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goodzyz
Guest
who can explain the concept of the voting system and simulcast system,What is the difference between them?Thank you
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nmfire10
Guest
Voting takes multiple receivers in strategic locations and picks the one with the best signal to be repeated or sent to the console. Lets say the one receiver at the main repeater site isn't enough for portables to reach on the east end of the town. You put a receiver on the east end somewhere and use a voter to pick which receiver to use on the fly.
Simulcast is the act of transmitting on one frequency using multiple syncronized transmitters at the same time to increase your coverage area. It is extremely expensive and requires time-synced transmitters. You can't just use any old transmitter.
Simucast is a term used for other things too. Some use it to signify transmitting on multiple different channels at once. Some call that multi-casting.
Simulcast is the act of transmitting on one frequency using multiple syncronized transmitters at the same time to increase your coverage area. It is extremely expensive and requires time-synced transmitters. You can't just use any old transmitter.
Simucast is a term used for other things too. Some use it to signify transmitting on multiple different channels at once. Some call that multi-casting.
jmp883
Member
Just some additional (useless) information regarding voters. The agency I dispatch for covers approximately 30 square miles. We operate UHF with 4 voter locations placed strategically around the town.
When we key up at the console, or when a mobile/W-T keys up, we will see all 4 voter lights come on on the console. A split second later all but one will go out. Obviously the remaining one that is lit is the one that is transmitting the signal. If a unit is between 2 of the voters you can watch the lights switch back and forth but under most normal conditions only one voter will rebroadcast the signal. We can turn on/off each voter independently and we have to sets of voters: 4 for the PD freqs. and 4 for the FD freqs.
If there is one drawback to our setup it is that when we key up from HQ we do not transmit directly to air. Our audio is sent via dedicated phone line to the transmitter site about 4-5 miles away. The phone line(s) are definitely not the best quality they could be, but the biggest flaw in the system is that if we lose the transmitter site we lose all communications, period. We have a back-up radio room in HQ, and each of the 5 firehouses here in town have full radio rooms capable of transmitting on all of our PD/FD/EMS/DPW channels, including paging capability. However they all operate at much lower power levels than the 60 watts/50 watts ERP that the main transmitter site puts out.
Oh well, ya gotta take the good with the bad.......
When we key up at the console, or when a mobile/W-T keys up, we will see all 4 voter lights come on on the console. A split second later all but one will go out. Obviously the remaining one that is lit is the one that is transmitting the signal. If a unit is between 2 of the voters you can watch the lights switch back and forth but under most normal conditions only one voter will rebroadcast the signal. We can turn on/off each voter independently and we have to sets of voters: 4 for the PD freqs. and 4 for the FD freqs.
If there is one drawback to our setup it is that when we key up from HQ we do not transmit directly to air. Our audio is sent via dedicated phone line to the transmitter site about 4-5 miles away. The phone line(s) are definitely not the best quality they could be, but the biggest flaw in the system is that if we lose the transmitter site we lose all communications, period. We have a back-up radio room in HQ, and each of the 5 firehouses here in town have full radio rooms capable of transmitting on all of our PD/FD/EMS/DPW channels, including paging capability. However they all operate at much lower power levels than the 60 watts/50 watts ERP that the main transmitter site puts out.
Oh well, ya gotta take the good with the bad.......
hcsd35-32
Member
The agency I dispatch for also uses voter/repeater system similar to what Joe mentioned. The only exception is that our system uses microwave trasmitters pointed directly at the 4 differant voter sites. Other than the fact that the 4 sites are not enough to cover our entire county the system works good.
Al42
Member
Assuming this is a repeater operation, why not just have 2 desk console radios (or even 2 W/Ts) at the dispatch point, for use if the phone lines go out?jmp883 said:
jmp883
Member
Al42 wrote:
It's not a question of console radios or W/T's for back-up, we have plenty of back-up in regard to consoles and W/T's. The problem is that we only have one transmitter for the entire system. We lose that transmitter (or the phone lines from HQ to the transmitter) and we're dead in the water. Fortunately in all the years I've been there we've never lost the transmitter itself...we have lost the phone lines and that's just as bad.
We need a 2nd transmitter, in a 2nd location, rated at the same power as the primary so that if we lose the primary we still have a way to communicate.
To get off the tech side of things for a minute.....I would think that most people would agree that PD/FD/EMS lives, as well as the lives of the citizens we protect are surely worth the cost of one transmitter. Those who don't are the people who are on the bottom of the foodchain-politicians. If they can't see a physical change or benefit when they drive through town they can't justify spending the money. That's why our radio system, which is going on 20 years old, is in dire need of upgrade/replacement. It's also why after 15 years of dispatching I'm still only making $29,000.00 a year. This is a quote from the business admin of the town I work in during contract negotiations: 'Because dispatchers, their equipment, and what they do can't be seen by the public there is no reason to spend any more than the minimum amount of money on salaries and equipment.' Nice attitude, huh?
Anyway, I slightly rambled off topic here.....I do apologize.
It's not a question of console radios or W/T's for back-up, we have plenty of back-up in regard to consoles and W/T's. The problem is that we only have one transmitter for the entire system. We lose that transmitter (or the phone lines from HQ to the transmitter) and we're dead in the water. Fortunately in all the years I've been there we've never lost the transmitter itself...we have lost the phone lines and that's just as bad.
We need a 2nd transmitter, in a 2nd location, rated at the same power as the primary so that if we lose the primary we still have a way to communicate.
To get off the tech side of things for a minute.....I would think that most people would agree that PD/FD/EMS lives, as well as the lives of the citizens we protect are surely worth the cost of one transmitter. Those who don't are the people who are on the bottom of the foodchain-politicians. If they can't see a physical change or benefit when they drive through town they can't justify spending the money. That's why our radio system, which is going on 20 years old, is in dire need of upgrade/replacement. It's also why after 15 years of dispatching I'm still only making $29,000.00 a year. This is a quote from the business admin of the town I work in during contract negotiations: 'Because dispatchers, their equipment, and what they do can't be seen by the public there is no reason to spend any more than the minimum amount of money on salaries and equipment.' Nice attitude, huh?
Anyway, I slightly rambled off topic here.....I do apologize.
You guys have the terminology incorrect. The voter is located at a central location and the satellite receivers are located at the outlying areas and receive the signal from the low power portable. The receiver puts the audio on a phone line or microwave system and routs it to the voter where it compares the audio quality of all of the receivers that have unsquelched.
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nmfire10
Guest
The reason you lose everything if you lose the phone line is that the voter is located at Dispatch and is controlling the repeater. If you lose the phone line, the repeater will receive but it won't have anything to re-transmit.
Many repeaters setup in this style have "in cabinet fallback" where if it loses connection with the voter, it will default to self-contained repeat mode.
Many repeaters setup in this style have "in cabinet fallback" where if it loses connection with the voter, it will default to self-contained repeat mode.
Al42
Member
That's was what I was addressing. If you lose the phone lines, and the transmitter is, or can revert to, a repeater, you can use it from the dispatch position.jmp883 said:
Someone should have made a huge stink about that one - publicly, in all the news media, pointing out that it needlessly endangers the lives not only of the emergency responders, but those for whom they work - the public. If you have a heart attack, and there's a problem with the ambulance's radio, you're dead. Does the public over there value its own lives so little?
Al42
Member
I've never seen one that doesn't, which is why my comment. (Only been in the busness since 1964, so I guess I've missed a few things.) But that's penny wise and ton foolish.nmfire10 said:
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nmfire10
Guest
Al42 said:
Wait, you calling a redundency foolish??? You've beem in the buisness since 1964 and you've never heard of this?? It's a programmable option on, for example, the Motorola Quantar, MSF5000, and probably the MTR2000. Hell, the option to enable is called "Fallback In Cabinet Repeat". If the voting system fails, or in this case becomes disconnected, the repeater will just repeat self-contained.
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N_Jay
Guest
READING TEST TIME
Al42
Member
No, I said exactly the opposite - that not providing the redundancy is foolish.nmfire10 said:
Of not having an on-site receiver as one of the voting receivers, reverting to single-site if the phone line fails? I've never heard of not doing it that way. If the transmitter is at a good location, RF-wise (and why wouldn't it be), there should be a receiver at the same site.
Al42 said:
In typical satellite receiver designs the in-cabinet receiver is part of the receiver network and is connected to the voter as a comparable signal. It is only in situations that the repeater logic doesn't see a COR or wake up tones from the voter but it sees a received signal from the in-cabinet receiver it will revert to an in-cabinet configuration until it does see a signal from the voter.
Now while talk-back from distant portables may be an issue, at least close in units or dispatch can advise all the users that they have to use their mobile radio if they have one as talk-out coverage isn't an issue.
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nmfire10
Guest
I guess I misread that.
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