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FM translator signal range in Metro Detroit

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MWmetalhead
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FM translator signal range in Metro Detroit

Post by MWmetalhead » Sat Dec 29, 2018 12:28 pm

Has anyone else noticed technical changes in 106.3's signal since K-Love moved to the big 102.7 stick?

Some have claimed W292DK was operating with more than its allotted 99 watts of maximum ERP. That theory certainly has some merit, IMO.

At my old house in NW Warren, W292DK almost always had a stronger indoor signal than 92.7 MHz W224CC and was even a tad stronger than W260CB.

At my current house - until recently - 106.3 always came in equally as well as 250 watt W260CB.

Recently, I've noticed a deterioration in W292DK's indoor signal strength.

These days, the pecking order (from best to worst) in terms of indoor signal strength at my house stands as follows:
#1: 99.9 MHz W260CB (tie). 250 watts max.
#1: 101.5 MHz W268CN (tie).. 99 watts max.
#3: 92.7 MHz W224CC. 99 watts max.
#4: 106.3 MHz W292DK. 99 watts max.
#5: 94.3 MHz W232CA. 99 watts max (barely weaker than W292DK, probably due to co-channel interference from Sarnia as opposed to inherent RF weakness).

All other FM translators have interference-riddled or weak signals at my house. W276DB can be heard OK if I position the antenna just right.

So, has anyone else observed a less robust than usual signal from W292DK lately?

Of all the translators on the above list, the two that really overachieve are W268CN and W232CA.

101.5 comes in great in portions of Wayne County & Macomb County where the signal should be fuzzy at best. In Redford, Livonia and Sterling Heights there is often little to no reception problem even though predicted strength in these areas is 50 dBu or less. The only place where 101.5's null seems to run "true" is in the azimuth that extends toward downtown Detroit. I strongly doubt their directional antenna meets the requirements of their FCC license.

94.3 performs as designed across Oakland and Macomb Counties but has a better signal in Detroit proper than it should. The signal is by no means great in midtown & new center but it is very readable. I've locked in the station on seek mode in places where the predicted signal is only ~45 dBu. My guess is their null toward Windsor is not nearly as wide & deep as depicted on their FCC license. Their real RF pattern more likely resembles the licensed pattern of W260CB. The irony is I get better reception from 94.3 in places where 99.9 is supposed to have the stronger signal of the two!



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Re: FM translator signal range in Metro Detroit

Post by Deleted User 14803 » Sat Dec 29, 2018 3:20 pm

EMF’s goal is to eventually get rid of translators in larger markets, and Detroit is one of those markets if in the future EMF can aquire another full power FM at a reasonable price than Air 1 will go on that station, the cost to maintain these translators is big so this is what they are trying to achieve according to Joe Miller at EMF’s California Headquarters. So if a translator is not at full potential it’s not a big enough problem to worry about, it just comes down to costs.



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Re: FM translator signal range in Metro Detroit

Post by Circle Seven » Sun Dec 30, 2018 8:29 am

I honestly ponder if W268CN was put up 180 out of phase inadvertently.
Last time I looked, the pattern I believe is due north.
When I go to Davison, they start dropping by the time I pass 59 on 23.
When I'm northbound on 75 in Monroe County, they already start picket fencing the Toledo station by the time I get to the 275 split.



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Re: FM translator signal range in Metro Detroit

Post by Arthur Mometer » Sun Dec 30, 2018 10:02 am

I assume you mean US-23 NB, not 23 Mile Rd. (I'd have to look at the map to see if M-59 turns North and intersects 23 Mile Rd.. They should go back to calling 23 Mile Rd. Coldwater Road (Historical Name) or Avon Rd., extending it into Macomb County, as there would probably be less confusion with the Coldwater Rd. that intersects US-23/I-75. Then of course I assume that you mean Davison, MI, not the Davison Expressway. It gets confusing when you start getting into WDIV-TV's Wet Zone, er, West Zone. Don't even get me started on all the Miller Roads and the two Silver Lake Roads.

Anyway, before all the translators, M-59 is usually about where you started hearing WWBN on NB US-23, and lost WRVF. So that might be where you are losing the translator. You have to realize that all of those signals are still there, even when the stronger signal captures the other.

The problem with translators is that at best they are 250 watts, and have at best a 111 mV/m inverse field at 1 km regardless of height. Those who illegally DX in airplanes (the least enforced law besides pot in college dormitories) are familiar with the anemic performance of Class Bs on tall buildings in airplanes. You cannot change the Laws of Physics, Jim.

I've just been self informed that W268CN is just 99 watts maximum, not 250. The inverse field with 99 watts is about 70 mV/m at 1 km.

The minimum inverse directional field ratio is 0.04, at around 150 degrees true, or about 2.8 mV/m at 1 km. That is in the inverse field range of signal prediction. The ERP in that direction is about 158 milliwatts. So the 70 dBu contour would go out about 0.8855 km, or 0.5502 miles. The power in that direction is -38 dBk. The HAAT in that direction is 287.7 meters. See below post for contours, both F(50,50) AND inverse field.
Last edited by Arthur Mometer on Sun Dec 30, 2018 7:03 pm, edited 5 times in total.


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Re: FM translator signal range in Metro Detroit

Post by MWmetalhead » Sun Dec 30, 2018 10:15 am

I honestly ponder if W268CN was put up 180 out of phase inadvertently.
Last time I looked, the pattern I believe is due north.
When I go to Davison, they start dropping by the time I pass 59 on 23.
When I'm northbound on 75 in Monroe County, they already start picket fencing the Toledo station by the time I get to the 275 split.
My guess is many of the radials that should be deeply nulled instead are receiving full power or near full power. In practice, their signal pattern seems to not be very different from that of 106.3 FM.

No wonder Salem had no qualms about moving WDTK's FM signal to 101.5 MHz. They figured "hey, we'll just operate illegally!"

If the station operated within its legal parameters, the signal in nearly all locales south of McNichols / 6 Mile would be very weak. Listeners in Dearborn, the south side of Livonia, Garden City, Plymouth and Northville shouldn't even be able to hear the station.



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Re: FM translator signal range in Metro Detroit

Post by Arthur Mometer » Sun Dec 30, 2018 10:50 am

It's been very recent that Longley Rice predictions have become more available. There is an old Rule Of Thumb that a clear unobstructed LOS gives you a 6 dB boost over F(50,50) curves in about the ~1.5 km to ~32 km range. And of course F(50,50) is based on about 30 foot AGL antennas, not the typical first floor 6 foot AGL. That throws the model off, favoring low ERP at very short distances. That may explain some of this.


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Re: FM translator signal range in Metro Detroit

Post by CK-722 » Sun Dec 30, 2018 12:13 pm

Some of the 1960s transistor projects for wireless FM BC mikes put out WAY over the Part 15 limit. 100 mW on FM is WAY OVER the limit. Nobody cared back then because not that many people listened to FM, the band was wide open in many areas, and unless you lived on top of one of the FCC monitoring stations, you probably could have gotten away with it for years. No one would have complained unless you were competing with a non simulcast FM or blotting out their favorite out of market stations. So legal FM translators with even 1 watt ERP can get out miles on a "clear channel".

https://www.ecfr.gov/graphics/pdfs/ec01mr91.085.pdf

Image

1 kW 100 feet 93 dBu at 1.5 km (~1 mile)

1 W 100 feet 63 dBu at 1.5 km (~1 mile)

100 mW 100 feet 53 dBu at 1.5 km (~1 mile)

1 W 100 feet 40 dBu at 5.6 km (~3.5 miles)


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Re: FM translator signal range in Metro Detroit

Post by Arthur Mometer » Sun Dec 30, 2018 3:38 pm

Using the F(50,50) graph, the 40 dBu contour goes out (40 dBu+38 dBk=78 dBu on the graph above). At 287.7 meters, that is about 11.7 km, or about 7.27 miles. The inverse field for the 40 dBu would be 2800 uV/m inverse field at 1 km/100 uV/m=28 km or 17.4 miles. That surprises even me, but I rechecked it several times in different ways. The kicker is that 287.7 meters HAAT isn't free space. So probably somewhere in between free space LOS and F(50, 50). Perhaps Rich could use his Fresnel Zone software to compute this. The 6 dB rule of thumb would put it at about 16 km or about 10 miles.
Last edited by Arthur Mometer on Sun Dec 30, 2018 7:11 pm, edited 1 time in total.


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Re: FM translator signal range in Metro Detroit

Post by Circle Seven » Sun Dec 30, 2018 6:02 pm

Yes. I was talking about M-59, US-23 and Davison Michigan. Thanks for the correction.



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Re: FM translator signal range in Metro Detroit

Post by Arthur Mometer » Sun Dec 30, 2018 6:19 pm

Circle Seven wrote:
Sun Dec 30, 2018 6:02 pm
Yes. I was talking about M-59, US-23 and Davison Michigan. Thanks for the correction.
And thanks to you for bringing these issues up. I learned some things too. Like they show M-59 turning north on the official MDOT Michigan Map and intersecting 23 Mile Rd., and Chris Bessert's Michigan Highways site says it doesn't. And I was surprised that the nulls on the translators are equivalent to such low ERP (158 milliwatts in the case of W268CN). And just how far 158 mW goes at ~300 meters HAAT. These loopholes in the rules show us that the interference modeling is clearly wrong without Longley Rice and inverse field considerations.


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Re: FM translator signal range in Metro Detroit

Post by Rich » Mon Dec 31, 2018 6:40 am

CK-722 wrote:
Sun Dec 30, 2018 12:13 pm
Some of the 1960s transistor projects for wireless FM BC mikes put out WAY over the Part 15 limit. 100 mW on FM is WAY OVER the limit. ...
How true. 47 CFR §15.239 covers the Iegal, unlicensed use of the FM broadcast band in the U.S. The maximum field intensity at a linear distance of 3 meters in all directions from the radiation center of its transmit antenna is limited to 250µV/m.

The amount of r-f power radiated by a simple, linear, 1/2-wave, center-fed dipole to produce that field intensity at that distance in free space is extremely small: 11.43 nanowatts (0.000 000 011 43... watts).

Obstructions and reflections from the earth and other physical structures near the transmit antenna along the propagation path to the receive antenna can greatly modify those transmitted fields.



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Re: FM translator signal range in Metro Detroit

Post by Rich » Mon Dec 31, 2018 10:35 am

Arthur Mometer wrote:
Sun Dec 30, 2018 3:38 pm
.. Perhaps Rich could use his Fresnel Zone software to compute this. ...
Below is a Longley-Rice graphic showing the fields present at an elevation of 2 meters AGL from a transmit antenna at 260 meters AGL radiating 99 watts ERP in/near the horizontal plane. Omnidirectional transmit and receive antennas are assumed.

The terrain profile and propagation path from the transmit site to a receive site near Farmington Hills is shown, and calculation parameters are included in the graphic.

Of course, no consideration is included for man-made reflectors/diffractors/obstructors such as buildings, etc that may affect the received fields.

In most browsers, right-clicking on the image will permit viewing it at an enlarged scale.

Image



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Re: FM translator signal range in Metro Detroit

Post by Arthur Mometer » Mon Dec 31, 2018 3:33 pm

Thanks, Rich, for the analysis. There is flatter and downhill terrain to the ~150 degrees null South of the TL, so except for ground clutter and a 2 meter AGL Receiving Antenna Height, I would expect less loss, and probably little to no loss or very little at 20+ feet AGL.


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Re: FM translator signal range in Metro Detroit

Post by fairbankshockeypuck » Tue Jan 01, 2019 10:01 am

Alaska again....our two FM translators on 97.5 for am 660 news talk and 107.9 for 820 ESPN. are 250 W and sit on Ester Dome 2000 feet up..they go out at least 25 miles//maybe further I will have to drive out farther// solid in a car/truck radio.....



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Re: FM translator signal range in Metro Detroit

Post by Arthur Mometer » Tue Jan 01, 2019 1:55 pm

Alaska again....our two FM translators on 97.5 for am 660 news talk and 107.9 for 820 ESPN. are 250 W and sit on Ester Dome 2000 feet up..they go out at least 25 miles//maybe further I will have to drive out farther// solid in a car/truck radio.....
What about the translator for KBHR 570 K-Bear? Is that the one on the roof with the little tower and vertically polarized folded dipoles? Wish I had a picture of that scene.

Oddly enough, KRSA AM 580 Petersburg, AK was one of the first AM stations, if not the first, to have a translator on FM in the US. To add further to the irony, URSA means Bear in Latin. It has since been deleted. It was on 580 with 5 kW DA-U, as it was close to Canadian and US stations.

It was so Art imitates life that I thought KBHR was 580.


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"Lies have to be repeated and repeated to be believed. Truth stands on its own merit."

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