Interesting comment! So was the Duluth dispatcher able to talk directly to the Thunder Bay OPP station via the Grand Marais (Bogus Lake ) radio tower? If so, was it on the Minnesota Highway Patrol frequency (an old diagram shows 42.54 MHz) or the OPP's frequency? ~75 miles between the two locations so curious about how this 'primitive' cross-country interoperability setup worked.
OPP Historical
- Thread starter LesWurk
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Interesting comment! So was the Duluth dispatcher able to talk directly to the Thunder Bay OPP station via the Grand Marais (Bogus Lake ) radio tower? If so, was it on the Minnesota Highway Patrol frequency (an old diagram shows 42.54 MHz) or the OPP's frequency? ~75 miles between the two locations so curious about how this 'primitive' cross-country interoperability setup worked.
lenk911
Member
Yes, they talked cross frequency. Duluth transmitted via MSP's Grand Marais tower on 42.54 with an initial preceding beep tone ( 1-2 seconds of 1200-2400 Hz) which would open our receiver at OPP's tower in Thunder Bay. The reverse from OPP to Duluth was on their 42 MHz to receiver at Grand Marais with a like beep tone. That way we didn't have to listen to each other's routine traffic.
Duluth was connected to Grand Marais via 72/75 MHz and VHF links via the tower at Palisades Head (Beaver Bay, MN). Not sure on the name Bogus Lake since I moved on and missed the ARMER construction. They may be the same tower different name. In my era, Grand Marais was a 180 foot free standing tower just above the town.
Propagation around the big lake was always unpredictable. Lots of ducting. If I recall the circuit was reliable and easy to engineer--we never had to touch each other's equipment. The difficult issue was the FCC rules about cross border communications had to be overcome.
Thanks for sharing this history. Yeah I'm sure the cross border communication legalities we're a bigger headache than the actual technical aspects.
My early-mid 80's diagram of the State Patrol and MnDOT radio networks lists the Grand Marais station as Bogus Lake, along with the 72/75 MHz link to Palisade Head. I was in the area in July and walked up the forest service road to see the tower as a short side trip. The design and condition definitely says state radio tower and is most likely well over half a century old, similar to the one at Palisade Head.
Back to the OPP, whenever they moved away from VHF they probably had to add a lot more radio tower sites along the highways of NW Ontario with how remote and rugged the terrain is. Do you know if they continued this interoperability circuit after MN State Patrol switched to VHF high band in the mid 80's, or after OPP went even higher in frequency? Cool to see the lowband ball mount on that OPP car mounted in the center of the vehicle roof, instead of the rear side like seemed to be the standard in the US. Probably produced a more omnidirectional pattern.
lenk911
Member
The Grand Marais tower was there in 1968 when I came to work for them. I changed the building out in the 1974-75 era.
The Palisades Head was one of the late 1940's-1950's Blau Knox "vertical bridges" specifically designed by the Minnesota Highway Department's engineers. Blau Knox was the contractor of the original AT&T Long-Lines microwave towers. These are 4 legged angle iron towers. There were about 28 or so constructed around the state--the last in 1968. It was the lead paint issues that caused many to be replaced. Not sure if it has been replaced under the ARMER project .
Prior to 1970, Grand Marais was the end of a 4 hop 72/75/150 MHZ link circuit emanating from Virginia, MN to Duluth to Palisades Head to Grand Marais. The 42.820 MHZ stations, many 10,000 watt Motorola Research Line, hung on the effective 4 wire circuit and were addressed like birds on a wire. Each had their own specific beep tone which would place the transmitter on the circuit. A talented technician could selectively whistle up each station along the circuit from a service microphone. After 1970 the circuit was broken at Duluth when Duluth became as dispatch center and the frequency changed to 42.56 MHZ. Additional circuits were added to the link to separate the audio.
The left rear 7 foot whip was standard for marked squads to minimize hitting of low hanging trees. Unmarks had a "broadcast" look alike on the right front fender. Center roof is the best place but aesthetics would never allow such!
The Palisades Head was one of the late 1940's-1950's Blau Knox "vertical bridges" specifically designed by the Minnesota Highway Department's engineers. Blau Knox was the contractor of the original AT&T Long-Lines microwave towers. These are 4 legged angle iron towers. There were about 28 or so constructed around the state--the last in 1968. It was the lead paint issues that caused many to be replaced. Not sure if it has been replaced under the ARMER project .
Prior to 1970, Grand Marais was the end of a 4 hop 72/75/150 MHZ link circuit emanating from Virginia, MN to Duluth to Palisades Head to Grand Marais. The 42.820 MHZ stations, many 10,000 watt Motorola Research Line, hung on the effective 4 wire circuit and were addressed like birds on a wire. Each had their own specific beep tone which would place the transmitter on the circuit. A talented technician could selectively whistle up each station along the circuit from a service microphone. After 1970 the circuit was broken at Duluth when Duluth became as dispatch center and the frequency changed to 42.56 MHZ. Additional circuits were added to the link to separate the audio.
The left rear 7 foot whip was standard for marked squads to minimize hitting of low hanging trees. Unmarks had a "broadcast" look alike on the right front fender. Center roof is the best place but aesthetics would never allow such!
It was MDC600 and it was used to steer radios to different channels. It was not an anti-scanner thing.
VA2XDJ
Member
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My apologies for my error! Thank you for clarifying!
Thanks for the additional history lesson, even if it's not directly related to the OPP! Yes those 50's era Blau-Knox towers like the one at Palisade Head certainly remind me of the robust AT&T Long Line tower design but minus the microwave horns. There is such a tower near Kimball, Minnesota south of St. Cloud and others still around the state that are 4 legged and painted red and white.. I'm guessing the Highway Department may have had nearby nuclear strikes in mind when specifying the tower designs as did AT&T. So it sounds like it was easier and safer to replace an entire tower vs. sanding off lead paint and repainting.
I learned on a different thread that the 10,000 watts was used/needed to overcome vehicle ignition noise. This must have saturated the entire Minnesota Arrowhead Region, the western UP of Michigan and probably a good portion of the Thunder Bay District. I wonder if the OPP ran the same kind of power on lowband base stations? This still seems insanely excessive considering that amateurs are restricted to 1500 watts.
I presume that side mounting lowband antennas made mobile stations less omnidirectional and pushed more signal in the direction of the vehicle due to ground plane. I guess aesthetics may have mattered less to the OPP with roof mounting of lowband antennas.
lenk911
Member
You are right, the lead paint and the EPA clean-up requirements ended the life of many of the Blau Knox towers for both Minnesota and AT&T. The design and choice was really foresighted. We never had to worry about structural analysis on these towers when we started adding microwave dishes to the site. They seemed to hold an unlimited load!
Regarding 10,000 watts: Minnesota had 6 sets of these stations, 3 cabinets per set. They were at towers associated with the dispatch centers, at Virginia, Thief River Falls, Brainerd, Saint Paul, Rochester, and Marshall. All the remote sites were either 300 or 100 watt stations. BTW: ND State Patrol also had about 6 of these same stations. You are exactly right, they were needed to to blast through the vehicle's ignition noise. When Motorola and GE developed the noise blanker, all the 10,000 watt stations were loafed to about 1000 watts because the finals (size of a quart mason jar) were so expensive. Finally with the multi-channel low band system conversion began in 1970 all were replaced with 300 or 100 watt stations.
One of the brilliant planning moves in the 1940s was to assign state police channels to states and I assume provinces east-west from one another with one state in between. For instance Minnesota and Wyoming shared the same pair as did North Dakota and Wisconsin. Otherwise the channel was clear for most of North America. The only time we heard Wyoming was when there was a big storm in between. We could run 10,000 watts, the maximum the FCC allowed, and didn't seem to bother anybody. Sheriff's that had north-south channel sharing were getting skip all summer long. Of course that fell apart as states moved from beyond the single channel pair to multiple channel pairs. Then we had to add tone squelch to the system to retain sanity.
Regarding 10,000 watts: Minnesota had 6 sets of these stations, 3 cabinets per set. They were at towers associated with the dispatch centers, at Virginia, Thief River Falls, Brainerd, Saint Paul, Rochester, and Marshall. All the remote sites were either 300 or 100 watt stations. BTW: ND State Patrol also had about 6 of these same stations. You are exactly right, they were needed to to blast through the vehicle's ignition noise. When Motorola and GE developed the noise blanker, all the 10,000 watt stations were loafed to about 1000 watts because the finals (size of a quart mason jar) were so expensive. Finally with the multi-channel low band system conversion began in 1970 all were replaced with 300 or 100 watt stations.
One of the brilliant planning moves in the 1940s was to assign state police channels to states and I assume provinces east-west from one another with one state in between. For instance Minnesota and Wyoming shared the same pair as did North Dakota and Wisconsin. Otherwise the channel was clear for most of North America. The only time we heard Wyoming was when there was a big storm in between. We could run 10,000 watts, the maximum the FCC allowed, and didn't seem to bother anybody. Sheriff's that had north-south channel sharing were getting skip all summer long. Of course that fell apart as states moved from beyond the single channel pair to multiple channel pairs. Then we had to add tone squelch to the system to retain sanity.
Diddley
Member
Who recalls the big white signs up and down the 400-series highways which indicated that OPP were monitoring CB Channel 9 for emergencies?
Man, those were the days.
Man, those were the days.
It also transmitted the Status updates of the vehicle as well as controlling the Mobile Repeater. If you were lucky and had the Phone option enabled you could make phone calls from the car as well.
The biggest issue with that system was its basic design. It was oriented towards dispatching one car at a time rather than letting the whole fleet hear the call. The big drawback being you could be right on top of a call and not even know it was happening because you were not dispatched to it. I guess it was overcompensation from everyone on lowband hearing stuff halfway across the province. Now you only heard what was directed at you. The PL was to prevent a radio from passing the MDC control bursts to the in car speaker.
The system was designed to give more control to the dispatcher. As far as the system design, it was way ahead of it'd time. It had Full telco interconnect and was was capable of Mobile Data. Some testing was done and they were able to get 9600 baud through the system but by then cellular data was more cost effective. The SIM system was also capable of binary paging but due to the microwave deployment delay, other paging options were more cost effective by then. This system was designed in the late 70's but wasn't deployed until the late 80's with District 2 London being the first area. The system did what it was exactly designed to do in my opinion. Just my 2 cents worth.
ChuckWillis55
Member
Correct. 42.06 was the Car to Car channel for all Districts, if memory serves me correctly.
I think Peterborough might have used it.
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Definitely. Spent time at Rice Lake in those days and 41.96 was how we monitored the OPP.
