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AM Commercial radio reception
Why is it that I can received WCBS @ 880kc fairly well at night but WABC @
770kc suffers from phase distortion like you wouldn't believe! (I'm about 175 miles from both transmitters.) They are both 50 kwatt stations. And why is it that both WBZ (Boston), WBT (Charlotte, NC), WJR (Detroit) and WBBM (Chicago) come in better than either of the New York City stations? Dave P. |
AM Commercial radio reception
Why is it that I can received WCBS @ 880kc fairly well at night but WABC @ 770kc suffers from phase distortion like you wouldn't believe! (I'm about 175 miles from both transmitters.) They are both 50 kwatt stations. And why is it that both WBZ (Boston), WBT (Charlotte, NC), WJR (Detroit) and WBBM (Chicago) come in better than either of the New York City stations? Dave P. ================================ Different frequencies, different directions, different sun angles (even when below the horizon), different ionospheric layer heights, different skip distances, different ground-path terrains and therefore different ground-path loss. ---- Reg. |
AM Commercial radio reception
Dave P. wrote:
"Why is it that I can receive WCBS @ 880 kc fairly well at night but WABC @ 770 kc suffers from phase distortion like you wouldn`t believe?" I havn`t looked up the directional patterns of the two stations and don`t know your location. If you should happen to be at the edge of a null in the nighttime directional pattern of WABC, that would likely cause distorted fading. WABC may be clear-channel non-directional day and night for all I know. Not many of these remain in the U.S.A. now. At 175 miles from both transmitters, you suffer interference between the ground wave and sky wave from either transmitter at night, at least occasionally. You probably have solid daytime reception from both stations, but at night, the signal may be stronger, though variable. The sky wave is susceptable to variations in the reflecting layers of the ionosphere at night. These are a function of frequency, reflecting carrier and sidebands differently at times. This can produce overmodulation at times in the received signal. Another factor is likely other stations on the same or adjacent channels which may fade in and out and cause variation from your automatic volume control action even when the interfering stations can not be readily identified. An Adcock, loop, or other directional antenna may produce a big improvement in reception of the desired signal. Finally, WABC is owned by the Walt Disney company. Maybe you should expect Mickey Mouse performance. Best regards, Richard Harrison, KB5WZI |
AM Commercial radio reception
Richard,
Both you and Reg have given excellent answers and I thank you both. By the way, you mention directional patterns and nulls. Is there any place I can find polar graphs of commercial broadcast station's antenna patterns? Thanks, Dave P. ==================== "Richard Harrison" wrote in message ... Dave P. wrote: "Why is it that I can receive WCBS @ 880 kc fairly well at night but WABC @ 770 kc suffers from phase distortion like you wouldn`t believe?" I havn`t looked up the directional patterns of the two stations and don`t know your location. If you should happen to be at the edge of a null in the nighttime directional pattern of WABC, that would likely cause distorted fading. WABC may be clear-channel non-directional day and night for all I know. Not many of these remain in the U.S.A. now. At 175 miles from both transmitters, you suffer interference between the ground wave and sky wave from either transmitter at night, at least occasionally. You probably have solid daytime reception from both stations, but at night, the signal may be stronger, though variable. The sky wave is susceptable to variations in the reflecting layers of the ionosphere at night. These are a function of frequency, reflecting carrier and sidebands differently at times. This can produce overmodulation at times in the received signal. Another factor is likely other stations on the same or adjacent channels which may fade in and out and cause variation from your automatic volume control action even when the interfering stations can not be readily identified. An Adcock, loop, or other directional antenna may produce a big improvement in reception of the desired signal. Finally, WABC is owned by the Walt Disney company. Maybe you should expect Mickey Mouse performance. Best regards, Richard Harrison, KB5WZI |
AM Commercial radio reception
There are undoubtedly official sources from the FCC, etc.
The best hand-held guide I could recommend would be the National Radio Club's "Night Pattern Book," a fantastic resource for MW DXers and broadcast listeners. Basically it is a book of maps of North America for each domestic broadcast frequency, with dots representing transmitting locations, and the night time radiation pattern around each. It's available from the following link: http://www.nrcdxas.org/catalog/books/ The 5th edition is sold out, but the new 2005-06 edition is scheduled to be out soon. Brent Taylor VE1JH Dave Pitzer wrote: Richard, Both you and Reg have given excellent answers and I thank you both. By the way, you mention directional patterns and nulls. Is there any place I can find polar graphs of commercial broadcast station's antenna patterns? Thanks, Dave P. |
AM Commercial radio reception
There are undoubtedly official sources from the FCC, etc. The best hand-held guide I could recommend would be the National Radio Club's "Night Pattern Book," a fantastic resource for MW DXers and broadcast listeners. Basically it is a book of maps of North America for each domestic broadcast frequency, with dots representing transmitting locations, and the night time radiation pattern around each. It's available from the following link: http://www.nrcdxas.org/catalog/books/ The 5th edition is sold out, but the new 2005-06 edition is scheduled to be out soon. Brent Taylor VE1JH Dave Pitzer wrote: Richard, Both you and Reg have given excellent answers and I thank you both. By the way, you mention directional patterns and nulls. Is there any place I can find polar graphs of commercial broadcast station's antenna patterns? Thanks, ====================================== Dave, http://www.nrcdxas.org/catalog/books/ Sounds exactly what you are looking for but may take some time to obtain. In the meantime, the basic groundwave radiation patterns of mediumwave broadcast antennas are either simple circles with the antenna at their centres, or heart-shaped with the antenna at the null. The first occurs when the antenna is a single vertical mast located near the centre of a large populated area. The second occurs when the antenna consists of a pair of masts, which radiate a very broad heart-shaped beam, located on one side of the populated area to be covered. Contour Maps of actual measured field strengths are useful when the basic groundwave patterns are distorted by the terrain, e.g., the existence of mountains, forests, rivers, built-up areas, high-rise cities, or seas, lakes or coastal regions. Radio frequency Field Strengths are usually measured in terms of "millivolts per meter" or in decibels relative to one volt per meter. ---- Reg. |
AM Commercial radio reception
"Dave Pitzer" bravely wrote to "All" (05 Nov 05 02:54:31)
--- on the heady topic of "AM Commercial radio reception" DP From: "Dave Pitzer" DP Xref: core-easynews rec.radio.amateur.antenna:219693 DP Why is it that I can received WCBS @ 880kc fairly well at night but DP WABC @ 770kc suffers from phase distortion like you wouldn't believe! DP (I'm about 175 miles from both transmitters.) They are both 50 kwatt DP stations. And why is it that both WBZ (Boston), WBT (Charlotte, NC), DP WJR (Detroit) and WBBM (Chicago) come in better than either of the New DP York City stations? DP Dave P. Perhaps there are a few mountains inbetween you and NYC that cause fringing effects? A*s*i*m*o*v .... Strip-mining prevents forest fires. |
AM Commercial radio reception
Dave P. wrote:
"Is there any place I can find polar graphs of commercial broadcast stations?" I have an old book, "Map Book, 540 kc to 1600 kc" published by "Cleveland Insritute of Radio Electronics". In it, WABC is 50 KW non-directional day and night. It shares 770 kc with KOB Albuquerque, 50 KW day and 25 KW night. Also, KUOM Minneapolis and WCAL Nortjhfield are both 5 KW and share the frequency on some schedule between themselves. WNEW St. Louis is on the frequency daytimes only, as is KWA Seattle, 1 KW. XEHB in San Francisco de Oro, Mexico is a 500 watt daytimer on the frequency, as are XELM, 150 watts at Lagos de Morens and XEDI at Queretaro, 1 KW. There is also CMDC, 1 KW at night when it could trouble you in Holquin, Cuba. So, at night there is possible same-channel interderence from New Mexico and Cuba. On 760 kc, you have WJR in Detroit 50 KW non-directional at night and on 780 kc, you have WBBM in Chicago 50 KW nondirectional at night. These non-directional 50KW adjacent channel stations may exercise your AVC. On 880 kc, WCBS has no same-channel night rivals but WLS (World`s Largest Store, Sears in Chicago) on 890 kc, onetime home of "The National Barn Dance", could work your AVC. Also, WWL in New Orleans occupies 870 kc with 50 KW. Good preselection will rid you of adjacent channel interference. I lived in Portugal for years and listened to WCBS nightly. I would rock my tuning from 880 to 870 for WWL during fades for my version of frequency diversity. Both stations carried the same CBS programs. My antenna was a Beverage aimed at New York. The receiver was a Hammarlund SP-600 which had plenty of preselection to avoid adjacent channels. Ed Murrow came in very well. Best regards, Richard Harrison, KB5WZI |
AM Commercial radio reception
On 2005-11-05, Dave Pitzer wrote:
Why is it that I can received WCBS @ 880kc fairly well at night but WABC @ 770kc suffers from phase distortion like you wouldn't believe! (I'm about 175 miles from both transmitters.) They are both 50 kwatt stations. And why is it that both WBZ (Boston), WBT (Charlotte, NC), WJR (Detroit) and WBBM (Chicago) come in better than either of the New York City stations? Dave P. WBZ in Boston is a clear channel station. I don't think they have any pattern restrictions; they run 50kw 24/7. |
AM Commercial radio reception
Richard Harrison wrote:
very well. Best regards, Richard Harrison, KB5WZI Slight change of subject, WCCO 830 and a couple others I've noticed, now have a tremendous amount of digital sounding crap around them that completely obscures stations such as KOA. Is this the new digital radio wonder weapon that I'm supposed to love? tom K0TAR |
AM Commercial radio reception
snip
In the meantime, the basic groundwave radiation patterns of mediumwave broadcast antennas are either simple circles with the antenna at their centres, or heart-shaped with the antenna at the null. The first occurs when the antenna is a single vertical mast located near the centre of a large populated area. The second occurs when the antenna consists of a pair of masts, which radiate a very broad heart-shaped beam, located on one side of the populated area to be covered. snip ---- Reg. Reg: I'm afraid you're way behind the practice on this one. In the US, there are many 4, 5 and 6 tower arrays providing as many nulls to protect co-channel stations. The UK got off easy with nationalized broadcasting, where the frequency and location was dictated by the government, and none of that nasty capitalism interfered. Here, the commercial interests are still fighting it out. Check and see if the KLIF website shows their pattern from a linear array of 5 towers just outside Dallas. -- Crazy George W5VPQ My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap. |
AM Commercial radio reception
"Tom Ring" wrote in message .. . Richard Harrison wrote: very well. Best regards, Richard Harrison, KB5WZI Slight change of subject, WCCO 830 and a couple others I've noticed, now have a tremendous amount of digital sounding crap around them that completely obscures stations such as KOA. Is this the new digital radio wonder weapon that I'm supposed to love? tom K0TAR You bet!!!! -- Crazy George W5VPQ My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap. |
AM Commercial radio reception
Thanks to you all for your excellent information
DP "Dave Pitzer" wrote in message ... Why is it that I can received WCBS @ 880kc fairly well at night but WABC @ 770kc suffers from phase distortion like you wouldn't believe! (I'm about 175 miles from both transmitters.) They are both 50 kwatt stations. And why is it that both WBZ (Boston), WBT (Charlotte, NC), WJR (Detroit) and WBBM (Chicago) come in better than either of the New York City stations? Dave P. |
AM Commercial radio reception
"Crazy George" wrote I'm afraid you're way behind the practice on this one. In the US, there are many 4, 5 and 6 tower arrays providing as many nulls to protect co-channel stations. ================================= What proportion of US MF broadcasting stations have antennas consisting of more than two towers ? ---- Reg. |
AM Commercial radio reception
Reg, G4FGQ wrote:
"What proportions of U.S. broadcasting stations have antennas consisting of more than two towers?" I don`t know but from my own experience, the number is large. A new applicant for a station must show he will not interfere with existing stations by limiting his radiation in the directions of the existing stations while providing minimum field intensity, 0.5 to 50 mV, depending on population, in the new service area. A two-tower array cannot satisfy some complicated pattern requirements. Most broadcasters want to provide more than 1 KW radiation in their areas. Well over one hundred channels in the medium wave broadcast band in North America allow that. There are well over 1000 regional medium wave broadcasters in North America. It is difficult to fit a new broadcaster in when he wants to use real power. Best regards, Richard Harrison, KB5WZI |
AM Commercial radio reception
Richard Harrison wrote:
I don`t know but from my own experience, the number is large. I would guess that the majority of US AM antennas that I have seen with my own eyes have more than one element. -- 73, Cecil http://www.qsl.net/w5dxp |
AM Commercial radio reception
"Dave Pitzer" wrote
... Is there any place I can find polar graphs of commercial broadcast station's antenna patterns? ___________________ Dave, Here http://www.radio-locator.com/ is a link to a website with calculated coverage areas/contours for US AM broadcast stations. The contours are based on their licensed radiation patterns (directional or not), AND ground conductivities for the geographic regions concerned. The polar radiation patterns of these stations most probably don't look much like these plots, because of the heavy influence that ground conductivity has on received field strength along the various azimuth bearings. Even the real coverage contours of AM broadcast stations using omni antennas usually are anything but omni, due to the effects of varying ground conductivities around their various azimuth sectors and ranges. Have fun. RF |
AM Commercial radio reception
Reg:
I don't have an accurate number for the entire country, but here in the local area, there is one clear channel station with a single radiator, a half dozen two tower arrays, two 3 tower arrays, five 4 tower arrays that I can recall off the top of my head. If you had asked a dozen years ago, I could have been more accurate. I don't think we have any 5 or 6 radiator arrays here locally, if so, I don't remember them. If my math is correct, that is a 50-50 split, so maybe half have more than 2 towers. -- Crazy George W5VPQ My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap. "Reg Edwards" wrote in message ... "Crazy George" wrote I'm afraid you're way behind the practice on this one. In the US, there are many 4, 5 and 6 tower arrays providing as many nulls to protect co-channel stations. ================================= What proportion of US MF broadcasting stations have antennas consisting of more than two towers ? ---- Reg. |
AM Commercial radio reception
"Crazy George" wrote I don't have an accurate number for the entire country, but here in the local area, there is one clear channel station with a single radiator, a half dozen two tower arrays, two 3 tower arrays, five 4 tower arrays that I can recall off the top of my head. If you had asked a dozen years ago, I could have been more accurate. I don't think we have any 5 or 6 radiator arrays here locally, if so, I don't remember them. If my math is correct, that is a 50-50 split, so maybe half have more than 2 towers. ======================================= Thanks George, I am amazed at the number of multi-tower MF antennas in the US. As you say, they are necessary to prevent co-channel interference, day and night, between a large number of broadcasters in the more densely populated regions of your vast country. ( Antenna salesmen have had a field day.) It is also interesting that the whole system is technically regulated by State and/or Central Government. It is not just a free-for-all for newcomers. I imagine the revenue comes solely from advertisers. Which makes me wonder what percentage of program time is allocated to adverts. Are such matters also regulated? Are any broadcast stations State or City owned? In this (UK) relatively densely populated country things settled down about 20 years ago. Few MF antennas have more than one tower (or masts as we call them). Although there is much broadcasting at MF for individual cities, most broadcasting takes place at FM VHF where 'capture effects' reduce interference from co-channel transmitters. It may be of interest that the BBC, still the World's finest broadcasting system, including its overseas services, no longer owns any transmitting stations, Mrs Thatcher quietly sold them off to a private party. Do some Googles for who the eventual owners are? ---- Reg. |
AM Commercial radio reception
Reg Edwards wrote:
SNIPPED I imagine the revenue comes solely from advertisers. Which makes me wonder what percentage of program time is allocated to adverts. Are such matters also regulated? Are any broadcast stations State or City owned? $$$ from advertisers ... YEP! Amount of advertising time is regulated. I can't state with any authority, but it seems to be 15 to 20 minutes per hour. Ownership is generally private. International propaganda, err news, may be indirectly government controlled through a straw man corporation. Certain public service stations, e.g. WWV, are government 'owned'. An several additional non sequitor comments. In the USA, although we claim FREE ENTERPRISE, it is a government influenced economy via interest rates, international treaties, anti-trust regulations, etc. Finally, the USA is succumbing to a creeping Socialism. This is contrary to the words of John F Kennedy: "Ask NOT what your country can do for you; ask what you can do for your country." Forty-five years after that statement from President Kennedy a large portion of the population want the government to do everything for them. A Keag In this (UK) relatively densely populated country things settled down about 20 years ago. Few MF antennas have more than one tower (or masts as we call them). Although there is much broadcasting at MF for individual cities, most broadcasting takes place at FM VHF where 'capture effects' reduce interference from co-channel transmitters. It may be of interest that the BBC, still the World's finest broadcasting system, including its overseas services, no longer owns any transmitting stations, Mrs Thatcher quietly sold them off to a private party. Do some Googles for who the eventual owners are? ---- Reg. |
AM Commercial radio reception
Amos Keag wrote:
Finally, the USA is succumbing to a creeping Socialism. This is contrary to the words of John F Kennedy: "Ask NOT what your country can do for you; ask what you can do for your country." Methinks you completely missed Kennedy's meaning. Here's Ayn Rand's take on that statement: "Ask NOT what your country can do for you ...", translation: Stop expecting the federal government to preserve and protect your individual constitutional rights; "... ask what you can do for your country.", translation: give up your constitutional rights, including your life, liberty, and possessions, in order to benefit the welfare state. -- 73, Cecil http://www.qsl.net/w5dxp |
AM Commercial radio reception
Reg, G4FGQ wrote:
"It is also interesting that the whole system is technically regulated by State and/or Central Government." In the beginning, there was no regulation. There were only wireless experimenters. Marconi invented the antenna which made the signal go far. Marconi`s antenna may have been seen as an elevated capactor plate. When the transmitter and receiver were each equipped with a plate, you had a coupling capacitor with the earth for a return path. The capacitor carries displacement current while the earth moves electrons.. Then, Marconi discovered the capacitor leads worked well enough without the plates, so plates were omitted. Marconi was soon using wireless for ship to shore communications. It was essential to safety of life at sea. When the Titanic sank on April 15, 1912, it had a Marconi operator aboard. The world was immediately aware of radio. Inept radio communications during the loss of the Titanic prompted the U.S. Congress to pass the Radio Act of 1912, which expanded on the Wireless Ship Act of 1910 which required all seafaring vessels to maintain 24-hour radio watch and keep contact with nearby ships and coastal radio stations. All radio communications were in code until Reginald Fessenden invented wireless telephony in 1906. In the early wireless days a lidtener had to understand code to make sense of wireless. The Radio Act of 1912 assigned three-letter and four-letter codes (call-letters) to radio stations and limited broadcasting to 340 meters. This jammed the signals. From the beginning, the U.S. Federal Government declared sole jurisdiction over radio as the waves don`t stop at state lines and must involve international cooperation. It`s the "Interstate Commerce Regulation Power" of the Federal Government. In 1920, KDKA in Pittsburgh, a Westinghouse station, transmitted the first commercial radio broadcast. In 1922, the U.S. Commerce Department allowed powerful stations to use 400 meters, as long as they only broadcast music. In 1925, A,C. Nielsen began reporting audience shares to advertisers, In 1925, the first soap opera (The Smith Family) was broadcast. In 1926, RCA, General Electric, and Westinghouse established The National Broadcasting Company (NBC). NBC operated two networks of stations (Red & Blue). In 1929, William S. Paley founded The Columbia Broadcasting System (CBS). In 1931, there were 40,000 U.S. TV sets, including 4,000 in New York City. In 1933, Edwin Armstrong introduced Frequency Modulation. The Communications Act of 1934 created the Federal Communicationsd Commission which regulates broadcasting. In 1936, The British Broadcasting Corporation (BBC) debuted the world`s first television service with three hours of programming a day. In 1937, Edgar Bergen and Charlie MCCarthy debuted on NBC TV. We live in interesting times. Advertising pays for broadcasting in the U.S. except for some public support of non-commercial or almost non-commercial stations. Program time devoted to advertising on commercial stations was limited by the FCC to just a few minutes per hour before Carter became president. He started the deregulation process which has now run amok. Commercial announcements were the topic of "Saturday Night Live". Satirically, they entertain. Mrs. Thatcher may have sold the BBC`s distribution facilities, but since BBC has done so well programming, I hope the production facilities are still in the hands of those responsible and that they continue and grow their product. Who bought the BBC`s transmitters depends on how big the bargains were. If a windfall was readily available, I suspect the Queen, her relatives and allies may have been the buyers. Like Russia, I suppose, except with more care that the buyers seem not to be profiteers. My daughter lives in London and pays her tax to support the BBC. She now owns a 99-year lease on her flat in Westminster. Only leases are available. The right people are the ownwers and they aren`t selling. Her married name is Edwards too, but her husband is an American. They are both lawyers. Best regards, Richard harrison, KB5WZI |
AM Commercial radio reception
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AM Commercial radio reception
Cecil Moore wrote:
Amos Keag wrote: Finally, the USA is succumbing to a creeping Socialism. This is contrary to the words of John F Kennedy: "Ask NOT what your country can do for you; ask what you can do for your country." Methinks you completely missed Kennedy's meaning. Here's Ayn Rand's take on that statement: "Ask NOT what your country can do for you ...", translation: Stop expecting the federal government to preserve and protect your individual constitutional rights; "... ask what you can do for your country.", translation: give up your constitutional rights, including your life, liberty, and possessions, in order to benefit the welfare state. YEP!!! Socialism. |
AM Commercial radio reception
Richard Clark, KB7QHC wrote:
"---by A. Frederick Collins inventor of the Wireless Telephone, 1899." Collins apparently connected an arc lamp to an arial and ground, using a microphone transmitter to modulate the oscillations it set up. I suppose a carbon button in series with the d-c to the arc would do that. Success has many authors. The airplane had many builders around this productive era, but it is the Wright brothers that are credited with the first practical success. Fessenden was a Canadian who happened to be Chief Engineer of the Radio Corporation of America, successor to the American Marconi Company. Fessenden holds more patents than aqnyone except Thomas Edison, who once employed Fessenden. Fessenden`s modulation method was control of the excitation of an r-f alternator by a magnetic amplifier which he modulated with audio, speech, music or whatever, even dots and dashes. Modulation of high r-f powers was commonplace. Hundreds of kilowatts were produced and modulated by the Fessenden method. A relic of the era in Sweeden is still revived annually for demonstration, I believe. Best regards, Richard Harrison, KB5WZI |
AM Commercial radio reception
"Richard Fry" wrote in message
... "Dave Pitzer" wrote ... Is there any place I can find polar graphs of commercial broadcast station's antenna patterns? ___________________ Dave, Here http://www.radio-locator.com/ is a link to a website with calculated coverage areas/contours for US AM broadcast stations. The contours are based on their licensed radiation patterns (directional or not), AND ground conductivities for the geographic regions concerned. The polar radiation patterns of these stations most probably don't look much like these plots, because of the heavy influence that ground conductivity has on received field strength along the various azimuth bearings. Even the real coverage contours of AM broadcast stations using omni antennas usually are anything but omni, due to the effects of varying ground conductivities around their various azimuth sectors and ranges. Have fun. Just a FYI...the contour maps at Radio-Locator.com are WRONG....the LOCAL on FM maps is actually the distant or Service Contour (1mv or 60dbu level)..LOCAL is defined as City Grade or 70dbu or 3.16mV level...which they do not show..On AM, they show lower levels on the map as well...If you want to really know what the signal level should be, draw another circle or line inside the LOCAL one they show...about the same distance between the LOCAL and Distant they show...Your line drawn will be local, their local becomes Distant and their Distant becomes Finge... Their Fringe is now DX :) Chris WB5ITT |
AM Commercial radio reception
"CWB" wrote:
Just a FYI...the contour maps at Radio-Locator.com are WRONG ....the LOCAL on FM maps is actually the distant or Service Contour (1mv or 60dbu level)..LOCAL is defined as City Grade or 70dbu or 3.16mV level...which they do not show..On AM, they show lower levels on the map as well. _____________ Their maps DO correctly show the distances to the contours for the field strengths they identify. Radio-Locator picked different field strength values for the "local" etc contours than those used by the FCC, but that doesn't invalidate the Radio-Locator maps. And their choices are reasonable. For example on AM, a 2.5 mV/m signal (Radio-Locator's local contour) does provide good service to a typical cheap table radio inside a home in an urban setting. |
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