Old LAPD VHF Frequencies

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N3KGD

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Wirelessly posted (BlackBerry8330m/4.5.0.175 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/104)

I'm curious if anyone has a copy or list of LAPDs old VHF Frequencies before they switched over to UHF. I am aware of those 5 or so KMA367 Hotshot and TAC Frequencies, but were there anymore VHF Frequencies? I'm not fron LA so I wouldn't know.

Any help is appreciated.

Thanks,
- Nick (Driv3r912)
 

N3KGD

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Thank you very much Mick. I'm working on a project somewhat and the data is relevant.

Thanks again,
Nick.
 

KMA367

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Here's the page from the 1979 Southern California "Police Call" book, which is the last version I have before the switch to UHF which occurred for all patrol and traffic divisions between March 1981 and July 1982. As you can see, Central and Newton were already using UHF on a test basis, and North Hollywood and West Valley had been moved off the Valley's overcrowded 159.03 dispatch frequency and onto simplex (ugh).

In 2001 Gene provided me permission to reprint and upload this list, as well as his original 1964 list which is online at "1964 Police Call - Southern California"
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N3KGD

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KMA367, thank you very much for that information. This data is great. I didn't realize that LA went to UHF so early in the 80s. I thought the Department made the transition in the mid 90s. But again, I wasn't sure off hand because I never lived in LA.

It is further interesting to see that North Hollywood and the West Valley Divisions moved their communications onto simplex frequencies. According to your "ugh", it sounds like it didn't go out so well. Probably loss of some communications in the field I assume.

In any event, thank you very much for this information. It is greatly appreciated and very informative.



- Driv3r912
 

KMA367

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KMA367, thank you very much for that information. This data is great. I didn't realize that LA went to UHF so early in the 80s. I thought the Department made the transition in the mid 90s. But again, I wasn't sure off hand because I never lived in LA.
You're welcome. In the 1981-82 switch to UHF, LAPD went to 8-channel Motorola MX350 analog radios - all portables, with convertacoms in the cars, no real mobile radios. For patrol there were four frequency configurations, one for each bureau. Channels 1, 2, and 3 varied by bureau, but channels 4-8 were the same in all radios. Note that there were two divisions on each dispatch frequency, except for Hollywood and 77th St, which had their freqs to themselves.

CENTRAL BUREAU
  • Central & Central Traffic - 506.7375 (Central 1)
  • Rampart & Northeast......- 506.9375 (Central 2)
  • Hollenbeck & Newton......- 507.1875 (Central 3)
VALLEY BUREAU
  • Van Nuys & Valley Traffic - 506.7125 (Valley 1)
  • W. Valley & Devonshire....- 506.8875 (Valley 2)
  • No. Hollywood & Foothill....- 507.1625 (Valley 3)
SOUTH BUREAU
  • Harbor & Southeast.......- 506.7875 (South 1)
  • Southwest & So. Traffic - 506.9875 (South 2)
  • 77th Street....................- 507.2375 (South 3)
WEST BUREAU
  • West LA & West Traffic - 506.7625 (West 1)
  • Wilshire & Pacific.........- 506.9625 (West 2)
  • Hollywood.....................- 507.2125 (West 3)
ALL RADIOS
  • Central Bureau Tactical - 506.5875 - "Tac 4"
  • Valley Bureau Tactical...- 507.2625 - "Tac 5"
  • West Bureau Tactical....- 506.8125 - "Tac 6"
  • South Bureau Tactical...- 507.0375 - "Tac 7"
  • Emergency "Trigger".....- 507.0875 - "Emergency Trigger"
Metropolitan Division
  • Metro & SWAT - 506.8375 - "Metro" (I don't know how Metro's radios were set up, or what channel that frequency was programmed into)

In 1994-95 they replaced the MX350s with 256-channel Astro Saber III handhelds. This may be the 1990s transition you're thinking of. The radios were dual-mode, analog/digital, but were used only in analog mode until June 18, 2004 when they switched everybody to digital.

The frequency assignments remained about the same until late 2004 when they were changed to approximately what they use today (with a few changes, such as two new divisions being added, some new tactical frequencies, etc). See Los Angeles County, California (CA) Scanner Frequencies and Radio Frequency Reference or my "abbreviated" site at Los Angeles Police Department Radio Frequencies - LAPD Scanner Frequencies

It is further interesting to see that North Hollywood and the West Valley Divisions moved their communications onto simplex frequencies. According to your "ugh", it sounds like it didn't go out so well. Probably loss of some communications in the field I assume.
This three-year period was the only time that LAPD's ever used straight simplex for dispatching, and while it was common with many PDs at the time, it was new and unwelcome by both the officers and dispatchers. Previously the dispatcher was always able to hear her officers on the uplink frequency even while she was transmitting, so an urgent message from an officer wouldn't be missed. But with simplex of course, whenever the dispatcher would key up, it would mute all incoming traffic... something they never liked or got used to. I was long gone by then, but I'm told by my wife that the WVal & NHwd officers couldn't have been happier when the UHF came in... not only were they no longer "muted," but LAPD now had repeaters for the dispatch and tac frequencies, something they'd never had before.
 
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N3KGD

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Thank you for that further information KMA367. I have a couple more questions that I hope you can answer if you don't mind.


How does the communications system work?

For example, Channel 12 (77th Street) is a dispatch frequency. Are units able to talk to each other or are they only capable of talking to the base for handling incidents?

Lets say 12A34 wants to talk to 12L16 at the scene of a call or en-route to a call. Would they move to a talk-around channel so they can talk to each other, such as Channel 112. I would imagine this is the case so it doesn't tie up the dispatch channel.


Basically, what I am getting to here is, what would the difference be between Dispatch Channels and Talkaround Channels communications-wise? I understand the difference between the two, but how does this configuration work in LA?

This question further relates to their present configuration as well.

Thanks,
Nick (Driv3r912)
 

KMA367

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Thank you for that further information KMA367. I have a couple more questions that I hope you can answer if you don't mind.

How does the communications system work?

For example, Channel 12 (77th Street) is a dispatch frequency. Are units able to talk to each other or are they only capable of talking to the base for handling incidents?

Lets say 12A34 wants to talk to 12L16 at the scene of a call or en-route to a call. Would they move to a talk-around channel so they can talk to each other, such as Channel 112. I would imagine this is the case so it doesn't tie up the dispatch channel.
Yes, that's exactly how it's supposed to work, and how it's usually done, precisely for the reason you suggest. However - and this seems to be happening more and more the last few years - during particularly hot incidents like "officer needs help" calls and foot pursuits the officers involved have enough going on without having to stop and mess with their radios. The dispatcher (RTO) may put the dispatch frequency on a "stand-by," either on her/his own accord, or upon the request of a unit or supervisor. If it becomes a drawn-out affair, like setting up a perimeter, it will be moved to either the division "simplex" frequency, or else to an available bureau or citywide tac frequency.

Basically, what I am getting to here is, what would the difference be between Dispatch Channels and Talkaround Channels communications-wise? I understand the difference between the two, but how does this configuration work in LA? This question further relates to their present configuration as well.
The so-called (and mis-named) Division "simplex" tactical frequencies, and the Bureau and Citywide Tac frequencies are all user-selectable for either simplex (direct) or duplex (repeater) mode. The divisional tac freqs, Channels 101 to 125, each have their repeaters within their division, most or all of them at the station, so their range is good, but it's more limited than the bureau and citywide tacs, whose repeaters are on mountaintops and a couple tall buildings. In addition, the seven citywide tacs use synchronized simulcast, and transmit from multiple sites simultaneously for even better range and coverage.

The dispatch frequencies are duplex only, and this goes back to the change from analog to digital. When they were analog, each division's "tactical" frequency was its dispatch frequency but used in true simplex (direct) mode on the talk-out side. As long as the officers were close enough to each other they could communicate, and usually could hear (but not be drowned out by) the dispatcher. So it was sort of a double benefit: they could talk car-to-car, but still have half an ear listening to dispatch in case a good call, or a message for them, came out. And "switch to simplex" became so entrenched in everyone's vocabulary that when the change I'll describe next occurred, it remained and "simplex" is still the word used today when officers want to talk on their division tac frequency

As you may know about digital, the signal is usually all or nothing. When they first went to digital the channels remained configured as before. However, all of a sudden they found that simplex was fine until their (or any) dispatcher would transmit a call on their frequency. The competing simplex and dispatch signals would essentially cancel each other out and they would hear either complete gobbledygook, or more likely, nothing at all. To my knowledge nobody has ever explained or fessed up to why this "feature" of digital either wasn't made known or provided for before they made the change. So between 2001 and the radio reconfiguration in 2004, there were no division tacs available. The Saber IIIs did however, have a number of unused frequency pairs that were later (2004) to become dispatch frequencies, so each bureau got a couple of them to use as tactical freqs in the meantime.

Clear as mud now?
 
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N3KGD

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The explanation given above sounds good to me. I understand how it works now. I myself have never been the big fan of digital modes of communications. The main reason in your statement being "you hear all or nothing". At least in analog, you can pick up a transmission if you listen close enough out of the static. Moving your radio in the air to the direction of the signal also helps in analog traffic.

I would clarify why UHF is used as opposed to VHF. I would bargain the main reason being because the signal can travel easier through all the buildings, high-rises, towers and other structures. But, with that, you lose some range as opposed to VHF - which would work great outside, but have a hard time navigating the terrain as it ping pongs off of structures. This might be why they made a transition to UHF.

In short, I have a general idea on the LAPDs communications systems. Thank you again for this vast amount of information. All help was appreciated.

Take care and stay safe,
73,
Nick,
KB3RDO,
Driv3r912
 
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