) in diameter,
- and sit on the DXers desk or shack table where they can be easily turned
- by hand for optimum peak or null of a signal. Each design works with a
- tuned circuit before feeding the signal into your receiver, and usually
- this circuit includes a small powered amplifier. Generally speaking, the
- longer the ferrite rod, or the larger the diameter of the aircore loop,
- (to a point), the sharper the null of the antenna. 45 to 55 cm (18 to
- 22 inches) would be optimum for a ferrite rod antenna.
-
- Air-core loops need to be made by hand, as there are none on the market.
- Ferrite loops, however, are available commercially from at least two
- manufacturers; Palomar Engineers and Radio West. Unfortunately, these
- two antennas do not have very long ferrite elements; and reviews of
- their performance in the mediumwave press tends to be mixed. Ideally,
- one would build their own antenna, or try to find either a used, older
- Radio West loop or Space Magnet antenna, both pre-1980. Plans for
- building all sorts of mediumwave loop antennas are available through
- National Radio Club publications. The address is found later in this
- FAQ.
-
- A more advanced antenna is the "beverage" antenna. This is a length of
- wire 300 m (1000 feet) or more, with extremely high gain and narrow-beam
- directional characteristics. It is usually, but not always, terminated
- at the far end with a 450 ohm resistor connected to a metal stake driven
- into the ground. It should be pointed in the direction of the desired
- station. The beverage antenna can, under good conditions, be used for
- transatlantic and transpacific DX.
-
- For VHF-FM, the important factor is height. The higher one can place an
- antenna, the better reception will be. A multielement Yagi antenna,
- which can be found in Radio Shack or similar stores, will often produce
- excellent reception. Since a yagi is quite directional, the use of a
- rotor is essential for reception of stations in different directions.
-
- V. WHAT'S OUT THERE TO LISTEN TO?
-
- There are over 10,000 radio stations in the United States alone. It's
- important to have some idea of what to expect to hear. A good directory
- is important (see STATION LISTINGS below), but it's essential to know
- what the station information means.
-
- For mediumwave, North American frequencies fall into three basic
- classes:
-
- * CLEAR CHANNEL: These frequencies are 540, 640-780, 800-900, 940,
- 990-1140, 1160-1220, and 1500-1580 kHz. Clear channels are home to one
- or two 50,000 watt powerhouse signals which can be heard reliably in
- half the country or more. Other stations also occupy the clear
- channels, frequently using less than 1000 watts and very restrictive
- antenna patterns. In recent years, the US FCC has added many more low
- power stations to the clear channels, making reception of the big,
- primary, stations more inteference prone than it once was, but providing
- excellent hunting for the serious mediumwave DXer. Also, the clear
- channels are the primary hunting area for Latin American DX due to the
- relatively small number of North American stations on them.
-
- * LOCAL: These frequencies are 1230, 1240, 1340, 1400, 1450, and 1490
- kHz, and are sometimes referred to as the 'graveyard' channels by DXers.
- Stations on local channels can use a maximum of 1000 watts (somewhat
- higher outside the US). At night, these six frequencies tend to become
- chaotic, as the hundred-plus stations on each channel cause each other
- tremendous interference. Although the primary service area of these
- stations may be twenty miles or less, these stations have been known to
- reach well over a thousand miles under good conditions. Identifying
- distant stations on these channels requires a directional antenna, a
- good ear, and plenty of patience. The National Radio Club keeps distance
- records for all of the stations on these channels and publishes them in
- their bulletin, _DX_News_, regularly.
-
- * REGIONAL: These are all the remaining channels, including the expanded
- band frequencies of 1610-1700 kHz. U.S. stations on these frequencies
- tend to be restricted to 5000 watts, although a recently signed
- international treaty allows for the possibility of 10,000 or even 50,000
- watt stations on these frequencies if they do not interfere with other
- stations. In practice, only Canada has yet assigned high power stations
- on these frequencies. While not as noisy as the locals, reception on
- regional channels can be quite interference prone, with a listener able
- to identify three or four stations coming in simultaneously on one
- frequency. Most regional, or class III stations, use directional
- antennas to reduce interference with distant stations.
-
- On VHF-FM, the American FCC has reduced its restrictions on power and
- antenna height considerably. Today, VHF-FM stations are allowed up to
- 50,000 watts from a 150 meter antenna in the Northeast and California;
- 100,000 watts from a 610 meter antenna elsewhere. Many stations,
- however, serve much smaller areas. These "Class A" stations use only
- 6000 watts or less. They were formerly restricted to just the following
- frequencies: 92.1, 92.7, 93.5, 94.3, 95.3, 95.9, 96.7, 97.7, 98.3, 99.3,
- 100.1, 100.9, 101.7, 102.3, 103.1, 103.9, 104.9, 105.5, 106.3, and 107.1
- MHz. While the FCC no longer restricts class A stations to those
- frequencies, most are still found there. Likewise, only a few of the
- high-power stations are found on the old class A channels. For stations
- with extemely high antenna, the FCC mandates that transmitter power be
- reduced proportionately; thus a station with only 430 watts from a 220
- meter antenna will reach about as far as a 3000 watt signal from the
- usual 91 meter antenna will.
-
- VI. TIPS FOR BEGINNING
-
- The most important element for beginning DXers is to get to know the
- dial. Spend a few hours scanning up and down the dial both during the
- day and at night. At night, many of the clear-channel 50kw stations,
- particularly the non-directional ones, should be easy to hear. Learn
- all the local stations. Find out which ones sign off at sunset, which
- ones go off late at night, and which stay on all night. This will affect
- which distant stations can be received. If you have a local station on
- all night, you shouldn't expect to hear another station on that
- frequency without some tedious nulling. Experiment with radio placement.
- As you slowly turn the radio, observe its directional characteristics.
- The Superadio III will receive signals coming from the front and back of
- the set the best, and attenuate the signals coming in `off the side' of
- the set. You can use this to your advantage and log several stations on
- a single frequency.
-
- By all means, keep a log of all new stations you hear; someday you'll be
- glad you did! Better yet, keep it on the computer; that way you can
- share it with others on the net. After a few months of listening; you
- should have a list of 200-300 stations you've heard. Most of these will
- be your `regulars', audible almost daily. Beyond that, you can hunt for
- the rarer stuff. Try for all 50 US states (very, very difficult), or 20
- countries (fairly easy in most locations). Within a few years, you'll
- likely have heard a thousand or so stations and have a very interesting
- logbook. Here's a `beginner's target list' of widely heard clear channel
- AM stations to start you out; from most locations in North America you
- should be able to hear all but four or five of these fairly easily.
-
- 540 CBK Canada SA Watrous 840 WHAS USA KY Louisville
- 540 XEWA Mexico SL Rio Verde 850 KOA USA CO Denver
- 640 KFI USA CA Los Angeles 860 CJBC Canada ON Toronto
- 650 WSM USA TN Nashville 870 WWL USA LA New Orleans
- 660 WFAN USA NY New York 880 WCBS USA NY New York
- 670 WMAQ USA IL Chicago 890 WLS USA IL Chicago
- 680 KNBR USA CA San Francisco 900 XEW Mexico DF Mexico City
- 700 WLW USA OH Cincinnati 990 CBW Canada MB Winnipeg
- 720 WGN USA IL Chicago 1020 KDKA USA PA Pittsburgh
- 730 XEX Mexico DF Mexico City 1030 WBZ USA MA Boston
- 740 CBL Canada ON Toronto 1040 WHO USA IA Des Moines
- 750 WSB USA GA Atlanta 1070 CBA Canada NB Moncton
- 760 WJR USA MI Detroit 1070 KNX USA CA Los Angeles
- 770 WABC USA NY New York 1100 WWWE USA OH Cleveland
- 780 WBBM USA IL Chicago 1120 KMOX USA MO Saint Louis
- 800 PJB Neth Ant. Bonaire 1160 KSL USA UT Salt Lake City
- 800 XEROK Mexico CH Juarez 1180 WHAM USA NY Rochester
- 810 WGY USA NY Schenectady 1200 WOAI USA TX San Antonio
- 820 WBAP USA TX Fort Worth 1210 WOGL USA PA Philadelphia
- 830 WCCO USA MN Minneapolis
-
-
- VII. SOME ADVANCED IDEAS
-
- Once you've mastered the basics, here are some suggestions for areas of
- specialty DX:
-
- * QSLing: Since broadcasters by and large don't use the "Q-codes" so
- popular in Ham and shortwave DX, QSLs are called `veries' or
- verification letters by mediumwave and VHF-FM DXers. You'll probably
- have to send a letter to the station's chief engineer (names of actual
- verification signers can be found in the NRC AM Log). Expect
- verification in card form from the 50kw AM stations, and verification
- letters from just about everybody else. Small stations are often excited
- to find out they've been heard thousands of miles away, but you'll need
- to take special care to explain to them exactly what you want as they
- are likely to not know what a `verie' is. Also, remember to always
- include return postage with your request.
-
- * DX Tests. A few stations still run special DX tests, usually arranged
- for either The NRC or The IRCA (International Radio Club of America) and
- published in advance in their respective bulletins (another reason to
- join!). In the past year alone, the following outstanding feats were
- accomplished via DX Tests: Hawaii (KUAI-720) was heard as far away as
- Ontario and Pennsylvania; New Jersey (via WJIC-1510) made it west of the
- Mississippi; and New Mexico (KHAC-880) made it to the East Coast! These
- are all fairly difficult states for most DXers (unless, of course, you
- happen to live in or near them).
-
- * Equipment Tests: Some stations run experimental tests with their
- daytime power after local midnight, in accordance with US FCC and
- Canadian CRTC rules. Often these will be late Sunday night/Monday
- morning, when some stations sign off for maintenance (although not as
- many as used to do so). For example, in Chicago Illinois, many DXers
- have logged KOMO-1000 from Seattle Washington, testing when Chicago
- local WLUP goes off on Monday mornings; thankfully Monday mornings just
- happen to be the time when KOMO seems to like to test with their
- non-directional day pattern. This makes an otherwise almost impossible
- state relatively easy around the midwestern US.
-
- * Sunrise/sunset DXing. Lots of interesting mediumwave DX can be had
- when your receiving station and/or the transmitter are in only partial
- darkness. It's possible to hear distant daytime-only stations this way.
- This requires a lot of skill, since there may be only ten or fifteen
- minutes in which to try. In fact most mediumwave DXers log the greatest
- number of stations in the hour or two right around local sunset,
- especially in the Fall and Winter months. Don't be surprised if, say,
- tiny KOKB in Blackwell, Oklahoma blasts right through CBJ and other East
- Coast powerhouse stations on 1580, for a few minutes right around
- Blackwell sunset! Anything can happen in the turbulent sunset and
- sunrise hours.
-
- * Transatlantic/Transpacific DX. Some DXers in North America specialize
- in trying to receive signals on the mediumwave band from across the
- ocean. This requires outstanding propagation characteristics and plenty
- of patience (a nice, quiet coastal location can yield some amazing
- results).
-
- * FM Subcarriers and Stereo. VHF-FM stations are allowed to transmit
- separate programming on a subcarrier. This requires a special decoder
- (one source is Bruce Elving's FM Atlas; see address below.) FM stations
- use their SCA (Secondary Communications Authority) subcarriers for
- transmitting data, background music, ethnic programming, and more. Some
- AM stations now transmit in stereo. With an AM stereo receiver, you can
- hear stereo signals from thousands of miles away.
-
- * Meteor Scatter. The most masochistic of all VHF-FM DXers attempt to
- hear VHF-FM signals reflected from --yes, it's true-- meteors in the
- atmosphere. These DXers learn to identify stations on the basis of a
- few seconds' listening.
-
- VIII. IDENTIFYING YOUR CATCH
-
- Radio stations in the United States are required to identify with their
- full call letters and city of license once an hour, between 10 minutes
- before and 10 minutes after the top of the hour. Canadian stations are
- never required to identify, and many never use any identifier other than
- "Q107" or "Toronto's 590 AM." It's therefore important to use other
- clues:
-
- * Time announcements. These can tell you at least what time zone a
- station is in. If there's only one or two stations on a frequency in a
- given time zone, this makes identification easier.
-
- * Format. If you have a list of stations that includes formats, use it.
- That includes knowing what network a station uses, whether the station
- uses a satellite-delivered music format, what slogans the station might
- use, etc.
-
- * Local color. You might be able to hear names of cities or streets or
- notable local personalities mentioned during commercials, newscasts,
- talk shows, or weather forecasts. If the announcer says, "Here's the
- weather for the beaches today...", the station you're hearing probably
- isn't in North Dakota (although note, interestingly, there IS a TOWN
- called Beach, North Dakota; go figure). Likewise, if the forecast is
- snow flurries and six degrees, you're probably not hearing Miami. These
- clues are among the most valuable.
-
- IX. STATION LISTINGS
-
- An essential tool for any DXer is a good station listing. This will
- help identify what's being received, as well as provide a way to contact
- the station being heard.
-
- For North American AM stations, one essential tool is The NRC AM Radio
- Logbook, now in its 13th Edition. It includes day and night antenna and
- power information, format, hours of operation, address, verie signers,
- network affiliations, etc. Price is $19.95 for US, $20.95 for Canadian,
- three dollars cheaper for NRC Members. To order write NRC Publications,
- Box 164, Mannsville NY 13661-0164 USA. NRC also publishes FM and TV
- Logs. To become a member (highly recommended) and receive a year's worth
- of `DX News', send $24.00 for US, $25.00 for Canadian to: NRC
- Subscription Center, Box 118, Poquonock, CT 06064-0118 USA. All other
- countries, write for price information.
-
- Another concise and inexpensive directory is the M Street Radio
- Directory, published annually. The M Street listing includes frequency,
- power, directionality, format, address, phone number, and other listings
- less important to DXing. M Street also is indexed by call letter order
- and by frequency. The M Street directory costs $29.95 + p/h. It can be
- purchased directly from M Street at 800-248-4242 or +1 212 473 4668
- voice, or +1 212 473 4626 fax. The address is M Street Corp., 304 Park
- Ave S Floor 7, New York, NY 10010 USA.
-
- Another guide for VHF-FM DXers is Bruce Elving's annual FM Atlas. This
- includes maps showing every VHF-FM transmitter in North America, plus
- listings by state and frequency indicating power, stereo status, format,
- subcarriers, and slogans. FM Atlas does not include addresses or phone
- numbers. It can be purchased directly from Bruce Elving, PO Box 336,
- Esko MN 55733-0336. It costs $10.95 + $1.05 p/h.
-
- Another listing is the Broadcasting Yearbook, which is available at some
- larger libraries. The Canadian Almanac and Directory includes call letters,
- frequency, and addresses for Canadian stations.
-
- For listings outside North America, consult the World Radio TV handbook,
- published annually and available through your local bookstore or radio
- specialty mail order outlets such as the Radio Collection and CRB
- Publishing.
-
- X. CONCLUSION
-
- Broadcast band DXing is an exciting way to hear the sounds of cities and
- towns around the nation and even around the world. It doesn't require
- hundreds of dollars of expensive equipment or huge antennas on the roof.
- All it asks of the would-be DXer is time, patience, and knowledge. Have
- fun!
-
- THANKS TO...
-
- Bob Foxworth, Garret W. Gengler (antenna ideas), Bob Parnass, Paul
- Schleck (Superadio information), and Bruce Werner, along with anyone
- else I may have forgotten.
-
- Scott Fybush -- fybush@world.std.com
- Earl Higgins -- higgins%tiss.decnet@mdcgwy.mdc.com
-
-
- --
-