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Author Topic: Radio station in the pipes  (Read 1219 times)

Benjamin Krumholz

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Radio station in the pipes
« on: June 03, 2019, 11:25:45 am »

Hey All,
So at an install recently, and a few other times in the past, I have run into AM Radio bleeding into mic lines that have a little distance to them. My typical fix would be something like a Shure A15RF.. Those filters work really well and they pass phantom. YAY.

So back to this current story. The install is at a pool club that is next to a 35KW AM Radio Station in a major market.. If I take my Fluke Toner/Sniffer i can hear the radio station almost EVERYWHERE in the pool club.. If I hold it to almost any an outlet, power main, drain pipe, phone line in the place you can hear the radio station clear as day... The outlets that my rack is connected to test fine with a multi meter and a outlet checker. I can hear the radio on my power.. The A15RF fixed the mic line i was having an issue with.. But what can i tell the owners, if anything?! Can this issue be fixed? I imagine the main ground for the building is connected to a pipe somewhere. Same for the phone systems. Any Suggestions?
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John Roberts {JR}

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Re: Radio station in the pipes
« Reply #1 on: June 03, 2019, 12:59:22 pm »

Hey All,
So at an install recently, and a few other times in the past, I have run into AM Radio bleeding into mic lines that have a little distance to them. My typical fix would be something like a Shure A15RF.. Those filters work really well and they pass phantom. YAY.

So back to this current story. The install is at a pool club that is next to a 35KW AM Radio Station in a major market.. If I take my Fluke Toner/Sniffer i can hear the radio station almost EVERYWHERE in the pool club.. If I hold it to almost any an outlet, power main, drain pipe, phone line in the place you can hear the radio station clear as day... The outlets that my rack is connected to test fine with a multi meter and a outlet checker. I can hear the radio on my power.. The A15RF fixed the mic line i was having an issue with.. But what can i tell the owners, if anything?! Can this issue be fixed? I imagine the main ground for the building is connected to a pipe somewhere. Same for the phone systems. Any Suggestions?
Don't locate there...

Back in the 80s I got called to exorcise an AM radio station from a console I designed. The customer's studio was in the main lobe of an AM radio station (960kHz)... I ended up reworking the console's internal PS ground structure... That day trip turned into two days with little sleep.  :o

The studio was in the basement of their lawyer/backer's building... So I had to make it right.  ::)

AM radio is worse because it is relatively low frequency so harder to filter out.

I'd keep doing what you are doing (whackamole it where it pops up), unless you can build a faraday cage around the entire property (you can't, so don't bother looking that up).

JR
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Chris Hindle

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Re: Radio station in the pipes
« Reply #2 on: June 03, 2019, 02:21:06 pm »


I'd keep doing what you are doing (whackamole it where it pops up), unless you can build a faraday cage around the entire property (you can't, so don't bother looking that up).

JR
Actually..........
My office is beside Dorval Airport, in Montreal.
There is an "establishment" nearby that IS wrapped in a faraday cage.
Quite impressive.
Now, question is..
What are they keeping out, or what are they keeping in?
No company name anywhere to be seen.
I'd say "Black Ops", but it's a white cage, and it's not in the U S of A.
and it's out in the open for anyone to see.
Chris.
Should I wear my tin-foil hat ? ::)
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Dave Garoutte

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Re: Radio station in the pipes
« Reply #3 on: June 03, 2019, 03:48:30 pm »


Should I wear my tin-foil hat ? ::)

As long as it's properly grounded. :o
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John Roberts {JR}

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Re: Radio station in the pipes
« Reply #4 on: June 03, 2019, 03:52:56 pm »

Actually..........
My office is beside Dorval Airport, in Montreal.
There is an "establishment" nearby that IS wrapped in a faraday cage.
Quite impressive.
Now, question is..
What are they keeping out, or what are they keeping in?
more likely keeping RF leakage from computers (and phones) in... sensitive receivers could sniff data, but not easily. 
Quote
No company name anywhere to be seen.
I'd say "Black Ops", but it's a white cage, and it's not in the U S of A.
and it's out in the open for anyone to see.
Chris.
Should I wear my tin-foil hat ? ::)
of course, but not during thunder storms.

JR
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Mike Sokol

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Re: Radio station in the pipes
« Reply #5 on: June 04, 2019, 07:14:09 am »

Hey All,
So at an install recently, and a few other times in the past, I have run into AM Radio bleeding into mic lines that have a little distance to them. My typical fix would be something like a Shure A15RF.. Those filters work really well and they pass phantom. YAY.

I've also had a lot of success with the Neutrik EMC line of XLR connectors. I have been called in to stop the football games on the local AM radio station from interfering with the pastor's sermon . https://www.neutrik.com/en/neutrik/products/xlr-connectors/xlr-cable-connectors/emc-series
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Jonathan Johnson

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Re: Radio station in the pipes
« Reply #6 on: June 04, 2019, 02:16:14 pm »

An accountant that I support had an office less than 100 feet from an AM radio station's transmitter antenna (don't know the wattage of the station). Naturally, the RF interference was impressive, and caused great amounts of interference on their computer network.

Their ultimate solution was to strip all of the siding from the building, install hardware cloth (1/2" steel mesh, I believe), properly grounded and bonded, and reinstall the siding. I think the radio station ended up sharing some of the cost.

So this nondescript downtown office building is a Faraday cage. The accountant eventually moved out, and an attorney moved in.
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Daniel Levi

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Re: Radio station in the pipes
« Reply #7 on: June 04, 2019, 04:10:01 pm »

and below the former Rampisham transmission site car remotes would not work and they would hear Russian coming out of their toasters!
ERP was a few MW if I remember correctly.
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1662
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Scott Holtzman

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Re: Radio station in the pipes
« Reply #8 on: June 04, 2019, 05:11:18 pm »

An accountant that I support had an office less than 100 feet from an AM radio station's transmitter antenna (don't know the wattage of the station). Naturally, the RF interference was impressive, and caused great amounts of interference on their computer network.

Their ultimate solution was to strip all of the siding from the building, install hardware cloth (1/2" steel mesh, I believe), properly grounded and bonded, and reinstall the siding. I think the radio station ended up sharing some of the cost.

So this nondescript downtown office building is a Faraday cage. The accountant eventually moved out, and an attorney moved in.

An office 100ft from an AM transmitter of the broadcast station?  Since AM stations either use the tower (or a series of towers for a directional array) or a wire going up tower as the antenna I just can't see an office constructed underneath one. 
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Stephen Swaffer

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Re: Radio station in the pipes
« Reply #9 on: June 04, 2019, 10:32:11 pm »

An office 100ft from an AM transmitter of the broadcast station?  Since AM stations either use the tower (or a series of towers for a directional array) or a wire going up tower as the antenna I just can't see an office constructed underneath one.

Unless an engineer is involved  ;D
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Tim McCulloch

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Re: Radio station in the pipes
« Reply #10 on: June 04, 2019, 10:50:31 pm »

and below the former Rampisham transmission site car remotes would not work and they would hear Russian coming out of their toasters!
ERP was a few MW if I remember correctly.
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1662

I see Auntie Beeb retired from that site a few years ago but the sign out front refers to Merlin Communications.  I see Merlin is considered a Telcom, so how much of Rampisham is actually putting out RF?
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Jonathan Johnson

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Re: Radio station in the pipes
« Reply #11 on: June 04, 2019, 11:48:48 pm »

An office 100ft from an AM transmitter of the broadcast station?  Since AM stations either use the tower (or a series of towers for a directional array) or a wire going up tower as the antenna I just can't see an office constructed underneath one.

I just researched this, and I was wrong. It's an FM station, not AM. (It may be that 20 years ago there was an AM transmitter at this site, too. The studio at the site serves several stations.)

But the transmitting antenna is literally in the center of downtown, only 15m above ground level. 2000 watts.

And this office building definitely had a problem.

https://radio-locator.com/info/KRQT-1-FB
« Last Edit: June 04, 2019, 11:51:26 pm by Jonathan Johnson »
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Daniel Levi

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Re: Radio station in the pipes
« Reply #12 on: June 05, 2019, 02:18:17 am »

I see Auntie Beeb retired from that site a few years ago but the sign out front refers to Merlin Communications.  I see Merlin is considered a Telcom, so how much of Rampisham is actually putting out RF?

Not much now, most of the towers have gone and the only one that are left either have satellite links, mobile phone equipment (although that is limited to a short stayed mast in front of the main building) and a low power TV relay.

In it's heyday it had BBC world service, Russia Today, Deutsche Welle amongst other broadcast using 34 wideband curtain arrays and 10 500kW transmitters.

It was quite a sight when you passed it (it was on a secondary "A" road between Crewkerne and Maiden Newton) but looks a bit forlorn now.

It's location is supposedly on a main electricity line and was originally built for war use, with civilian use coming later on. 

As for being owned by Merlin/Babcock, despite merlin being a telecommunications company they ended up owning all? of our SW sites.
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Kevin Graf

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Re: Radio station in the pipes
« Reply #13 on: June 13, 2019, 06:12:27 pm »

Jim Brown has some AES papers on RF interference in mic and audio circuits:

"Testing for Radio-Frequency Common Impedance Coupling (the "Pin 1 Problem") in Microphones and Other Audio Equipment"
http://www.audiosystemsgroup.com/AESPaperNYPin1-ASGWeb.pdf

"A Novel Method of Testing for Susceptibility of Audio Equipment to Interference from Medium and High Frequency Radio Transmitters"
http://www.audiosystemsgroup.com/AESPaperNY-SCIN-ASGWeb.pdf

"Radio Frequency Susceptibility of Capacitor Microphones"
http://www.audiosystemsgroup.com/AES-RFMicrophonesASGWeb.pdf

About 50 more Jim Brown papers and Power Points:
http://www.audiosystemsgroup.com/publish.htm
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Re: Radio station in the pipes
« Reply #13 on: June 13, 2019, 06:12:27 pm »


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