Police Repeaters once discouraged?

[W2MR]

Several old timers have told me over the years that in old police duplex radio systems going back to the first medium frequency (1.6 MHz to 3.0 MHz) systems, repeating the mobile (which was on 30 MHz or so) was discouraged or even illegal unless there was an emergency. I got involved in radio in the mid-70's and there was no restriction by that time. Unofically there were "hot buttons" on the police desk that connected input to output or they just used accoustic coupling back when. The last remnent of this is the FDNY with their "Mixer on/off" switches.

Any old timers out there know?

 

[DaveNF2G]

Repeater operation became possible/legal when VHF high band was occupied. Automatic repeaters became feasible with the change of mode from AM to FM.

I remember a sheriff who hated repeater operations. He didn't want the deputies talking to each other, so the repeater was only to be activated when absolutely necessary. If he heard any car to car communications at other times, he would get on the air and tell the dispatcher to "turn that 3-way off!"

I also recall that some departments would turn off their repeaters when an officer wanted to transmit something "confidential."

 

[RKG]

Repeaters were also highly discouraged (I don't recall that they were illegal -- that is to say, not licensable -- per se for operations on VHF Low Band. The problem was that coverage was already too broad on simplex and repeaters just made things worse. At one time the MDC PD operated a repeater on 39.58 and it could be heard in Kansas and Los Angeles.

 

[CrabbyMilton]

Here in Milwaukee at one time, the old UHF system was mostly full duplex and the dispatcher would turn on the repeater if a squad needed to transmit some important info or if there was a chase or some other tense situation. But with crime the way it is now, it would be counter productive for officers not being able to hear or talk to each other.

 

[W2MR]

All of this seems true. Recently old TV shows such as ADAM-12 and DRAGNET are being shown on "Antenna TV". The producer of both shows, Jack Webb, had a passion for even small details being correct. My impression is that the patrol cars had a duplex dispatch channel which could become a repeater in an emergency and a simplex "TAC-2" channel. I believe that the detective cars had a patrol 2 frequency radio and a additional 1 frequency detectives radio.The detectives had 2 ASPG-80 disguised antennas on the rear cowls.

Things only a radioman would notice.

 

[W2NJS]

I've told this story in other threads but this is a good place to repeat it since it's relevant. Nassau County, New York for years had a police dispatch system with the dispatch on 2.5 mHz AM, and the cars in the 30-some mHz region, I would assume FM. The dispatch signal was transmitted from a tower on top of the PD HQ in Mineola and blanketed the entire county with a fantastically strong, high-quality signal. No one had a receiver for the car channel, which in accordance with common practice at the time was not repeated, but everyone who had an SW receiver could hear the dispatch. Years later all of the 2.5 mHz receivers for the cars ended up for sale at Gregory Electronics in New Jersey, but unless you wanted a good WWV monitor there was no real use for them by that time.

 

[radioman2001]

As far as Adam12 goes and up to when LA went UHF and still to this day for the SO (maybe not sure) they ran split simplex (KMA367 not a valid license anymore). Meaning the cars TX on one channel and RX on another. The radios had dual RX'ers, at least that's what it appears by the size looking at the Motorola Motrac trunk pack in a still shot from the very first Adam 12. I have a few similar designed radios in my archives (basement). TAC 1 and 2 appear to be simplex only frequencies, and I always really loved the disguised antenna setup on the 67 Ford Galaxy 500 Gannon and Friday drove.
To this day our department refuses to go with PL or voters, never mind a repeater on VHF. Instead we have appx. 50ea 30-110 watt simplex bases all over our territory.
One time I bought a few 330 watt Motrac low band repeaters from Gregory Electronics, they came from some mid-west state police. They had split simplex and a dual RX'er. Unfortunately I disposed of them years ago, I would love a nice low band repeater to replace my 470 channel I will lose in 9 years. 130 watts TX on 47mhx and RX on 33mhx would be the best, antenna wouldn't be too long. Could go with a disguised ASP cowl mount antenna with AM/FM coupler.

 

[Russell]

Dallas Police continue to make full use of both sides of the repeater. Aside from regular use of the 'B' channel - talking on the repeater out from mobile/portable (simplex). The system is full duplex to the dispatcher who can hear and talk at the same time (half duplex???); to prevent some stuff from going out the dispatcher will simply hold down the mic key while listening to the mobile traffic. During the 1984 Republican National Convention all the cops got a refresher on their radio capabilities. After that, you would routinely hear them say "turn off the 3 ways" or "repeats off". They use that to this day but not as much. Also, since portables are notorious for not always getting out; the dispatcher will say "can anybody else hear him?" That confused me for quite awhile, especially when somebody in the field would say "yes" and ID the guy or repeat his traffic. Then I figured out they were flipping the TX/RX freqs and listening the mobile transmit side from their mobiles/portables. They still use this quite often; this way anyone in the area can talk directly to a guy screaming for backup without him having to take any action on his radio.

Listening from the 'burbs is quite different from listening in town. There's tons more radio traffic on the same frequency if you're in the middle of the action; tons of chatter in simplex on the output side - you just don't hear that from 20 miles away. Sometimes, I hear what sounds like a cop talking to nobody, but one guy is simplex and the other is repeated.

Trunked systems do not have these simple capabilities. I can't even count how many cops got help because another cop could flip his freqs and listen to the mobile tx side. Many PDs lose out because they don't or can't use simplex freqs or listen to the input. I'm not talking about switching to a simplex channel; I mean full use of the freqs you're already on.

Russell

 

[DickH]

I've told this story in other threads but this is a good place to repeat it since it's relevant. Nassau County, New York for years had a police dispatch system with the dispatch on 2.5 mHz AM, and the cars in the 30-some mHz region, ...

I heard my first police radio around 1935 in Newton, Mass., a Boston suburb. The cop who directed traffic at my grammer school crossing got a new car with a radio. He used to leave the window open so he could hear it.
When I returned from the Korean War in 1954, I moved to adjacent Needham, Mass. and they were on the same AM freq., 1.714MHz. I used to retune the oscillator in our car radios to receive them. There were 4 cities and towns around Boston on the same freq.,; Needham, Newton, Everett and Revere. The PD, FD and Public Works all used the same freq. The cars in Needham transmitted on Hi Band, 155MHz, I think.

After that we used Army surplus tunable tank radios for Lo Band (30-40MHz)
Then it was surplus taxi and business Motorola and GE two-ways on Lo Band and Hi Band.. Then, finally, scanners.

 

[DickH]

Sorry, duplicate.

 

[AC2OY]

Great stories I just learned so much more about radio,repeaters,trunked systems...ect!! I remember Adam-12 like it was yesterday! One guy was Kent Mc Cord I think forgot the other actor's name.

 

[CrabbyMilton]

The other actor was Martin Milner. That was one of the first shows I remember watching when after my mom bought me my first TV in the mid 1970's. Jack Webb created great public safety TV shows as my other favorite was EMERGENCY.

 

[kb2vxa]

Adam-12 shows up in strange places like Rise of Planet of the Apes (2011) when the PD gets attacked on the Golden Gate Bridge. One of the cars crashes into the traffic jam and flips on its side where the 012 on the roof is clearly seen. The laughs come when a female dispatcher (Remember her?) comes on the radio "One adam twelve, one adam twelve..."

The paradox of how apes overthrew Man in the original was explained, now we have another. What was the LAPD car doing in San Francisco or did they move the bridge to Los Angeles? Well, anything can happen in Hollywood when CGI runs amok, and usually does.