| Re: 1800 Foot cable run [message #321974 is a reply to message #321939 ] |
Mon, 12 May 2008 10:19   |
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Henry Cohen
Messages: 759
Registered: January 2006
Location: Westchester Co., NY |
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| John Fritz wrote on Mon, 12 May 2008 09:01 |
with a little research...one might find that the low level fm broadcast might be an answer....
some require a license, etc...
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Any FM Broadcast transmission system that exceeds a power level of 250 microvolts/meter at 3 meters requires a license (final range depends on propagation path, obstacles and receiver sensitivity).
Also, FM Broadcast is actually not the best method to transmit firing counts or time code for fireworks control. It is arguably a viable option for the music, but there are [generally better] alternatives as well.
Henry Cohen
Production Radio Rentals
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"Every new [intentional] radio emitter since Marconi’s 2nd transmitter has caused interference to other systems!" - Michael Marcus, Oct '07
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| Re: 1800 Foot cable run [message #321978 is a reply to message #321960 ] |
Mon, 12 May 2008 10:24 |
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Henry Cohen
Messages: 759
Registered: January 2006
Location: Westchester Co., NY |
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| Robert Carrell wrote on Mon, 12 May 2008 10:45 |
A commercial FM station will be broadcasting the event and has connections to the PA.
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Is the FM station broadcasting the music? If so, there's your music transmission system; just provide an FM receiver(s) at the fire control position(s).
Fire counts or time code could be sent via the FM station's subcarrier if they can provide an extra audio path back to the transmitter. You would of course need to provide receivers capable of receiving the subcarrier.
Henry Cohen
Production Radio Rentals
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"Every new [intentional] radio emitter since Marconi’s 2nd transmitter has caused interference to other systems!" - Michael Marcus, Oct '07
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| Re: 1800 Foot cable run [message #321984 is a reply to message #321981 ] |
Mon, 12 May 2008 11:08 |
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Henry Cohen
Messages: 759
Registered: January 2006
Location: Westchester Co., NY |
Has No Life |
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| John Fritz wrote on Mon, 12 May 2008 11:50 |
Again, if its a "of-quality" type event.. if permits, licenses are needed,,IF you need broadcast power....
affiliated members of the event can lend
some influence to assist in getting this done.
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Unless one of the "affiliated members" is an FCC commissioner (or can guarantee one of the commissioners a 7 figure salary job when their term ends), the only proper course of action is to formally apply for an STA (Special Temporary Authorization) and provide the corresponding engineering study. http://edocket.access.gpo.gov/cfr_2007/octqtr/47cfr73.1635.h tm
Henry Cohen
Production Radio Rentals
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"Every new [intentional] radio emitter since Marconi’s 2nd transmitter has caused interference to other systems!" - Michael Marcus, Oct '07
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| Re: 1800 Foot cable run [message #322196 is a reply to message #321677 ] |
Mon, 12 May 2008 22:09 |
 Jim Cutshall
Messages: 344
Registered: April 2004
Location: St. Louis, MO |
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I've worked with Zambeli MANY time and their x-local guys with their new company are officed' in my warehouse. With that said, the CD has always been Music on Left / FSK Time Code on the right - NOT audible cues. You may want to double (triple) check with them again. Who is the shooter?
Usually, what happens is that they supply a Marti transmitter to transmit the FSK time code to their firing computer. If they are doing something differently, I'd be surprised. Due to the delays, they will never be able to sync properly otherwise.
FWIW
Jim
[Updated on: Mon, 12 May 2008 22:11]
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| Re: 1800 Foot cable run [message #322243 is a reply to message #322196 ] |
Tue, 13 May 2008 02:06 |
Dexter McNeil
Messages: 16
Registered: September 2007 |
Here Often |
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FWIW, I have a pair of old Western Electric 111C transformers that the phone companies used to use to drive broadcast lines at remote locations with. These are mounted in boxes with binding posts and xlr jacks on them, and I use them to do exactly what you are trying to do. They were frequently installed in locations where remote broadcasts for FM stations were done, back in the days before digital ruled the world. Several thousand feet of cable between the end point and the central office where the equalizing amplifier was located was not uncommon, I've gone as far as 3000 ft, using 1000 ft spools of 24ga cross connect wire, with little loss in fidelity. If there are some older radio stations in your area you might find a crusty old radio engineer who'd part with a pair for a six pack or two.
Use your choice of HP amp and cans at the pyro end of things. If you need to get stereo to them, you'll need two pairs of transformers.
They've got high isolation, great CMR and reasonable fidelity, in a totally passive solution.
Cheers,
Dexter McNeil
Backstage Technologies
Bellows Falls, VT
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| Re: 1800 Foot cable run [message #322265 is a reply to message #322196 ] |
Tue, 13 May 2008 06:25 |
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Henry Cohen
Messages: 759
Registered: January 2006
Location: Westchester Co., NY |
Has No Life |
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| Jim Cutshall wrote on Mon, 12 May 2008 23:09 |
I've worked with Zambeli MANY time and their x-local guys with their new company are officed' in my warehouse. With that said, the CD has always been Music on Left / FSK Time Code on the right - NOT audible cues. You may want to double (triple) check with them again. Who is the shooter?
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Although FSK is arguably the most used data format in computer controlled firings, with SMPTE a distant second, many smaller shoots and companies do simply continue to use a voice countdown. Further, many of the bigger shows have stereo music and time code employing a computer, DA88, ADAT or some other multichannel format.
Henry Cohen
Production Radio Rentals
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"Every new [intentional] radio emitter since Marconi’s 2nd transmitter has caused interference to other systems!" - Michael Marcus, Oct '07
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| Re: 1800 Foot cable run [message #322334 is a reply to message #322312 ] |
Tue, 13 May 2008 10:27 |
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Henry Cohen
Messages: 759
Registered: January 2006
Location: Westchester Co., NY |
Has No Life |
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| Tim McCulloch wrote on Tue, 13 May 2008 10:39 |
Another possibility for you might be ClearCom. You can inject the firing cues as "program" into the com system. I've run 1000' doing this... Someone else here might have more info, or you can contact ClearCom to ask how much line they can drive.
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I'd be vary wary of running an unbalanced signal nearly 2000'.
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{RANT} Pyro companies do this all the time. Most of the firms I've worked with consider delivering cues to not be their problem even though it's *mission critical* for their work. It amazes me that they don't have their own basic solutions for this. {/RANT}
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My experience with the larger fireworks companies who regularly do large scale high profile events is that they take very seriously the delivery of time code, cues and/or music. They spend considerable money and advance time with us to get it right.
Henry Cohen
Production Radio Rentals
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"Every new [intentional] radio emitter since Marconi’s 2nd transmitter has caused interference to other systems!" - Michael Marcus, Oct '07
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| Re: 1800 Foot cable run [message #322348 is a reply to message #322309 ] |
Tue, 13 May 2008 11:41 |
Dexter McNeil
Messages: 16
Registered: September 2007 |
Here Often |
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| Robert Carrell wrote on Tue, 13 May 2008 10:35 |
Hi Dexter,
Thanks. I may not have time to hunt down an old radio engineer, I'm an old sound guy and can't shoot straight.
Seriously, there are tons of radio stations in the LA marketplace. A few are my clients. I will talk with them. If I remember right, fidelity is limited a little (maybe 80 - 12kHz), but isn't noticable to most and won't matter on spoken word.
Appreciate the suggestion.
Best regards,
Robert
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Robert,
This link http://radiomagonline.com/notebook/radio_western_electric_c_ 2/ has schematics and brief specs on the 111C and 119C repeater coil/transformers. BTW, the equalized broadcast lines were set up to be flat from 30hz to 15khz, anything more than 15K was lost in the transmitter anyway. It's a pretty impressive spec when you consider that the phone company could do this for you over MILES of cable.
Good luck and let us know how you solve the problem!
Dexter
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