How far do your local AM's go during the day?

[davideduardo]

How old is that [Neilsen study]? When it mentions "prior to..." a network affiliation change, I suspect it is relatively ancient.

That does not change its validity for whatever time period it measured, relative to the competing, daytime AM signals of that same time period.

Since I can see WJR as a CBS station back to 1938, and Nielsen began in the early 30's I can only assume that the data is about 70-some years old.

That far back in time a 0.5 mV/m signal might have been listenable in the areas shown on the map you posted. Most receivers were fairly robust at the time, particularly those sold in rural zones. And we did not have computers, CFLs, dimmers and a wealth of other interference producing devices; we did have an FCC that enforced interference rules and power companies that would act on complaints of line noise.

While the contours may or may not have moved over time, the ability to listen to stations on the AM band has been shrinking constantly and incrementally over the last 50 years. As a consequence, the useful coverage area of a station has shrunken to the point that many stations that afforded relatively complete coverage of their markets in the 50's now may cover, in usable fashion, less than half of the market.

 

[davideduardo]

You say that the signal of WLS has deteriorated over time. However I have had many in person and e-mail contacts with their chief engineer over the last 20+ years, and can report from that that their measured, present-day groundwave field at 1 km is very close to its inverse distance value for the efficiency of their radiator and their applied power -- despite anecdotal/undocumented comments to the contrary.

What is their field strength at the periphery of the market, or in finge areas in adjacent markets?

Non Directional former Class 1 A stations probably have no early readings to compare with toady's readings because they were not required and even if done, they likely don't survive.

 

[jd]

Since I can see WJR as a CBS station back to 1938, and Nielsen began in the early 30's I can only assume that the data is about 70-some years old.

This history of WJR shows that they switched from NBC to CBS in 1935 and continued with it until 1959, resuming with a "pick and choose" arrangement in 1962 which lasted until 1976 when they returned to NBC: www.michiguide.com/dials/rad-j/wjr.html

 

[davideduardo]

This history of WJR shows that they switched from NBC to CBS in 1935 and continued with it until 1959..

So the WJR daytime listener map, predating that change, would have been created in 1934 in all probability.

That was about a year before GE decided to proceed with full scale commercialization of the fluorescent lamp and many, many years before dimmers and other RF interference devices became widely available.

It was also well before there were any other stations in much of the state to listen to as alternatives to WJR.

Grand Rapids had two high-band 500 watters. Lansing had a 100 watter. Bay City had a 500 watt station and Jackson a 100 watt one. Battle Creek was blessed with a 50 watt station, Flint had 100 watts... all of these, too, on the high end of the dial. Muskegon was 100 watts at 1500. North of a line from Grand Rapids to Bay City, there were no stations until you got to the UP. The only decent facility outside of Detroit was 1 kw WKZO on 590, in fact.

And there were only 15 stations outside of Detroit in the whole state, 3 of them in the UP. So it's no coincidence that folks would listen to WJR... they had no choice.

 

[radioman148]

You say that the signal of WLS has deteriorated over time. However I have had many in person and e-mail contacts with their chief engineer over the last 20+ years, and can report from that that their measured, present-day groundwave field at 1 km is very close to its inverse distance value for the efficiency of their radiator and their applied power -- despite anecdotal/undocumented comments to the contrary.

What is their field strength at the periphery of the market, or in finge areas in adjacent markets?

Non Directional former Class 1 A stations probably have no early readings to compare with toady's readings because they were not required and even if done, they likely don't survive.

I realize this is totally non scientific, but I live 40 miles from the WLS tower & their signal during the day is not as strong as it was 20 or 30 years ago. Also, if you're driving in the Milwaukee area WLS has the noisiest signal of all the 50KW Chicago stations except WYLL.

 

[Schroedingers Cat]

Actually, quite a few of the Class A/Class I stations did contour measurements, both groundwave and skywave. I believe WJR did a skywave study when KGU tried to upgrade or go fulltime. Some results are shown in the pages of broadcasting publications shown on your site as I recall, David. The fact that there is a patch of 15 mS/m shown on M-3 between the WLS tower and St. Louis shaped something like a bowling pin is a good indication that they did measured contours. They were done for promotional purposes, and probably also for advertising brochures for proving their signal in certain cities, and to comply with network affiliation and exclusivity rules, as I recall. WBCM probably had a better signal on 1410 than you would expect with 500 watts, and WKZO with 1000 watts on 590 a worse signal due to the conducitivity. WKZO was a daytime only station at that time as I recall. WKAR (5000 watts) was always noncommercial, but probably would have had a better signal with even 1000 watts on 850 as WKZO would have on 590 due to conductivity.

Art Vuolo's first WJR Michigan Radioguide in 1975 has an adaptation of the WJR Map that R. Fry linked.

Another thing to recall is that the FCC changed the conductivity map sometime in the 1950s, but hasn't since. An old NAB Engineering Handbook (1948 was the one I saw) showed the old map.

I think the engineer at WJR did a measured map in the 1960s. He was ready to retire about 1990, so probably would not have been there before 1950 at the earliest.

 

[Schroedingers Cat]

Art Vuolo's first WJR Michigan Radioguide in 1975 had an adaptation of the map linked by R. Fry. It just showed the 0.5 mV/m though.

 

[davideduardo]

WBCM probably had a better signal on 1410 than you would expect with 500 watts, and WKZO with 1000 watts on 590 a worse signal due to the conducitivity.

I believe that WBCM was on a hotel rooftop; not sure if it was a tower with counterpoise (in part because I can't determine when the first such system was built) or a "T" but in either case, not efficient. I believe 590 was also a T, but held up by big towers with a nice vertical component.

WKZO was a daytime only station at that time as I recall.

It was, but since we're looking at all of these vs. the WJR survey, I thought it was likely the better covering station outside of Detroit.

WKAR (5000 watts) was always noncommercial, but probably would have had a better signal with even 1000 watts on 850 as WKZO would have on 590 due to conductivity.

WKAR was a limited-time station (less than daytimers, even) on 1040 with 1 kw at that time. I have no idea what kind of radiator it had.

Another thing to recall is that the FCC changed the conductivity map sometime in the 1950s, but hasn't since. An old NAB Engineering Handbook (1948 was the one I saw) showed the old map.

If AM were of more importance and value today, we'd likely see many more conductivity studies that invalidate the FCC maps or modify them in more limited areas. I know of several stations in LA that have done them to show lower conductivity, and at least one in the desert to the east showing depletion of the water table had altered conductivity to the point that it resembles that of glass. I suspect there is a lot more of this sort of change or variance than anyone knows about... but who is going to spend money on an AM today?

I think the engineer at WJR did a measured map in the 1960s. He was ready to retire about 1990, so probably would not have been there before 1950 at the earliest.

I know there were a lot of skywave studies, but am not aware of any surviving daytime coverage measurements. As you said, the object was likely sales, and it's been decades since I saw a "real" coverage map in a sales kit. That's why my suspicion is that none of that stuff survived to be compared with any measurement that might be made today.

 

[K4WRF]

I know for a fact that most (if not all) of the Clear Channel Broadcast Service (CCBS) affiliated stations consisting of Class A licenses conducted ongoing, rather extensive and detailed field surveys of both day-time and night-time signals. This included WSM, WSB, WLW, WHO, WGN, WJR, WBAP, KSL, KFI, WCCO, WWL and WHAS. In the basement at WSM there are reams of paper reports and studies concerning coverage and measured soil conductivity across a wide area as well as near field measurements in rows of file cabinets in the basement. The most recent study was conducted as late as 1998. At one time, these operators were mostly very proud of and concerned about their respective signals. Many, many measurements were conducted and analyzed in support of FCC filings concerning the Super Power initiative that went on for decades. WHO,WCAU, WLW and WSM conducted distant field measurements to quantify the high take-off angle lobes that were prevalent with the wide-face over 200 degree Blaw-Knox antennas and caused near fade-wall cancellations. These measurements resulted in reductions in height to minimize signal cancellation in the regional coverage areas. Today, the main problems with AM signals are, 1) Part 15 noise issues with many devices from computers, power distribution lines to lighting products. 2) Poor receiver sensitivity, selectivity and phase noise. 3) AM band crowding. Listeners fleeing to other stable medium is another topic.

 

[Schroedingers Cat]

The FCC and a lot of station engineering files do have directional proof of performance files, and many applications for changes by them and other stations are also part of these files. I have seen a couple of files, but not recently. A proof of performance map from 1952 was copied for me in 1971, and a copy of that was provided by me back to the station in the late 1990s for another proof of performance comparsion, as it couldn't be located. The 1952 map was done by Russell May. For the FCC files, until the computerized databases were readily available, it is my understanding that they were filed under the call letters of the station at the time the study was done, making it difficult to locate unless an accurate record of call letters was also available.

 

[davideduardo]

I know for a fact that most (if not all) of the Clear Channel Broadcast Service (CCBS) affiliated stations consisting of Class A licenses conducted ongoing, rather extensive and detailed field surveys of both day-time and night-time signals.

Is anything being done to preserve these documents? There is scant evidence of any of this type of material, particularly since it was not a required filing for a non-directional 1 A.

At one time, these operators were mostly very proud of and concerned about their respective signals.

But when Martha White's flour ceased to be interested in night coverage of AM stations, and barter type shows such as Art Bell took over nights, stations lost interest in any part of the signal that was expended beyond the local metro.

Many, many measurements were conducted and analyzed in support of FCC filings concerning the Super Power initiative that went on for decades.

But the clear channel group, after the 1968 FCC rejection of medium power operation (500 kw) on AM in the US, disbanded. WSM is likely the exception if it still has the files from that era... I've never run across a station that had much in its files beyond whatever their counsel considers legally mandated.

But, again, my point is that there is not much that survives that can be used as a basis to compare the coverage from 40 or 50 years ago with that of today. And you add a good point: most operators today would not care enough to spend any money to verify that the facility is operating as well as it could.

WHO,WCAU, WLW and WSM conducted distant field measurements to quantify the high take-off angle lobes that were prevalent with the wide-face over 200 degree Blaw-Knox antennas and caused near fade-wall cancellations. These measurements resulted in reductions in height to minimize signal cancellation in the regional coverage areas.

I thought the only reduction in the WSM tower was removal of the mast at the top. Was there additional shortening?

Today, the main problems with AM signals are, 1) Part 15 noise issues with many devices from computers, power distribution lines to lighting products. 2) Poor receiver sensitivity, selectivity and phase noise. 3) AM band crowding. Listeners fleeing to other stable medium is another topic.

In addition to the receiver issues, add NRSC, narrow bandwidth for IBOC, and the perception that AM sounds bad. Add that all up and that's why the AM share in a market like Nashville is around 8% and the share under age 50 is about half that.

 

[davideduardo]

The FCC and a lot of station engineering files do have directional proof of performance files, and many applications for changes by them and other stations are also part of these files. I have seen a couple of files, but not recently. A proof of performance map from 1952 was copied for me in 1971, and a copy of that was provided by me back to the station in the late 1990s for another proof of performance comparsion, as it couldn't be located. The 1952 map was done by Russell May. For the FCC files, until the computerized databases were readily available, it is my understanding that they were filed under the call letters of the station at the time the study was done, making it difficult to locate unless an accurate record of call letters was also available.

I was referring to the non-directional 1-A's, as represented by WJR. As a frequent user of the FCC Public File on M Street around 1970, I saw many of those files... some station files were a file box or two full of stuff, and call changes often resulted in split files. The move to The Portals obviously sent a lot of stuff off into the dumpster; I have corresponded with a person who rescued a bunch of the card files with technical histories of stations that had been intended for disposal.

 

[pianoplayer88key]

That far back in time a 0.5 mV/m signal might have been listenable in the areas shown on the map you posted. Most receivers were fairly robust at the time, particularly those sold in rural zones. And we did not have computers, CFLs, dimmers and a wealth of other interference producing devices; we did have an FCC that enforced interference rules and power companies that would act on complaints of line noise.

While the contours may or may not have moved over time, the ability to listen to stations on the AM band has been shrinking constantly and incrementally over the last 50 years. As a consequence, the useful coverage area of a station has shrunken to the point that many stations that afforded relatively complete coverage of their markets in the 50's now may cover, in usable fashion, less than half of the market.

So the WJR daytime listener map, predating that change, would have been created in 1934 in all probability.

That was about a year before GE decided to proceed with full scale commercialization of the fluorescent lamp and many, many years before dimmers and other RF interference devices became widely available.

I'd love to see the day when it would again be possible for the signal level implied below to be sufficient for coverage, for example, inside office buildings in urban areas using only the built-in ferrite loopsticks on shirt pocket size radios.

Quote by Glenn Hauser in the IRCA list:

I just realized there were some errors in Giella`s post.

``WSB 650 kc from Nashville.``

Obviously (?) it had to be either WSM 650 or WSB 750 Atlanta.

``I visited Signal Hill in St. Johns, NF in September 1988, at the peak of
Solar Cycle 22. At the time I was an SWL, not yet licensed as a Ham, which came
in December 1989. I had with me a Sony ICF-6500W receiver and at daytime on
ground wave I was able to clearly copy WQAM 560 kc 5 kw in Miami, FL. At the
time WQAM's single tower was out in Biscayne Bay. That was an approximate
distance of 2158 km, 3474 mi. Part of the ground wave path in NF was over land
but the signal probably skewed along and around the coast to Signal Hill.``

km and miles are reversed; I get more like 2100 miles, 3380 km

Glenn Hauser

I attempted to calculate the field strength with the FCC groundwave curves, but fell off the bottom of the graph at 2100 km, where the estimated groundwave field (after conversion of WQAM's field for calculating with the graph) was 0.664 µV/m, or 664 nV/m -- yes, that's 664 NANOvolts/meter, less than one microvolt/meter (if I calculated what I could correctly)! Obviously over a land path the distances would be MUCH less, but still...! Even with today's absurdly high noise levels (which are, what? maybe 180-240dB (or whatever is the difference between inability to detect a QRSS CW carrier in the absense of any noise (not even any thunderstorm activity) vs. totally frying (physically, literally, reducing it to not even a pile of ashes) a high-quality receiver) higher for man-made noise than they need to be?), I'm able to get a fairly strong (if not quite "clear" - see below) signal from 1070 KNX at a distance of 111 miles in broad daylight.

Also, the poster that Glenn was quoting said he was "able to clearly copy" the station. To me, there's a huge difference between "100% copy" and "clear copy". For me, 100% copy still allows for a significant amount of noise present in the signal, as long as every word is understandable (assuming you speak the language). Clear copy, to me, implies that the S/N ratio matches or exceeds the dynamic range of human hearing. For me, this would be an example of "almost" clear copy.

 

[rfry]

This history of WJR shows that they switched from NBC to CBS in 1935 and continued with it until 1959..

So the WJR daytime listener map, predating that change, would have been created in 1934 in all probability. ... And there were only 15 stations outside of Detroit in the whole state, 3 of them in the UP. So it's no coincidence that folks would listen to WJR... they had no choice.

In fact the Neilsen survey in my link is one page of a brochure titled WJR Detroit, One of a Kind, which was published in 1964 shortly after Capital Cities bought WJR. The Cap Cities ID and station lineup is shown on the back cover of the brochure.

Michigan, Ohio and Indiana were well-populated with AM broadcast stations by the 1960s, so there were many choices other than WJR when that survey was made.

 

[rfry]

Quote by Glenn Hauser in the IRCA list: ``I visited Signal Hill in St. Johns, NF in September 1988, at the peak of Solar Cycle 22. ... and at daytime on ground wave I was able to clearly copy WQAM 560 kc 5 kw in Miami, FL

The h-plane, inverse distance field (IDF) 1 mile from WQAM is about 413 mV/m. The IDF at the end of a 2100 mile path over a zero-loss, flat ground plane then would be 413 / 2100 = 0.197 mV/m.

But sea water is not a zero-loss conductor, and the earth is not flat. So the actual groundwave field from WQAM in Newfoundland will be considerably less than this, regardless of the solar cycle.

Most likely this report is based on some form of daytime skywave propagation.

 

[rfry]

... if you're driving in the Milwaukee area WLS has the noisiest signal of all the 50KW Chicago stations except WYLL.

Here is what Doug Vernier's V-Soft web app says for the fields of the stations shown, at the intersection of I-94 with I-894 on the west side of Milwaukee:

WGN 7.8 mV/m
WSCR 7.3
WBBM 6.4
WLS 1.5
WYLL 1.2

Presumably these calculations are referenced to the M3 chart, which shows mostly 15 mS/m paths for WGN, WSCR and WBBM.

WLS has a stretch of 8 mS/m conductivity close to their transmit site on their path, then turning to 15 mS/m. The path of WLS to this location in Milwaukee is also about 31 miles further than from WGN, WSCR and WBBM.

This together with the higher frequency for WLS accounts for the difference, probably.

 

[radioman148]

... if you're driving in the Milwaukee area WLS has the noisiest signal of all the 50KW Chicago stations except WYLL.

Here is what Doug Vernier's V-Soft web app says for the fields of the stations shown, at the intersection of I-94 with I-894 on the west side of Milwaukee:

WGN 7.8 mV/m
WSCR 7.3
WBBM 6.4
WLS 1.5
WYLL 1.2

Presumably these calculations are referenced to the M3 chart, which shows mostly 15 mS/m paths for WGN, WSCR and WBBM.

WLS has a stretch of 8 mS/m conductivity close to their transmit site on their path, then turning to 15 mS/m. The path of WLS to this location in Milwaukee is also about 31 miles further than from WGN, WSCR and WBBM.

This together with the higher frequency for WLS accounts for the difference, probably.

Very true. If you go south of Chicago WLS has a much stronger groundwave signal. However, at my location 30 miles north of the city, WLS' groundwave is weaker than it was many years ago.

 

[Schroedingers Cat]

Another source might be the engineering consultant files, though I suspect you are right, David, about a lot of stuff being thrown out.

I want to make another inquiry as to whether anyone out there has a copy of a really old AM database, and any other source of directional antenna information from the 1940s and 1950s especially.

Seeing all those DA-1s and DA-2s shown in the old Broadcasting images has inspired my interest. DA-1 stations often gave up a lot of territory in the day pattern for the sake of only having one phasor. When a lot of stations went up from 1 kW to 5 kW day and/or night, I suspect that there were a lot of compromises of that type. I would like to see the old 1 kW patterns and antenna parameters that were probably less restrictive.

For instance, I saw the license for a three tower in line pattern at an antenna site posted and memorized the parameters. However, I didn't look at the date, and it may have been the old DA-1 pattern. It had phases of about -160 and +140, and the more recent data which was much closer to -150 and +150 which would create deeper nulls. The currents in each tower were also shown, not field ratios as would be the case today. I could have mixed up the phases and currents, but I am almost sure of the phases I saw.

 

[BRNout]

... if you're driving in the Milwaukee area WLS has the noisiest signal of all the 50KW Chicago stations except WYLL.

Here is what Doug Vernier's V-Soft web app says for the fields of the stations shown, at the intersection of I-94 with I-894 on the west side of Milwaukee:

WGN 7.8 mV/m
WSCR 7.3
WBBM 6.4
WLS 1.5
WYLL 1.2

Presumably these calculations are referenced to the M3 chart, which shows mostly 15 mS/m paths for WGN, WSCR and WBBM.

WLS has a stretch of 8 mS/m conductivity close to their transmit site on their path, then turning to 15 mS/m. The path of WLS to this location in Milwaukee is also about 31 miles further than from WGN, WSCR and WBBM.

This together with the higher frequency for WLS accounts for the difference, probably.

Very true. If you go south of Chicago WLS has a much stronger groundwave signal. However, at my location 30 miles north of the city, WLS' groundwave is weaker than it was many years ago.

Absolutely. Driving around eastern Lake County, even during the day, reveals significant drop out areas for WLS' signal where power lines and nearby interference make the signal difficult or impossible to hear for a short period of time while you pass by. Around Waukegan (for example), WISN actually has a better daytime signal than WLS - but disappears after dark. However, this phenomenon is true even in places like Vernon Hills and Lake Forest. It's annoying enough that I am sure some people would just bail out and go to FM. And the same thing does not happen when you're tuned to WSCR, WGN or WBBM (or WTMJ for that matter).

WLS' signal in the northern suburbs is simply not good. In fact, it's hardly any stronger than that of 5 kw WIND - which is another station that transmits from south of downtown Chicago (somewhere around Gary, IN - I believe). It reminds me of listening to an adjacent market signal (like hearing WABC in CT or WJR near Cleveland) as opposed to a 50 kw signal that's in MY market.

 

[Schroedingers Cat]

WLS tried to move to Grace and Fullerton back in the 1970s for that very reason. A Wisconsin station on 900 stopped them from moving due to disputed overlap. That would be a good application to try to find and look at. WMVP has used the WLS tower recently for STAs and there have been a lot of signal complaints.