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AM BCB reception
I live approx 80 miles from the xmitter of station WABC (New York) 50,000
watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM. The stations night-time signal is directional but I live in the direction of the major lobe. The station advertises covering 27 eastern US states at night -- which I don't doubt. I can receive a Boston station (WBZ, 50k watts) and a Charlotte, NC station (WBT, 50k watts)at night loud and clear. Both of these hundreds of miles from me. (Also get WJR in Detroit and WLS in Chicago loud & clear.) I seem to be in a "shadow" for the relatively close WABC. I'm using a high quality (Sangean) table radio with a built-in ferrite loop antenn. Any suggestions for improving my WABC night time reception?? Dave Pitzer ======================================= |
"Dave Pitzer" wrote in message ... I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM. The stations night-time signal is directional but I live in the direction of the major lobe. The station advertises covering 27 eastern US states at night -- which I don't doubt. I can receive a Boston station (WBZ, 50k watts) and a Charlotte, NC station (WBT, 50k watts)at night loud and clear. Both of these hundreds of miles from me. (Also get WJR in Detroit and WLS in Chicago loud & clear.) I seem to be in a "shadow" for the relatively close WABC. I'm using a high quality (Sangean) table radio with a built-in ferrite loop antenn. Any suggestions for improving my WABC night time reception?? Dave Pitzer ======================================= Dave I'm curious about a similar situation. in California. Are you able to receive the stations equally well, or poorly, with the radio oin a car at this location? Jerry |
Don't they reduce power at night fall to prevent interference with other
stations Art "Dave Pitzer" wrote in message ... I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM. The stations night-time signal is directional but I live in the direction of the major lobe. The station advertises covering 27 eastern US states at night -- which I don't doubt. I can receive a Boston station (WBZ, 50k watts) and a Charlotte, NC station (WBT, 50k watts)at night loud and clear. Both of these hundreds of miles from me. (Also get WJR in Detroit and WLS in Chicago loud & clear.) I seem to be in a "shadow" for the relatively close WABC. I'm using a high quality (Sangean) table radio with a built-in ferrite loop antenn. Any suggestions for improving my WABC night time reception?? Dave Pitzer ======================================= |
Not these stations. They are so-called "clear channel" stations.
DP ============ " wrote in message news:%pfTc.147043$eM2.107369@attbi_s51... Don't they reduce power at night fall to prevent interference with other stations Art "Dave Pitzer" wrote in message ... I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM. The stations night-time signal is directional but I live in the direction of the major lobe. The station advertises covering 27 eastern US states at night -- which I don't doubt. I can receive a Boston station (WBZ, 50k watts) and a Charlotte, NC station (WBT, 50k watts)at night loud and clear. Both of these hundreds of miles from me. (Also get WJR in Detroit and WLS in Chicago loud & clear.) I seem to be in a "shadow" for the relatively close WABC. I'm using a high quality (Sangean) table radio with a built-in ferrite loop antenn. Any suggestions for improving my WABC night time reception?? Dave Pitzer ======================================= |
On Sat, 14 Aug 2004 03:11:55 GMT, "
wrote: Don't they reduce power at night fall to prevent interference with other stations Art Hi Art, Historically, three letter calls in the AM band were designated as "clear channel" stations and are generally always lit up at full power. "Clear channel" was meant to serve a vast region out of major metropolitan centers. KVI is one here in Seattle, KGO in San Francisco, WGN & WLS in Chicago, KOA in Denver, KFI & KNX in Los Angeles, WSM in Nashville, WWL in New Orleans, WBZ in Boston, WHO in Des Moines, KYW in Philadelphia (strange listing) and so on. Almost across the board all transmit 24/7 at 50KW with omnidirectional antennas. Not all three letter calls are clear channel, what with the change of time and market and financial backing. 73's Richard Clark, KB7QHC |
"Bill Turner" wrote in message ... On Fri, 13 Aug 2004 22:27:48 GMT, "Dave Pitzer" wrote: I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM. The stations night-time signal is directional but I live in the direction of the major lobe. The station advertises covering 27 eastern US states at night -- which I don't doubt. I can receive a Boston station (WBZ, 50k watts) and a Charlotte, NC station (WBT, 50k watts)at night loud and clear. Both of these hundreds of miles from me. (Also get WJR in Detroit and WLS in Chicago loud & clear.) I seem to be in a "shadow" for the relatively close WABC. I'm using a high quality (Sangean) table radio with a built-in ferrite loop antenn. Any suggestions for improving my WABC night time reception?? Dave Pitzer ======================================= __________________________________________________ _______ I have the same situation here in California. I'm about 100 miles from KFI, another 50 kW station, and during the day reception is a bit weak, but adequate. Come sundown however, reception begins fading and is very distorted. The reason is that the groundwave portion of the signal is still present, but is now being interfered with by the skywave portion, which is not present during the day. If I were to move farther away, out of groundwave reception, the signal would become much clearer, but only at night. During daytime it would not be heard at all. It doesn't matter whether I'm using a home or car radio, the effect is the same. At night, the clearest stations here are from the San Francisco area about 400 miles away, but they are inaudible during the day One help (which I do use at home) is to listen using an SSB receiver. The internal BFO in the receiver inserts the sometimes-missing carrier and improves things a lot, but still not perfect. There are some high-end shortwave radios available which can be set to work this way and the improvement is considerable. Outside of that, using only a radio, not much can be done unless you want to try diversity reception using automatically switched antennas. At BCB frequencies this takes lots of real estate since the antennas have to be separated quite a bit to be effective. If you want to skip the radio completely (at home) and you have high speed internet access, many radio stations have streaming audio available. I suppose in time this will be available in cars too. -- Bill, W6WRT QSLs via LoTW This would account for the strange undulating "out of phase" sound -- with the ground and sky waves canceling and reinforcing in a random manner. Seems to me that there is not much use having 50k watts if the signal in the station's market area is virtually unlistenable. Then again, most of the commercials at night are "national", not "local". DP ================ |
"Jerry Martes" wrote in message ... "Dave Pitzer" wrote in message ... I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM. The stations night-time signal is directional but I live in the direction of the major lobe. The station advertises covering 27 eastern US states at night -- which I don't doubt. I can receive a Boston station (WBZ, 50k watts) and a Charlotte, NC station (WBT, 50k watts)at night loud and clear. Both of these hundreds of miles from me. (Also get WJR in Detroit and WLS in Chicago loud & clear.) I seem to be in a "shadow" for the relatively close WABC. I'm using a high quality (Sangean) table radio with a built-in ferrite loop antenn. Any suggestions for improving my WABC night time reception?? Dave Pitzer ======================================= Dave I'm curious about a similar situation. in California. Are you able to receive the stations equally well, or poorly, with the radio oin a car at this location? Jerry Hmmmmm.... haven't tried that. The use of a non-directional "whip" (car) antenna might actually help to seriously attenuate the ground wave yet "grab" the sky wave. AM BCB DXing in a car/truck at night is a popular hobby I understand. DP ============== DP ========= |
"Bill Turner" wrote
I have the same situation here in California. I'm about 100 miles from KFI, another 50 kW station, and during the day reception is a bit weak, but adequate. Come sundown however, reception begins fading and is distorted. The reason is that the groundwave portion of the signal is still present, but is now being interfered with by the skywave portion, which is not present during the day. If I were to move farther away, out of groundwave reception, the signal would become much clearer, but only at night. During daytime it would not be heard at all. ______________ Various types of "anti-fade" radiators are used by many of the 50kW stations to try to minimize this effect. There is a tradeoff in the electrical height of the usual AM broadcast transmit antenna between producing the greatest groundwave and generating an excessive high angle skywave that can interfere with that groundwave at night. A 225 degree vertical is about optimum for groundwave, but has a high angle lobe that can cause this type of interference problem. A 195 degree vertical has less groundwave but little/no high angle lobe, and so is used by many full time 50kW stations. WJR, Detroit is an example of a station using a 195 degree vertical (700 foot guyed tower). Other antenna types also have been used for this, such as the "Franklin," which is a sectionalized antenna with one vertical radiator above another, each driven separately. Note also that the carrier frequency of the station, the conductivity along the groundwave path, and skywave propagation conditions will have an affect on the location of this zone, and the extent of interference there. R. Fry (WJR staff engineer, mid 1960s) |
Bill Have you seen the homes they built at the base of KNX's tower? It makes me wonder about how much tolerance we have to radiation. Jerry "Bill Turner" wrote in message ... On Sat, 14 Aug 2004 03:11:55 GMT, " wrote: Don't they reduce power at night fall to prevent interference with other stations __________________________________________________ _______ KFI runs 50 kW, 24/7. I went on a tour of the site last year and if I recall correctly, the only time they reduce power is during tours when the tour group is at the base of the antenna, or when maintenance is being done on the main antenna and they have to switch to the secondary antenna. A fascinating tour, by the way. Take it if you ever have the chance. -- Bill, W6WRT QSLs via LoTW |
"Richard Fry" wrote in message ... "Bill Turner" wrote I have the same situation here in California. I'm about 100 miles from KFI, another 50 kW station, and during the day reception is a bit weak, but adequate. Come sundown however, reception begins fading and is distorted. The reason is that the groundwave portion of the signal is still present, but is now being interfered with by the skywave portion, which is not present during the day. If I were to move farther away, out of groundwave reception, the signal would become much clearer, but only at night. During daytime it would not be heard at all. ______________ Various types of "anti-fade" radiators are used by many of the 50kW stations to try to minimize this effect. There is a tradeoff in the electrical height of the usual AM broadcast transmit antenna between producing the greatest groundwave and generating an excessive high angle skywave that can interfere with that groundwave at night. A 225 degree vertical is about optimum for groundwave, but has a high angle lobe that can cause this type of interference problem. A 195 degree vertical has less groundwave but little/no high angle lobe, and so is used by many full time 50kW stations. WJR, Detroit is an example of a station using a 195 degree vertical (700 foot guyed tower). Other antenna types also have been used for this, such as the "Franklin," which is a sectionalized antenna with one vertical radiator above another, each driven separately. Note also that the carrier frequency of the station, the conductivity along the groundwave path, and skywave propagation conditions will have an affect on the location of this zone, and the extent of interference there. R. Fry (WJR staff engineer, mid 1960s) Richard, Thanks for the response and the "inside", technical information about Broadcast-band-AM stations. I'm happy to say that here in eastern Pennsylvania, WJR has a beautiful night-time signal. About the only thing that disturbs it is "local" weather-based QRM --- i.e. Mother Nature!!!. I even recall listening to WJR in my college days in Charleston, SC in the early 1960's (along with WLS in Chicage and WOR in NYC). Without knowing, I would guess that WABC (770 KHz) has a rather high angle skywave since its ground- and skywave seem in a constant "tug-of-war" at night --- at least ~80 miles to the northwest of the xmitter. Thanks, Dave Pitzer ============================ |
"Richard Fry" schreef in bericht ... Various types of "anti-fade" radiators are used by many of the 50kW stations to try to minimize this effect. There is a tradeoff in the electrical height of the usual AM broadcast transmit antenna between producing the greatest groundwave and generating an excessive high angle skywave that can interfere with that groundwave at night. A 225 degree vertical is about optimum for groundwave, but has a high angle lobe that can cause this type of interference problem. A 195 degree vertical has less groundwave but little/no high angle lobe, and so is used by many full time 50kW stations. WJR, Detroit is an example of a station using a 195 degree vertical (700 foot guyed tower). Other antenna types also have been used for this, such as the "Franklin," which is a sectionalized antenna with one vertical radiator above another, each driven separately. Have a look at this: http://www.waniewski.de/id35.htm The text is in German, but the diagrams and photos show an aerial system with its feed at 90 meters above ground level, to reduce skywave. You can click through several pages at the top (1-15). gr, hwh |
"hwh" schreef in bericht ... Have a look at this: http://www.waniewski.de/id35.htm The text is in German, except when you find the small flag and choose English :-) gr, hwh |
"Richard Fry" wrote in message ... .................................................. ........................... ............................................. Note also that the carrier frequency of the station, the conductivity along the groundwave path, and skywave propagation conditions will have an affect on the location of this zone, and the extent of interference there. R. Fry (WJR staff engineer, mid 1960s) Richard, I think he is just too close for night time sky wave, and too far for ground wave. When I lived in western Ohio, I had no trouble picking up WABC with the built in loopstick. I have also picked up WABC in Bermuda and Florida. So, I don't doubt the 27 states coverage statement. I noiced I had trouble getting NY AM stations on the car radio in eastern PA. BTW, You mentioned WJR. I can pick that up here in NJ, even though it is only 10 KHz from WABC, which is about 25 miles from me. All it takes is a receiver with *very* good selectivity. This is where the BC DX people bark up the wrong tree when they want more antenna gain. WLW (700) became problematic after WOR (710) went digital AM. They now broadcast hash at least +/- 20 KHz from the carrier. Tam/WB2TT |
"Tam/WB2TT" wrote re WABC night time reception in PA:
Richard, I think he is just too close for night time sky wave, and too far for ground wave. _________________ Quoting the original post, "I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM." WABC radiates the same power from the same radiator 24 hours a day, and provides good daytime reception at this receive location, so it is not too far for the groundwave. The ground wave is more or less constant day and night, so it is likely that the poor/unlistenable signal there at night must be the result of interference to the groundwave from whatever high-angle skywave WABC produces, plus the higher co- and adjacent-channel interference usually present at night. RF |
"Richard Fry" wrote in message ... "Tam/WB2TT" wrote re WABC night time reception in PA: Richard, I think he is just too close for night time sky wave, and too far for ground wave. _________________ Quoting the original post, "I live approx 80 miles from the xmitter of station WABC (New York) 50,000 watts. During the day my reception is good-to-very good. After sunset however, the signal is poor to unlistenable -- due to fading and man-made QRM." WABC radiates the same power from the same radiator 24 hours a day, and provides good daytime reception at this receive location, so it is not too far for the groundwave. The ground wave is more or less constant day and night, so it is likely that the poor/unlistenable signal there at night must be the result of interference to the groundwave from whatever high-angle skywave WABC produces, plus the higher co- and adjacent-channel interference usually present at night. RF Isn't there a zone where you tend to get cancellation between groundwave and skywave? Tam |
"Tam/WB2TT" wrote
Isn't there a zone where you tend to get cancellation between groundwave and skywave? ______________ Yes, that is what I have been writing in my posts on this subject line. The RF phase of the skywave varies independently from the ground wave. Some times it reinforces the ground wave; some times reduces it. Further, both reinforcement and reduction can occur at the same time for different RF frequencies across the AM channel, leading to a selective combing effect in the program audio, and/or near loss of the carrier while most of the sidebands are still present. Of course, that produces very high distortion in an envelope detector. AM receivers using synchronous detectors reduce this problem. Most full time 50kW AM broadcast stations use an antenna system with relatively low radiation at elevation angles above about 45 degrees in order to reduce (but not eliminate) night time interference to their own groundwave. I made up a simple graphic comparing the elevation patterns of vertical antennas used in AM broadcast for four different electrical heights: 90, 180, 195, and 225 degrees. The difference in their high-angle radiation is apparent. Please email me if you would like a copy. RF Visit http://rfry.org for FM broadcast RF system papers. |
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