Police car antenna question

[ARCHIVED THREAD] - Police car antenna question

Posted: 9/13/2017 12:32:47 PM EDT

I mainly see these 2 roundish antennas on the back of police cars, but in the picture it's actually a fire department truck. I also see them on city code official trucks.

What are they for, internet connection? If so, why do they need these, and I assume a lot of other expensive equipment and installation costs, when I get high speed 4G internet connectivity to my cell phone without external antennas? I see these in all cities and towns here where it's very densely populated and cell signals are very good anywhere you go.

Posted: 9/13/2017 12:46:07 PM EDT

[#1]

AVL (Automatic Vehicle Locator)
GPS

Posted: 9/13/2017 1:06:05 PM EDT

[#2]

They have computers in their cars. They need to talk to various data bases. They cannot do that with a phone screwed to their ear.

Posted: 9/13/2017 1:38:21 PM EDT

[#3]

Quote History

Quoted:
They have computers in their cars. They need to talk to various data bases. They cannot do that with a phone screwed to their ear.

View Quote

What do you mean when you say a phone screwed to their ear?

If that was in reply to what I said about 4G cellular connection, why would they have a phone near their ear?

Posted: 9/13/2017 1:40:28 PM EDT

[#4]

Quote History

Quoted:
AVL (Automatic Vehicle Locator)
GPS

View Quote

Why would code officials and firefighters have AVL?

GPS? 2 giant antennas for GPS? I doubt it. GPS antennas are small and in many instances aren't mounted externaly anymore.

I think you two are just throwing out wild guesses. I am still laughing about the phone at the ear comment

Posted: 9/13/2017 1:56:48 PM EDT

[#5]

There are some 700/800 mhz and uhf/450 mhz radio antennas that look like the gps antenna too.

Posted: 9/13/2017 2:08:25 PM EDT

[#6]

Usually they are black like this:

https://uploads.thealternativepress.com/uploads/photos/[email protected]

Posted: 9/13/2017 2:09:03 PM EDT

[#7]

Quote History

Quoted:

Why would code officials and firefighters have AVL?

GPS? 2 giant antennas for GPS? I doubt it. GPS antennas are small and in many instances aren't mounted externaly anymore.

I think you two are just throwing out wild guesses. I am still laughing about the phone at the ear comment

View Quote

Some departments are using AVL on fire and EMS vehicles combined with GIS backed dispatch systems to dispatch "the closest vehicle in service to a call".

A recent example of this poorly implemented is in Baltimore

Posted: 9/13/2017 5:02:34 PM EDT

[#8]

Quote History

Quoted:

Why would code officials and firefighters have AVL?

GPS? 2 giant antennas for GPS? I doubt it. GPS antennas are small and in many instances aren't mounted externaly anymore.

I think you two are just throwing out wild guesses. I am still laughing about the phone at the ear comment

View Quote

Not a wild guess. My patrol car has a similar antenna for the AVL.

Posted: 9/13/2017 9:37:40 PM EDT

[#9]

I thought our gps/avl antennas were ugly. I don't feel bad now!

Posted: 9/14/2017 11:05:19 PM EDT

[#10]

Those look like GPS antennas, the 2 antennas make me think not radio (7/800 or VHF) related.

Posted: 9/14/2017 11:10:38 PM EDT

[#11]

I looked through a bunch of antennas but didn't see that exact model. It's probably some combination of GPS, WiFi, 700MHz, 800MHz, 1900 & 2100MHz. Maybe even 450MHz.

Posted: 9/15/2017 7:45:38 PM EDT

[#12]

The GPS antena in our cars are about 3" across and 1/2" thick. We mount them on the center of our dash and they plug into a USB port on our laptops.

Posted: 9/15/2017 9:03:05 PM EDT

[#13]

Quote History

Quoted:
AVL (Automatic Vehicle Locator)
GPS

View Quote

this (on our cars at least) please the cell link for our in car radio/computer modem. we have two puck antennae on each car for these systems.

J-

Posted: 9/15/2017 9:05:15 PM EDT

[#14]

Quote History

Quoted:

Why would code officials and firefighters have AVL?

GPS? 2 giant antennas for GPS? I doubt it. GPS antennas are small and in many instances aren't mounted externaly anymore.

I think you two are just throwing out wild guesses. I am still laughing about the phone at the ear comment

View Quote

to find them in an emergency and/or to use for admin purposes and/or to help substantiate/refute complaints and/or asset management by dispatch.............

J-

Posted: 9/16/2017 1:35:33 AM EDT

[#15]

Quote History

Quoted:
The GPS antena in our cars are about 3" across and 1/2" thick. We mount them on the center of our dash and they plug into a USB port on our laptops.

View Quote

like this one?
I got my trunk replaced just before the storm, and they didn't have time to run this. Up front it sits and waits...

Posted: 9/17/2017 7:54:05 AM EDT

[#16]

My data antenna is built into my Verizon JetPack and my GPS antenna is about 2" across and is suction cupped to the inside of my windshield.

I've seen similar looking antennas installed on the cars used for LivePD, but there are usually 4 of them.

Posted: 9/17/2017 7:56:32 AM EDT

[#17]

Those 2 round antennas are very common around here, pretty much every newer police car in every town has them.

Always the same size and shape.

Posted: 9/17/2017 8:39:29 AM EDT

[#18]

Something like that sure seems like it would be more durable and less sensitive to temperature extremes than the off-the-shelf Verizon jetpacks we use for our connectivity.

Posted: 9/17/2017 8:47:15 AM EDT

[#19]

Quote History

Quoted:
Something like that sure seems like it would be more durable and less sensitive to temperature extremes than the off-the-shelf Verizon jetpacks we use for our connectivity.

View Quote

What happens with temperature extremes? I've never noticed any difference in connection.

I finally was able to find the antenna: https://3gstore.com/product/6231_panorama-5-in-1-antenna-black.html

So it is for data. But why do they need 2?

Posted: 9/17/2017 8:55:08 AM EDT

[#20]

It's nice your cell phone can 4g, but after a 8 - 12 hrs shift you'd have no plan left. Alway talking / streaming data.

Posted: 9/17/2017 9:11:33 AM EDT

[#21]

Quote History

Quoted:
It's nice your cell phone can 4g, but after a 8 - 12 hrs shift you'd have no plan left. Alway talking / streaming data.

View Quote

Another one

I'm not recommending police officers use their own cell phones.

My point is that cell phones, tablets, and mobile hot spots can get LTE data rates easily within the car without 2 giant antenna on the roof.

Is that really so hard to understand?

Posted: 9/17/2017 9:20:26 AM EDT

[#22]

Quote History

Quoted:

What happens with temperature extremes? I've never noticed any difference in connection.

I finally was able to find the antenna: https://3gstore.com/product/6231_panorama-5-in-1-antenna-black.html

So it is for data. But why do they need 2?

View Quote

The Jetpacks will stop functioning entirely if left on the dash on a hot summer day.
They're also not designed for the beating they take rising around in a patrol car 24/7.

Not much of a lifespan

Posted: 9/17/2017 10:03:15 AM EDT

[#23]

Quote History

Quoted:

The Jetpacks will stop functioning entirely if left on the dash on a hot summer day.
They're also not designed for the beating they take rising around in a patrol car 24/7.

Not much of a lifespan

View Quote

If you have enough of them you get free upgrades to replace the broken ones. Win win.

Posted: 9/17/2017 10:27:36 AM EDT

[#24]

Quote History

Quoted:

If you have enough of them you get free upgrades to replace the broken ones. Win win.

View Quote

We've had the jetpacks for about a decade now, since the current MDT system was stood up. We've periodically replaced the jetpacks with new ones, never for free that I know of.
They all suffer from the same heat sensitivity.
We're actually in the middle of a transition to a new wireless provider with their own stuff, so the jetpacks are going away.
We shall see how the new units perform over time.

Posted: 9/17/2017 11:18:59 AM EDT

[#25]

Quote History

Quoted:
My data antenna is built into my Verizon JetPack and my GPS antenna is about 2" across and is suction cupped to the inside of my windshield.

I've seen similar looking antennas installed on the cars used for LivePD, but there are usually 4 of them.

View Quote

The LivePD antennas are Inmarsat BGAN for the high throughput video link for TV production.

Posted: 9/17/2017 11:33:01 AM EDT

[#26]

Quote History

Quoted:

The Jetpacks will stop functioning entirely if left on the dash on a hot summer day.
They're also not designed for the beating they take rising around in a patrol car 24/7.

Not much of a lifespan

View Quote

I see what you are saying! I thought you meant the temperature affected the signal.

I have the same issue with my iPad, which I run my business off of. I wish I could leave it in the truck fulltime, but even after a few hours in the hot sun it won't turn on and gives this little "HOT" icon.

Posted: 9/17/2017 5:28:42 PM EDT

[#27]

Quote History

Quoted:
My point is that cell phones, tablets, and mobile hot spots can get LTE data rates easily within the car without 2 giant antenna on the roof.

Is that really so hard to understand?

View Quote

Cell phones, tablets, and mobile hot spots have massive wireless networks with very expensive and (usually) carefully engineered systems to support that ubiquitous use of technology.

Public safety mobile communications systems are generally engineered with vastly less infrastructure, such that higher performance is needed at the user end. Overall reliability is higher and more cost effective.

The reason for two antennas is diversity reception, which reduces dropouts. In the cell phone industry, the towers have diversity receive antennas. Some mobile devices have diversity antennas built in.

Posted: 9/17/2017 5:42:56 PM EDT

[#28]

That pic has three antennas, one towards the front in the middle.

Posted: 9/17/2017 5:44:35 PM EDT

[#29]

Quote History

Quoted:
That pic has three antennas, one towards the front in the middle.

View Quote

Yes, but not all of them have the third antenna so I assume that's for something different.

Posted: 9/17/2017 8:43:41 PM EDT

[#30]

Quote History

Quoted:
like this one?
I got my trunk replaced just before the storm, and they didn't have time to run this. Up front it sits and waits...
https://www.AR15.Com/media/mediaFiles/32167/IMG_4689_JPG-308772.jpg

View Quote

Yeah, do you guys use spillman also?

Posted: 9/17/2017 11:05:53 PM EDT

[#31]

those are combo antennas, with a whole bunch of stuff packed into one enclosure.
-- LTE band 13 & 14 ('D block') MIMO antenna (*)
-- GPS receive antenna
-- UHF transceiver antenna (incl. VRS/DVRS)
-- Wifi local access point
-- and some optional stuff

(*) the separation of the multiple antennas on the vehicle rooftop makes MIMO very effective, especially in urban areas prone to MP.

ar-jedi

Posted: 9/20/2017 9:54:18 AM EDT

[#32]

Quote History

Quoted:
What happens with temperature extremes? I've never noticed any difference in connection.

I finally was able to find the antenna: https://3gstore.com/product/6231_panorama-5-in-1-antenna-black.html

So it is for data. But why do they need 2?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Something like that sure seems like it would be more durable and less sensitive to temperature extremes than the off-the-shelf Verizon jetpacks we use for our connectivity.

What happens with temperature extremes? I've never noticed any difference in connection.

I finally was able to find the antenna: https://3gstore.com/product/6231_panorama-5-in-1-antenna-black.html

So it is for data. But why do they need 2?

When we used BlueTree cellular modems for in-car data there were always 2 antennas on the cars. I don't know why.

Posted: 9/20/2017 9:57:06 AM EDT

[#33]

Quote History

Quoted:
We've had the jetpacks for about a decade now, since the current MDT system was stood up. We've periodically replaced the jetpacks with new ones, never for free that I know of.
They all suffer from the same heat sensitivity.
We're actually in the middle of a transition to a new wireless provider with their own stuff, so the jetpacks are going away.
We shall see how the new units perform over time.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:

If you have enough of them you get free upgrades to replace the broken ones. Win win.

We've had the jetpacks for about a decade now, since the current MDT system was stood up. We've periodically replaced the jetpacks with new ones, never for free that I know of.
They all suffer from the same heat sensitivity.
We're actually in the middle of a transition to a new wireless provider with their own stuff, so the jetpacks are going away.
We shall see how the new units perform over time.

Our JetPacks work well, as long as you keep them out of the sun. I keep mine on the printer shelf of my seat organizer with a white towel over it or on a non-skid mat on the transmission hump in front of the console. The biggest issues we have with them is that the batteries swell over time from heat or continuous charging, but IT has a shit load of spare batteries laying around.

Posted: 9/20/2017 9:57:38 AM EDT

[#34]

Quote History

Quoted:
The LivePD antennas are Inmarsat BGAN for the high throughput video link for TV production.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
My data antenna is built into my Verizon JetPack and my GPS antenna is about 2" across and is suction cupped to the inside of my windshield.

I've seen similar looking antennas installed on the cars used for LivePD, but there are usually 4 of them.

The LivePD antennas are Inmarsat BGAN for the high throughput video link for TV production.

I figured they were for the live video feed, just didn't know what they were called. Thanks.

Posted: 9/20/2017 6:02:07 PM EDT

[#35]

Quote History

Quoted:

When we used BlueTree cellular modems for in-car data there were always 2 antennas on the cars. I don't know why.

View Quote

MIMO.

https://en.wikipedia.org/wiki/MIMO
https://meraki.cisco.com/blog/2011/02/mimo-why-multiple-antennas-matter/
https://www.telcoantennas.com.au/site/how-does-mimo-work

Posted: 9/25/2017 1:06:02 PM EDT

[#36]

Quote History

Quoted:

MIMO.

https://en.wikipedia.org/wiki/MIMO
https://meraki.cisco.com/blog/2011/02/mimo-why-multiple-antennas-matter/
https://www.telcoantennas.com.au/site/how-does-mimo-work

View Quote

Interesting. Thanks.

Posted: 9/25/2017 3:29:31 PM EDT

[#37]

GPS we have WiFi cards from verizon for internet. Some of those may be proximity antennas. where is when you drive by certain places they upload your dash camera wirelessly like if you're at the office it will download your dashcam so you dont have to manually do it which can be a pain in the ass some places

Posted: 9/25/2017 4:28:17 PM EDT

[#38]

Quote History

Quoted:

Why would code officials and firefighters have AVL?

GPS? 2 giant antennas for GPS? I doubt it. GPS antennas are small and in many instances aren't mounted externaly anymore.

I think you two are just throwing out wild guesses. I am still laughing about the phone at the ear comment

View Quote

Lots of FD's use closest unit response or generalized GPS tracking of units

Posted: 9/30/2017 5:49:32 PM EDT

[#39]

wifi sticks out to me.

Does the city have a buncha antennas on the street lights? They may have their own mesh network.

The reason for two is called diversity. The receiver samples the two antennas, and using elfin magic can determine more gooder what is signal, and what is a reflection or intermod.

The reason they aren't using 4g like your phone, is probably the system was bidded out, and governments make no fucking sense some times when it's not their money to blow. Plus reliability, plus maybe the comms suite was a package deal with radio, vehicle location, and maybe even streaming from the camera systems if available back to a command post.

Just guessing, call the city radio tech and ask him!

Posted: 10/4/2017 6:19:35 AM EDT

[#40]

Quote History

Quoted:
The GPS antena in our cars are about 3" across and 1/2" thick. We mount them on the center of our dash and they plug into a USB port on our laptops.

View Quote

Yup, mine is the size of a silver dollar. My guys can track me and I can track them. I can't think of any other features I'd need.
It was cheaper to go with the external, otherwise it would have been mounted in my computer (even smaller).

And my wifi is the size of a business card.

I don't know what those things are.

Posted: 10/20/2017 1:51:46 AM EDT

[#41]

Quote History

Quoted:

those are combo antennas, with a whole bunch of stuff packed into one enclosure.
-- LTE band 13 & 14 ('D block') MIMO antenna (*)
-- GPS receive antenna
-- UHF transceiver antenna (incl. VRS/DVRS)
-- Wifi local access point
-- and some optional stuff

(*) the separation of the multiple antennas on the vehicle rooftop makes MIMO very effective, especially in urban areas prone to MP.

ar-jedi

View Quote

Winner winner, chicken dinner.

I just got one of these installed on my car a couple months ago. It's hooked to two separate cellular modems (Verizion and US Cellular) and uses which ever one has the best service, or so the tech guys tell me. There is a wi-fi hot spot inside the car (more antennas) and my MDT connects via wi-fi.

Posted: 10/20/2017 8:54:27 AM EDT

[#42]

Quote History

Quoted:
The reason for two is called diversity. The receiver samples the two antennas, and using elfin magic can determine more gooder what is signal, and what is a reflection or intermod.

View Quote

no.

MIMO is fundamentally different than antenna diversity. MIMO is a technique to take advantage of multipath propagation, instead of trying to avoid it completely. the result is greater bandwidth and better availability (= link reliability).

from a post earlier in this thread:
https://en.wikipedia.org/wiki/MIMO

ar-jedi

[ARCHIVED THREAD] - Police car antenna question

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