Quick Question About GSP
- Thread starter thos201
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AerialEars
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Except for Metro Atlanta, where they're on a trunked repeater system, GSP operates on semi-duplex between mobile and base units. You're probably used to hearing agencies that use repeater systems, where a base unit retransmits the mobile signals on the same frequency the base transmits on. Than means everyone who hears the base can also hear the mobiles.
Semi-duplex means different transmit and receive frequencies and stations transmit one at a time. Full duplex means different frequencies but both stations can transmit and receive at the same time, like talking on a cell phone.
In GSP's case, bases transmit to mobiles on 154.680 and mobiles listen there. Mobiles transmit to the base on 154.800 and the base listens there. They don't use repeaters.
Also, GSP mobiles transmit to each other (car to car) on 154.680 and bases also transmit to each other on 154.680.
Be sure to have both frequencies programmed in your radio. You will only hear mobiles when they're close to you, typically less than five miles. You may hear them either on 154.680 talking to each other or 154.800 talking to the base. You'll want the delay off on these two channels to allow the scanner to switch frequencies quickly so you can hear both sides of the conversation.
Hope this helps. Welcome to scanning!
Semi-duplex means different transmit and receive frequencies and stations transmit one at a time. Full duplex means different frequencies but both stations can transmit and receive at the same time, like talking on a cell phone.
In GSP's case, bases transmit to mobiles on 154.680 and mobiles listen there. Mobiles transmit to the base on 154.800 and the base listens there. They don't use repeaters.
Also, GSP mobiles transmit to each other (car to car) on 154.680 and bases also transmit to each other on 154.680.
Be sure to have both frequencies programmed in your radio. You will only hear mobiles when they're close to you, typically less than five miles. You may hear them either on 154.680 talking to each other or 154.800 talking to the base. You'll want the delay off on these two channels to allow the scanner to switch frequencies quickly so you can hear both sides of the conversation.
Hope this helps. Welcome to scanning!
N8IAA
Member
AerialEars, excellent description of how semi-duplex works. Thank you.
Larry
Larry
jrm5265
Member
Gsp
good answer to his question
my question: Why was that set up like that, I know Ive seen some older taxi set ups like that, the thing with GSP is bad they cant hear each other talking if theyr talking to the base. I have trooper freinds that are at Non-metro posts so theyt on VHF and its bad.
By the way they do now have 800mhz talkies that are like what we used to call pac-rt units , that work back through the VHF mobiles
good answer to his question
my question: Why was that set up like that, I know Ive seen some older taxi set ups like that, the thing with GSP is bad they cant hear each other talking if theyr talking to the base. I have trooper freinds that are at Non-metro posts so theyt on VHF and its bad.
By the way they do now have 800mhz talkies that are like what we used to call pac-rt units , that work back through the VHF mobiles
AerialEars
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I think GSP has the most outdated radio system of ANY law enforcement agency in Georgia. It goes back to the 60s (or maybe even the 50s). Every city and county that I know of still on VHF has a repeater for system-wide coverage for their handheld and mobile radios. The Georgia Forestry Commission and Department of Natural Resources, both still on VHF, also have repeaters.
Considering today's technology, it's like the troopers use tin cans and string to communicate. I have heard troopers call a neighboring post when their own post couldn't hear them.
GSP tried SouthernLinc, but the coverage was spotty. Even people I know who work for Georgia Power, owner of SouthernLinc, complain about the coverage. Georgia Power serves primarily urban areas, so their system is not geared to cover rural areas.
This is my guess as to why the system was set up as semi-duplex: First, the patrol posts are close geographically. Around me, there is Madison, Conyers, Athens and Lawrenceville, all within 30 minutes of my location.
So if everyone was on the same frequency, or in other words, if the bases were listening for their mobiles on the same frequency as the other bases transmit on, chances are the mobiles would be frequently stepped on by the bases, especially if the mobiles were a ways from the base.
Having a frequency for the weaker mobile stations by themselves means they're not competing with the relatively close high-power tall-antenna base stations.
Maybe someone who knows more can verify or debunk my theory.
Considering today's technology, it's like the troopers use tin cans and string to communicate. I have heard troopers call a neighboring post when their own post couldn't hear them.
GSP tried SouthernLinc, but the coverage was spotty. Even people I know who work for Georgia Power, owner of SouthernLinc, complain about the coverage. Georgia Power serves primarily urban areas, so their system is not geared to cover rural areas.
This is my guess as to why the system was set up as semi-duplex: First, the patrol posts are close geographically. Around me, there is Madison, Conyers, Athens and Lawrenceville, all within 30 minutes of my location.
So if everyone was on the same frequency, or in other words, if the bases were listening for their mobiles on the same frequency as the other bases transmit on, chances are the mobiles would be frequently stepped on by the bases, especially if the mobiles were a ways from the base.
Having a frequency for the weaker mobile stations by themselves means they're not competing with the relatively close high-power tall-antenna base stations.
Maybe someone who knows more can verify or debunk my theory.
roadranger
Member
Hey, buddy!
I thought that GSP talked back to the base on 800 MHZ?
I thought that GSP talked back to the base on 800 MHZ?
b7spectra
EMS Dispatcher
GSP in the Metro Atlanta area works off the Atlanta TRS. They use both mobiles and portables. Outside of the Metro area, they are on the VHF system, but use UHF pac-rat radio's, not 800 MHz.
Julian1
Member
Gsp Radios
Alabama is on the same set up. Tennessee is split frequencies too.
Base to car & car to car are same channel
Car to base on a different channel
GSP cars can hear each within several miles depending on terrain. Their radios scan. Car to base 154.800 is a second priority channel.
The explanation on why car to base / base to car is exactly correct in my opinion.
Take care....
Alabama is on the same set up. Tennessee is split frequencies too.
Base to car & car to car are same channel
Car to base on a different channel
GSP cars can hear each within several miles depending on terrain. Their radios scan. Car to base 154.800 is a second priority channel.
The explanation on why car to base / base to car is exactly correct in my opinion.
Take care....
I agree with ya AerialEars... the radio system for GSP is way outdated IMO. I live in Thomson and I can hear the Thomson GSP post and the Washington GSP post, approx. 25 miles from me, equally well. If a trooper is working near the Wilkes/McDuffie county line the Washington post interferes with Thomson and vice versa. I hear them tell their dispatch, be it Washington or Thomson, that they couldn't hear because the other post stepped on them. Seems like an officer safety issue to me... especially if a trooper can't hear another trooper calling for assistance and the dispatch has to relay the info. I hear them do that ALL the time. That wouldn't happen if they used a repeater system and everyone could hear each other.
Julian1
Member
While traveling in Virginia in late 90's I listened to their State Police. They used a repeater system. Each troop or post would have its own repeater. A given repeater freq pair might be duplicated, but far enough away not to interfere. It sounded great.
Georgia DNR Pine Mountain tower gives DNR a better set up than GSP. Hard to imagine GA can't find 8 to 10 vhf freq pairs to use - one per troop. Example: Newnan, Lagrange, Manchester - use one dispatcher / one freq pair on repeater. Same as Troop-C for Atlanta. It doesn't have to be an expensive 800/P-25 to do the job......unless you work for Moto or M/A Comm.
Now that I think of it.... Georgia Forestry is a good example of a repeater system for different parts of the state.
They could even take over the mostly unused GBI 151.205.
Sorry.... I'm trying to be practical.
**PS - Clocks move back an hour tonight! ** Returning to Standard Time.
Happy Scanning
Georgia DNR Pine Mountain tower gives DNR a better set up than GSP. Hard to imagine GA can't find 8 to 10 vhf freq pairs to use - one per troop. Example: Newnan, Lagrange, Manchester - use one dispatcher / one freq pair on repeater. Same as Troop-C for Atlanta. It doesn't have to be an expensive 800/P-25 to do the job......unless you work for Moto or M/A Comm.
Now that I think of it.... Georgia Forestry is a good example of a repeater system for different parts of the state.
They could even take over the mostly unused GBI 151.205.
Sorry.... I'm trying to be practical.
**PS - Clocks move back an hour tonight! ** Returning to Standard Time.
Happy Scanning
kc4wwu
Member
Gsp
In my area of Ga, Camden County, the GSP units, while IN Camden, use the Camden County 911 center. When they are running tags, or investigating an accident, or backing up a deputy, they call it all in to the Camden 911 center. I rarely hear much activity on the GSP 154.680 frequency. At least in my part of Ga anyway. I believe GSP on Jekyll Island uses the Glynn County 800 TRS also. They have a T/G on that system.
73, Pete
K4QHR
/\/\ Astro Spectra W7 UHF
/\/\ Astro Spectra W7 VHF
/\/\ XTS5000 UHF M3 FPP
/\/\ XTS3000 UHF M1 (use at work)
/\/\ Astro Saber 3 VHF
Uniden BC 996
In my area of Ga, Camden County, the GSP units, while IN Camden, use the Camden County 911 center. When they are running tags, or investigating an accident, or backing up a deputy, they call it all in to the Camden 911 center. I rarely hear much activity on the GSP 154.680 frequency. At least in my part of Ga anyway. I believe GSP on Jekyll Island uses the Glynn County 800 TRS also. They have a T/G on that system.
73, Pete
K4QHR
/\/\ Astro Spectra W7 UHF
/\/\ Astro Spectra W7 VHF
/\/\ XTS5000 UHF M3 FPP
/\/\ XTS3000 UHF M1 (use at work)
/\/\ Astro Saber 3 VHF
Uniden BC 996
b7spectra
EMS Dispatcher
If Georgia ever wanted to consolidate, it would be exceptionally simple. All they would have to do is connect each base station to a private voice line that would be fed straight to Troop C. That way, dozens of radio operators would be out of work, but the state would save untold thousands of dollars. Troop C would be able to communicate with EVERY unit in the state and never have to worry about a RO going to the bathroom and missing a call. Why won't Georgia do this? Makes too much sense.
In most of South Ga GSP is now equiping all troopers with 700/800 Mhz band portable radios which transmit Pac/rt on a 700 Mhz conventional freq. to the vehicle which then transmits on the VHF system. Troopers also have local south GA 800 systems programmed into the portables such as Lowndes County, Tift County and Thomas County 800 systems. Oftem times during a chase or a man hunt or big wreck Troopers will switch over to the local system to speak with EMS, or local Deputies.
For mobile monotoring of GSP you will need a custom cut whip antenna. These arent very expensive but you need it cut to GSP's freq to get the best results. Without 5 foot antnenna on your vehicle you will only ever hear base and never the Troopers unless your right on them.
Yes GA needs to update their system, but this system is very simple which means there isnt much to break or fix, and right now Georgia doesnt have the money to build something new.
For mobile monotoring of GSP you will need a custom cut whip antenna. These arent very expensive but you need it cut to GSP's freq to get the best results. Without 5 foot antnenna on your vehicle you will only ever hear base and never the Troopers unless your right on them.
Yes GA needs to update their system, but this system is very simple which means there isnt much to break or fix, and right now Georgia doesnt have the money to build something new.
rafale01010
Member
This has probably been asked before, but how would i get a piece of wire tuned to their freq?
thunderbritches174
Member
A 1/4 wave would be just a tad shorter than .5 meters long. IF band = "FM" THEN
wavelength = SPEED OF LIGHT x 1000/frequency and a full wave about 6.35 feet.
Many commercially-available scanner antennas are available at low cost ($20).
Or, 468/freq = antenna length in feet (one wavelength)
If listening to 154.680 & 154.800 only, use 154.740 as the freq in the above equation. Most antennas are not full wavelengths (e.g., 1/4 or 1/2 wavelengths will do, as will 5/8), but cut it long to be safe.
A thicker piece of wire should have a wider bandwidth; that is, don't use the thinnest piece to listen to the entire VHF-high band.
Ask your local amateur radio operators for help.........we're notorious for building antennas with coax cable, wire, etc.
Or, 468/freq = antenna length in feet (one wavelength)
If listening to 154.680 & 154.800 only, use 154.740 as the freq in the above equation. Most antennas are not full wavelengths (e.g., 1/4 or 1/2 wavelengths will do, as will 5/8), but cut it long to be safe.
A thicker piece of wire should have a wider bandwidth; that is, don't use the thinnest piece to listen to the entire VHF-high band.
Ask your local amateur radio operators for help.........we're notorious for building antennas with coax cable, wire, etc.
What happened to the GEWIN network? I thought that was supposed to be a statewide network like we have MARCS here in Ohio. Or has lack of money slowed its progress since I see its only operational in the Metro Atlanta and Cobb County area?
No $$$$
b7spectra
EMS Dispatcher
GEWIN is the biggest joke around. Yeah, Cobb County is using it, and Douglasville is piggy backing off of it, and there is a site in North Atlanta, but it doesn't appear that the Atlanta, DeKalb or Gwinnett systems are going to be part of it. Forsyth and Hall County are not part of it either. Seems like GEWIN is more like GEWIZ!
N8IAA
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