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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Mike Kahrs on February 29, 2016, 08:21:45 PM
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Here in 92802 land (Anaheim), IAS shows no TV 14 or TV 16, nor does my TTi scan (indoors). An outdoor scan does show 14 and 16 activity. However, when inputting 475.000 to test, I get a warning "475.00 is within Ch 14 LM which is marked as a deny zone." If I go to "Edit Active Spectrum" there it is, box checked.
I cant find / don't remember what LM stands for. I avoid 470-500 whenever possible (I'm superstitious) however we're loading up an 16 ch Axient System with freqs so I'm shopping for spectrum, and most of our transmitters are G1, so I can't just re-band the receivers.
Thanks,
Mike
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Here in 92802 land (Anaheim), IAS shows no TV 14 or TV 16, nor does my TTi scan (indoors). An outdoor scan does show 14 and 16 activity. However, when inputting 475.000 to test, I get a warning "475.00 is within Ch 14 LM which is marked as a deny zone." If I go to "Edit Active Spectrum" there it is, box checked.
I cant find / don't remember what LM stands for. I avoid 470-500 whenever possible (I'm superstitious) however we're loading up an 16 ch Axient System with freqs so I'm shopping for spectrum, and most of our transmitters are G1, so I can't just re-band the receivers.
Thanks,
Mike
LM is short for Land Mobile Radio Service used in portable communications between vehicles and/or walkie-talkies.
Ch 14 is public safety in Los Angeles, so that's why the deny box is checked.
In the newer version of IAS, the public safety allocations show up as pink bars on the spectrum graph.
Cheers
John
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In the greater Los Angeles metropolitan area, TV channels 14 (470-476MHz), 16 (482-488MHz) & 20 (506-512MHz) are assigned to public safety land mobile radio (LMR) operations. Wireless microphones, and similar low power broadcast auxiliary service equipment (IEMs, intercoms, IFBs, video assist, etc), are not permitted to operate within these channels. Interference to public safety radio systems is taken very seriously by law enforcement and the FCC.
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The LM designation in IAS refers to the Land Mobile Radio used by Public Safety in the T-Band, 470MHz-512MHz(TV14-TV20). These frequencies are typically the 'walkie-talkies' used by your local public safety personnel. And in the case of my home town, they are the dispatch channels for each Police Precinct.
In previous versions of IAS these channels would be identified in the TV Station Wizard but would not be selected as occupied spectrum by default. Starting in version 5 these Public Safety occupied channels are now automatically excluded from possible spectrum. Editing the spectrum IAS will maintain coordination within can be edited by going to Edit > Edit Active Spectrum. Common ISM bands and other broadcast bands can be included or excluded in that menu along with any custom band you wish to exclude or include.
For those of you interested in the nuts-n-bolts: this spectrum allocation occurs in the 13 metropolitan areas listed below. The protected area for this Public Safety service is 30miles(48km) from each listed location below. When utilizing zip codes in IAS's TV Station Wizard the Wizard will exclude all zip codes that overlap the protection area. So even if you are on the opposite side of a Zip from the metropolitan area in question, IAS will assume the most restrictive scenario and exclude the LM channels. BY using exact LAT-LON in the Wizard you can avoid this err on the side of caution.
Urbanized area North latitude West longitude Bands (MHz) TV channels
Boston, MA 42°21′24.4″ 71°03′23.2″ 470-476, 482-488 14, 16
Chicago, IL 41°52′28.1″ 87°38′22.2″ 470-476, 476-482 14, 15
Cleveland, OH 41°29′51.2″ 81°49′49.5″ 470-476, 476-482 14, 15
Dallas/Fort Worth, TX 32°47′09.5″ 96°47′38.0″ 482-488 16
Detroit, MI 42°19′48.1″ 83°02′56.7″ 476-482, 482-488 15, 16
Houston, TX 29°45′26.8″ 95°21′37.8″ 488-494 17
Los Angeles, CA 34°03′15.0″ 118°14′31.3″ 470-476, 482-488, 506-512 14, 16, 20
Miami, FL 25°46′38.4″ 80°11′31.2″ 470-476 14
New York, NY/NE NJ 40°45′06.4″ 73°59′37.5″ 470-476, 476-482, 482-488 14, 15, 16
Philadelphia, PA 39°56′58.4″ 75°09′19.6″ 500-506, 506-512 19, 20
Pittsburgh, PA 40°26′19.2″ 79°59′59.2″ 470-476, 494-500 14, 18
San Francisco/Oakland, CA 37°46′38.7″ 122°24′43.9″ 482-488, 488-494 16, 17
Washington, DC/MD/VA 38°53′51.4″ 77°00′31.9″ 488-494, 494-500 17, 18
Cameron Stuckey
Professional Wireless
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Thanks for the nuts and bolts info Cameron!
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The LM designation in IAS refers to the Land Mobile Radio used by Public Safety in the T-Band, 470MHz-512MHz(TV14-TV20). These frequencies are typically the 'walkie-talkies' used by your local public safety personnel. And in the case of my home town, they are the dispatch channels for each Police Precinct.
In previous versions of IAS these channels would be identified in the TV Station Wizard but would not be selected as occupied spectrum by default. Starting in version 5 these Public Safety occupied channels are now automatically excluded from possible spectrum. Editing the spectrum IAS will maintain coordination within can be edited by going to Edit > Edit Active Spectrum. Common ISM bands and other broadcast bands can be included or excluded in that menu along with any custom band you wish to exclude or include.
For those of you interested in the nuts-n-bolts: this spectrum allocation occurs in the 13 metropolitan areas listed below. The protected area for this Public Safety service is 30miles(48km) from each listed location below. When utilizing zip codes in IAS's TV Station Wizard the Wizard will exclude all zip codes that overlap the protection area. So even if you are on the opposite side of a Zip from the metropolitan area in question, IAS will assume the most restrictive scenario and exclude the LM channels. BY using exact LAT-LON in the Wizard you can avoid this err on the side of caution.
Urbanized area North latitude West longitude Bands (MHz) TV channels
Boston, MA 42°21′24.4″ 71°03′23.2″ 470-476, 482-488 14, 16
Chicago, IL 41°52′28.1″ 87°38′22.2″ 470-476, 476-482 14, 15
Cleveland, OH 41°29′51.2″ 81°49′49.5″ 470-476, 476-482 14, 15
Dallas/Fort Worth, TX 32°47′09.5″ 96°47′38.0″ 482-488 16
Detroit, MI 42°19′48.1″ 83°02′56.7″ 476-482, 482-488 15, 16
Houston, TX 29°45′26.8″ 95°21′37.8″ 488-494 17
Los Angeles, CA 34°03′15.0″ 118°14′31.3″ 470-476, 482-488, 506-512 14, 16, 20
Miami, FL 25°46′38.4″ 80°11′31.2″ 470-476 14
New York, NY/NE NJ 40°45′06.4″ 73°59′37.5″ 470-476, 476-482, 482-488 14, 15, 16
Philadelphia, PA 39°56′58.4″ 75°09′19.6″ 500-506, 506-512 19, 20
Pittsburgh, PA 40°26′19.2″ 79°59′59.2″ 470-476, 494-500 14, 18
San Francisco/Oakland, CA 37°46′38.7″ 122°24′43.9″ 482-488, 488-494 16, 17
Washington, DC/MD/VA 38°53′51.4″ 77°00′31.9″ 488-494, 494-500 17, 18
Cameron Stuckey
Professional Wireless
A little fun history. One of my first "real" electronics jobs was with a Radio Common Carrier (RCC) Gabriel Communications actually in Ft. Lauderdale. Long before Cellular the T-Band (T for TV) channels were used for full duplex mobile communications. Huge 30 watt radios with cavity type duplexers that even with a perfect tune still desensitized the receivers. I forgot if the T-Band system was Seacode Smart or IMTS signalling.
There were sites from West. Palm down to the Keys all linked with 2.4Ghz GTE Lenkurt radio with these Side Band multiplexors that shifted the audio up for each channel and output a baseband signal for transmission. Tuning those filters was an ungodly job that was done with a dual trace scope, a signal generator to form a lissajous pattern http://www.electrical4u.com/lissajous-patterns-of-cro/ an old fashioned technique for analyzing the phase difference between two signals.
Anyway I digressed too far, there is another thread going on about teaching electronics. These early experiences that taught me about analog filters, phase alignment and all sorts of RF and Antenna theory have been completely analogous to the audio world.
Nice to see the T-Band channels are still being used for public safety. UHF 400Mhz IMHO has just the right combination of penetration and propagation. Very valuable spectrum IMHO.
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In the newer version of IAS, the public safety allocations show up as pink bars on the spectrum graph.
Cheers
John
Good to know - thanks. I'm red/green colorblind, so the bars looked grey to me.
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Good to know - thanks. I'm red/green colorblind, so the bars looked grey to me.
HA! The thing is that the LM transmitters are not always operational in the area you may be.. They come and go.. As Henry said, stay away from them.