Dane county VHF paging

[biglaz]

Howdy,

If you've ever monitored the Dane county VHF paging channel you've probably noticed that every page gets broadcast twice, repeating itself. Does anyone know why they do this?

Secondly, occasionally I'll notice situations where two pages are happening on top of each other because they were done too close in succession. This seems to usually happen when the first page is fairly long (thus it takes a while for it to repeat) such as for a structure fire, and then the dispatcher realizes they forgot to page someone so they immediately send a second page while the first is still repeating. Usually what I've noticed happen in that situation is the repeat of page 1 will stop (or be muted), page 2 will begin, and then the rest of page 1's repeat will finish after page 2. Then, page 2 will repeat, including the part of page 1 that happened during/after page 2. Though I've also seen it happen where the first page is successfully interrupted. What causes this? Is the dispatcher doing something they shouldn't, or is it just some sort of quirk in the software that repeats the page transmissions?

 

[kc9fnm]

Dane pages from two sites in the county, east and west. The page goes out on one side of the county...say the WEST tower. The EAST tower has a receiver that hears the WEST tower. The EAST receiver is connected to a VOX type recorder. After the WEST tower is done the EAST recorder keys up the EAST transmitter and plays back the recorded audio. Thus you hear the same thing twice. It is like a simplex repeater. And yes I too have heard many times when they page OVER another page. I don't ecxactly know why but my guess is they don't monitor the page channel before sending another page. They page from two sites for better coverage over the county and building penetration.

 

[biglaz]

I thought it was simulcasted from 5 sites? Either way, is it common to set something up that way?

 

[RevGary]

If I remember correctly, a lawsuit in the mid 1980's in another state regarding a single page out and NO rescue response where a person died due to a significant time lapse, was the determining factor in the Fire/Rescue industry duplicating pages for all dispatches. Since the double page out procedure was adopted there is now a backup dispatch to the original in case personal pagers or a radio system glitch didn't allow the first to be heard.

In Dane County, If overlapping dispatches ARE being sent out from a single tower, that HAS to be looked into. There should be a sequencing feature built into the dispatch consoles that would prevent the sending of more than ONE at a time. If this IS taking place, they are opening themselves up for the same type of lawsuit because there is a chance that NEITHER page would be heard by the receivers or pagers under certain signal related circumstances.

 

[OpSec]

I've never heard multiple pages of the same call anywhere but Dane....they don't do it in my neck of the woods.

If no one ack's the first page, they will re-page but there are not repeated pages.

 

[SCPD]

I've never heard multiple pages of the same call anywhere but Dane....they don't do it in my neck of the woods.

Quite a few counties do multiple pages for the same call. Dodge, Washington, Fond du Lac, Jefferson to name a few.

Why can't Dane county just key up both at the sametime insead of using a VOX recorder, via a microwave link?

 

[RevGary]

Around the north central part of the state in my 'listening' area most all departments dispatch the same call twice so the Volunteers and First Responders won't miss the page out while at their other jobs, etc. Very common procedure up in this neck of the weeds as well as in our alternate home location in south Alabama.

 

[ffemtbland]

my pager (minitor V) for the rescue pages it twice, just as if you were to scan 158.775 MHz. it does the motorola "bee bee bee bee beep" ... then our tones, then the page ... i've noticed that when i'm monitoring with my handheld (ft60 with stock antenna) the page is much clearer the SECOND time ... I live on the east side on madison (downtown ish)
Lars B
Monona Fire Rescue
RESCUE 62
ENGINE 4

 

[kc9fnm]

....Why can't Dane county just key up both at the sametime insead of using a VOX recorder, via a microwave link?

Transmitting from multiple sites at the same time is called simulcasting but it can't be done with just any old crusty repeater. It requires all the sites to be synced together for exact timing and phase control. Simulcasting is not cheep and Dane may be upgrading the page system when they upgrade the entire county system anyway.

Its not a 5 site simulcast. A simulcast system has a unique sound to it when you monitor it from outside its engineered coverage area (outside the county). The further away from the transmitter sites the more delay and phase cancellations cause the audio to sound distorted, swishy and garbeled. From Dane try listening to the Marquette co. nightly pager test on 155.88 this should give you an idea of how it sounds.

I have seen dispatch centers page twice in a row right away and others send one page, start a timer, wait for an ack, if the timer goes off with no ack they page again. The latter being the most common around here.

 

[biglaz]

The Bird St water tower paging site in Sun Prairie is operational; all county
paging now occurs off a five-site simulcast system.

That came out of the PSC Operating Practices Advisory Committee minutes. It very well could be a misuse of the world simulcast. But if they're not simulcasting, then which towers would they be using?

Are the sheriff and fireground/EMS frequencies simulcast, or do they have the ability to select a transmit tower?

Thanks!

 

[OpSec]

Quite a few counties do multiple pages for the same call. Dodge, Washington, Fond du Lac, Jefferson to name a few.

Why can't Dane county just key up both at the sametime insead of using a VOX recorder, via a microwave link?

Those are all counties that I have never listened to, so that explains my ignorance on this topic. All I know for sure is that the county I listen to FD operations in does not double-page. Right, wrong or indifferent...either you hear it or you don't.

As for Dane, like it was mentioned you can not just set up any old repeaters to simulcast. If you don't believe me, listen to the WSP Southeast Region frequency. You will find a perfect example of what happens when 2 repeaters are transmitting without the proper timing and phasing. The worst sounding area is driving on I-94 between Milwaukee and Madison, which is between the two repeaters...it sounds aweful.

 

[biglaz]

I'm just listening to the ID tones right now on the paging frequency. The initial broadcast of the tones are very weak (I'm in Verona) using my indoor 2-meter j-pole antenna, and it's too weak for the scanner w/ the rubber duck. The repeat of the tones though are with a very strong signal, which would indicate to me different transmitting sites. I've never noticed a difference in signal strength when a page is being transmitted though; could the ID tones be transmitted at a lower power level? Although there are also other times where I hear the ID tones both times at full signal. So I have no clue...

 

[OpSec]

Sounds like they may be sending the pager wake-up tones from one tower then the other so they don't cover each other and prevent the pagers from waking up, then transmitting the voice page from both towers at the same time (simulcast) with the hope that the pager receivers capture the strong(er) signal on it's side of the county.

 

[wirr]

Dane County does have true simulcast on paging (and only on paging). I believe I heard that they do one page on the simulcast and one on the central tower.