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St Louis Super Tower

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Turkeytop
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St Louis Super Tower

Post by Turkeytop » Tue Nov 15, 2022 12:41 am

I hope I'm doing this right. This is supposed to be a link to the video.

https://www.youtube.com/watch?v=6_u8x8V4YYs


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k8jd
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Re: St Louis Super Tower

Post by k8jd » Tue Nov 15, 2022 12:17 pm

I did see the video on U-tube a few night ago, recalling the big tower sites from working in BC engr in Chicago and Detroit and Two way radio service across Michigan. I was in the middle of a transition from Analog to digi near the end of my carreer.



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Turkeytop
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Re: St Louis Super Tower

Post by Turkeytop » Tue Nov 15, 2022 1:02 pm

There must be some awfully powerful fields in and around that building. I can't imagine it's a healthy work environment.


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Rich F.
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Re: St Louis Super Tower

Post by Rich F. » Wed Nov 16, 2022 8:20 am

The greatest radiation from the FM broadcast stations is centered in the horizontal plane, radiating from the middle of this 8-bay vertical array, near the top of a ~1,000 foot tower. The fields that radiation produces don't ~reach the surface of the Earth at distances less than the "radio horizon" from that antenna elevation (dozens of miles).

A multi-bay transmit antenna array such as used here produces sidelobes/radiation that will reach the Earth near the base of the tower. The graphic below shows the value and distribution of them out to 1 mile from the tower, for the assumptions stated there.

A conservative estimate of the total, nearby power densities when ten stations with 100 kW ERP circular polarization each use this antenna at the same time can be found by multiplying the power density values in the graphic by ten.

In this exercise, the ~77 µW/cm² peak power density 74 meters from the tower base even for ten stations would be less than one-half of the 200 µW/cm² (= 0.2 mW/cm²) allowed for uncontrolled exposure of the general population.

Image



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Ben Zonia
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Re: St Louis Super Tower

Post by Ben Zonia » Wed Nov 16, 2022 9:37 am

This is probably the tower. This shows all the services on that tower.

https://www.fccdata.org/?lang=en&qmenu= ... n=-90.3255

Of course, you could design an antenna with half wave spacing, which would reduce downward radiation, but it would have less gain and it would take considerably more TPO to achieve the ERP. There is a sweet spot around 0.8 to 0.9 wavelength spacing that maximizes gain and lessens the downward radiation from close to what 1.0 wavelength does. There are other engineering complications like phasing the bays. With diplexed stations all over the band, the wavelength for each station varies considerably, complicating matters even more.

I don't know if anyone besides Rich here who remembers Jeremy Ruck, who did a lot of the engineering for the Sears/Willis Tower facilities. Sadly, along with several other consulting engineers, Jeremy passed away within the last few years, and not just from the virus. I used to email and talk to him quite a bit. We worked on an FM upgrade project together with the late Bill Sanderson. Jeremy was only 50. I miss talking to all of them.


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Marcus
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Re: St Louis Super Tower

Post by Marcus » Wed Nov 16, 2022 6:57 pm

I've wondered where you would want go to put the mixer of a FM radio to test as far as an overloading goes. One location that comes to mind is David Pecaut Square in Downtown Toronto. The CN tower is to the South and the tall building with the blue BMO letters + the red symbol on it to the East are both master antennas.

CBC Radio One is 98 KW. Fourteen stations are over 8 KW ERP. The specification that helps you out there is RF Intermodulation, and most consumer products fail to mention it. The kind of filtering that determines a radios selectivity does not eliminate this kind of overloading. The two links I have found regarding this are here. Battery operated radios and car audio are not included.

http://ham-radio.com/k6sti/

https://fmtunerinfo.com/tunercomparison.pdf



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Turkeytop
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Re: St Louis Super Tower

Post by Turkeytop » Wed Nov 16, 2022 9:06 pm

I was staying on one of the upper floors in a downtown Toronto Hotel. When travelling I always take along my own radio, a Sangean portable. I turned it on that day and not a sound came out of it. The digital display was just flashing a lot of random characters. I looked out the window and there was the CN tower a couple of blocks away.

I figured the powerful signals must have been messing up the electronics in ny radio. I collapsed the telescopic antenna down into the radio and then it was OK.

Later that evening I turned on my laptop. Every time it would just boot up and then crash. I had to take it down into the underground parking garage to use it.


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Marcus
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Re: St Louis Super Tower

Post by Marcus » Fri Nov 18, 2022 12:06 am

The RF spectrum from VHF and up is so utilized there that people must have been running into problems like that for years. I would like to know what kind of solutions people who live in apartments in that area have come up with. I know there is a tunable FM antenna that shows up on Ebay. It is the Audioprism 6500, and it is intended for tuning between very strong FM signals. It is not cheap, though. Even ones with scratches on them tend to be over $150 U.S. after shipping.

Another location that appears to be a hot RF area is Ferndale, Michigan. I could see some radios struggling to get Ann Arbor and Windsor FM broadcasts there.



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Ben Zonia
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Re: St Louis Super Tower

Post by Ben Zonia » Fri Nov 18, 2022 12:39 am

I knew a college professor who had a turnstile FM antenna on the building his office was in, which was within a mile of two FM transmitters. It was a Sony Table Radio from circa 1970. He had all kinds of problems with just those two stations nearby. He had the college engineering technician come up with a solution. It appeared to be two hand wound coils from #14 or #16 copper wire and two 35 pF variable air dielectric capacitors. I assume that they were in series across the 300 ohm input, and were tuned to to have a low impedance to each signal. Or possibly in parallel to create a high impedance at each frequency connected to each terminal. I'm not sure what he was trying to listen to, probably WRIF, a semi fringe signal, as young people got receivers and antennas just to do that. My HS Electronics teacher had student projects every year. One year they built a Heathkit FM Tuner and Heathkit Amplifier and put a 5 Element Channel 6 Yagi, possibly shortened the elements a bit, up on the roof of my HS. As I recall, they listened to WKNR-FM and WXYZ-FM/WRIF on it mostly. But if you have 15 or 20 nearby stations, you would need a selective front end and or DSP to eliminate RITOIE and even oscillator created third order products, a common problem with older FM receivers. Those only have one station heard, as opposed to RITOIE, where you usually would hear two stations' audio.


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Re: St Louis Super Tower

Post by Deleted User 15905 » Sun Nov 20, 2022 1:54 pm

I’m curious as to the height of that tower and how it compares to the 8 Mile tower here in Detroit.



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Ben Zonia
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Re: St Louis Super Tower

Post by Ben Zonia » Sun Nov 20, 2022 2:15 pm

ultrakilocycle wrote:
Sun Nov 20, 2022 1:54 pm
I’m curious as to the height of that tower and how it compares to the 8 Mile tower here in Detroit.
Here's the one on Radio Plaza. The St. Louis tower is 340 meters high, and the Radio Plaza tower is 305 meters high. Radio Plaza has a bunch of FM stations and auxiliaries, but not as many as the St. Louis tower.

https://www.fccdata.org/?lang=en&qmenu= ... n=-83.1638

Here's the one on 8 Mile. It has several TV transmitters and several FM Translators, and WDTR-FM. It is about 331 meters high.

https://www.fccdata.org/?lang=en&qmenu= ... n=-83.1731
Last edited by Ben Zonia on Sun Nov 20, 2022 2:26 pm, edited 4 times in total.


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Turkeytop
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Re: St Louis Super Tower

Post by Turkeytop » Sun Nov 20, 2022 2:17 pm

The CN tower in Toronto is 1815 ft tall, has one antenna and broadcasts over 30 Toronto television and FM radio signals across Southern Ontario in addition to wireless paging and cellular telephone signals.

The claim to be broadcasting across Southern Ontario is a bit of a stretch. Maybe within a 60 mile radius of Toronto.

Image

Toronto is 1204 miles from Niceville.


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Ben Zonia
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Re: St Louis Super Tower

Post by Ben Zonia » Sun Nov 20, 2022 3:07 pm

Perhaps it reaches the Northern shore of Lake Ontario in Canada further out, and the Southern shore of Lake Ontario in New York. Surprisingly, New York is a Great Lake State, but you would never know it around New York City. From the CN tower to a 30 foot receiving tower, the line of sight would go out about 55 miles.


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Re: St Louis Super Tower

Post by Marcus » Sun Nov 20, 2022 3:40 pm

The CN tower is 553 meters tall overall. The FM's are at 420 m HAAT. The TV signals range from 469 m HAAT for RF 8 to a little over 500 m HAAT for UHF TV. The CBC Toronto signal gets out far by using 107 KW at 491 m HAAT, but it is NOT the biggest signal in North America. In the Tri Cities and Brantford you might get it. As far west as Woodstock it's weak at best.

https://en.wikipedia.org/wiki/CN_Tower



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Re: St Louis Super Tower

Post by Turkeytop » Sun Nov 20, 2022 3:51 pm

For a lot of years I lived up in Bruce County, about 130 miles north west of Toronto. With an outdoor antenna it wasn't too unusual to get FM from Toronto. But it was never reliable. Even when I could get it there was always fading in and out,

I used to have more success with the MI stations from across L huron.


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