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AM RADIO PATTERNS
- Thread starter OldChicago
- Start date
As R. Fry, and a few others on this and other message boards have noted, WLS was always noticeably weaker in North Suburban Chicago. WYLL (WJJD) was the strongest, then WGN, WBBM, WSCR (WMAQ), WMVP (WCFL), WCPT (WAIT), WMBI, and WSBC days (yes, WSBC) were all observably stronger. WNTD (WGRT) days, WRDZ days (WTAQ at old site) days, and WLS were all of similar strength. WIND was also stronger than WLS from empirical obeservation. R. Fry doubts this (WLS vs. WIND from V-Soft Zip Code and his software). Glen Clark (designed and oversaw the new WMVP array construction) says the Chicago area conducitvities are quite close to M-3. I think W9WI is right though about the path from WLS to northern Illinois near US 45 being worse. When WMVP on STA diplexed the WLS tower during WMVP tower reconstruction, there were many signal complaints.
Schroedingers Cat said:
When WMVP diplexed the WLS tower did they run ND at night with 50KW?
The problem with using traditional engineering methods is that you have to assume the conductivity maps are accurate. That assumption just doesn't really pass the "smell test". (I refuse to believe the conductivity instantly jumps from 8 to 15 mmho when you cross the Stevenson 
)
When you're working before the FCC you have to have *something* that has some certainty to it. Unless someone is willing to come up with the $$ to make an awful lot of measurements, the maps are your best shot. Unfortunately the best isn't very good. Obviously that 8mmho figure north of the Stevenson assumes the natural condition of the terrain -- but in Greater Chicago, us humans have made some pretty serious changes to that terrain!, most of them involving materials which probably reduce conductivity considerably.
So we work with what we've got, ensuring everyone plays by the same (flawed) rules, understanding that the numbers our computers deliver are likely to disagree with the numbers our FIMs deliver!
)When you're working before the FCC you have to have *something* that has some certainty to it. Unless someone is willing to come up with the $$ to make an awful lot of measurements, the maps are your best shot. Unfortunately the best isn't very good. Obviously that 8mmho figure north of the Stevenson assumes the natural condition of the terrain -- but in Greater Chicago, us humans have made some pretty serious changes to that terrain!, most of them involving materials which probably reduce conductivity considerably.
So we work with what we've got, ensuring everyone plays by the same (flawed) rules, understanding that the numbers our computers deliver are likely to disagree with the numbers our FIMs deliver!
The STA applications are in the FCC files online as I recall. Seems like they used 1/4 power at Downer's Grove at night while one tower was still up, and then put one new tower up and then took the last one down. During daytime work at Downer's Grove, they used the WLS tower. I forget the power. They may have licensed it as an auxiliary at WLS, which would allow them to run at the omni power that kept them within the 0.5 mV/m day contour.
This is just from memory, I do think they were at 15kW day from the WLS site, I believe they were 7.5kW from one tower at night.
They did recieve a lot of complaints from up in the northern suburbs. I seem to remember that the FCC allowed them to use a lower daytime power from one tower at the licsensed site, when it was safe for the workers, to do so during the construction.
A couple of other stations that I know of in Chicago have used STA's in last couple of year for various reasons.
When there was roadwork very near WYLL'S daytime site near 294 and Dempster in Park Ridge, they were allowed to use the nightime site in Lockport at 15kW, until sunset, to keep workers safe from RF when they were working very close to the site.
WNTD 950 AM also had an STA to use their nightime site in Burnham at 500 watts when emergency work neeed to be down on the warehouse roof on Western Ave, where the 1kW daytime tower is.
These were STA's not permanent backup sites.
They did recieve a lot of complaints from up in the northern suburbs. I seem to remember that the FCC allowed them to use a lower daytime power from one tower at the licsensed site, when it was safe for the workers, to do so during the construction.
A couple of other stations that I know of in Chicago have used STA's in last couple of year for various reasons.
When there was roadwork very near WYLL'S daytime site near 294 and Dempster in Park Ridge, they were allowed to use the nightime site in Lockport at 15kW, until sunset, to keep workers safe from RF when they were working very close to the site.
WNTD 950 AM also had an STA to use their nightime site in Burnham at 500 watts when emergency work neeed to be down on the warehouse roof on Western Ave, where the 1kW daytime tower is.
These were STA's not permanent backup sites.
Here is the link to the STA application. I would think that they could license an auxiliary from the WLS tower with more power than 12.5 kW in the daytime, since the licensed daytime pattern has very shallow nulls. The old pattern had shallow nulls in the daytime also. It has to fit inside the 0.5 mV/m contour.
https://licensing.fcc.gov/cdbs/CDBS...?appn=101193873&qnum=5370©num=1&exhcnum=1
https://licensing.fcc.gov/cdbs/CDBS...?appn=101193873&qnum=5370©num=1&exhcnum=1
w9wi said:The problem with using traditional engineering methods is that you have to assume the conductivity maps are accurate. That assumption just doesn't really pass the "smell test". (I refuse to believe the conductivity instantly jumps from 8 to 15 mmho when you cross the Stevenson
When you're working before the FCC you have to have *something* that has some certainty to it. Unless someone is willing to come up with the $$ to make an awful lot of measurements, the maps are your best shot. Unfortunately the best isn't very good. Obviously that 8mmho figure north of the Stevenson assumes the natural condition of the terrain -- but in Greater Chicago, us humans have made some pretty serious changes to that terrain!, most of them involving materials which probably reduce conductivity considerably.
So we work with what we've got, ensuring everyone plays by the same (flawed) rules, understanding that the numbers our computers deliver are likely to disagree with the numbers our FIMs deliver!
You can modify conductivity with readings at any time as long as you use a calibrated meter.
zwoodrow said:w9wi said:The problem with using traditional engineering methods is that you have to assume the conductivity maps are accurate. That assumption just doesn't really pass the "smell test". (I refuse to believe the conductivity instantly jumps from 8 to 15 mmho when you cross the Stevenson
When you're working before the FCC you have to have *something* that has some certainty to it. Unless someone is willing to come up with the $$ to make an awful lot of measurements, the maps are your best shot. Unfortunately the best isn't very good. Obviously that 8mmho figure north of the Stevenson assumes the natural condition of the terrain -- but in Greater Chicago, us humans have made some pretty serious changes to that terrain!, most of them involving materials which probably reduce conductivity considerably.
So we work with what we've got, ensuring everyone plays by the same (flawed) rules, understanding that the numbers our computers deliver are likely to disagree with the numbers our FIMs deliver!
You can modify conductivity with readings at any time as long as you use a calibrated meter.
You certainly can, for purposes of getting a facility approved. (I suppose you could take readings just to satisfy curiousity, but who's going to pay for them?
)The point I was trying to make (probably not very well) is that the WLS signal in areas north of Chicago is probably worse than predicted, because the actual conductivity is probably worse than the maps.
Living in the Northern suburbs of Chicago I've found that WLS' signal here is worse than anywhere else in the metro area. However, if you go west or south of Chicago the WLS signal is the best of any Chicago station--especially south in downstate Illinois.
You have me curious now, how much more did 820 get out in the fringe areas of the signal as opposed to being on Belmont in the city?cyberdad said:
I know that is hard to answer exactly, just a guestimate is fine. Now on a good car reciever I can pickup 820 almost all the way to Springfield, Il. Once in a great while I can here it very faintly. Ironically, at 5kw, their coverage is very close to WYLL with the 50kw day signal which is a tad stronger in Springfield.
You guy's are so good with this info I wanted to ask if there is anyway to get a coverage map from their 1kw night signal from Elmhurst? There are quite a few stations from the past I would like to see.
I had never seen the Elmhurst site, I was under the impression they had a side by side four tower array, recently while in Chicago I was talking with a friend who told me it was a four tower in line array, is that true? If you had to draw the signal pattern on paper what station would it resemble.
I recall it being a very good signal in the north suburbs like Wilmette, while not great on the near north side of the city.
There were four towers on a 38/218 degree axis. I suspect it was designed with three multiplicative two tower patterns (1-3-3-1*) around 120 degrees spacing and phased around +60 degrees consecutively going in the 218 degree direction to give a very wide lobe cardioid pattern with a very wide null or very small minor lobe to protect WBAP. I think when they filed the application, there were no other 820s to protect at night. I think they filed the application years before they allowed clear channel duplication, with the stipulation that it not be rejected but granted when duplication was finally allowed.
*The end towers function as one and the middle two as three towers each from a design standpoint. The field ratios and phases add vectorially to a single field ratio and phase.
*The end towers function as one and the middle two as three towers each from a design standpoint. The field ratios and phases add vectorially to a single field ratio and phase.
You have me curious now, how much more did 820 get out in the fringe areas of the signal as opposed to being on Belmont in the city?
[/quote]
It got out somewhat better, but nothing all that dramatic.
Admittedly, this is very unscientific, just a few of my observations as a business traveler....
Going south, I'd lose 820 somewhere between Champaign and Effingham. To the southwest on a car radio, I'd have it until just a little beyond Springfield (IL). To the west, they'd easily make it to most of the river counties in Iowa that border Illinois. To the Northwest, they'd be audible to around the Wisconsin Dells.
[/quote]
It got out somewhat better, but nothing all that dramatic.
Admittedly, this is very unscientific, just a few of my observations as a business traveler....
Going south, I'd lose 820 somewhere between Champaign and Effingham. To the southwest on a car radio, I'd have it until just a little beyond Springfield (IL). To the west, they'd easily make it to most of the river counties in Iowa that border Illinois. To the Northwest, they'd be audible to around the Wisconsin Dells.
You could get WAIT 820 very well along the Michigan Lakeshore, and it probably is still pretty good. People in Grand Haven and Muskegon, as well as in Chicago resort destinations from Michiana up to South Haven and Saugatuck, listened to WAIT on their AM only car radios for Beautiful Music back in the day. Before CHAM moved to 820, you could here WAIT in Southeast Michigan by nulling out WOSU on a sensitive TRF stage radio. When WMAQ was on Auxiliary with 5 kW on its 1/4 wave backup tower (at least that is the way I was told it was), WAIT was stronger in SE Michigan than WMAQ. I think WAIT's tower in Elmhurst was around 1/2 wave, and was several miles closer than WMAQ.
Going east I could hear WAIT to the Ohio/Indiana border.
Going back to Nashville said:
Check out a picture of the Elmhurst antenna site on my web page here: http://home.earthlink.net/~dxchicago/AM_Chcgo_Scan.htm
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