Band scan 88-92FM

[e-dawg]

I know in Chicago area, between 88.1 and 91.9 FM is very crowded, just curiosity, if I were in the Loop right by Union Station or N Wacker Dr/Michigan Ave, what radio stations can I hear between 88.1 and 91.9 FM (I-pod nano, Walkman, and car)?

 

[fybush]

With all the RF coming down at you from Sears (yes, Sears, dammit!) and the Hancock, your Walkman will probably get WBEZ on 91.5 (Hancock), probably WMBI-FM on 90.1, and likely very little else. A car radio will add a few signals to that equation in the Loop - WCRX from Columbia College on 88.1, maybe WLUW from Loyola on 88.7, but not much else. All the rest of those little signals at 88.something and 89.something and 90.something are very, very small ones (ranging from just a few watts to 100 watts) scattered around the city's neighborhoods and nearby suburbs. You don't get to anything more powerful until you get up to WNUR at Northwestern in Evanston (7200 watts on 89.3) and way out to WDCB in Glen Ellyn (5000 watts on 90.9).

 

[w9wi]

Agreed.

A semi-scientific survey witih a LOT of holes in it (i.e., the FCC's propagation curves calculator) suggests the five strongest signals in the 88-92 band in the Loop should be:

WBEZ 91.5 108dBu
WCRX 88.1 81dBu (because it's only 2km away)
WMBI-FM 90.1 73dBu
WNUR-FM 89.3 59dBu
WIIT 88.9 54dBu (5km away)

Only the first three are strong enough to provide a "protected contour" signal.

There are a number of problems with Curves:
- It doesn't take receiver overload into account. The Chicago Loop is the ONLY place where I've experienced significant overload on my car radios. Well, there and Mt. Washington. And admittedly I've never done a bandscan from Manhattan. But seriously, with 19 high-powered FMs within a km or two, plus a pile of digital TVs, plus all the non-broadcast RF, that's going to be a pretty noisy place.

- It doesn't take large buildings into account. I'd bet if you walk one lap around the Sears Tower, you're going to get a different bandscan on each side.

- It doesn't take the vertical radiation pattern of the transmitting antenna into account. (usually not a big deal at significant distances from the antenna. Probably a big deal when you look up, rather than out, to see it...)


Scott, for what little it's worth, Curves suggests the next five signals would be:

WDCB 90.9 Glen Ellyn (53dBu)
WLUW 88.7 Chicago (53dBu)
WRTE 90.5 Chicago (53dBu)
WHPK-FM 88.5 Chicago (52dBu)
WBEW 89.5 Chesterton, Indiana (49dBu, 3.364kW ERP in the direction of the Loop)


There are 39 stations in the reserved band within 60km of the Loop. (counting two translators, and not counting WLFM )

 

[djdanska]

I know in Chicago area, between 88.1 and 91.9 FM is very crowded, just curiosity, if I were in the Loop right by Union Station or N Wacker Dr/Michigan Ave, what radio stations can I hear between 88.1 and 91.9 FM (I-pod nano, Walkman, and car)?

In general:
88.1 easily
91.5 duhh.
90.1 a little stereo interference but listenable
If i walk west, i can usually get 99.9 fm, 90.9 fm on most days. Walk or face the lake and they're gone on my amaze.

 

[PTBoardOp94]

- It doesn't take large buildings into account. I'd bet if you walk one lap around the Sears Tower, you're going to get a different bandscan on each side.

- It doesn't take the vertical radiation pattern of the transmitting antenna into account. (usually not a big deal at significant distances from the antenna. Probably a big deal when you look up, rather than out, to see it...)

I think this would be a rather interesting exercise now that you mention it... I remember reading that an ideal broadcast antenna produces a spherical pattern, but directly beneath Willis you could see some really interesting effects on account of the shape of the building, its height, the relatively low ERP of the stations mounted there, and the efforts of the antenna manufacturer(s) to waste less power in the vertical plane.

 

[w9wi]

I think this would be a rather interesting exercise now that you mention it... I remember reading that an ideal broadcast antenna produces a spherical pattern, but directly beneath Willis you could see some really interesting effects on account of the shape of the building, its height, the relatively low ERP of the stations mounted there, and the efforts of the antenna manufacturer(s) to waste less power in the vertical plane.

(please don't call it "Willis", I can never remember whether that means "Sears" or "John Hancock"...)

There's a hypothetical "isotropic" antenna that produces a spherical pattern -- for reasons that go over my head, I'm told such an antenna cannot be built...

I suppose an "ideal" antenna for use in Chicago would put as much along the horizon as possible, to extend coverage around the outermost suburbs, while still maintaining enough below the horizon in the Loop to overcome computer noise in the central high-rises, and to not waste power over the lake.

That would probably be VERY different from an ideal antenna for use at 92.5 (DeKalb) or 99.9 (Park Forest) or most of the other outlying stations.

 

[DX]

From a building 20 or 30 stories up in downtown Chicago, we used to pick up Lyons Township High School's WLTL from LaGrange on 88.1.